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Pluvinage JV, Ngo T, Fouassier C, McDonagh M, Holmes BB, Bartley CM, Kondapavulur S, Hurabielle C, Bodansky A, Pai V, Hinman S, Aslanpour A, Alvarenga BD, Zorn KC, Zamecnik C, McCann A, Asencor AI, Huynh T, Browne W, Tubati A, Haney MS, Douglas VC, Louine M, Cree BAC, Hauser SL, Seeley W, Baranzini SE, Wells JA, Spudich S, Farhadian S, Ramachandran PS, Gillum L, Hales CM, Zikherman J, Anderson MS, Yazdany J, Smith B, Nath A, Suh G, Flanagan EP, Green AJ, Green R, Gelfand JM, DeRisi JL, Pleasure SJ, Wilson MR. Transcobalamin receptor antibodies in autoimmune vitamin B12 central deficiency. Sci Transl Med 2024; 16:eadl3758. [PMID: 38924428 DOI: 10.1126/scitranslmed.adl3758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2023] [Accepted: 06/05/2024] [Indexed: 06/28/2024]
Abstract
Vitamin B12 is critical for hematopoiesis and myelination. Deficiency can cause neurologic deficits including loss of coordination and cognitive decline. However, diagnosis relies on measurement of vitamin B12 in the blood, which may not accurately reflect the concentration in the brain. Using programmable phage display, we identified an autoantibody targeting the transcobalamin receptor (CD320) in a patient with progressive tremor, ataxia, and scanning speech. Anti-CD320 impaired cellular uptake of cobalamin (B12) in vitro by depleting its target from the cell surface. Despite a normal serum concentration, B12 was nearly undetectable in her cerebrospinal fluid (CSF). Immunosuppressive treatment and high-dose systemic B12 supplementation were associated with increased B12 in the CSF and clinical improvement. Optofluidic screening enabled isolation of a patient-derived monoclonal antibody that impaired B12 transport across an in vitro model of the blood-brain barrier (BBB). Autoantibodies targeting the same epitope of CD320 were identified in seven other patients with neurologic deficits of unknown etiology, 6% of healthy controls, and 21.4% of a cohort of patients with neuropsychiatric lupus. In 132 paired serum and CSF samples, detection of anti-CD320 in the blood predicted B12 deficiency in the brain. However, these individuals did not display any hematologic signs of B12 deficiency despite systemic CD320 impairment. Using a genome-wide CRISPR screen, we found that the low-density lipoprotein receptor serves as an alternative B12 uptake pathway in hematopoietic cells. These findings dissect the tissue specificity of B12 transport and elucidate an autoimmune neurologic condition that may be amenable to immunomodulatory treatment and nutritional supplementation.
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Affiliation(s)
- John V Pluvinage
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Thomas Ngo
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Camille Fouassier
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Maura McDonagh
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Brandon B Holmes
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Christopher M Bartley
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
- Department of Psychiatry and Behavioral Sciences, UCSF, San Francisco, CA 94158, USA
| | - Sravani Kondapavulur
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
- Department of Neurological Surgery, UCSF, San Francisco, CA 94158, USA
| | - Charlotte Hurabielle
- Department of Medicine, Division of Rheumatology, UCSF, San Francisco, CA, 94158, USA
| | - Aaron Bodansky
- Department of Pediatrics, Division of Critical Care, UCSF, San Francisco, CA 94158, USA
| | - Vincent Pai
- Bruker Cellular Analysis, Emeryville, CA, 94608, USA
| | - Sam Hinman
- Bruker Cellular Analysis, Emeryville, CA, 94608, USA
| | - Ava Aslanpour
- Bruker Cellular Analysis, Emeryville, CA, 94608, USA
| | - Bonny D Alvarenga
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Kelsey C Zorn
- Department of Biochemistry and Biophysics, UCSF, San Francisco, CA 94158, USA
| | - Colin Zamecnik
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | | | - Andoni I Asencor
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Trung Huynh
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Weston Browne
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Asritha Tubati
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Michael S Haney
- Department of Neurology, Stanford University, Stanford, CA 94304, USA
| | - Vanja C Douglas
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Martineau Louine
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Bruce A C Cree
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Stephen L Hauser
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - William Seeley
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Sergio E Baranzini
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - James A Wells
- Department of Pharmaceutical Chemistry, UCSF, San Francisco, CA 94158, USA
| | - Serena Spudich
- Department of Neurology, Yale School of Medicine, New Haven, CT 06520, USA
| | - Shelli Farhadian
- Department of Internal Medicine, Section of Infectious Diseases, Yale School of Medicine, New Haven, CT 06520, USA
| | - Prashanth S Ramachandran
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | | | - Chadwick M Hales
- Department of Neurology, Emory University, Atlanta, GA 30322, USA
| | - Julie Zikherman
- Department of Medicine, Division of Rheumatology, UCSF, San Francisco, CA, 94158, USA
| | - Mark S Anderson
- Diabetes Center, UCSF, San Francisco, CA 94143, USA
- Department of Medicine, Division of Endocrinology, UCSF, San Francisco, CA 94158, USA
| | - Jinoos Yazdany
- Department of Neurological Surgery, UCSF, San Francisco, CA 94158, USA
| | - Bryan Smith
- Division of Neuroimmunology and Neurovirology, National Institute of Neurologic Disorders and Stroke, Bethesda, MD 20824, USA
| | - Avindra Nath
- Division of Neuroimmunology and Neurovirology, National Institute of Neurologic Disorders and Stroke, Bethesda, MD 20824, USA
| | - Gina Suh
- Department of Medicine, Division of Infectious Disease, Mayo Clinic, Rochester, MN 55905, USA
| | - Eoin P Flanagan
- Department of Neurology and Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA
| | - Ari J Green
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Ralph Green
- Department of Pathology and Laboratory Medicine, University of California, Davis, CA 95616, USA
| | - Jeffrey M Gelfand
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Joseph L DeRisi
- Bruker Cellular Analysis, Emeryville, CA, 94608, USA
- Chan Zuckerberg Biohub San Francisco, San Francisco, CA 94158, USA
| | - Samuel J Pleasure
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
| | - Michael R Wilson
- Department of Neurology, University of California, San Francisco (UCSF), San Francisco, CA 94158, USA
- Weill Institute for Neurosciences, UCSF, San Francisco, CA 94158, USA
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Diogo R, Rua IB, Ferreira S, Nogueira C, Pereira C, Rosmaninho-Salgado J, Diogo L. Methylmalonyl Coenzyme A (CoA) Epimerase Deficiency, an Ultra-Rare Cause of Isolated Methylmalonic Aciduria With Predominant Neurological Features. Cureus 2023; 15:e48017. [PMID: 38034150 PMCID: PMC10687495 DOI: 10.7759/cureus.48017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/30/2023] [Indexed: 12/02/2023] Open
Abstract
Methylmalonyl coenzyme A (CoA) epimerase (MCE) converts D-methylmalonyl-CoA into L-methylmalonyl CoA in the final common degradation pathway of valine, isoleucine, methionine, threonine, odd-chain fatty acids, and cholesterol side chains. Methylmalonyl-CoA epimerase deficiency is an ultra-rare autosomal recessive disorder where methylmalonic acid, methylcitrate, 3-hydroxypropionate, and propionylcarnitine are accumulated. We describe two novel pediatric patients and review the previously reported cases of MCE deficiency. Including our two novel patients, at least 24 cases of MCE deficiency have been described, with a broad clinical spectrum ranging from asymptomatic to severely neurologically impaired patients. Our patients are siblings of Arabic origin who presented with metabolic decompensation with coma and epilepsy during infancy. Methylmalonic aciduria was disclosed, L-methylmalonyl-CoA mutase deficiency was assumed, and they were treated accordingly. When first seen in our country, aged 10 and four years, respectively, both presented severe intellectual disability and spasticity. The younger had an ataxic gait, and the older was wheelchair-ridden. The study of the MMUT, MMAA, MMAB, and MMADHC genes was normal. Subsequently, the pathogenic variant c.139C>T (p.Arg47*) in the MCEE gene was identified in homozygosity in both patients, leading to the diagnosis of MCE deficiency (Online Mendelian Inheritance in Man (OMIM®) 251120, McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University, MD, USA). Most patients were homozygous for that variant (83% of the alleles). Correct diagnosis allowed treatment adequacy and genetic counseling. Methylmalonyl-CoA epimerase deficiency shares a similar biochemical profile with other rare genetic disorders. Patients present with overlapping clinical features with predominant neurological manifestations; genetic testing is indispensable for diagnosis. We found no association between genotype and biochemical and clinical phenotypes.
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Affiliation(s)
- Rui Diogo
- Pediatrics, Reference Centre of Hereditary Metabolic Diseases, member of MetabERN; Centre for Child Development, Coimbra Hospital and University Centre, Coimbra, PRT
| | - Inês B Rua
- Pediatrics, Reference Centre of Hereditary Metabolic Diseases, member of MetabERN; Centre for Child Development, Coimbra Hospital and University Centre, Coimbra, PRT
| | - Sara Ferreira
- Pediatrics, Reference Centre of Hereditary Metabolic Diseases, member of MetabERN; Centre for Child Development, Coimbra Hospital and University Centre, Coimbra, PRT
| | - Célia Nogueira
- Genetics, National Institute of Health Dr Ricardo Jorge, Porto, PRT
| | - Cristina Pereira
- Pediatrics, Reference Centre of Refractory Epilepsies, member of EpiCARE; Coimbra Hospital and University Centre, Coimbra, PRT
| | | | - Luísa Diogo
- Pediatrics and Inherited Metabolic Diseases, Reference Centre of Hereditary Metabolic Diseases member of MetabERN; Centre for Child Development, Coimbra Hospital and University Centre, Coimbra, PRT
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McCaddon A, Carr DF, Peter H, Moat SJ, Quadros EV. Transcobalamin receptor gene polymorphisms and mutation in an elderly population. Clin Nutr ESPEN 2023; 55:425-427. [PMID: 37202078 DOI: 10.1016/j.clnesp.2023.04.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 04/05/2023] [Accepted: 04/27/2023] [Indexed: 05/20/2023]
Abstract
BACKGROUND & AIMS Cellular uptake of the essential nutrient vitamin B12 (cobalamin) occurs via the transcobalamin receptor (TCblR/CD320), a ubiquitous membrane receptor. Polymorphisms in the receptor exist, though the effect of such variants across patient populations is unknown. METHODS We determined CD320 genotype in 377 randomly selected elderly individuals. RESULTS Three polymorphisms and a codon deletion were identified in the exon 2 region. Haplotype variants had significantly higher holotranscobalamin (holo-TC) values and a higher holo-TC/total cobalamin ratio. TCblR haplotype explained 46% of the variability in holo-TC values. CONCLUSIONS This has significant implications for the clinical utility of the 'combined indicator' of B12 status since it is based on a standard rate of intracellular flux via the TC-Cbl receptor. Modification of the model may be required to account for CD320 haplotype.
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Affiliation(s)
- Andrew McCaddon
- Faculty of Social and Life Sciences, Wrexham Glyndwr University, Wrexham, UK.
| | - Daniel F Carr
- Department of Pharmacology and Therapeutics, University of Liverpool, UK
| | | | - Stuart J Moat
- School of Medicine and Department of Medical Biochemistry, Cardiff University, UK
| | - Edward V Quadros
- Department of Medicine, SUNY Downstate Medical Center, Brooklyn, NY, USA
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Linagliptin treatment is associated with altered cobalamin (VitB12) homeostasis in mice and humans. Sci Rep 2023; 13:601. [PMID: 36635409 PMCID: PMC9837112 DOI: 10.1038/s41598-023-27648-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 01/05/2023] [Indexed: 01/14/2023] Open
Abstract
Linagliptin is a dipeptidyl peptidase-4 (DPP-4) inhibitor used for the treatment of type 2 diabetes, with additional beneficial effects for the kidney. Treatment of mice with linagliptin revealed increased storage of cobalamin (Cbl, Vitamin B12) in organs if a standard Cbl diet (30 µg Cbl/kg chow) is given. In order to translate these findings to humans, we determined methylmalonic acid (MMA), a surrogate marker of functional Cbl homeostasis, in human plasma and urine samples (n = 1092) from baseline and end of trial (6 months after baseline) of the previously completed MARLINA-T2D clinical trial. We found that individuals with medium Cbl levels (MMA between 50 and 270 nmol/L for plasma, 0.4 and 3.5 µmol/mmol creatinine for urine, at baseline and end of trial) exhibited higher MMA values at the end of study in placebo compared with linagliptin. Linagliptin might inhibit the N-terminal degradation of the transcobalamin receptor CD320, which is necessary for uptake of Cbl into endothelial cells. Because we demonstrate that linagliptin led to increased organ levels of Cbl in mice, sustained constant medium MMA levels in humans, and inhibited CD320 processing by DPP-4 in-vitro, we speculate that linagliptin promotes intra-cellular uptake of Cbl by prolonging half-life of CD320.
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Martín-Rivada Á, Cambra Conejero A, Martín-Hernández E, Moráis López A, Bélanger-Quintana A, Cañedo Villarroya E, Quijada-Fraile P, Bellusci M, Chumillas Calzada S, Bergua Martínez A, Stanescu S, Martínez-Pardo Casanova M, Ruíz-Sala P, Ugarte M, Pérez González B, Pedrón-Giner C. Newborn screening for propionic, methylmalonic acidemia and vitamin B12 deficiency. Analysis of 588,793 newborns. J Pediatr Endocrinol Metab 2022; 35:1223-1231. [PMID: 36112821 DOI: 10.1515/jpem-2022-0340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 08/13/2022] [Indexed: 11/15/2022]
Abstract
OBJECTIVES We present the results of our experience in the diagnosis and follow up of the positive cases for propionic, methylmalonic acidemias and cobalamin deficiencies (PA/MMA/MMAHC) since the Expanded Newborn Screening was implemented in Madrid Region. METHODS Dried blood samples were collected 48 h after birth. Amino acids and acylcarnitines were quantitated by MS/MS. Newborns with alterations were referred to the clinical centers for follow-up. Biochemical and molecular genetic studies for confirmation of a disease were performed. RESULTS In the period 2011-2020, 588,793 children were screened, being 953 of them were referred to clinical units for abnormal result (192 for elevated C3 levels). Among them, 88 were false positive cases, 85 maternal vitamin B12 deficiencies and 19 were confirmed to suffer an IEM (8 PA, 4 MMA, 7 MMAHC). Ten out 19 cases displayed symptoms before the NBS results (6 PA, 1 MMA, 3 MMAHC). C3, C16:1OH+C17 levels and C3/C2 and C3/Met ratios were higher in newborns with PA/MMA/MMAHC. Cases diagnosed with B12 deficiency had mean B12 levels of 187.6 ± 76.9 pg/mL and their mothers 213.7 ± 95.0; 5% of the mothers were vegetarian or had poor eating while 15% were diagnosed of pernicious anemia. Newborns and their mothers received treatment with B12 with different posology, normalizing their levels and the secondary alterations disappeared. CONCLUSIONS Elevated C3 are a frequent cause for abnormal result in newborn screening with a high rate of false positive cases. Presymptomatic diagnosis of most of PA and some MMA/MMAHC is difficult. Vitamin B12 deficiency secondary to maternal deprivation is frequent with an heterogenous clinical and biochemical spectrum.
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Affiliation(s)
- Álvaro Martín-Rivada
- Sección de Gastroenterología y Nutrición, Hospital Infantil Universitario Niño Jesús, Madrid, Spain
| | - Ana Cambra Conejero
- Laboratorio de Cribado Neonatal de la Comunidad de Madrid, Servicio de Bioquímica Clínica, Hospital General Universitario GregorioMarañón, Madrid, Spain
| | - Elena Martín-Hernández
- Unidad de Enfermedades Mitocondriales-Metabólicas Hereditarias, Centro de Referencia Nacional (CSUR) y Europeo (MetabERN) en Enfermedades Metabólicas, Madrid, Spain
| | - Ana Moráis López
- Unidad de Nutrición Infantil y Enfermedades Metabólicas, Hospital Universitario La Paz, Madrid, Spain
| | - Amaya Bélanger-Quintana
- Centro de Referencia Nacional (CSUR) en Enfermedades Metabólicas, Hospital Universitario Ramón y Cajal, Madrid, Spain
| | - Elvira Cañedo Villarroya
- Sección de Gastroenterología y Nutrición, Hospital Infantil Universitario Niño Jesús, Madrid, Spain
| | - Pilar Quijada-Fraile
- Unidad de Enfermedades Mitocondriales-Metabólicas Hereditarias, Centro de Referencia Nacional (CSUR) y Europeo (MetabERN) en Enfermedades Metabólicas, Madrid, Spain
| | - Marcelo Bellusci
- Unidad de Enfermedades Mitocondriales-Metabólicas Hereditarias, Centro de Referencia Nacional (CSUR) y Europeo (MetabERN) en Enfermedades Metabólicas, Madrid, Spain
| | - Silvia Chumillas Calzada
- Unidad de Enfermedades Mitocondriales-Metabólicas Hereditarias, Centro de Referencia Nacional (CSUR) y Europeo (MetabERN) en Enfermedades Metabólicas, Madrid, Spain
| | - Ana Bergua Martínez
- Unidad de Nutrición Infantil y Enfermedades Metabólicas, Hospital Universitario La Paz, Madrid, Spain
| | - Sinziana Stanescu
- Centro de Referencia Nacional (CSUR) en Enfermedades Metabólicas, Hospital Universitario Ramón y Cajal, Madrid, Spain
| | | | - Pedro Ruíz-Sala
- Centro de Diagnóstico de Enfermedades Moleculares, Universidad Autónoma de Madrid, IdiPAZ, CIBERER, Madrid, Spain
| | - Magdalena Ugarte
- Centro de Diagnóstico de Enfermedades Moleculares, Universidad Autónoma de Madrid, IdiPAZ, CIBERER, Madrid, Spain
| | - Belén Pérez González
- Centro de Diagnóstico de Enfermedades Moleculares, Universidad Autónoma de Madrid, IdiPAZ, CIBERER, Madrid, Spain
| | - Consuelo Pedrón-Giner
- Sección de Gastroenterología y Nutrición, Hospital Infantil Universitario Niño Jesús, Madrid, Spain
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Wiedemann A, Oussalah A, Lamireau N, Théron M, Julien M, Mergnac JP, Augay B, Deniaud P, Alix T, Frayssinoux M, Feillet F, Guéant JL. Clinical, phenotypic and genetic landscape of case reports with genetically proven inherited disorders of vitamin B 12 metabolism: A meta-analysis. Cell Rep Med 2022; 3:100670. [PMID: 35764087 PMCID: PMC9381384 DOI: 10.1016/j.xcrm.2022.100670] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 11/22/2021] [Accepted: 06/02/2022] [Indexed: 10/31/2022]
Abstract
Inherited disorders of B12 metabolism produce a broad spectrum of manifestations, with limited knowledge of the influence of age and the function of related genes. We report a meta-analysis on 824 patients with a genetically proven diagnosis of an inherited disorder of vitamin B12 metabolism. Gene clusters and age categories are associated with patients' manifestations. The "cytoplasmic transport" cluster is associated with neurological and ophthalmological manifestations, the "mitochondrion" cluster with hypotonia, acute metabolic decompensation, and death, and the "B12 availability" and "remethylation" clusters with anemia and cytopenia. Hypotonia, EEG abnormalities, nystagmus, and strabismus are predominant in the younger patients, while neurological manifestations, such as walking difficulties, peripheral neuropathy, pyramidal syndrome, cerebral atrophy, psychiatric disorders, and thromboembolic manifestations, are predominant in the older patients. These results should prompt systematic checking of markers of vitamin B12 status, including homocysteine and methylmalonic acid, when usual causes of these manifestations are discarded in adult patients.
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Affiliation(s)
- Arnaud Wiedemann
- Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, INSERM UMR_S 1256, 54000 Nancy, France; Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France; Reference Center for Inborn Errors of Metabolism (ORPHA67872), University Hospital of Nancy, 54000 Nancy, France
| | - Abderrahim Oussalah
- Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, INSERM UMR_S 1256, 54000 Nancy, France; Reference Center for Inborn Errors of Metabolism (ORPHA67872), University Hospital of Nancy, 54000 Nancy, France; Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France
| | - Nathalie Lamireau
- Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France
| | - Maurane Théron
- Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France
| | - Melissa Julien
- Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France
| | | | - Baptiste Augay
- Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France
| | - Pauline Deniaud
- Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France
| | - Tom Alix
- Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France
| | - Marine Frayssinoux
- Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France
| | - François Feillet
- Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, INSERM UMR_S 1256, 54000 Nancy, France; Department of Pediatrics, University Hospital of Nancy, 54000 Nancy, France; Reference Center for Inborn Errors of Metabolism (ORPHA67872), University Hospital of Nancy, 54000 Nancy, France
| | - Jean-Louis Guéant
- Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, University of Lorraine, INSERM UMR_S 1256, 54000 Nancy, France; Reference Center for Inborn Errors of Metabolism (ORPHA67872), University Hospital of Nancy, 54000 Nancy, France; Department of Molecular Medicine, Division of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, 54000 Nancy, France.
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7
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Lyon E, Temple-Smolkin RL, Hegde M, Gastier-Foster JM, Palomaki GE, Richards CS. An Educational Assessment of Evidence Used for Variant Classification: A Report of the Association for Molecular Pathology. J Mol Diagn 2022; 24:555-565. [PMID: 35429647 DOI: 10.1016/j.jmoldx.2021.12.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/12/2021] [Accepted: 12/10/2021] [Indexed: 11/25/2022] Open
Abstract
The Association for Molecular Pathology Variant Interpretation Testing Among Laboratories (VITAL) Working Group convened to evaluate the Standards and Guidelines for the Interpretation of Sequence Variants implementation into clinical practice, identify problematic classification rules, and define implementation challenges. Variants and associated clinical information were provided to volunteer respondents. Participant variant classifications were compared with intended consensus-derived classifications of the Working Group. The 24 variant challenges received 1379 responses; 1119 agreed with the intended response (81%; 95% CI, 79% to 83%). Agreement ranged from 44% to 100%, with 16 challenges (67%; 47% to 82%) reaching consensus (≥80% agreement). Participant classifications were also compared to a calculated interpretation of the ACMG Guidelines using the participant-reported criteria as input. The 24 variant challenges had 1368 responses with specific evidence provided and 1121 (82%; 80% to 84%) agreed with the calculated interpretation. Agreement for challenges ranged from 63% to 98%; 15 (63%; 43% to 79%) reaching consensus. Among 81 individual participants, 32 (40%; 30% to 50%) reached agreement with at least 80% of the intended classifications and 42 (52%; 41% to 62%) with the calculated classifications. This study demonstrated that although variant classification remains challenging, published guidelines are being utilized and adapted to improve variant calling consensus. This study identified situations where clarifications are warranted and provides a model for competency assessment.
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Affiliation(s)
- Elaine Lyon
- The Variant Interpretation Testing Among Laboratories (VITAL) Working Group of the Clinical Practice Committee, Association for Molecular Pathology (AMP), Rockville, Maryland; HudsonAlpha Institute for Biotechnology, Huntsville, Alabama
| | | | - Madhuri Hegde
- The Variant Interpretation Testing Among Laboratories (VITAL) Working Group of the Clinical Practice Committee, Association for Molecular Pathology (AMP), Rockville, Maryland; Global Genetics Laboratory, PerkinElmer Genomics, Pittsburgh, Pennsylvania
| | - Julie M Gastier-Foster
- The Variant Interpretation Testing Among Laboratories (VITAL) Working Group of the Clinical Practice Committee, Association for Molecular Pathology (AMP), Rockville, Maryland; Departments of Pediatrics and Pathology/Immunology, Baylor College of Medicine, Houston, Texas; Pathology Department, Texas Children's Hospital, Houston, Texas; Department of Pathology, The Ohio State University College of Medicine, Columbus, Ohio
| | - Glenn E Palomaki
- The Variant Interpretation Testing Among Laboratories (VITAL) Working Group of the Clinical Practice Committee, Association for Molecular Pathology (AMP), Rockville, Maryland; Department of Pathology and Laboratory Medicine, Women & Infants Hospital and the Alpert Medical School at Brown University, Providence, Rhode Island
| | - C Sue Richards
- The Variant Interpretation Testing Among Laboratories (VITAL) Working Group of the Clinical Practice Committee, Association for Molecular Pathology (AMP), Rockville, Maryland; Department of Molecular and Medical Genetics and Knight Diagnostic Laboratories, Oregon Health & Science University, Portland, Oregon.
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8
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Watkins D, Rosenblatt DS. Inherited defects of cobalamin metabolism. VITAMINS AND HORMONES 2022; 119:355-376. [PMID: 35337626 DOI: 10.1016/bs.vh.2022.01.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Cobalamin (vitamin B12) is required for activity of the enzymes methylmalonyl-CoA mutase and methionine synthase in human cells. Inborn errors affecting cobalamin uptake or metabolism are characterized by accumulation of the substrates for these enzymes, methylmalonic acid and homocysteine, in blood and urine. Inborn errors affecting synthesis of the adenosylcobalamin coenzyme required by methylmalonyl-CoA mutase (cblA and cblB) result in isolated methylmalonic aciduria; inborn errors affecting synthesis of the methylcobalamin coenzyme required by methionine synthase (cblE and cblG) result in isolated homocystinuria. Combined methylmalonic aciduria and homocystinuria is seen in patients with impaired intestinal cobalamin absorption (intrinsic factor deficiency, Imerslund-Gräsbeck syndrome) and with defects affecting synthesis of both cobalamin coenzymes (cblC, cblD, cblF and cblJ). A series of disorders caused by pathogenic variant mutations affecting gene regulators (transcription factors) of the MMACHC gene have recently been described (HCFC1 [cblX disorder] and deficiencies of THAP11, and ZNF143 [the cblK disorder]).
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Affiliation(s)
- David Watkins
- Department of Human Genetics, McGill University, The Research Institute of the McGill University Health Centre, Montreal, QC, Canada.
| | - David S Rosenblatt
- Department of Human Genetics, McGill University, The Research Institute of the McGill University Health Centre, Montreal, QC, Canada
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9
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Abuyaman O, Hatmal MM, Hijjawi N, Deeb AA, Abuothman M, Taha M. Vitamin B12 binding to mutated human transcobalamin, in-silico study of TCN2 alanine scanning and ClinVar missense mutations/SNPs. J Biomol Struct Dyn 2022; 41:3222-3233. [PMID: 35261335 DOI: 10.1080/07391102.2022.2046638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Many missense mutations/SNPs of the TCN2 gene (which yield Transcobalamin (TC)) were reported in the literature but no study is available about their effect on binding to vitamin B12(B12) at the structural level experimentally nor computationally. Predict the effect of TC missense mutations/SNPs on binding affinity to B12 and characterize their contacts to B12 at the structural level. TC-B12 binding energy difference from the wildtype (ΔΔGmut) was calculated for 378 alanine scanning mutations and 76 ClinVar missense mutations, repeated on two distinct X-ray structures of holoTC namely 2BB5 and 4ZRP. Destabilizing mutations then went through 100 ns molecular dynamics simulation to study their effect on TC-B12 binding at the structural level employing 2BB5 structure. Out of the studied 454 mutations (378 alanine mutations + 76 ClinVar mutations), 19 were destabilizing representing 17 amino acid locations. Mutation energy results show a neutral effect on B12 binding of several missense SNPs reported in the literature including I23V, G94S, R215W, P259R, S348F, L376S, and R399Q. Compared to the wildtype, all the destabilizing mutations have higher average RMSD-Ligand in the last 25% of the MD simulation trajectories and lower average hydrogen bond count while the other parameters vary. Previously reported TCN2 SNPs with an unknown effect on TC-B12 binding were found to have a neutral effect in the current study based on mutation energy calculations. Also, we reported 17 possible amino acids that destabilize TC-B12 binding upon mutation (four listed in ClinVar) and studied their structural effect computationally. Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Omar Abuyaman
- Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, The Hashemite University, Zarqa, Jordan
| | - Ma'mon M Hatmal
- Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, The Hashemite University, Zarqa, Jordan
| | - Nawal Hijjawi
- Department of Medical Laboratory Sciences, Faculty of Applied Medical Sciences, The Hashemite University, Zarqa, Jordan
| | - Ahmad A Deeb
- Faculty of Pharmacy, Department of Pharmacy, Al-Zaytoonah University of Jordan, Amman, Jordan
| | | | - Mutasem Taha
- Faculty of Pharmacy, Department of Pharmaceutical Sciences, University of Jordan, Amman, Jordan
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10
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Bloch JS, Sequeira JM, Ramírez AS, Quadros EV, Locher KP. Generation of nanobodies targeting the human, transcobalamin-mediated vitamin B 12 uptake route. FASEB J 2022; 36:e22222. [PMID: 35218573 DOI: 10.1096/fj.202101376rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 02/04/2022] [Accepted: 02/10/2022] [Indexed: 11/11/2022]
Abstract
Cellular uptake of vitamin B12 in humans is mediated by the endocytosis of the B12 carrier protein transcobalamin (TC) via its cognate cell surface receptor TCblR, encoded by the CD320 gene. Because CD320 expression is associated with the cell cycle and upregulated in highly proliferating cells including cancer cells, this uptake route is a potential target for cancer therapy. We developed and characterized four camelid nanobodies that bind holo-TC (TC in complex with B12 ) or the interface of the human holo-TC:TCblR complex with nanomolar affinities. We determined X-ray crystal structures of these nanobodies bound to holo-TC:TCblR, which enabled us to map their binding epitopes. When conjugated to the model toxin saporin, three of our nanobodies caused growth inhibition of HEK293T cells and therefore have the potential to inhibit the growth of human cancer cells. We visualized the cellular binding and endocytic uptake of the most potent nanobody (TC-Nb4) using fluorescent light microscopy. The co-crystal structure of holo-TC:TCblR with another nanobody (TC-Nb34) revealed novel features of the interface of TC and the LDLR-A1 domain of TCblR, rationalizing the decrease in the affinity of TC-B12 binding caused by the Δ88 mutation in CD320.
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Affiliation(s)
- Joël S Bloch
- Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich, Switzerland
| | - Jeffrey M Sequeira
- Department of Medicine, SUNY-Downstate Medical Center, Brooklyn, New York, USA
| | - Ana S Ramírez
- Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich, Switzerland
| | - Edward V Quadros
- Department of Medicine, SUNY-Downstate Medical Center, Brooklyn, New York, USA
| | - Kaspar P Locher
- Institute of Molecular Biology and Biophysics, ETH Zürich, Zürich, Switzerland
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11
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Pangilinan F, Watkins D, Bernard D, Chen Y, Dong N, Wu Q, Ozel-Abaan H, Kaur M, Caggana M, Morrissey M, Browne ML, Mills JL, Van Ryzin C, Shchelochkov O, Sloan J, Venditti CP, Sarafoglou K, Rosenblatt DS, Kay DM, Brody LC. Probing the functional consequence and clinical relevance of CD320 p.E88del, a variant in the transcobalamin receptor gene. Am J Med Genet A 2022; 188:1124-1141. [PMID: 35107211 DOI: 10.1002/ajmg.a.62627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 11/12/2021] [Accepted: 11/20/2021] [Indexed: 11/06/2022]
Abstract
The biological and clinical significance of the p.E88del variant in the transcobalamin receptor, CD320, is unknown. This allele is annotated in ClinVar as likely benign, pathogenic, and of uncertain significance. To determine functional consequence and clinical relevance of this allele, we employed cell culture and genetic association studies. Fibroblasts from 16 CD320 p.E88del homozygotes exhibited reduced binding and uptake of cobalamin. Complete ascertainment of newborns with transiently elevated C3 (propionylcarnitine) in New York State demonstrated that homozygosity for CD320 p.E88del was over-represented (7/348, p < 6 × 10-5 ). Using population data, we estimate that ~85% of the p.E88del homozygotes born in the same period did not have elevated C3, suggesting that cobalamin metabolism in the majority of these infants with this genotype is unaffected. Clinical follow-up of 4/9 homozygous individuals uncovered neuropsychological findings, mostly in speech and language development. None of these nine individuals exhibited perturbation of cobalamin metabolism beyond the newborn stage even during periods of acute illness. Newborns homozygous for this allele in the absence of other factors are at low risk of requiring clinical intervention, although more studies are required to clarify the natural history of various CD320 variants across patient populations.
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Affiliation(s)
- Faith Pangilinan
- Genetics and Environment Interaction Section, National Human Genome Research Institute, National Institutes of Health, Maryland, USA
| | - David Watkins
- Department of Human Genetics, McGill University and Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada
| | - David Bernard
- Genetics and Environment Interaction Section, National Human Genome Research Institute, National Institutes of Health, Maryland, USA
| | - Yue Chen
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Soochow University, Suzhou, China
| | - Ningzheng Dong
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Soochow University, Suzhou, China.,MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou, China
| | - Qingyu Wu
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Soochow University, Suzhou, China
| | - Hatice Ozel-Abaan
- Genetics and Environment Interaction Section, National Human Genome Research Institute, National Institutes of Health, Maryland, USA
| | - Manjit Kaur
- Genetics and Environment Interaction Section, National Human Genome Research Institute, National Institutes of Health, Maryland, USA
| | - Michele Caggana
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Mark Morrissey
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Marilyn L Browne
- Birth Defects Registry, New York State Department of Health, Albany, New York and University at Albany School of Public Health, Rensselaer, New York, USA
| | - James L Mills
- Epidemiology Branch, Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA
| | - Carol Van Ryzin
- Organic Acid Research Section, National Human Genome Research Institute, National Institutes of Health, Maryland, USA
| | - Oleg Shchelochkov
- Organic Acid Research Section, National Human Genome Research Institute, National Institutes of Health, Maryland, USA
| | - Jennifer Sloan
- Organic Acid Research Section, National Human Genome Research Institute, National Institutes of Health, Maryland, USA
| | - Charles P Venditti
- Organic Acid Research Section, National Human Genome Research Institute, National Institutes of Health, Maryland, USA
| | - Kyriakie Sarafoglou
- Department of Pediatrics, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - David S Rosenblatt
- Department of Human Genetics, McGill University and Research Institute of the McGill University Health Centre, Montreal, Quebec, Canada.,Division of Medical Biochemistry, Department of Specialized Medicine, McGill University Health Centre, Montreal, Quebec, Canada.,Division of Medical Genetics, Department of Specialized Medicine, McGill University Health Centre, Montreal, Quebec, Canada
| | - Denise M Kay
- Division of Genetics, Wadsworth Center, New York State Department of Health, Albany, New York, USA
| | - Lawrence C Brody
- Genetics and Environment Interaction Section, National Human Genome Research Institute, National Institutes of Health, Maryland, USA
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12
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Chen Y, Gu X, Zhang Y, Zhang X, Zhang C, Liu M, Sun S, Dong N, Wu Q. CD320 expression and apical membrane targeting in renal and intestinal epithelial cells. Int J Biol Macromol 2022; 201:85-92. [PMID: 34998874 DOI: 10.1016/j.ijbiomac.2021.12.158] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 12/21/2021] [Accepted: 12/24/2021] [Indexed: 02/06/2023]
Abstract
Vitamin B12 is an essential nutrient acquired via dietary intake. Receptor-mediated endocytosis is a key mechanism in vitamin B12 absorption, cellular uptake, and reabsorption. CD320 is a type I transmembrane protein responsible for cellular uptake of vitamin B12 in peripheral tissues. In this study, we examined segmental distribution and cellular expression of CD320 in mouse kidneys and intestines. We show that CD320 is expressed on the luminal surface in the small intestine and in proximal tubules in the kidney, suggesting that, in addition to its role in vitamin B12 uptake in peripheral tissues, CD320 may participate in vitamin B12 absorption in the small intestine and reabsorption in the kidney. Moreover, we show that an amino acid motif, DSSDE, in the second low-density lipoprotein receptor class A domain of CD320 is a key apical membrane targeting signal in both renal and intestinal epithelial cells. Mutations or deletion of this motif abolish the specific apical membrane expression of CD320 in polarized Madin-Darby canine kidney cells and human colon cancer-derived Caco-2 cells. In short-hairpin RNA-based gene knockdown experiments, we show that the apical membrane targeting of CD320 is mediated by a Rab11a-dependent mechanism. These results extend our knowledge regarding the cell biology of CD320 and its role in vitamin B12 metabolism.
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Affiliation(s)
- Yue Chen
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China
| | - Xiabing Gu
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Yikai Zhang
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Xianrui Zhang
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Ce Zhang
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China
| | - Meng Liu
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China
| | - Shijin Sun
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Ningzheng Dong
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China; MOH Key Laboratory of Thrombosis and Hemostasis, Jiangsu Institute of Hematology, the First Affiliated Hospital of Soochow University, Suzhou 215006, China
| | - Qingyu Wu
- Cyrus Tang Hematology Center, Collaborative Innovation Center of Hematology, State Key Laboratory of Radiation Medicine and Prevention, Medical School, Soochow University, Suzhou 215123, China.
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13
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Pappas KB, Younan M, Conway R. Transcobalamin receptor deficiency in seven asymptomatic patients ascertained through newborn screening. Am J Med Genet A 2022; 188:1102-1108. [PMID: 34978764 DOI: 10.1002/ajmg.a.62623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 11/03/2021] [Accepted: 12/13/2021] [Indexed: 11/08/2022]
Abstract
We report seven cases from our clinic with transcobalamin receptor deficiency (TCRD). None of our cases have experienced health issues or metabolic decompensation. All have experienced typical growth and development throughout childhood, with our oldest case now 10 years old. Every case has had normalization of initial biochemical abnormalities following parenteral hydroxocobalamin administration. Several cases had trace elevations of methylmalonic acid throughout childhood, all which normalized without further hydroxocobalamin administration. Population data from our state's newborn screening program suggest the incidence of TCRD is comparable to other metabolic disorders associated with elevations of C3 acylcarnitine including propionic academia, isolated methylmalonic academia and combined methylmalonic academia and hyperhomocysteinemia due to cobalamin metabolism disorders. Based on the generally benign nature of this condition, we assert that TCRD may be considered an incidental finding on newborn screen. However, additional long-term data are needed to ascertain the long term outcomes of children identified with TCRD.
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Affiliation(s)
- Kara B Pappas
- Department of Genetics, Genomics, and Metabolic Disorders, Children's Hospital of Michigan, Detroit, Michigan, USA.,Department of Pediatrics, Central Michigan University School of Medicine, Mt Pleasant, Michigan, USA
| | - Marissa Younan
- Department of Genetics, Genomics, and Metabolic Disorders, Children's Hospital of Michigan, Detroit, Michigan, USA
| | - Robert Conway
- Department of Genetics, Genomics, and Metabolic Disorders, Children's Hospital of Michigan, Detroit, Michigan, USA
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14
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Koslová A, Trefil P, Mucksová J, Krchlíková V, Plachý J, Krijt J, Reinišová M, Kučerová D, Geryk J, Kalina J, Šenigl F, Elleder D, Kožich V, Hejnar J. Knock-Out of Retrovirus Receptor Gene Tva in the Chicken Confers Resistance to Avian Leukosis Virus Subgroups A and K and Affects Cobalamin (Vitamin B 12)-Dependent Level of Methylmalonic Acid. Viruses 2021; 13:v13122504. [PMID: 34960774 PMCID: PMC8708277 DOI: 10.3390/v13122504] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 12/06/2021] [Accepted: 12/08/2021] [Indexed: 01/18/2023] Open
Abstract
The chicken Tva cell surface protein, a member of the low-density lipoprotein receptor family, has been identified as an entry receptor for avian leukosis virus of classic subgroup A and newly emerging subgroup K. Because both viruses represent an important concern for the poultry industry, we introduced a frame-shifting deletion into the chicken tva locus with the aim of knocking-out Tva expression and creating a virus-resistant chicken line. The tva knock-out was prepared by CRISPR/Cas9 gene editing in chicken primordial germ cells and orthotopic transplantation of edited cells into the testes of sterilized recipient roosters. The resulting tva −/− chickens tested fully resistant to avian leukosis virus subgroups A and K, both in in vitro and in vivo assays, in contrast to their susceptible tva +/+ and tva +/− siblings. We also found a specific disorder of the cobalamin/vitamin B12 metabolism in the tva knock-out chickens, which is in accordance with the recently recognized physiological function of Tva as a receptor for cobalamin in complex with transcobalamin transporter. Last but not least, we bring a new example of the de novo resistance created by CRISPR/Cas9 editing of pathogen dependence genes in farm animals and, furthermore, a new example of gene editing in chicken.
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Affiliation(s)
- Anna Koslová
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (A.K.); (V.K.); (J.P.); (M.R.); (D.K.); (J.G.); (F.Š.); (D.E.)
| | - Pavel Trefil
- BIOPHARM, Research Institute of Biopharmacy and Veterinary Drugs, Pohoří-Chotouň 90, 254 49 Jílové u Prahy, Czech Republic; (P.T.); (J.M.); (J.K.)
| | - Jitka Mucksová
- BIOPHARM, Research Institute of Biopharmacy and Veterinary Drugs, Pohoří-Chotouň 90, 254 49 Jílové u Prahy, Czech Republic; (P.T.); (J.M.); (J.K.)
| | - Veronika Krchlíková
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (A.K.); (V.K.); (J.P.); (M.R.); (D.K.); (J.G.); (F.Š.); (D.E.)
| | - Jiří Plachý
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (A.K.); (V.K.); (J.P.); (M.R.); (D.K.); (J.G.); (F.Š.); (D.E.)
| | - Jakub Krijt
- Department of Pediatrics and Inherited Metabolic Disorders, Charles University, First Faculty of Medicine and General University Hospital in Prague, 128 08 Prague, Czech Republic; (J.K.); (V.K.)
| | - Markéta Reinišová
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (A.K.); (V.K.); (J.P.); (M.R.); (D.K.); (J.G.); (F.Š.); (D.E.)
| | - Dana Kučerová
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (A.K.); (V.K.); (J.P.); (M.R.); (D.K.); (J.G.); (F.Š.); (D.E.)
| | - Josef Geryk
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (A.K.); (V.K.); (J.P.); (M.R.); (D.K.); (J.G.); (F.Š.); (D.E.)
| | - Jiří Kalina
- BIOPHARM, Research Institute of Biopharmacy and Veterinary Drugs, Pohoří-Chotouň 90, 254 49 Jílové u Prahy, Czech Republic; (P.T.); (J.M.); (J.K.)
| | - Filip Šenigl
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (A.K.); (V.K.); (J.P.); (M.R.); (D.K.); (J.G.); (F.Š.); (D.E.)
| | - Daniel Elleder
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (A.K.); (V.K.); (J.P.); (M.R.); (D.K.); (J.G.); (F.Š.); (D.E.)
| | - Viktor Kožich
- Department of Pediatrics and Inherited Metabolic Disorders, Charles University, First Faculty of Medicine and General University Hospital in Prague, 128 08 Prague, Czech Republic; (J.K.); (V.K.)
| | - Jiří Hejnar
- Institute of Molecular Genetics, Czech Academy of Sciences, Videnska 1083, 142 20 Prague, Czech Republic; (A.K.); (V.K.); (J.P.); (M.R.); (D.K.); (J.G.); (F.Š.); (D.E.)
- Correspondence:
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15
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Selhub J, Miller JW, Troen AM, Mason JB, Jacques PF. Perspective: The High-Folate-Low-Vitamin B-12 Interaction Is a Novel Cause of Vitamin B-12 Depletion with a Specific Etiology-A Hypothesis. Adv Nutr 2021; 13:16-33. [PMID: 34634124 PMCID: PMC8803489 DOI: 10.1093/advances/nmab106] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 08/26/2021] [Accepted: 09/02/2021] [Indexed: 11/12/2022] Open
Abstract
Vitamin B-12 is a water-soluble vitamin that plays important roles in intermediary metabolism. Vitamin B-12 deficiency has many identifiable causes, including autoimmune and other gastrointestinal malabsorption disorders, dietary deficiency, and congenital defects in genes that are involved in vitamin B-12 trafficking and functions. Another putative cause of vitamin B-12 deficiency is the high-folate-low vitamin B-12 interaction, first suspected as the cause for observed relapse and exacerbation of the neurological symptoms in patients with pernicious anemia who were prescribed high oral doses of folic acid. We propose that this interaction is real and represents a novel cause of vitamin B-12 depletion with specific etiology. We hypothesize that excessive intake of folic acid depletes serum holotranscobalamin (holoTC), thereby decreasing active vitamin B-12 in the circulation and limiting its availability for tissues. This effect is specific for holoTC and does not affect holohaptocorrin, the inert form of serum vitamin B-12. Depletion of holoTC by folic acid in individuals with already low vitamin B-12 status further compromises the availability of vitamin B-12 coenzymes to their respective enzymes, and consequently a more pronounced state of biochemical deficiency. This hypothesis is drawn from evidence of observational and intervention studies of vitamin B-12-deficient patients and epidemiological cohorts. The evidence also suggests that, in a depleted state, vitamin B-12 is diverted to the hematopoietic system or the kidney. This most likely reflects a selective response of tissues expressing folate receptors with high affinity for unmetabolized folic acid (UMFA; e.g., hematopoietic progenitors and renal tubules) compared with those tissues (e.g., liver) that only express the reduced folate carrier, which is universally expressed but has poor affinity for UMFA. The biochemical and physiological mechanisms underlying this interaction require elucidation to clarify its potential public health significance.
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Affiliation(s)
| | | | - Aron M Troen
- School of Nutritional Sciences and Institute of Biochemistry Food Science and Nutrition, The Robert H Smith Faculty of Agriculture Food and Environment, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Joel B Mason
- Tufts–USDA Human Nutrition Research Center on Aging, Boston, MA, USA
| | - Paul F Jacques
- Tufts–USDA Human Nutrition Research Center on Aging, Boston, MA, USA
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16
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Behringer S, Wingert V, Oria V, Schumann A, Grünert S, Cieslar-Pobuda A, Kölker S, Lederer AK, Jacobsen DW, Staerk J, Schilling O, Spiekerkoetter U, Hannibal L. Targeted Metabolic Profiling of Methionine Cycle Metabolites and Redox Thiol Pools in Mammalian Plasma, Cells and Urine. Metabolites 2019; 9:metabo9100235. [PMID: 31635306 PMCID: PMC6836102 DOI: 10.3390/metabo9100235] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 10/13/2019] [Accepted: 10/15/2019] [Indexed: 12/12/2022] Open
Abstract
The concentration of thiol and thioether metabolites in plasma has diagnostic value in genetic diseases of B-vitamin metabolism linked to methionine utilization. Among these, cysteine/cystine (Cys/CSSC) and glutathione/oxidized glutathione (GSH/GSSG) act as cellular redox buffers. A new LC-MS/MS method was developed for the simultaneous detection of cystathionine (Cysta), methionine (Met), methionine sulfoxide (MSO), creatinine and the reduced and oxidized pairs of homocysteine (Hcy/HSSH), cysteine (Cys/CSSC) and glutathione (GSH/GSSG). A one-step thiol-blocking protocol with minimal sample preparation was established to determine redox thiol pairs in plasma and cells. The concentrations of diagnostic biomarkers Hcy, Met, Cysta, and Cys in a cohort of healthy adults (n = 53) agreed with reference ranges and published values. Metabolite concentrations were also validated in commercial samples of human, mouse, rat and Beagle dog plasma and by the use of a standardized ERNDIM quality control. Analysis of fibroblasts, endothelial and epithelial cells, human embryonic stem cells, and cancer cell lines showed cell specificity for both the speciation and concentration of thiol and thioether metabolites. This LC-MS/MS platform permits the fast and simultaneous quantification of 10 thiol and thioether metabolites and creatinine using 40 µL plasma, urine or culture medium, or 500,000 cells. The sample preparation protocols are directly transferable to automated metabolomic platforms.
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Affiliation(s)
- Sidney Behringer
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
| | - Victoria Wingert
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
| | - Victor Oria
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
- Spemann Graduate School of Biology and Medicine, Faculty of Biology, University of Freiburg, 79104 Freiburg, Germany.
| | - Anke Schumann
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
| | - Sarah Grünert
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
| | - Artur Cieslar-Pobuda
- Nordic European Molecular Laboratory (EMBL) Partnership, Centre for Molecular Medicine Norway, University of Oslo, 0318 Oslo, Norway.
| | - Stefan Kölker
- Center for Pediatrics and Adolescent Medicine, Division of Pediatric Neurology and Metabolic Medicine, University Hospital Heidelberg, 69120 Heidelberg, Germany.
| | - Ann-Kathrin Lederer
- Center for Complementary Medicine, Institute for Infection Prevention and Hospital Epidemiology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
| | - Donald W Jacobsen
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44106, USA.
| | - Judith Staerk
- Nordic European Molecular Laboratory (EMBL) Partnership, Centre for Molecular Medicine Norway, University of Oslo, 0318 Oslo, Norway.
- Norwegian Center for Stem Cell Research, Department of Immunology, Oslo University Hospital, 0372 Oslo, Norway.
| | - Oliver Schilling
- Institute of Surgical Pathology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
| | - Ute Spiekerkoetter
- Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
| | - Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department of General Pediatrics, Adolescent Medicine and Neonatology, Faculty of Medicine, Medical Center, University of Freiburg, 79106 Freiburg, Germany.
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17
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Huemer M, Baumgartner MR. The clinical presentation of cobalamin-related disorders: From acquired deficiencies to inborn errors of absorption and intracellular pathways. J Inherit Metab Dis 2019; 42:686-705. [PMID: 30761552 DOI: 10.1002/jimd.12012] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2018] [Revised: 09/25/2018] [Accepted: 09/27/2018] [Indexed: 12/11/2022]
Abstract
This review gives an overview of clinical characteristics, treatment and outcome of nutritional and acquired cobalamin (Cbl; synonym: vitamin B12) deficiencies, inborn errors of Cbl absorption and intracellular trafficking, as well as methylenetetrahydrofolate dehydrogenase (MTHFD1) and methylene tetrahydrofolate reductase (MTHFR) deficiencies, which impair Cbl-dependent remethylation. Acquired and inborn Cbl-related disorders and MTHFR deficiency cause multisystem, often severe disease. Failure to thrive, neurocognitive or psychiatric symptoms, eye disease, bone marrow alterations, microangiopathy and thromboembolic events are characteristic. The recently identified MTHFD1 defect additionally presents with severe immune deficiency. Deficient Cbl-dependent enzymes cause reduced methylation capacity and metabolite toxicity. Further net-effects of perturbed Cbl function or reduced Cbl supply causing oxidative stress, altered cytokine regulation or immune functions are discussed.
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Affiliation(s)
- Martina Huemer
- Division of Metabolism and Children's Research Center, University Children's Hospital Zürich, Zürich, Switzerland
- Department of Paediatrics, Landeskrankenhaus Bregenz, Bregenz, Austria
| | - Matthias R Baumgartner
- Division of Metabolism and Children's Research Center, University Children's Hospital Zürich, Zürich, Switzerland
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18
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Arora K, Sequeira JM, Alarcon JM, Wasek B, Arning E, Bottiglieri T, Quadros EV. Neuropathology of vitamin B 12 deficiency in the Cd320 -/- mouse. FASEB J 2019; 33:2563-2573. [PMID: 30303736 PMCID: PMC6338625 DOI: 10.1096/fj.201800754rr] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 09/10/2018] [Indexed: 12/24/2022]
Abstract
In humans, vitamin B12 deficiency causes peripheral and CNS manifestations. Loss of myelin in the peripheral nerves and the spinal cord (SC) contributes to peripheral neuropathy and motor deficits. The metabolic basis for the demyelination and brain disorder is unknown. The transcobalamin receptor-knockout mouse ( Cd320-/-) develops cobalamin (Cbl) deficiency in the nervous system, with mild anemia. A decreased S-adenosylmethionine: S-adenosylhomocysteine ratio and increased methionine were seen in the brain with no significant changes in neurotransmitter metabolites. The structural pathology in the SC presented as loss of myelin in the axonal tracts with inflammation. The sciatic nerve (SN) showed increased nonuniform, internodal segments suggesting demyelination, and remyelination in progress. Consistent with these changes, the Cd320-/- mouse showed an increased latency to thermal nociception. Further, lower amplitude of compound action potential in the SN suggested that the functional capacity of the heavily myelinated axons were preferentially compromised, leading to loss of peripheral sensation. Although the metabolic basis for the demyelination and the structural and functional alterations of the nervous system in Cbl deficiency remain unresolved, the Cd320-/- mouse provides a unique model to investigate the pathologic consequences of vitamin B12 deficiency. -Arora, K., Sequeira, J. M., Alarcon, J. M., Wasek, B., Arning, E., Bottiglieri, T., Quadros, E. V. Neuropathology of vitamin B12 deficiency in the Cd320-/- mouse.
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Affiliation(s)
- Kaveri Arora
- The School of Graduate Studies, SUNY Downstate Medical Center, Brooklyn, New York, USA
| | - Jeffrey M. Sequeira
- Department of Medicine, and SUNY Downstate Medical Center, Brooklyn, New York, USA
| | - Juan M. Alarcon
- Department of Pathology, SUNY Downstate Medical Center, Brooklyn, New York, USA
| | - Brandi Wasek
- Institute of Metabolic Disease, Baylor Research Institute, Dallas, Texas, USA
| | - Erland Arning
- Institute of Metabolic Disease, Baylor Research Institute, Dallas, Texas, USA
| | - Teodoro Bottiglieri
- Institute of Metabolic Disease, Baylor Research Institute, Dallas, Texas, USA
| | - Edward V. Quadros
- Department of Medicine, and SUNY Downstate Medical Center, Brooklyn, New York, USA
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19
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Bernard DJ, Pangilinan FJ, Cheng J, Molloy AM, Brody LC. Mice lacking the transcobalamin-vitamin B12 receptor, CD320, suffer from anemia and reproductive deficits when fed vitamin B12-deficient diet. Hum Mol Genet 2018; 27:3627-3640. [PMID: 30124850 PMCID: PMC6168973 DOI: 10.1093/hmg/ddy267] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 06/29/2018] [Accepted: 07/12/2018] [Indexed: 11/12/2022] Open
Abstract
In humans, poor nutrition, malabsorption and variation in cobalamin (vitamin B12) metabolic genes are associated with hematological, neurological and developmental pathologies. Cobalamin is transported from blood into tissues via the transcobalamin (TC) receptor encoded by the CD320 gene. We created mice carrying a targeted deletion of the mouse ortholog, Cd320. Knockout (KO) mice lacking this TC receptor have elevated levels of plasma methylmalonic acid and homocysteine but are otherwise healthy, viable, fertile and not anemic. To challenge the Cd320 KO mice we maintained them on a vitamin B12-deficient diet. After 5 weeks on this diet, reproductive failure develops in Cd320 KO females but not males. In vitro, homozygous Cd320 KO embryos from cobalamin-deficient Cd320 KO dams develop normally to embryonic day (E) 3.5, while in vivo, few uterine decidual implantation sites are observed at E7.5, suggesting that embryos perish around the time of implantation. Dietary restriction of vitamin B12 induces a severe macrocytic anemia in Cd320 KO mice after 10-12 months while control mice on this diet are anemia-free up to 2 years. Despite the severe anemia, cobalamin-deficient KO mice do not exhibit obvious neurological symptoms. Our results with Cd320 KO mice suggest that an alternative mechanism exists for mice to transport cobalamin independent of the Cd320 encoded receptor. Our findings with deficient diet are consistent with historical and epidemiological data suggesting that low vitamin B12 levels in humans are associated with infertility and developmental abnormalities. Our Cd320 KO mouse model is an ideal model system for studying vitamin B12 deficiency.
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Affiliation(s)
- David J Bernard
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Faith J Pangilinan
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Jun Cheng
- Transgenic Mouse Core, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Anne M Molloy
- School of Medicine, Trinity College, Dublin, Ireland
| | - Lawrence C Brody
- Division of Intramural Research, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
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20
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Peng G, Shen P, Gandotra N, Le A, Fung E, Jelliffe-Pawlowski L, Davis RW, Enns GM, Zhao H, Cowan TM, Scharfe C. Combining newborn metabolic and DNA analysis for second-tier testing of methylmalonic acidemia. Genet Med 2018; 21:896-903. [PMID: 30209273 PMCID: PMC6416784 DOI: 10.1038/s41436-018-0272-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 08/03/2018] [Indexed: 11/27/2022] Open
Abstract
Purpose Improved second-tier tools are needed to reduce false-positive outcomes in newborn screening (NBS) for inborn metabolic disorders on the Recommended Universal Screening Panel (RUSP). Methods We designed an assay for multiplex sequencing of 72 metabolic genes (RUSPseq) from newborn dried blood spots. Analytical and clinical performance was evaluated in 60 screen-positive newborns for methylmalonic acidemia (MMA) reported by the California Department of Public Health NBS program. Additionally, we trained a Random Forest machine learning classifier on NBS data to improve prediction of true and false-positive MMA cases. Results Of 28 MMA patients sequenced, we found two pathogenic or likely pathogenic (P/LP) variants in a MMA-related gene in 24 patients, and one pathogenic variant and a variant of unknown significance (VUS) in 1 patient. No such variant combinations were detected in MMA false positives and healthy controls. Random Forest–based analysis of the entire NBS metabolic profile correctly identified the MMA patients and reduced MMA false-positive cases by 51%. MMA screen-positive newborns were more likely of Hispanic ethnicity. Conclusion Our two-pronged approach reduced false positives by half and provided a reportable molecular finding for 89% of MMA patients. Challenges remain in newborn metabolic screening and DNA variant interpretation in diverse multiethnic populations.
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Affiliation(s)
- Gang Peng
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA.,Department of Biostatistics, Yale University School of Public Health, New Haven, CT, USA
| | - Peidong Shen
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA, USA
| | - Neeru Gandotra
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA
| | - Anthony Le
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Eula Fung
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Laura Jelliffe-Pawlowski
- Department of Epidemiology and Biostatistics, University of California San Francisco School of Medicine, San Francisco, CA, USA
| | - Ronald W Davis
- Stanford Genome Technology Center, Stanford University, Palo Alto, CA, USA
| | - Gregory M Enns
- Department of Pediatrics, Stanford University School of Medicine, Stanford, CA, USA
| | - Hongyu Zhao
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA.,Department of Biostatistics, Yale University School of Public Health, New Haven, CT, USA
| | - Tina M Cowan
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA
| | - Curt Scharfe
- Department of Genetics, Yale University School of Medicine, New Haven, CT, USA.
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21
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Brasil S, Leal F, Vega A, Navarrete R, Ecay MJ, Desviat LR, Riera C, Padilla N, de la Cruz X, Couce ML, Martin-Hernández E, Morais A, Pedrón C, Peña-Quintana L, Rigoldi M, Specola N, de Almeida IT, Vives I, Yahyaoui R, Rodríguez-Pombo P, Ugarte M, Pérez-Cerda C, Merinero B, Pérez B. Improving the diagnosis of cobalamin and related defects by genomic analysis, plus functional and structural assessment of novel variants. Orphanet J Rare Dis 2018; 13:125. [PMID: 30041674 PMCID: PMC6057060 DOI: 10.1186/s13023-018-0862-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 06/29/2018] [Indexed: 12/04/2022] Open
Abstract
Background Cellular cobalamin defects are a locus and allelic heterogeneous disorder. The gold standard for coming to genetic diagnoses of cobalamin defects has for some time been gene-by-gene Sanger sequencing of individual DNA fragments. Enzymatic and cellular methods are employed before such sequencing to help in the selection of the gene defects to be sought, but this is time-consuming and laborious. Furthermore some cases remain undiagnosed because no biochemical methods have been available to test for cobalamin absorption and transport defects. Results This paper reports the use of massive parallel sequencing of DNA (exome analysis) for the accurate and rapid genetic diagnosis of cobalamin-related defects in a cohort of affected patients. The method was first validated in an initial cohort with different cobalamin defects. Mendelian segregation, the frequency of mutations, and the comprehensive structural and functional analysis of gene variants, identified disease-causing mutations in 12 genes involved in the absorption and synthesis of active cofactors of vitamin B12 (22 cases), and in the non-cobalamin metabolism-related genes ACSF3 (in four biochemically misdiagnosed patients) and SUCLA2 (in one patient with an unusual presentation). We have identified thirteen new variants all classified as pathogenic according to the ACGM recommendation but four were classified as variant likely pathogenic in MUT and SUCLA2. Functional and structural analysis provided evidences to classify them as pathogenic variants. Conclusions The present findings suggest that the technology used is sufficiently sensitive and specific, and the results it provides sufficiently reproducible, to recommend its use as a second-tier test after the biochemical detection of cobalamin disorder markers in the first days of life. However, for accurate diagnoses to be made, biochemical and functional tests that allow comprehensive clinical phenotyping are also needed. Electronic supplementary material The online version of this article (10.1186/s13023-018-0862-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sandra Brasil
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - Fátima Leal
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - Ana Vega
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - Rosa Navarrete
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - María Jesús Ecay
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - Lourdes R Desviat
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - Casandra Riera
- Grupo de Bioinformática Translacional Vall d'Hebron Institute of Research (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Natàlia Padilla
- Grupo de Bioinformática Translacional Vall d'Hebron Institute of Research (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Xavier de la Cruz
- Grupo de Bioinformática Translacional Vall d'Hebron Institute of Research (VHIR), Universitat Autònoma de Barcelona, Barcelona, Spain.,ICREA, Barcelona, Spain
| | - Mari Luz Couce
- Hospital Clínico Universitario de Santiago, Santiago de Compostela, CIBERER, Santiago de Compostela, Spain
| | | | - Ana Morais
- Hospital Universitario La Paz, Madrid, Spain
| | | | - Luis Peña-Quintana
- Hospital Universitario Materno Infantil, CIBEROBN, Universidad de Las Palmas de Gran Canaria, Las Palmas de Gran Canaria, Spain
| | - Miriam Rigoldi
- Center for Rare Disorders, ASST- Monza, Ospedale San Gerardo, Monza, Italy
| | - Norma Specola
- Unidad de Metabolismo Hospital de Niños de La Plata, La Plata, Argentina
| | | | | | - Raquel Yahyaoui
- Hospital Universitario Regional de Málaga, Instituto de Investigación Biomédica de Málaga (IBIMA), Málaga, Spain
| | - Pilar Rodríguez-Pombo
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - Magdalena Ugarte
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - Celia Pérez-Cerda
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - Begoña Merinero
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain
| | - Belén Pérez
- Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular, Universidad Autónoma de Madrid, CIBERER, IdiPAZ, Madrid, Spain.
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22
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Kinoshita Y, Nogami K, Jomura R, Akanuma SI, Abe H, Inouye M, Kubo Y, Hosoya KI. Investigation of Receptor-Mediated Cyanocobalamin (Vitamin B 12) Transport across the Inner Blood-Retinal Barrier Using Fluorescence-Labeled Cyanocobalamin. Mol Pharm 2018; 15:3583-3594. [PMID: 29966424 DOI: 10.1021/acs.molpharmaceut.8b00617] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The blood-to-retina supply of cyanocobalamin (vitamin B12) across the blood-retinal barrier (BRB) was investigated by synthesizing a fluorescence-labeled cyanocobalamin (Cy5-cyanocobalamin). In the in vivo analysis following internal jugular injection of Cy5-cyanocobalamin, confocal microscopy showed the distribution of Cy5-cyanocobalamin in the inner plexiform layer (IPL), the outer plexiform layer (OPL), and the retinal pigment epithelium (RPE). In the in vitro analysis with TR-iBRB2 cells, an in vitro model cell line of the inner BRB, Cy5-cyanocobalamin uptake by TR-iBRB2 cells exhibited a time-dependent increase after preincubation with transcobalamin II (TCII) protein, during its residual uptake without preincubation with TCII protein. The Cy5-cyanocobalamin uptake by TR-iBRB2 cells was significantly reduced in the presence of unlabeled cyanocobalamin, chlorpromazine, and chloroquine and was also significantly reduced under Ca2+-free conditions. Confocal microscopy of the TR-iBRB2 cells showed fluorescence signals of Cy5-cyanocobalamin and GFP-TCII protein, and these signals merged with each other. The RT-PCR, Western blot, and immunohistochemistry clearly suggested the expression of TCII receptor (TCII-R) in the inner and outer BRB. These results suggested the involvement of receptor-mediated endocytosis in the blood-to-retina transport of cyanocobalamin at the inner BRB with implying its possible involvement at the outer BRB.
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Affiliation(s)
- Yuri Kinoshita
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
| | | | - Ryuta Jomura
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
| | - Shin-Ichi Akanuma
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
| | | | | | - Yoshiyuki Kubo
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
| | - Ken-Ichi Hosoya
- Department of Pharmaceutics and ‡Department of Chemical Biology, Graduate School of Medicine and Pharmaceutical Sciences , University of Toyama , Toyama 930-0194 , Japan
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23
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Hannibal L, Bolisetty K, Axhemi A, DiBello PM, Quadros EV, Fedosov S, Jacobsen DW. Transcellular transport of cobalamin in aortic endothelial cells. FASEB J 2018; 32:5506-5519. [PMID: 29741927 DOI: 10.1096/fj.201701141rr] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Cobalamin [Cbl (or B12)] deficiency causes megaloblastic anemia and a variety of neuropathies. However, homeostatic mechanisms of cyanocobalamin (CNCbl) and other Cbls by vascular endothelial cells are poorly understood. Herein, we describe our investigation into whether cultured bovine aortic endothelial cells (BAECs) perform transcytosis of B12, namely, the complex formed between serum transcobalamin and B12, designated as holo-transcobalamin (holo-TC). We show that cultured BAECs endocytose [57Co]-CNCbl-TC (source material) via the CD320 receptor. The bound Cbl is transported across the cell both via exocytosis in its free form, [57Co]-CNCbl, and via transcytosis as [57Co]-CNCbl-TC. Transcellular mobilization of Cbl occurred in a bidirectional manner. A portion of the endocytosed [57Co]-CNCbl was enzymatically processed by methylmalonic aciduria combined with homocystinuria type C (cblC) with subsequent formation of hydroxocobalamin, methylcobalamin, and adenosylcobalamin, which were also transported across the cell in a bidirectional manner. This demonstrates that transport mechanisms for Cbl in vascular endothelial cells do not discriminate between various β-axial ligands of the vitamin. Competition studies with apoprotein- and holo-TC and holo-intrinsic factor showed that only holo-TC was effective at inhibiting transcellular transport of Cbl. Incubation of BAECs with a blocking antibody against the extracellular domain of the CD320 receptor inhibited uptake and transcytosis by ∼40%. This study reveals that endothelial cells recycle uncommitted intracellular Cbl for downstream usage by other cell types and suggests that the endothelium is self-sufficient for the specific acquisition and subsequent distribution of circulating B12 via the CD320 receptor. We posit that the endothelial lining of the vasculature is an essential component for the maintenance of serum-tissue homeostasis of B12.-Hannibal, L., Bolisetty, K., Axhemi, A., DiBello, P. M., Quadros, E. V., Fedosov, S., Jacobsen, D. W. Transcellular transport of cobalamin in aortic endothelial cells.
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Affiliation(s)
- Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg, Freiburg, Germany.,Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Keerthana Bolisetty
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Armend Axhemi
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Patricia M DiBello
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
| | - Edward V Quadros
- Department of Medicine, State University of New York (SUNY) Downstate Medical Center, Brooklyn, New York, USA; and
| | - Sergey Fedosov
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark
| | - Donald W Jacobsen
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, USA
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24
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Hannah-Shmouni F, Cruz V, Schulze A, Mercimek-Andrews S. Transcobalamin receptor defect: Identification of two new cases through positive newborn screening for propionic/methylmalonic aciduria and long-term outcome. Am J Med Genet A 2018; 176:1411-1415. [PMID: 29663633 DOI: 10.1002/ajmg.a.38696] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Revised: 03/06/2018] [Accepted: 03/09/2018] [Indexed: 11/08/2022]
Abstract
Likely pathogenic variants in CD320 cause transcobalamin receptor defect, a recently discovered inborn errors of cobalamin metabolism. Only 12 cases have been reported to date. There are no long-term clinical and biochemical outcome reports since its first description. In this report, we present two new cases and report their long-term treatment outcome. Two asymptomatic cases were identified through a positive newborn screening for propionic/methylmalonic aciduria. Biochemical abnormalities were normalized on a short course of oral cyanocobalamin (1 mg/day). Direct sequencing of CD320 identified a known pathogenic variant (c.262_264GAG; p.Glu88del) confirming the diagnosis of transcobalamin receptor defect. To date, both patients remain asymptomatic with normal neurodevelopment more than 6 years. Our two new cases with transcobalamin receptor defect due to pathogenic variants in CD320 further expand our knowledge and provide a reassuring long-term good neurodevelopmental outcome. Identification of additional cases requires the consideration of transcobalamin receptor defect in the differential diagnosis of newborns with confirmed positive newborn screening for methylmalonic acidurias.
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Affiliation(s)
- Fady Hannah-Shmouni
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Vivian Cruz
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Andreas Schulze
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada.,Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Saadet Mercimek-Andrews
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada.,Genetics and Genome Biology Research Program, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada
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25
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26
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Velkova A, Diaz JEL, Pangilinan F, Molloy AM, Mills JL, Shane B, Sanchez E, Cunningham C, McNulty H, Cropp CD, Bailey-Wilson JE, Wilson AF, Brody LC. The FUT2 secretor variant p.Trp154Ter influences serum vitamin B12 concentration via holo-haptocorrin, but not holo-transcobalamin, and is associated with haptocorrin glycosylation. Hum Mol Genet 2017; 26:4975-4988. [PMID: 29040465 PMCID: PMC5886113 DOI: 10.1093/hmg/ddx369] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 09/19/2017] [Accepted: 09/20/2017] [Indexed: 11/14/2022] Open
Abstract
Vitamin B12 deficiency is common in older individuals. Circulating vitamin B12 concentration can be used to diagnose deficiency, but this test has substantial false positive and false negative rates. We conducted genome-wide association studies (GWAS) in which we resolved total serum vitamin B12 into the fractions bound to transcobalamin and haptocorrin: two carrier proteins with very different biological properties. We replicated reported associations between total circulating vitamin B12 concentrations and a common null variant in FUT2. This allele determines the secretor phenotype in which blood group antigens are found in non-blood body fluids. Vitamin B12 bound to haptocorrin (holoHC) remained highly associated with FUT2 rs601338 (p.Trp154Ter). Transcobalamin bound vitamin B12 (holoTC) was not influenced by this variant. HoloTC is the bioactive the form of the vitamin and is taken up by all tissues. In contrast, holoHC is only taken up by the liver. Using holoHC from individuals with known FUT2 genotypes, we demonstrated that FUT2 rs601338 genotype influences the glycosylation of haptocorrin. We then developed an experimental model demonstrating that holoHC is transported into cultured hepatic cells (HepG2) via the asialoglycoprotein receptor (ASGR). Our data challenge current published hypotheses on the influence of genetic variation on this clinically important measure and are consistent with a model in which FUT2 rs601338 influences holoHC by altering haptocorrin glycosylation, whereas B12 bound to non-glycosylated transcobalamin (i.e. holoTC) is not affected. Our findings explain some of the observed disparity between use of total B12 or holoTC as first-line clinical tests of vitamin B12 status.
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Affiliation(s)
- Aneliya Velkova
- Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, Bethesda, MD 20892, USA
| | - Jennifer E L Diaz
- Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, Bethesda, MD 20892, USA
| | - Faith Pangilinan
- Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, Bethesda, MD 20892, USA
| | - Anne M Molloy
- Department of Clinical Medicine, School of Medicine, Trinity College Dublin, Dublin 2, Ireland
| | - James L Mills
- Division of Intramural Population Health Research, Eunice Kennedy Shriver NICHD, Bethesda, MD 20852, USA
| | - Barry Shane
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720, USA
| | - Erica Sanchez
- Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, Bethesda, MD 20892, USA
| | | | - Helene McNulty
- Northern Ireland Centre for Food and Health, University of Ulster, Coleraine BT52 1SA, Northern Ireland
| | - Cheryl D Cropp
- Computational and Statistical Genomics Branch, National Human Genome Research Institute, Bethesda, MD 21224, USA
| | - Joan E Bailey-Wilson
- Computational and Statistical Genomics Branch, National Human Genome Research Institute, Bethesda, MD 21224, USA
| | - Alexander F Wilson
- Computational and Statistical Genomics Branch, National Human Genome Research Institute, Bethesda, MD 21224, USA
| | - Lawrence C Brody
- Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, Bethesda, MD 20892, USA
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McDonald MK, Fritz JA, Jia D, Scheuchner D, Snyder FF, Stanislaus A, Curle J, Li L, Stabler SP, Allen RH, Mains PE, Gravel RA. Identification of ABC transporters acting in vitamin B 12 metabolism in Caenorhabditis elegans. Mol Genet Metab 2017; 122:160-171. [PMID: 29153845 DOI: 10.1016/j.ymgme.2017.11.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 11/10/2017] [Accepted: 11/10/2017] [Indexed: 01/19/2023]
Abstract
Vitamin B12 (cobalamin, Cbl) is a micronutrient essential to human health. Cbl is not utilized as is but must go through complex subcellular and metabolic processing to generate two cofactor forms: methyl-Cbl for methionine synthase, a cytosolic enzyme; and adenosyl-Cbl for methylmalonyl-CoA mutase, a mitochondrial enzyme. Some 10-12 human genes have been identified responsible for the intracellular conversion of Cbl to cofactor forms, including genes that code for ATP-binding cassette (ABC) transporters acting at the lysosomal and plasma membranes. However, the gene for mitochondrial uptake is not known. We hypothesized that ABC transporters should be candidates for other uptake and efflux functions, including mitochondrial transport, and set out to screen ABC transporter mutants for blocks in Cbl utilization using the nematode roundworm Caenorhabditis elegans. Thirty-seven mutant ABC transporters were screened for the excretion of methylmalonic acid (MMA), which should result from loss of Cbl transport into the mitochondria. One mutant, wht-6, showed elevated MMA excretion and reduced [14C]-propionate incorporation, pointing to a functional block in methylmalonyl-CoA mutase. In contrast, the wht-6 mutant appeared to have a normal cytosolic pathway based on analysis of cystathionine excretion, suggesting that cytosolic methionine synthase was functioning properly. Further, the MMA excretion in wht-6 could be partially reversed by including vitamin B12 in the assay medium. The human ortholog of wht-6 is a member of the G family of ABC transporters. We propose wht-6 as a candidate for the transport of Cbl into mitochondria and suggest that a member of the corresponding ABCG family of ABC transporters has this role in humans. Our ABC transporter screen also revealed that mrp-1 and mrp-2 mutants excreted lower MMA than wild type, suggesting they were concentrating intracellular Cbl, consistent with the cellular efflux defect proposed for the mammalian MRP1 ABC transporter.
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Affiliation(s)
- Megan K McDonald
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada
| | - Julie-Anne Fritz
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada
| | - Dongxin Jia
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada
| | - Deborah Scheuchner
- Department of Medical Genetics, University of Calgary, Calgary, T2N 4N1, Canada
| | - Floyd F Snyder
- Department of Medical Genetics, University of Calgary, Calgary, T2N 4N1, Canada
| | - Avalyn Stanislaus
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada
| | - Jared Curle
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada
| | - Liang Li
- Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada
| | - Sally P Stabler
- Division of Hematology, University of Colorado Denver, Aurora, CO, USA
| | - Robert H Allen
- Division of Hematology, University of Colorado Denver, Aurora, CO, USA
| | - Paul E Mains
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada
| | - Roy A Gravel
- Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, T2N 4N1, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, T2N 4N1, Canada.
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28
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Arora K, Sequeira JM, Quadros EV. Maternofetal transport of vitamin B 12: role of TCblR/ CD320 and megalin. FASEB J 2017; 31:3098-3106. [PMID: 28351841 DOI: 10.1096/fj.201700025r] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 03/13/2017] [Indexed: 11/11/2022]
Abstract
Vitamin B12 deficiency causes megaloblastic anemia and neurologic disorder in humans. Gene defects of transcobalamin (TC) and the transcobalamin receptor (TCblR), needed for cellular uptake of the TC-bound B12, do not confer embryonic lethality. TC deficiency can produce the hematologic and neurologic complications after birth, whereas TCblR/CD320 gene defects appear to produce mild metabolic changes. Alternate maternofetal transport mechanisms appear to provide adequate B12 to the fetus. To understand this mechanism, we evaluated the role of TC, TCblR/CD320, and megalin in maternofetal transport of B12 in a TCblR/CD320-knockout (KO) mouse. Our results showed high expression of TCblR/CD320 in the labyrinth of the placenta, embryonic brain, and spinal column in wild-type (WT) mice. Megalin expression was about the same in both WT and KO mouse visceral yolk sac, brain, and spinal column. Megalin mRNA was down-regulated in the KO embryonic spinal cord (SC) and kidneys. Megalin expression remained unaltered in adult WT and KO mouse brain, SC, and kidneys. Injected dsRed-TC-B12 and TC-57CoB12 accumulated in the visceral yolk sac of KO mice where megalin is expressed and provides an alternate mechanism for the maternofetal transport of Cbl during fetal development.-Arora, K., Sequeira, J. M., Quadros, E. V. Maternofetal transport of vitamin B12: role of TCblR/CD320 and megalin.
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Affiliation(s)
- Kaveri Arora
- Department of Cell Biology, School of Graduate Studies, State University of New York (SUNY) Downstate Medical Center, Brooklyn, New York, USA
| | - Jeffrey M Sequeira
- Department of Medicine, SUNY Downstate Medical Center, Brooklyn, New York, USA
| | - Edward V Quadros
- Department of Medicine, SUNY Downstate Medical Center, Brooklyn, New York, USA
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29
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Zhao H, Ruberu K, Li H, Garner B. Cell Type-Specific Modulation of Cobalamin Uptake by Bovine Serum. PLoS One 2016; 11:e0167044. [PMID: 27893837 PMCID: PMC5125665 DOI: 10.1371/journal.pone.0167044] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 11/07/2016] [Indexed: 12/04/2022] Open
Abstract
Tracking cellular 57Co-labelled cobalamin (57Co-Cbl) uptake is a well-established method for studying Cbl homeostasis. Previous studies established that bovine serum is not generally permissive for cellular Cbl uptake when used as a supplement in cell culture medium, whereas supplementation with human serum promotes cellular Cbl uptake. The underlying reasons for these differences are not fully defined. In the current study we address this question. We extend earlier observations by showing that fetal calf serum inhibits cellular 57Co-Cbl uptake by HT1080 cells (a fibrosarcoma-derived fibroblast cell line). Furthermore, we discovered that a simple heat-treatment protocol (95°C for 10 min) ameliorates this inhibitory activity for HT1080 cell 57Co-Cbl uptake. We provide evidence that the very high level of haptocorrin in bovine serum (as compared to human serum) is responsible for this inhibitory activity. We suggest that bovine haptocorrin competes with cell-derived transcobalamin for Cbl binding, and that cellular Cbl uptake may be minimised in the presence of large amounts of bovine haptocorrin that are present under routine in vitro cell culture conditions. In experiments conducted with AG01518 cells (a neonatal foreskin-derived fibroblast cell line), overall cellular 57Co-Cbl uptake was 86% lower than for HT1080 cells, cellular TC production was below levels detectable by western blotting, and heat treatment of fetal calf serum resulted in only a modest increase in cellular 57Co-Cbl uptake. We recommend a careful assessment of cell culture protocols should be conducted in order to determine the potential benefits that heat-treated bovine serum may provide for in vitro studies of mammalian cell lines.
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Affiliation(s)
- Hua Zhao
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
- School of Biological Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Kalani Ruberu
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
- School of Biological Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Hongyun Li
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
- School of Biological Sciences, University of Wollongong, Wollongong, NSW, Australia
| | - Brett Garner
- Illawarra Health and Medical Research Institute, University of Wollongong, Wollongong, NSW, Australia
- School of Biological Sciences, University of Wollongong, Wollongong, NSW, Australia
- * E-mail:
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30
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Homocysteine and disease: Causal associations or epiphenomenons? Mol Aspects Med 2016; 53:36-42. [PMID: 27876556 DOI: 10.1016/j.mam.2016.11.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 11/18/2016] [Indexed: 01/08/2023]
Abstract
Nutritional and genetic deficiencies of folate and vitamin B12 lead to elevation of cellular homocysteine (Hcy), which translates in increased plasma Hcy. The sources and role of elevated plasma Hcy in pathology continues to be a subject of intense scientific debate. Whether a cause, mediator or marker, little is known about the molecular mechanisms and interactions of Hcy with cellular processes that lead to disease. The use of folic acid reduces the incidence of neural tube defects, but the effect of Hcy-lowering interventions with folic acid in cardiovascular disease and cognitive impairment remains controversial. The fact that levels of Hcy in plasma do not always reflect cellular status of this amino acid may account for the substantial gaps that exist between epidemiological, intervention and basic research studies. Understanding whether plasma Hcy is a mechanistic player or an epiphenomenon in pathogenesis requires further investigation, and this research is essential to improve the assessment and potential treatment of hyperhomocysteinemias.
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31
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Structural basis of transcobalamin recognition by human CD320 receptor. Nat Commun 2016; 7:12100. [PMID: 27411955 PMCID: PMC4947154 DOI: 10.1038/ncomms12100] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 05/27/2016] [Indexed: 12/20/2022] Open
Abstract
Cellular uptake of vitamin B12 (cobalamin) requires capture of transcobalamin (TC) from the plasma by CD320, a ubiquitous cell surface receptor of the LDLR family. Here we present the crystal structure of human holo-TC in complex with the extracellular domain of CD320, visualizing the structural basis of the TC-CD320 interaction. The observed interaction chemistry can rationalize the high affinity of CD320 for TC and lack of haptocorrin binding. The in vitro affinity and complex stability of TC-CD320 were quantitated using a solid-phase binding assay and thermostability analysis. Stable complexes with TC were also observed for the disease-causing CD320ΔE88 mutant and for the isolated LDLR-A2 domain. We also determined the structure of the TC-CD320ΔE88 complex, which revealed only minor changes compared with the wild-type complex. Finally, we demonstrate significantly reduced in vitro affinity of TC for CD320 at low pH, recapitulating the proposed ligand release during the endocytic pathway. Cellular uptake of vitamin B12 (cobalamin) requires the binding of holo-transcobalamin (TC) from plasma by CD320. Here, the authors report the structure of a complex between CD320 and TC loaded with cyanocobalamin, alongside additional functional analysis.
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32
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Hannibal L, Lysne V, Bjørke-Monsen AL, Behringer S, Grünert SC, Spiekerkoetter U, Jacobsen DW, Blom HJ. Biomarkers and Algorithms for the Diagnosis of Vitamin B12 Deficiency. Front Mol Biosci 2016; 3:27. [PMID: 27446930 PMCID: PMC4921487 DOI: 10.3389/fmolb.2016.00027] [Citation(s) in RCA: 164] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 06/07/2016] [Indexed: 12/12/2022] Open
Abstract
Vitamin B12 (cobalamin, Cbl, B12) is an indispensable water-soluble micronutrient that serves as a coenzyme for cytosolic methionine synthase (MS) and mitochondrial methylmalonyl-CoA mutase (MCM). Deficiency of Cbl, whether nutritional or due to inborn errors of Cbl metabolism, inactivate MS and MCM leading to the accumulation of homocysteine (Hcy) and methylmalonic acid (MMA), respectively. In conjunction with total B12 and its bioactive protein-bound form, holo-transcobalamin (holo-TC), Hcy, and MMA are the preferred serum biomarkers utilized to determine B12 status. Clinically, vitamin B12 deficiency leads to neurological deterioration and megaloblastic anemia, and, if left untreated, to death. Subclinical vitamin B12 deficiency (usually defined as a total serum B12 of <200 pmol/L) presents asymptomatically or with rather subtle generic symptoms that oftentimes are mistakenly ascribed to unrelated disorders. Numerous studies have now established that serum vitamin B12 has limited diagnostic value as a stand-alone marker. Low serum levels of vitamin B12 not always represent deficiency, and likewise, severe functional deficiency of the micronutrient has been documented in the presence of normal and even high levels of serum vitamin B12. This review discusses the usefulness and limitations of current biomarkers of B12 status in newborn screening, infant and adult diagnostics, the algorithms utilized to diagnose B12 deficiency and unusual findings of vitamin B12 status in various human disorders.
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Affiliation(s)
- Luciana Hannibal
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
| | - Vegard Lysne
- Department of Clinical Sciences, University of Bergen Bergen, Norway
| | | | - Sidney Behringer
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
| | - Sarah C Grünert
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
| | - Ute Spiekerkoetter
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
| | - Donald W Jacobsen
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Cleveland, OH, USA
| | - Henk J Blom
- Laboratory of Clinical Biochemistry and Metabolism, Department for Pediatrics, Medical Center, University of Freiburg Freiburg, Germany
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33
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Malvagia S, Haynes CA, Grisotto L, Ombrone D, Funghini S, Moretti E, McGreevy KS, Biggeri A, Guerrini R, Yahyaoui R, Garg U, Seeterlin M, Chace D, De Jesus VR, la Marca G. Heptadecanoylcarnitine (C17) a novel candidate biomarker for newborn screening of propionic and methylmalonic acidemias. Clin Chim Acta 2015; 450:342-8. [PMID: 26368264 DOI: 10.1016/j.cca.2015.09.012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 09/10/2015] [Accepted: 09/10/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND 3-Hydroxypalmitoleoyl-carnitine (C16:1-OH) has recently been reported to be elevated in acylcarnitine profiles of patients with propionic acidemia (PA) or methylmalonic acidemia (MMA) during expanded newborn screening (NBS). High levels of C16:1-OH, combined with other hydroxylated long chain acylcarnitines are related to long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) and trifunctional protein (TFP) deficiency. METHODS The acylcarnitine profile of two LCHADD patients was evaluated using liquid chromatography-tandem mass spectrometric method. A specific retention time was determined for each hydroxylated long chain acylcarnitine. The same method was applied to some neonatal dried blood spots (DBSs) from PA and MMA patients presenting abnormal C16:1-OH concentrations. RESULTS The retention time of the peak corresponding to C16:1-OH in LCHADD patients differed from those in MMA and PA patients. Heptadecanoylcarnitine (C17) has been identified as the novel biomarker specific for PA and MMA patients through high resolution mass spectrometry (Orbitrap) experiments. We found that 21 out of 23 neonates (22 MMA, and 1PA) diagnosed through the Tuscany region NBS program exhibited significantly higher levels of C17 compared to controls. Twenty-three maternal deficiency (21 vitamin B12 deficiency, 1 homocystinuria and 1 gastrin deficiency) samples and 82 false positive for elevated propionylcarnitine (C3) were also analyzed. CONCLUSIONS We have characterized a novel biomarker able to detect propionate disorders during expanded newborn screening (NBS). The use of this new biomarker may improve the analytical performances of NBS programs especially in laboratories where second tier tests are not performed.
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Affiliation(s)
- Sabrina Malvagia
- Newborn Screening, Biochemistry and Pharmacology Laboratory, Pediatric Neurology Unit and Laboratories, Meyer Children's University Hospital, Florence, Italy
| | - Christopher A Haynes
- Newborn Screening and Molecular Biology Branch, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Laura Grisotto
- Department of Statistics, Computer Science and Applications 'G. Parenti' University of Florence, Florence, Italy
| | - Daniela Ombrone
- Newborn Screening, Biochemistry and Pharmacology Laboratory, Pediatric Neurology Unit and Laboratories, Meyer Children's University Hospital, Florence, Italy
| | - Silvia Funghini
- Newborn Screening, Biochemistry and Pharmacology Laboratory, Pediatric Neurology Unit and Laboratories, Meyer Children's University Hospital, Florence, Italy
| | - Elisa Moretti
- Analytics and Early Formulations Department, Chiesi Farmaceutici S.P.A., Parma, Italy
| | - Kathleen S McGreevy
- Research, Innovation and International Relations Office, Meyer Children's University Hospital, Florence, Italy
| | - Annibale Biggeri
- Department of Statistics, Computer Science and Applications 'G. Parenti' University of Florence, Florence, Italy
| | - Renzo Guerrini
- Pediatric Neurology Unit and Laboratories, Meyer Children's University Hospital, Viale Pieraccini 24, 50139 Florence, Italy
| | - Raquel Yahyaoui
- Newborn Screening and Clinical Laboratory, Málaga Regional Hospital, Málaga, Spain
| | - Uttam Garg
- Department of Pathology and laboratory Medicine, Children's Mercy Hospital, Kansas City, MO, USA
| | - Mary Seeterlin
- Newborn Screening Section, Michigan Department of Community Health, Bureau of Laboratories, Chemistry and Toxicology, Lansing, MI, USA
| | - Donald Chace
- The Pediatrix Center for Research, Education and Quality Pediatrix Medical Group, Concord Terrace Sunrise, FL, USA
| | - Victor R De Jesus
- Newborn Screening and Molecular Biology Branch, Centers for Disease Control and Prevention, Atlanta, GA USA
| | - Giancarlo la Marca
- Newborn Screening, Biochemistry and Pharmacology Laboratory, Pediatric Neurology Unit and Laboratories, Meyer Children's University Hospital, Florence, Italy.
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34
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Devalia V, Hamilton MS, Molloy AM. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. Br J Haematol 2014; 166:496-513. [PMID: 24942828 DOI: 10.1111/bjh.12959] [Citation(s) in RCA: 223] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The clinical picture is the most important factor in assessing the significance of test results assessing cobalamin status because there is no 'gold standard' test to define deficiency. Serum cobalamin currently remains the first-line test, with additional second-line plasma methylmalonic acid to help clarify uncertainties of underlying biochemical/functional deficiencies. Serum holotranscobalamin has the potential as a first-line test, but an indeterminate 'grey area' may still exist. Plasma homocysteine may be helpful as a second-line test, but is less specific than methylmalonic acid. The availability of these second-line tests is currently limited. Definitive cut-off points to define clinical and subclinical deficiency states are not possible, given the variety of methodologies used and technical issues, and local reference ranges should be established. In the presence of discordance between the test result and strong clinical features of deficiency, treatment should not be delayed to avoid neurological impairment. Treatment of cobalamin deficiency is recommended in line with the British National Formulary. Oral therapy may be suitable and acceptable provided appropriate doses are taken and compliance is not an issue. Serum folate offers equivalent diagnostic capability to red cell folate and is the first-line test of choice to assess folate status.
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35
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Quadros EV, Sequeira JM. Cellular uptake of cobalamin: transcobalamin and the TCblR/CD320 receptor. Biochimie 2013; 95:1008-18. [PMID: 23415653 PMCID: PMC3902480 DOI: 10.1016/j.biochi.2013.02.004] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2013] [Accepted: 02/01/2013] [Indexed: 02/06/2023]
Abstract
Cellular uptake of cobalamin is facilitated by a receptor-mediated endocytosis process involving transcobalamin, a plasma protein that binds cobalamin and a cell surface receptor that specifically binds transcobalamin saturated with cobalamin. Intracellular Cbl concentration is maintained by modulating the expression of the receptor, which is cell cycle associated with highest expression in actively proliferating cells and an efflux system that shunts the excess cobalamin out of the cells for mobilization to other tissues where it is most needed. This review describes the process, proteins involved and genes encoding these proteins.
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Affiliation(s)
- Edward V Quadros
- Departments of Medicine / Cell Biology, SUNY- Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
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36
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Jiang W, Nakayama Y, Sequeira JM, Quadros EV. Mapping the functional domains of TCblR/CD320, the receptor for cellular uptake of transcobalamin-bound cobalamin. FASEB J 2013; 27:2988-94. [PMID: 23603833 DOI: 10.1096/fj.13-230185] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The membrane receptor TCblR/CD320 binds transcobalamin (TC) saturated with vitamin B12 [cobalamin (Cbl)] and mediates cellular uptake of the vitamin. The specificity of TC for Cbl and of the receptor for TC-Cbl ensures efficient uptake of Cbl into cells. The high-affinity interaction of TCblR with TC-Cbl (Ka=10 nM(-1)) was investigated using deletions and mutations of amino acid sequences in TCblR. Only the extracellular region (aa 32-229) is needed for TC-Cbl binding, but the N-glycosylation sites (N126, N195, and N213) are of no importance for this function. Deleting the cysteine-rich region (aa 95-141) that separates the two low-density lipoprotein receptor type A (LDLR-A) domains does not affect TC-Cbl binding (Ka = 19-24 nM(-1)). The two LDLR-A domains (aa 54-89 and 132-167) with the negatively charged acidic residues involved in Ca(2+) binding are critical determinants of ligand binding. The cytoplasmic tail is apparently crucial for internalization of the ligand. Within this region, the RPLGLL motif and the PDZ binding motifs (QERL/KESL) appear to be involved in initiating and completing the process of ligand internalization. Mutations and deletions of these regions involved in binding and internalization of TC-Cbl are likely to produce the biochemical and clinical phenotype of Cbl deficiency.
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Affiliation(s)
- Wenxia Jiang
- School of Graduate Studies, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
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Gherasim C, Hannibal L, Rajagopalan D, Jacobsen DW, Banerjee R. The C-terminal domain of CblD interacts with CblC and influences intracellular cobalamin partitioning. Biochimie 2013; 95:1023-32. [PMID: 23415655 DOI: 10.1016/j.biochi.2013.02.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Accepted: 02/01/2013] [Indexed: 11/15/2022]
Abstract
Mutations in cobalamin or B12 trafficking genes needed for cofactor assimilation and targeting lead to inborn errors of cobalamin metabolism. The gene corresponding to one of these loci, cblD, affects both the mitochondrial and cytoplasmic pathways for B12 processing. We have demonstrated that fibroblast cell lines from patients with mutations in CblD, can dealkylate exogenously supplied methylcobalamin (MeCbl), an activity catalyzed by the CblC protein, but show imbalanced intracellular partitioning of the cofactor into the MeCbl and 5'-deoxyadenosylcobalamin (AdoCbl) pools. These results confirm that CblD functions downstream of CblC in the cofactor assimilation pathway and that it plays an important role in controlling the traffic of the cofactor between the competing cytoplasmic and mitochondrial routes for MeCbl and AdoCbl synthesis, respectively. In this study, we report the interaction of CblC with four CblD protein variants with variable N-terminal start sites. We demonstrate that a complex between CblC and CblD can be isolated particularly under conditions that permit dealkylation of alkylcobalamin by CblC or in the presence of the corresponding dealkylated and oxidized product, hydroxocobalamin (HOCbl). A weak CblC·CblD complex is also seen in the presence of cyanocobalamin. Formation of the CblC·CblD complex is observed with all four CblD variants tested suggesting that the N-terminal 115 residues missing in the shortest variant are not essential for this interaction. Furthermore, limited proteolysis of the CblD variants indicates the presence of a stable C-terminal domain spanning residues ∼116-296. Our results are consistent with an adapter function for CblD, which in complex with CblC·HOCbl, or possibly the less oxidized CblC·cob(II)alamin, partitions the cofactor between AdoCbl and MeCbl assimilation pathways.
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Affiliation(s)
- Carmen Gherasim
- Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI 48109-0600, USA
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Watkins D, Rosenblatt DS. Lessons in biology from patients with inborn errors of vitamin B12 metabolism. Biochimie 2013; 95:1019-22. [PMID: 23402785 DOI: 10.1016/j.biochi.2013.01.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 01/28/2013] [Indexed: 01/14/2023]
Abstract
BACKGROUND Since 1975 cells lines from patients with suspected inborn errors of vitamin B12 metabolism have been referred to our laboratory because of elevations of homocysteine, methylmalonic acid, or both. DESIGN Cultured fibroblasts from patients were subjected to a battery of tests: incorporation of labelled propionate and methyltetrahydrofolate into cellular macromolecules, to test the functional integrity of methylmalonyl-CoA mutase and methionine synthase, respectively; uptake of labelled cyanocobalamin and synthesis of adenosylcobalamin and methylcobalamin; and, where applicable, complementation analysis. RESULTS This approach has allowed for the discovery of novel steps in the cellular transport and metabolism of vitamin B12, including those involving cellular uptake, the efflux of vitamin B12 from lysosomes, and the synthesis of adenosylcobalamin and methylcobalamin. For all of these disorders, the responsible genes have been discovered. CONCLUSION The study of highly selected patients with suspected inborn errors of metabolism has consistently resulted in the discovery of previously unknown metabolic steps and has provided new lessons in biology.
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Affiliation(s)
- David Watkins
- Department of Human Genetics, McGill University, Montreal, Quebec, Canada
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Börnigen D, Tranchevent LC, Bonachela-Capdevila F, Devriendt K, De Moor B, De Causmaecker P, Moreau Y. An unbiased evaluation of gene prioritization tools. Bioinformatics 2012; 28:3081-8. [PMID: 23047555 DOI: 10.1093/bioinformatics/bts581] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
MOTIVATION Gene prioritization aims at identifying the most promising candidate genes among a large pool of candidates-so as to maximize the yield and biological relevance of further downstream validation experiments and functional studies. During the past few years, several gene prioritization tools have been defined, and some of them have been implemented and made available through freely available web tools. In this study, we aim at comparing the predictive performance of eight publicly available prioritization tools on novel data. We have performed an analysis in which 42 recently reported disease-gene associations from literature are used to benchmark these tools before the underlying databases are updated. RESULTS Cross-validation on retrospective data provides performance estimate likely to be overoptimistic because some of the data sources are contaminated with knowledge from disease-gene association. Our approach mimics a novel discovery more closely and thus provides more realistic performance estimates. There are, however, marked differences, and tools that rely on more advanced data integration schemes appear more powerful. CONTACT yves.moreau@esat.kuleuven.be SUPPLEMENTARY INFORMATION Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Daniela Börnigen
- Department of Electrical Engineering, ESAT-SCD, Katholieke Universiteit Leuven, Leuven, Belgium
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Tanner SM, Sturm AC, Baack EC, Liyanarachchi S, de la Chapelle A. Inherited cobalamin malabsorption. Mutations in three genes reveal functional and ethnic patterns. Orphanet J Rare Dis 2012; 7:56. [PMID: 22929189 PMCID: PMC3462684 DOI: 10.1186/1750-1172-7-56] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 08/23/2012] [Indexed: 01/26/2023] Open
Abstract
BACKGROUND Inherited malabsorption of cobalamin (Cbl) causes hematological and neurological abnormalities that can be fatal. Three genes have been implicated in Cbl malabsorption; yet, only about 10% of ~400-500 reported cases have been molecularly studied to date. Recessive mutations in CUBN or AMN cause Imerslund-Gräsbeck Syndrome (IGS), while recessive mutations in GIF cause Intrinsic Factor Deficiency (IFD). IGS and IFD differ in that IGS usually presents with proteinuria, which is not observed in IFD. The genetic heterogeneity and numerous differential diagnoses make clinical assessment difficult. METHODS We present a large genetic screening study of 154 families or patients with suspected hereditary Cbl malabsorption. Patients and their families have been accrued over a period spanning >12 years. Systematic genetic testing of the three genes CUBN, AMN, and GIF was accomplished using a combination of single strand conformation polymorphism and DNA and RNA sequencing. In addition, six genes that were contenders for a role in inherited Cbl malabsorption were studied in a subset of these patients. RESULTS Our results revealed population-specific mutations, mutational hotspots, and functionally distinct regions in the three causal genes. We identified mutations in 126/154 unrelated cases (82%). Fifty-three of 126 cases (42%) were mutated in CUBN, 45/126 (36%) were mutated in AMN, and 28/126 (22%) had mutations in GIF. We found 26 undescribed mutations in CUBN, 19 in AMN, and 7 in GIF for a total of 52 novel defects described herein. We excluded six other candidate genes as culprits and concluded that additional genes might be involved. CONCLUSIONS Cbl malabsorption is found worldwide and genetically complex. However, our results indicate that population-specific founder mutations are quite common. Consequently, targeted genetic testing has become feasible if ethnic ancestry is considered. These results will facilitate clinical and molecular genetic testing of Cbl malabsorption. Early diagnosis improves the lifelong care required by these patients and prevents potential neurological long-term complications. This study provides the first comprehensive overview of the genetics that underlies the inherited Cbl malabsorption phenotype.
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Affiliation(s)
- Stephan M Tanner
- Human Cancer Genetics, Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210, USA.
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Karth P, Singh R, Kim J, Costakos D. Bilateral central retinal artery occlusions in an infant with hyperhomocysteinemia. J AAPOS 2012; 16:398-400. [PMID: 22819238 DOI: 10.1016/j.jaapos.2012.04.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Revised: 04/04/2012] [Accepted: 04/21/2012] [Indexed: 11/18/2022]
Abstract
A previously healthy 7-week-old boy developed bilateral central retinal artery occlusions in the presence of hyperhomocysteinemia and elevated serum methylmalonic acid and was found to have a transcobalamin receptor mutation. Retinal arterial occlusion is uncommon in young patients and typically prompts a systemic workup. In cases of atypical retinal arterial occlusion, hyperhomocysteinemia should be investigated.
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Affiliation(s)
- Peter Karth
- Medical College of Wisconsin, 925 N. 87th Street, Milwaukee, Wisconsin, USA
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Solomon BD, Hadley DW, Pineda-Alvarez DE, Kamat A, Teer JK, Cherukuri PF, Hansen NF, Cruz P, Young AC, Berkman BE, Chandrasekharappa SC, Mullikin JC, Mullikin JC. Incidental medical information in whole-exome sequencing. Pediatrics 2012; 129:e1605-11. [PMID: 22585771 PMCID: PMC3362899 DOI: 10.1542/peds.2011-0080] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Genomic technologies, such as whole-exome sequencing, are a powerful tool in genetic research. Such testing yields a great deal of incidental medical information, or medical information not related to the primary research target. We describe the management of incidental medical information derived from whole-exome sequencing in the research context. We performed whole-exome sequencing on a monozygotic twin pair in which only 1 child was affected with congenital anomalies and applied an institutional review board-approved algorithm to determine what genetic information would be returned. Whole-exome sequencing identified 79525 genetic variants in the twins. Here, we focus on novel variants. After filtering artifacts and excluding known single nucleotide polymorphisms and variants not predicted to be pathogenic, the twins had 32 novel variants in 32 genes that were felt to be likely to be associated with human disease. Eighteen of these novel variants were associated with recessive disease and 18 were associated with dominantly manifesting conditions (variants in some genes were potentially associated with both recessive and dominant conditions), but only 1 variant ultimately met our institutional review board-approved criteria for return of information to the research participants.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Benjamin E. Berkman
- Department of Bioethics, Clinical Center, and Office of the Clinical Director, and
| | - Settara C. Chandrasekharappa
- Cancer Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland
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Abstract
Vitamin B(12) (B(12); also known as cobalamin) is a cofactor in many metabolic processes; deficiency of this vitamin is associated with megaloblastic anaemia and various neurological disorders. In contrast to many prokaryotes, humans and other mammals are unable to synthesize B(12). Instead, a sophisticated pathway for specific uptake and transport of this molecule has evolved. Failure in the gastrointestinal part of this pathway is the most common cause of nondietary-induced B(12) deficiency disease. However, although less frequent, defects in cellular processing and further downstream steps in the transport pathway are also known culprits of functional B(12) deficiency. Biochemical and genetic approaches have identified novel proteins in the B(12) transport pathway--now known to involve more than 15 gene products--delineating a coherent pathway for B(12) trafficking from food to the body's cells. Some of these gene products are specifically dedicated to B(12) transport, whereas others embrace additional roles, which explains the heterogeneity in the clinical picture of the many genetic disorders causing B(12) deficiency. This Review describes basic and clinical features of this multistep pathway with emphasis on gastrointestinal transport of B(12) and its importance in clinical medicine.
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Arendt JFB, Quadros EV, Nexo E. Soluble transcobalamin receptor, sCD320, is present in human serum and relates to serum cobalamin – establishment and validation of an ELISA. Clin Chem Lab Med 2012; 50:515-9. [DOI: 10.1515/cclm.2011.810] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Accepted: 11/10/2011] [Indexed: 11/15/2022]
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Stone N, Pangilinan F, Molloy AM, Shane B, Scott JM, Ueland PM, Mills JL, Kirke PN, Sethupathy P, Brody LC. Bioinformatic and genetic association analysis of microRNA target sites in one-carbon metabolism genes. PLoS One 2011; 6:e21851. [PMID: 21765920 PMCID: PMC3134459 DOI: 10.1371/journal.pone.0021851] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 06/07/2011] [Indexed: 01/26/2023] Open
Abstract
One-carbon metabolism (OCM) is linked to DNA synthesis and methylation, amino acid metabolism and cell proliferation. OCM dysfunction has been associated with increased risk for various diseases, including cancer and neural tube defects. MicroRNAs (miRNAs) are ∼22 nt RNA regulators that have been implicated in a wide array of basic cellular processes, such as differentiation and metabolism. Accordingly, mis-regulation of miRNA expression and/or activity can underlie complex disease etiology. We examined the possibility of OCM regulation by miRNAs. Using computational miRNA target prediction methods and Monte-Carlo based statistical analyses, we identified two candidate miRNA “master regulators” (miR-22 and miR-125) and one candidate pair of “master co-regulators” (miR-344-5p/484 and miR-488) that may influence the expression of a significant number of genes involved in OCM. Interestingly, miR-22 and miR-125 are significantly up-regulated in cells grown under low-folate conditions. In a complementary analysis, we identified 15 single nucleotide polymorphisms (SNPs) that are located within predicted miRNA target sites in OCM genes. We genotyped these 15 SNPs in a population of healthy individuals (age 18–28, n = 2,506) that was previously phenotyped for various serum metabolites related to OCM. Prior to correction for multiple testing, we detected significant associations between TCblR rs9426 and methylmalonic acid (p = 0.045), total homocysteine levels (tHcy) (p = 0.033), serum B12 (p < 0.0001), holo transcobalamin (p < 0.0001) and total transcobalamin (p < 0.0001); and between MTHFR rs1537514 and red blood cell folate (p < 0.0001). However, upon further genetic analysis, we determined that in each case, a linked missense SNP is the more likely causative variant. Nonetheless, our Monte-Carlo based in silico simulations suggest that miRNAs could play an important role in the regulation of OCM.
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Affiliation(s)
- Nicole Stone
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Faith Pangilinan
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Anne M. Molloy
- School of Immunology and Biochemistry, Trinity College, Dublin, Ireland
| | - Barry Shane
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California, United States of America
| | - John M. Scott
- School of Immunology and Biochemistry, Trinity College, Dublin, Ireland
| | - Per Magne Ueland
- Section of Pharmacology, Institute of Medicine, University of Bergen and Haukeland University Hospital, Bergen, Norway
| | - James L. Mills
- Division of Epidemiology, Statistics, and Prevention Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Peader N. Kirke
- Child Health Epidemiology Unit, Health Research Board of Ireland, Dublin, Ireland
| | - Praveen Sethupathy
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (PS); (LCB)
| | - Lawrence C. Brody
- Genome Technology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (PS); (LCB)
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Watkins D, Rosenblatt DS. Inborn errors of cobalamin absorption and metabolism. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2011; 157C:33-44. [PMID: 21312325 DOI: 10.1002/ajmg.c.30288] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Derivatives of cobalamin (vitamin B(12)) are required for activity of two enzymes in humans. Adenosylcobalamin is required for activity of mitochondrial methylmalonylCoA mutase and methylcobalamin is required for activity of cytoplasmic methionine synthase. Deficiency in cobalamin, or inability to absorb cobalamin normally, can result in accumulation of methylmalonic acid and homocysteine in blood and urine. Methylmalonic acidemia can result in metabolic acidosis which in severe cases may be fatal. Hyperhomocysteinemia along with hypomethioninemia can result in hematologic (megaloblastic anemia, neutropenia, thrombocytopenia) and neurologic (subacute combined degeneration of the cord, dementia, psychosis) defects. Inborn errors affecting cobalamin absorption (inherited intrinsic factor deficiency, Imerslund–Gra¨ sbeck syndrome) and transport (transcobalamin deficiency) have been described. A series of inborn errors of intracellular cobalamin metabolism, designated cblA-cblG, have been differentiated by complementation analysis. These can give rise to isolated methylmalonic acidemia (cblA, cblB, cblD variant 2), isolated hyperhomocysteinemia (cblD variant 1, cblE, cblG) or combined methylmalonic acidemia and hyperhomocysteinemia (cblC, classic cblD, cblF). All these disorders are inherited as autosomal recessive traits. The genes underlying each of these disorders have been identified. Two other disorders, haptocorrin deficiency and transcobalamin receptor deficiency, have been described, but it is not clear that they have any consistent clinical phenotype.
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Affiliation(s)
- David Watkins
- Department of Human Genetics, McGill University, Canada.
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Abstract
Vitamin B12 (cobalamin, Cbl) is an essential nutrient in human metabolism. Genetic diseases of vitamin B12 utilisation constitute an important fraction of inherited newborn disease. Functionally, B12 is the cofactor for methionine synthase and methylmalonyl CoA mutase. To function as a cofactor, B12 must be metabolised through a complex pathway that modifies its structure and takes it through subcellular compartments of the cell. Through the study of inherited disorders of vitamin B12 utilisation, the genes for eight complementation groups have been identified, leading to the determination of the general structure of vitamin B12 processing and providing methods for carrier testing, prenatal diagnosis and approaches to treatment.
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