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Kingma SDK, Neven J, Bael A, Meuwissen MEC, van den Akker M. Imerslund-Gräsbeck syndrome: a comprehensive review of reported cases. Orphanet J Rare Dis 2023; 18:291. [PMID: 37710296 PMCID: PMC10500774 DOI: 10.1186/s13023-023-02889-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 08/25/2023] [Indexed: 09/16/2023] Open
Abstract
Imerslund-Gräsbeck syndrome (IGS) is a rare autosomal recessive disorder characterized by vitamin B12 malabsorption. Most patients present with non-specific symptoms attributed to vitamin B12 deficiency, and proteinuria. Patients may if untreated, develop severe neurocognitive manifestations. If recognized and treated with sufficient doses of vitamin B12, patients recover completely. We provide, for the first time, an overview of all previously reported cases of IGS. In addition, we provide a complete review of IGS and describe two new patients.
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Affiliation(s)
- Sandra D K Kingma
- Centre for Metabolic Diseases, University Hospital Antwerp, University of Antwerp, Drie Eikenstraat 655, Edegem, Antwerp, 2650, Belgium
- Department of Pediatrics, University Hospital Antwerp, University of Antwerp, Drie Eikenstraat 655, Edegem, 2650, Belgium
- Faculty of medicine and health sciences, University of Antwerp, Antwerp, Belgium
| | - Julie Neven
- Department of Pediatrics, University Hospital Antwerp, University of Antwerp, Drie Eikenstraat 655, Edegem, 2650, Belgium
| | - An Bael
- Faculty of medicine and health sciences, University of Antwerp, Antwerp, Belgium
- Department of Pediatric Nephrology, ZNA Queen Paola Children's Hospital, Lindendreef 1, Antwerp, 2020, Belgium
| | - Marije E C Meuwissen
- Center of Medical Genetics, University Hospital Antwerp, Drie Eikenstraat 655, Edegem, 2650, Belgium
| | - Machiel van den Akker
- Department of Pediatrics, University Hospital Antwerp, University of Antwerp, Drie Eikenstraat 655, Edegem, 2650, Belgium.
- Faculty of medicine and health sciences, University of Antwerp, Antwerp, Belgium.
- Department of Pediatrics, ZNA Queen Paola Children's Hospital, Lindendreef 1, Antwerp, 2020, Belgium.
- Pediatric Hematology and Oncology, Department of Pediatrics, University Hospital Antwerp, Drie Eikenstraat 655, Edegem, Antwerp, 2650, Belgium.
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2
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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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3
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Guéant JL, Guéant-Rodriguez RM, Alpers DH. Vitamin B12 absorption and malabsorption. VITAMINS AND HORMONES 2022; 119:241-274. [PMID: 35337622 DOI: 10.1016/bs.vh.2022.01.016] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Vitamin B12 is assimilated and transported by complex mechanisms that involve three transport proteins, intrinsic factor (IF), haptocorrin (HC) and transcobalamin (TC) and their respective membrane receptors. Vitamin deficiency is mainly due to inadequate dietary intake in vegans, and B12 malabsorption is related to digestive diseases. This review explores the physiology of vitamin B12 absorption and the mechanisms and diseases that produce malabsorption. In the stomach, B12 is released from food carrier proteins and binds to HC. The degradation of HC by pancreatic proteases and the pH change trigger the transfer of B12 to IF in the duodenum. Cubilin and amnionless are the two components of the receptor that mediates the uptake of B12 in the distal ileum. Part of liver B12 is excreted in bile, and undergoes an enterohepatic circulation. The main causes of B12 malabsorption include inherited disorders (Intrinsic factor deficiency, Imerslund-Gräsbeck disease, Addison's pernicious anemia, obesity, bariatric surgery and gastrectomies. Other causes include pancreatic insufficiency, obstructive Jaundice, tropical sprue and celiac disease, bacterial overgrowth, parasitic infestations, Zollinger-Ellison syndrome, inflammatory bowel diseases, chronic radiation enteritis of the distal ileum and short bowel. The assessment of B12 deficit is recommended in the follow-up of subjects with bariatric surgery. The genetic causes of B12 malabsorption are probably underestimated in adult cases with B12 deficit. Despite its high prevalence in the general population and in the elderly, B12 malabsorption cannot be anymore assessed by the Schilling test, pointing out the urgent need for an equivalent reliable test.
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Affiliation(s)
- Jean-Louis Guéant
- University of Lorraine, INSERM UMR_S 1256, Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, Nancy, France; Department of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, Nancy, France; Department of Hepato-Gastroenterology, University Hospital of Nancy, Nancy, France.
| | - Rosa-Maria Guéant-Rodriguez
- University of Lorraine, INSERM UMR_S 1256, Nutrition, Genetics, and Environmental Risk Exposure (NGERE), Faculty of Medicine of Nancy, Nancy, France; Department of Biochemistry, Molecular Biology, Nutrition, and Metabolism, University Hospital of Nancy, Nancy, France
| | - David H Alpers
- Department of Internal Medicine, Division of Gastroenterology, Washington University School of Medicine, St Louis, MO, United States.
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4
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Issler N, Afonso S, Weissman I, Jordan K, Cebrian-Serrano A, Meindl K, Dahlke E, Tziridis K, Yan G, Robles-López JM, Tabernero L, Patel V, Kesselheim A, Klootwijk ED, Stanescu HC, Dumitriu S, Iancu D, Tekman M, Mozere M, Jaureguiberry G, Outtandy P, Russell C, Forst AL, Sterner C, Heinl ES, Othmen H, Tegtmeier I, Reichold M, Schiessl IM, Limm K, Oefner P, Witzgall R, Fu L, Theilig F, Schilling A, Shuster Biton E, Kalfon L, Fedida A, Arnon-Sheleg E, Ben Izhak O, Magen D, Anikster Y, Schulze H, Ziegler C, Lowe M, Davies B, Böckenhauer D, Kleta R, Falik Zaccai TC, Warth R. A Founder Mutation in EHD1 Presents with Tubular Proteinuria and Deafness. J Am Soc Nephrol 2022; 33:732-745. [PMID: 35149593 PMCID: PMC8970462 DOI: 10.1681/asn.2021101312] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 12/17/2021] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND The endocytic reabsorption of proteins in the proximal tubule requires a complex machinery and defects can lead to tubular proteinuria. The precise mechanisms of endocytosis and processing of receptors and cargo are incompletely understood. EHD1 belongs to a family of proteins presumably involved in the scission of intracellular vesicles and in ciliogenesis. However, the relevance of EHD1 in human tissues, in particular in the kidney, was unknown. METHODS Genetic techniques were used in patients with tubular proteinuria and deafness to identify the disease-causing gene. Diagnostic and functional studies were performed in patients and disease models to investigate the pathophysiology. RESULTS We identified six individuals (5-33 years) with proteinuria and a high-frequency hearing deficit associated with the homozygous missense variant c.1192C>T (p.R398W) in EHD1. Proteinuria (0.7-2.1 g/d) consisted predominantly of low molecular weight proteins, reflecting impaired renal proximal tubular endocytosis of filtered proteins. Ehd1 knockout and Ehd1R398W/R398W knockin mice also showed a high-frequency hearing deficit and impaired receptor-mediated endocytosis in proximal tubules, and a zebrafish model showed impaired ability to reabsorb low molecular weight dextran. Interestingly, ciliogenesis appeared unaffected in patients and mouse models. In silico structural analysis predicted a destabilizing effect of the R398W variant and possible inference with nucleotide binding leading to impaired EHD1 oligomerization and membrane remodeling ability. CONCLUSIONS A homozygous missense variant of EHD1 causes a previously unrecognized autosomal recessive disorder characterized by sensorineural deafness and tubular proteinuria. Recessive EHD1 variants should be considered in individuals with hearing impairment, especially if tubular proteinuria is noted.
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Affiliation(s)
- Naomi Issler
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Sara Afonso
- Medical Cell Biology, University of Regensburg, Regensburg, Germany
| | - Irith Weissman
- Pediatric Nephrology, Galilee Medical Center, Nahraia, Israel
| | - Katrin Jordan
- Medical Cell Biology, University of Regensburg, Regensburg, Germany
| | | | - Katrin Meindl
- Medical Cell Biology, University of Regensburg, Regensburg, Germany
| | - Eileen Dahlke
- Institute of Anatomy, University of Kiel, Kiel, Germany
| | - Konstantin Tziridis
- Ear, Nose, and Throat Clinic, University Hospital Erlangen, Erlangen, Germany
| | - Guanhua Yan
- Division of Molecular and Cellular Function, University of Manchester, United Kingdom
| | - José M. Robles-López
- Division of Molecular and Cellular Function, University of Manchester, United Kingdom
| | - Lydia Tabernero
- Division of Molecular and Cellular Function, University of Manchester, United Kingdom
| | - Vaksha Patel
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Anne Kesselheim
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Enriko D. Klootwijk
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Horia C. Stanescu
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Simona Dumitriu
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Daniela Iancu
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Mehmet Tekman
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Monika Mozere
- Department of Renal Medicine, University College London, London, United Kingdom
| | | | - Priya Outtandy
- Department of Renal Medicine, University College London, London, United Kingdom
| | | | - Anna-Lena Forst
- Medical Cell Biology, University of Regensburg, Regensburg, Germany
| | | | | | - Helga Othmen
- Medical Cell Biology, University of Regensburg, Regensburg, Germany
| | - Ines Tegtmeier
- Medical Cell Biology, University of Regensburg, Regensburg, Germany
| | - Markus Reichold
- Medical Cell Biology, University of Regensburg, Regensburg, Germany
| | | | - Katharina Limm
- Institute of Functional Genomics, University of Regensburg, Regensburg, Germany
| | - Peter Oefner
- Institute of Functional Genomics, University of Regensburg, Regensburg, Germany
| | - Ralph Witzgall
- Molecular and Cellular Anatomy, University of Regensburg, Regensburg, Germany
| | - Lifei Fu
- Structural Biology, University of Regensburg, Regensburg, Germany
| | | | - Achim Schilling
- Ear, Nose, and Throat Clinic, University Hospital Erlangen, Erlangen, Germany
| | | | - Limor Kalfon
- Institute of Human Genetics, Galilee Medical Center, Nahraia, Israel
| | - Ayalla Fedida
- Institute of Human Genetics, Galilee Medical Center, Nahraia, Israel
| | | | - Ofer Ben Izhak
- Department of Pathology, Rambam Health Care Campus, Technion Faculty of Medicine, Haifa, Israel
| | - Daniella Magen
- Pediatric Nephrology Institute, Rambam Health Care Campus, Technion Faculty of Medicine, Haifa, Israel
| | | | - Holger Schulze
- Ear, Nose, and Throat Clinic, University Hospital Erlangen, Erlangen, Germany
| | | | - Martin Lowe
- Division of Molecular and Cellular Function, University of Manchester, United Kingdom
| | - Benjamin Davies
- Wellcome Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Detlef Böckenhauer
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Robert Kleta
- Department of Renal Medicine, University College London, London, United Kingdom
| | - Tzipora C. Falik Zaccai
- The Azrieli Faculty of Medicine, Bar Ilan, Safed, Israel
- Institute of Human Genetics, Galilee Medical Center, Nahraia, Israel
| | - Richard Warth
- Medical Cell Biology, University of Regensburg, Regensburg, Germany
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5
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Kozyraki R, Verroust P, Cases O. Cubilin, the intrinsic factor-vitamin B12 receptor. VITAMINS AND HORMONES 2022; 119:65-119. [PMID: 35337634 DOI: 10.1016/bs.vh.2022.01.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Cubilin (CUBN), the intrinsic factor-vitamin B12 receptor is a large endocytic protein involved in various physiological functions: vitamin B12 uptake in the gut; reabsorption of albumin and maturation of vitamin D in the kidney; nutrient delivery during embryonic development. Cubilin is an atypical receptor, peripherally associated to the plasma membrane. The transmembrane proteins amnionless (AMN) and Lrp2/Megalin are the currently known molecular partners contributing to plasma membrane transport and internalization of Cubilin. The role of Cubilin/Amn complex in the handling of vitamin B12 in health and disease has extensively been studied and so is the role of the Cubilin-Lrp2 tandem in renal pathophysiology. Accumulating evidence strongly supports a role of Cubilin in some developmental defects including impaired closure of the neural tube. Are these defects primarily caused by the dysfunction of a specific Cubilin ligand or are they secondary to impaired vitamin B12 or protein uptake? We will present the established Cubilin functions, discuss the developmental data and provide an overview of the emerging implications of Cubilin in the field of cardiovascular disease and cancer pathogenesis.
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Affiliation(s)
- Renata Kozyraki
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, Paris, France.
| | - Pierre Verroust
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, Paris, France
| | - Olivier Cases
- Centre de Recherche des Cordeliers, Sorbonne Université, INSERM, Université de Paris, Paris, France
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6
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Baker KM, Parikh NS, Salsbery KT, Shaw GR, Steiner RD, Oelstrom MJ, Manalang MA. A 17-Month-old Boy With Pancytopenia Caused by a Rare Genetic Defect of Vitamin B12 Malabsorption. J Pediatr Hematol Oncol 2022; 44:e444-e446. [PMID: 34054045 DOI: 10.1097/mph.0000000000002213] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Accepted: 04/25/2021] [Indexed: 11/26/2022]
Abstract
Imerslund-Gräsbeck syndrome is an autosomal recessive disorder of vitamin B12 malabsorption presenting with megaloblastic anemia and mild proteinuria in childhood. The disorder is caused by biallelic pathogenic variants in the CUBN or AMN genes, which encode proteins involved in B12 absorption. We present the case of a 17-month-old boy with failure to thrive, pancytopenia, and fevers. His megaloblastic anemia was overlooked leading to unnecessary invasive testing. Findings on bone marrow biopsy prompted investigation for genetic disorders of B12 metabolism. Exome sequencing uncovered 1 known pathogenic variant and 1 novel likely pathogenic variant in CUBN, confirming the diagnosis of Imerslund-Gräsbeck syndrome.
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Affiliation(s)
| | | | | | | | - Robert D Steiner
- Pediatrics and Prevention Genetics LLC
- Department of Pediatrics, University of Wisconsin School of Medicine and Public Health, Madison, WI
| | - Matthew J Oelstrom
- Pediatric Intensive Care Unit, Marshfield Children's Hospital, Marshfield
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7
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Yang J, Xu Y, Deng L, Zhou L, Qiu L, Zhang Y, Zhou J. CUBN gene mutations may cause focal segmental glomerulosclerosis (FSGS) in children. BMC Nephrol 2022; 23:15. [PMID: 34979989 PMCID: PMC8725476 DOI: 10.1186/s12882-021-02654-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 12/20/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Imerslund-Gräsbeck Syndrome (IGS) is mainly caused by CUBN gene biallelic mutations. Proteinuria accompanies IGS specific symptoms in about half of the patients, isolated proteinuria is rarely reported. Here we present 3 patients with isolated proteinuria and focal segmental glomerulosclerosis (FSGS) caused by CUBN gene biallelic pathogenic variants. METHOD Whole exome sequencing was performed on three children with isolated proteinuria. CUBN gene biallelic pathogenic variants were found and then verified by sanger sequencing. Their clinical, pathological and molecular genetic characteristics were analyzed and correlated accordingly. RESULTS All three children presented with isolated proteinuria, no megaloblastic anemia. Their urine levels of β2 microglobulin were normal or slightly higher. Renal biopsies showed focal segmental glomerulosclerosis with mild glomerular mesangial hypercellularity, partial effacement of foot processes and podocyte microvillation. Two of them were found to carry compound heterozygous mutations and one homozygous mutation of CUBN gene. Totally four CUBN gene biallelic pathogenic variants were identified, including c.9287 T > C (p.L3096P), c.122 + 1G > A, c.7906C > T (p.R2636*), c.10233G > A (p.W3411*). Except for intron splice-site mutation, all other variants are located in highly conserved sites of CUB domain for binding to albumin. CONCLUSION The results demonstrate that CUBN gene mutations may cause isolated proteinuria pathologically presented as FSGS. Our cases extend the spectrum of renal manifestation and genotype of CUBN gene mutations.
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Affiliation(s)
- Jing Yang
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Yongli Xu
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Linxia Deng
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Luowen Zhou
- Department of Neurosurgery, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Wuhan, China
| | - Liru Qiu
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Yu Zhang
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China
| | - Jianhua Zhou
- Department of Pediatrics, Tongji Hospital, Tongji Medical college, Huazhong University of Science and Technology, Jiefang Ave. No. 1095, Wuhan, 430030, China.
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8
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Rovira P, Demontis D, Sánchez-Mora C, Zayats T, Klein M, Mota NR, Weber H, Garcia-Martínez I, Pagerols M, Vilar-Ribó L, Arribas L, Richarte V, Corrales M, Fadeuilhe C, Bosch R, Martin GE, Almos P, Doyle AE, Grevet EH, Grimm O, Halmøy A, Hoogman M, Hutz M, Jacob CP, Kittel-Schneider S, Knappskog PM, Lundervold AJ, Rivero O, Rovaris DL, Salatino-Oliveira A, da Silva BS, Svirin E, Sprooten E, Strekalova T, Arias-Vasquez A, Sonuga-Barke EJS, Asherson P, Bau CHD, Buitelaar JK, Cormand B, Faraone SV, Haavik J, Johansson SE, Kuntsi J, Larsson H, Lesch KP, Reif A, Rohde LA, Casas M, Børglum AD, Franke B, Ramos-Quiroga JA, Soler Artigas M, Ribasés M. Shared genetic background between children and adults with attention deficit/hyperactivity disorder. Neuropsychopharmacology 2020; 45:1617-1626. [PMID: 32279069 PMCID: PMC7419307 DOI: 10.1038/s41386-020-0664-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2019] [Revised: 02/25/2020] [Accepted: 03/03/2020] [Indexed: 12/14/2022]
Abstract
Attention deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder characterized by age-inappropriate symptoms of inattention, impulsivity, and hyperactivity that persist into adulthood in the majority of the diagnosed children. Despite several risk factors during childhood predicting the persistence of ADHD symptoms into adulthood, the genetic architecture underlying the trajectory of ADHD over time is still unclear. We set out to study the contribution of common genetic variants to the risk for ADHD across the lifespan by conducting meta-analyses of genome-wide association studies on persistent ADHD in adults and ADHD in childhood separately and jointly, and by comparing the genetic background between them in a total sample of 17,149 cases and 32,411 controls. Our results show nine new independent loci and support a shared contribution of common genetic variants to ADHD in children and adults. No subgroup heterogeneity was observed among children, while this group consists of future remitting and persistent individuals. We report similar patterns of genetic correlation of ADHD with other ADHD-related datasets and different traits and disorders among adults, children, and when combining both groups. These findings confirm that persistent ADHD in adults is a neurodevelopmental disorder and extend the existing hypothesis of a shared genetic architecture underlying ADHD and different traits to a lifespan perspective.
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Affiliation(s)
- Paula Rovira
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
| | - Ditte Demontis
- Department of Biomedicine (Human Genetics), and Centre for Integrative Sequencing, iSEQ, Aarhus University, Aarhus, Denmark
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus, Denmark
- Center for Genomics and Personalized Medicine, Aarhus, Denmark
| | - Cristina Sánchez-Mora
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
- Department of Genetics, Microbiology, and Statistics, Faculty of Biology, Universitat de Barcelona, Barcelona, Spain
| | - Tetyana Zayats
- Department of Biomedicine, University of Bergen, Bergen, Norway
- Analytic and Translational Genetics Unit, Department of Medicine, Massachusetts General Hospital, and Harvard Medical School, Boston, MA, USA
- Stanley Center for Psychiatric Research, Broad Institute of MIT, and Harvard, Cambridge, MA, USA
| | - Marieke Klein
- Department of Human Genetics, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
- University Medical Center Utrecht, UMC Utrecht Brain Center, Department of Psychiatry, Utrecht, The Netherlands
| | - Nina Roth Mota
- Department of Human Genetics, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
- ADHD Outpatient Program, Adult Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
- Department of Psychiatry, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Heike Weber
- Department of Psychiatry, Psychosomatics, and Psychotherapy, University of Würzburg, Würzburg, Germany
- Department of Psychiatry, Psychosomatic Medicine, and Psychotherapy, University Hospital Frankfurt, Frankfurt am Main, Germany
| | - Iris Garcia-Martínez
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
- Banc de Sang i Teixits (BST), Barcelona, Spain
- Grup de Medicina Transfusional, Vall d'Hebron Institut de Recerca, Universitat Autònoma de Barcelona (VHIR-UAB), Barcelona, Spain
| | - Mireia Pagerols
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
| | - Laura Vilar-Ribó
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
| | - Lorena Arribas
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
| | - Vanesa Richarte
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
- Department of Psychiatry and Legal Medicine, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - Montserrat Corrales
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
- Department of Psychiatry and Legal Medicine, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - Christian Fadeuilhe
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
- Department of Psychiatry and Legal Medicine, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - Rosa Bosch
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
- Department of Psychiatry and Legal Medicine, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - Gemma Español Martin
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
- Department of Psychiatry and Legal Medicine, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Barcelona, Catalonia, Spain
| | - Peter Almos
- Division of Molecular Psychiatry, Center of Mental Health, University of Würzburg, Würzburg, Germany
| | - Alysa E Doyle
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, USA
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Eugenio Horacio Grevet
- ADHD Outpatient Program, Adult Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
- Department of Psychiatry, Faculty of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Oliver Grimm
- Department of Psychiatry, Psychosomatic Medicine, and Psychotherapy, University Hospital Frankfurt, Frankfurt am Main, Germany
| | - Anne Halmøy
- Department of Biomedicine, University of Bergen, Bergen, Norway
- Division of Psychiatry, Haukeland University Hospital, Bergen, Norway
| | - Martine Hoogman
- Department of Human Genetics, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Mara Hutz
- Department of Genetics, Institute of Biosciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Christian P Jacob
- Division of Molecular Psychiatry, Center of Mental Health, University of Würzburg, Würzburg, Germany
| | - Sarah Kittel-Schneider
- Department of Psychiatry, Psychosomatic Medicine, and Psychotherapy, University Hospital Frankfurt, Frankfurt am Main, Germany
| | - Per M Knappskog
- Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Astri J Lundervold
- Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway
| | - Olga Rivero
- Division of Molecular Psychiatry, Center of Mental Health, University of Würzburg, Würzburg, Germany
| | - Diego Luiz Rovaris
- ADHD Outpatient Program, Adult Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
- Department of Genetics, Institute of Biosciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Angelica Salatino-Oliveira
- Department of Genetics, Institute of Biosciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Bruna Santos da Silva
- ADHD Outpatient Program, Adult Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
- Department of Genetics, Institute of Biosciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Evgeniy Svirin
- Division of Molecular Psychiatry, Center of Mental Health, University of Würzburg, Würzburg, Germany
- Laboratory of Psychiatric Neurobiology, Institute of Molecular Medicine, IM Sechenov First Moscow State Medical University, Moscow, Russia
| | - Emma Sprooten
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Tatyana Strekalova
- Division of Molecular Psychiatry, Center of Mental Health, University of Würzburg, Würzburg, Germany
- Laboratory of Psychiatric Neurobiology, Institute of Molecular Medicine, IM Sechenov First Moscow State Medical University, Moscow, Russia
- Department of Neuroscience, School for Mental Health and Neuroscience (MHeNS), Maastricht University, Maastricht, The Netherlands
| | - Alejandro Arias-Vasquez
- Department of Human Genetics, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Psychiatry, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Edmund J S Sonuga-Barke
- Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London, UK
- Department of Child and Adolescent Psychiatry, Aarhus University, Aarhus, Denmark
| | - Philip Asherson
- Social Genetic and Developmental Psychiatry, Institute of Psychiatry Psychology and Neuroscience, King's College London, London, UK
| | - Claiton Henrique Dotto Bau
- ADHD Outpatient Program, Adult Division, Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil
- Department of Genetics, Institute of Biosciences, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Jan K Buitelaar
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Centre, Nijmegen, The Netherlands
- Karakter Child and Adolescent Psychiatry, Nijmegen, The Netherlands
| | - Bru Cormand
- Department of Genetics, Microbiology, and Statistics, Faculty of Biology, Universitat de Barcelona, Barcelona, Spain
- Institut de Biomedicina de la Universitat de Barcelona (IBUB), Barcelona, Catalonia, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Barcelona, Spain
- Institut de Recerca Sant Joan de Déu (IRSJD), Esplugues de Llobregat, Catalonia, Spain
| | - Stephen V Faraone
- Departments of Psychiatry, of Neuroscience, and Physiology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Jan Haavik
- Department of Biomedicine, University of Bergen, Bergen, Norway
- Division of Psychiatry, Haukeland University Hospital, Bergen, Norway
| | - Stefan E Johansson
- Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Norway
- Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Jonna Kuntsi
- Social Genetic and Developmental Psychiatry, Institute of Psychiatry Psychology and Neuroscience, King's College London, London, UK
| | - Henrik Larsson
- School of medical Sciences, Örebro University, Örebro, Sweden
- Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
| | - Klaus-Peter Lesch
- Division of Molecular Psychiatry, Center of Mental Health, University of Würzburg, Würzburg, Germany
- Laboratory of Psychiatric Neurobiology, Institute of Molecular Medicine, IM Sechenov First Moscow State Medical University, Moscow, Russia
- Department of Neuroscience, School for Mental Health and Neuroscience (MHeNS), Maastricht University, Maastricht, The Netherlands
| | - Andreas Reif
- Department of Psychiatry, Psychosomatic Medicine, and Psychotherapy, University Hospital Frankfurt, Frankfurt am Main, Germany
| | - Luis Augusto Rohde
- Division of Child Psychiatry, Hospital de Clinicas de Porto Alegre, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
| | - Miquel Casas
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
- Department of Psychiatry and Legal Medicine, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - Anders D Børglum
- Department of Biomedicine (Human Genetics), and Centre for Integrative Sequencing, iSEQ, Aarhus University, Aarhus, Denmark
- The Lundbeck Foundation Initiative for Integrative Psychiatric Research, iPSYCH, Aarhus, Denmark
- Center for Genomics and Personalized Medicine, Aarhus, Denmark
| | - Barbara Franke
- Department of Human Genetics, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Psychiatry, Donders Institute for Brain, Cognition, and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Josep Antoni Ramos-Quiroga
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain
- Biomedical Network Research Centre on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain
- Department of Psychiatry and Legal Medicine, Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain
| | - María Soler Artigas
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain.
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain.
- Biomedical Network Research Centre on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain.
- Department of Genetics, Microbiology, and Statistics, Faculty of Biology, Universitat de Barcelona, Barcelona, Spain.
| | - Marta Ribasés
- Psychiatric Genetics Unit, Group of Psychiatry, Mental Health, and Addiction, Vall d'Hebron Research Institute (VHIR), Universitat Autònoma de Barcelona, Barcelona, Catalonia, Spain.
- Department of Psychiatry, Hospital Universitari Vall d'Hebron, Barcelona, Catalonia, Spain.
- Biomedical Network Research Centre on Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain.
- Department of Genetics, Microbiology, and Statistics, Faculty of Biology, Universitat de Barcelona, Barcelona, Spain.
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9
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Urae S, Harita Y, Udagawa T, Ode KL, Nagahama M, Kajiho Y, Kanda S, Saito A, Ueda HR, Nangaku M, Oka A. A cellular model of albumin endocytosis uncovers a link between membrane and nuclear proteins. J Cell Sci 2020; 133:jcs242859. [PMID: 32482797 DOI: 10.1242/jcs.242859] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 05/20/2020] [Indexed: 12/21/2022] Open
Abstract
Cubilin (CUBN) and amnionless (AMN), expressed in kidney and intestine, form a multiligand receptor complex called CUBAM that plays a crucial role in albumin absorption. To date, the mechanism of albumin endocytosis mediated by CUBAM remains to be elucidated. Here, we describe a quantitative assay to evaluate albumin uptake by CUBAM using cells expressing full-length CUBN and elucidate the crucial roles of the C-terminal part of CUBN and the endocytosis signal motifs of AMN in albumin endocytosis. We also demonstrate that nuclear valosin-containing protein-like 2 (NVL2), an interacting protein of AMN, is involved in this process. Although NVL2 was mainly localized in the nucleolus in cells without AMN expression, it was translocated to the extranuclear compartment when coexpressed with AMN. NVL2 knockdown significantly impaired internalization of the CUBN-albumin complex in cultured cells, demonstrating an involvement of NVL2 in endocytic regulation. These findings uncover a link between membrane and nucleolar proteins that is involved in endocytic processes.
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Affiliation(s)
- Seiya Urae
- Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan
- Division of Nephrology and Endocrinology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Yutaka Harita
- Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Tomohiro Udagawa
- Department of Pediatrics and Developmental Biology, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Koji L Ode
- Department of Systems Pharmacology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Masami Nagahama
- Laboratory of Molecular and Cellular Biochemistry, Meiji Pharmaceutical University, Kiyose-shi, Tokyo 204-8588, Japan
| | - Yuko Kajiho
- Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Shoichiro Kanda
- Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Akihiko Saito
- Department of Applied Molecular Medicine, Niigata University Graduate School of Medical and Dental Sciences, Niigata-shi, Niigata 951-8510, Japan
| | - Hiroki R Ueda
- Department of Systems Pharmacology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-8654, Japan
- Laboratory for Synthetic Biology, RIKEN Center for Biosystems Dynamics Research, Wako-shi, Saitama 351-0198, Japan
| | - Masaomi Nangaku
- Division of Nephrology and Endocrinology, The University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan
| | - Akira Oka
- Department of Pediatrics, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo 113-8655, Japan
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10
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Gurlek Gokcebay D, Akpinar Tekgunduz S, Cavdarli B. Imerslund-Gräsbeck Syndrome presenting with microangiopathic hemolytic anemia in a child. Eur J Med Genet 2020; 63:103880. [PMID: 32045704 DOI: 10.1016/j.ejmg.2020.103880] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2019] [Revised: 02/03/2020] [Accepted: 02/07/2020] [Indexed: 11/24/2022]
Abstract
Imerslund-Gräsbeck Syndrome is a rare autosomal recessive disorder characterized by proteinuria and selective malabsorption of cobalamin. Deficiency of cobalamin can lead to megaloblastic anemia, pancytopenia and even "pseudo"-thrombotic microangiopathy (TMA). Signs of mechanical hemolysis on peripheral blood smear, elevated lactate dehydrogenase and thrombocytopenia are common findings of TMA. We report a child presenting with TMA features with cobalamin deficiency. Because of her family history of vitamin B12 deficiency and proteinuria, the performed genetic analysis revealed that an Imerslund-Gräsbeck Syndrome with the detection of a homozygous mutation in AMN gene.
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Affiliation(s)
- Dilek Gurlek Gokcebay
- University of Health Sciences Kecioren Training and Research Hospital, Department of Pediatric Hematology, Turkey.
| | - Sibel Akpinar Tekgunduz
- University of Health Sciences Kecioren Training and Research Hospital, Department of Pediatric Hematology, Turkey
| | - Busranur Cavdarli
- University of Health Sciences Ankara Numune Training and Research Hospital, Department of Medical Genetics, Turkey
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11
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Brito A, Habeych E, Silva-Zolezzi I, Galaffu N, Allen LH. Methods to assess vitamin B12 bioavailability and technologies to enhance its absorption. Nutr Rev 2019; 76:778-792. [PMID: 29931214 DOI: 10.1093/nutrit/nuy026] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Vitamin B12 (B-12) deficiency is still relatively common in low-, medium-, and high-income countries, mainly because of dietary inadequacy and, to a lesser extent, malabsorption. This narrative review is based on a systematic search of evidence on methods to assess B-12 bioavailability and technologies to enhance its absorption. A total of 2523 scientific articles identified in PubMed and 1572 patents identified in Orbit Intelligence were prescreened. Among the reviewed methods, Schilling's test and/or its food-based version (using cobalamin-labeled egg yolk) were used for decades but have been discontinued, largely because they required radioactive cobalt. The qualitative CobaSorb test, based on changes in circulating holo-transcobalamin before and after B-12 administration, and the 14C-labeled B-12 test for quantitative measurement of absorption of a low-dose radioactive tracer are currently the best available methods. Various forms of B-12 co-formulated with chemical enhancers (ie, salcaprozate sodium, 8-amino caprylate) or supplied via biotechnological methods (ie, microbiological techniques, plant cells expressing cobalamin binding proteins), encapsulation techniques (ie, emulsions, use of chitosan particles), and alternative routes of administration (ie, intranasal, transdermal administration) were identified as potential technologies to enhance B-12 absorption in humans. However, in most cases the evidence of absorption enhancement is limited.
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Affiliation(s)
- Alex Brito
- I.M. Sechenov First Moscow State Medical University, Moscow, Russia
| | | | | | | | - Lindsay H Allen
- United States Department of Agriculture, Agricultural Research Service, Western Human Nutrition Research Center, Davis, California, USA
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12
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Podzolkov VI, Dragomiretskaya NA, Dambaeva OT, Auvinen ST, Medvedev ID. Hypervitaminosis B12 - a new marker and predictor of prognostically unfavorable diseases. TERAPEVT ARKH 2019; 91:160-167. [DOI: 10.26442/00403660.2019.08.000378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Indexed: 11/22/2022]
Abstract
A high serum vitamin B12 level (hypercobalaminemia) is a underestimated anomaly. Clinically, it can be paradoxically accompanied by signs of deficiency, which are related to defects in tissue uptake of vitamin B12. The increase in the level of serum cobalamin occurs mainly in serious diseases that require early diagnosis: hemoblastosis, liver and kidney diseases, etc. This review presents data on the metabolism of vitamin B12 and the potential significance of increasing its level as a marker for the early diagnosis of these diseases.
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13
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Froese DS, Fowler B, Baumgartner MR. Vitamin B 12 , folate, and the methionine remethylation cycle-biochemistry, pathways, and regulation. J Inherit Metab Dis 2019; 42:673-685. [PMID: 30693532 DOI: 10.1002/jimd.12009] [Citation(s) in RCA: 179] [Impact Index Per Article: 35.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Revised: 09/27/2018] [Accepted: 10/19/2018] [Indexed: 12/16/2022]
Abstract
Vitamin B12 (cobalamin, Cbl) is a nutrient essential to human health. Due to its complex structure and dual cofactor forms, Cbl undergoes a complicated series of absorptive and processing steps before serving as cofactor for the enzymes methylmalonyl-CoA mutase and methionine synthase. Methylmalonyl-CoA mutase is required for the catabolism of certain (branched-chain) amino acids into an anaplerotic substrate in the mitochondrion, and dysfunction of the enzyme itself or in production of its cofactor adenosyl-Cbl result in an inability to successfully undergo protein catabolism with concomitant mitochondrial energy disruption. Methionine synthase catalyzes the methyl-Cbl dependent (re)methylation of homocysteine to methionine within the methionine cycle; a reaction required to produce this essential amino acid and generate S-adenosylmethionine, the most important cellular methyl-donor. Disruption of methionine synthase has wide-ranging implications for all methylation-dependent reactions, including epigenetic modification, but also for the intracellular folate pathway, since methionine synthase uses 5-methyltetrahydrofolate as a one-carbon donor. Folate-bound one-carbon units are also required for deoxythymidine monophosphate and de novo purine synthesis; therefore, the flow of single carbon units to each of these pathways must be regulated based on cellular needs. This review provides an overview on Cbl metabolism with a brief description of absorption and intracellular metabolic pathways. It also provides a description of folate-mediated one-carbon metabolism and its intersection with Cbl at the methionine cycle. Finally, a summary of recent advances in understanding of how both pathways are regulated is presented.
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Affiliation(s)
- D Sean Froese
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | - Brian Fowler
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
| | - Matthias R Baumgartner
- Division of Metabolism and Children's Research Center, University Children's Hospital, Zurich, Switzerland
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14
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Pacitto A, Prontera P, Stangoni G, Stefanelli M, Ceppi S, Cerri C, Gurdo G, Mencarelli A, Esposito S. Imerslund-Gräsbeck Syndrome in an Infant with a Novel Intronic Variant in the AMN Gene: A Case Report. Int J Mol Sci 2019; 20:ijms20030527. [PMID: 30691194 PMCID: PMC6387074 DOI: 10.3390/ijms20030527] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 01/09/2019] [Accepted: 01/15/2019] [Indexed: 11/25/2022] Open
Abstract
Imerslund-Gräsbeck syndrome (IGS) is a rare autosomal recessive disorder clinically characterized by megaloblastic anemia, benign mild proteinuria, and other nonspecific symptoms. Several pathogenetic variants in the amnionless (AMN) or cubilin (CUBN) genes have been described in IGS. We describe a case of IGS with urinary tract infection and mild but persistent proteinuria at onset in an 11-month-old female child. With the appearance of macrocytic anemia, aphthous stomatitis, and neurological signs, IGS was clinically suspected, and vitamin B12 parenteral therapy was started. Sequence analysis showed the presence of a novel intronic variant c.513+5G>A of AMN, never before described in the literature, that was in compound heterozygosity with the known pathogenetic variant c.1006+34_1007-31del. Analysis extension to the parents revealed the presence of variant c.1006+34_1007-31 in the father and c.513+5G>A in the mother. In the present case with IGS, the novel intronic variant of AMN was identified in “trans” with a known pathogenic variant (c.1006-31 del) and the new variant was interpreted to be pathogenetic since it was not found in the public database of polymorphisms and because it was predicted to alter a donor splicing site. Our case underlines the relevance in detecting certain subtle symptoms, such as mild but persistent proteinuria associated with megaloblastic anemia, to reach a correct diagnosis of a rare but treatable disorder.
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Affiliation(s)
- Alessandra Pacitto
- Pediatric Clinic, Department of Surgical and Biomedical Sciences, Università degli Studi di Perugia, Piazza Menghini 1, 06129 Perugia, Italy.
| | - Paolo Prontera
- Medical Genetics Unit, Santa Maria della Misericordia Hospital, Piazza Menghini 1, 06129 Perugia, Italy.
| | - Gabriela Stangoni
- Medical Genetics Unit, Santa Maria della Misericordia Hospital, Piazza Menghini 1, 06129 Perugia, Italy.
| | - Maurizio Stefanelli
- Pediatric Clinic, Department of Surgical and Biomedical Sciences, Università degli Studi di Perugia, Piazza Menghini 1, 06129 Perugia, Italy.
| | - Stefania Ceppi
- Pediatric Clinic, Department of Surgical and Biomedical Sciences, Università degli Studi di Perugia, Piazza Menghini 1, 06129 Perugia, Italy.
| | - Carla Cerri
- Pediatric Oncohematology Unit, Santa Maria della Misericordia Hospital, Piazza Menghini 1, 06129 Perugia, Italy.
| | - Grazia Gurdo
- Pediatric Oncohematology Unit, Santa Maria della Misericordia Hospital, Piazza Menghini 1, 06129 Perugia, Italy.
| | - Annalisa Mencarelli
- Pediatric Clinic, Department of Surgical and Biomedical Sciences, Università degli Studi di Perugia, Piazza Menghini 1, 06129 Perugia, Italy.
| | - Susanna Esposito
- Pediatric Clinic, Department of Surgical and Biomedical Sciences, Università degli Studi di Perugia, Piazza Menghini 1, 06129 Perugia, Italy.
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15
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Fyfe JC, Hemker SL, Frampton A, Raj K, Nagy PL, Gibbon KJ, Giger U. Inherited selective cobalamin malabsorption in Komondor dogs associated with a CUBN splice site variant. BMC Vet Res 2018; 14:418. [PMID: 30591068 PMCID: PMC6309081 DOI: 10.1186/s12917-018-1752-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Accepted: 12/19/2018] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Three Komondor dogs in a small family and 3 sporadic cases exhibited a constellation of signs that included juvenile-onset of failure-to-thrive, inappetence, vomiting and/or diarrhea, and weakness. In each we documented dyshematopoiesis, increased anion gap, methylmalonic acidemia/-uria, and serum cobalamin deficiency. Urine protein electrophoresis demonstrated excretion of cubam ligands. All clinical signs and metabolic abnormalities, except proteinuria, were reversed by regular parenteral cobalamin administration. The pattern of occurrence and findings in the disorder suggested an autosomal recessive inheritance of cobalamin malabsorption with proteinuria, a condition in humans called Imerslund-Gräsbeck syndrome. The purpose of this study was to determine the molecular cause of this disorder in Komondors. RESULTS Whole genome sequencing of two affected Komondor dogs of unknown relatedness and one parent and a clinically-normal littermate of an affected dog revealed a pathogenic single-base change in the CUBN intron 55 splice donor consensus sequence (NM_001003148.1: c.8746 + 1G > A) that was homozygous in affected dogs and heterozygous in the unaffected parents. Alleles of the variant co-segregated with alleles of the disease locus in the entire family and all more distantly-related sporadic cases. A population study using a simple allele-specific DNA test indicated mutant allele frequencies of 8.3 and 4.5% among North American and Hungarian Komondors, respectively. CONCLUSIONS DNA testing can be used diagnostically in Komondors when clinical signs are suggestive of cobalamin deficiency or to inform Komondor breeders prospectively and prevent occurrence of future affected dogs. This represents the third cubilin variant causing inherited selective cobalamin malabsorption in a large animal ortholog of human Imerslund-Gräsbeck syndrome.
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Affiliation(s)
- John C. Fyfe
- Laboratory of Comparative Medical Genetics, Michigan State University, 567 Wilson Road, East Lansing, MI 48824 USA
- Department of Microbiology & Molecular Genetics, Michigan State University, 567 Wilson Road, East Lansing, MI 48824 USA
| | - Shelby L. Hemker
- Laboratory of Comparative Medical Genetics, Michigan State University, 567 Wilson Road, East Lansing, MI 48824 USA
- Present address: Department of Pediatrics, Division of Nephrology, UPMC Children’s Hospital of Pittsburgh, University of Pittsburgh, 4401 Penn Ave, Pittsburgh, PA 15224 USA
| | - Alycia Frampton
- Section of Medical Genetics, University of Pennsylvania, 3900 Delancey Street, Philadelphia, PA 19104-6010 USA
| | - Karthik Raj
- Section of Medical Genetics, University of Pennsylvania, 3900 Delancey Street, Philadelphia, PA 19104-6010 USA
| | - Peter L. Nagy
- Laboratory of Personalized Genomic Medicine, Department of Pathology & Cell Biology, Columbia University - College of Physicians & Surgeons, 630 West 168th Street, New York, NY 10032 USA
- Present address: MNG Laboratories™, 5424 Glenridge Drive NE, Atlanta, GA 30342 USA
| | - Kristi J. Gibbon
- Oregon Veterinary Referral Associates, 444 B Street, Springfield, OR 97477 USA
- Cottonwood Heights, USA
| | - Urs Giger
- Section of Medical Genetics, University of Pennsylvania, 3900 Delancey Street, Philadelphia, PA 19104-6010 USA
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16
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Structural assembly of the megadalton-sized receptor for intestinal vitamin B 12 uptake and kidney protein reabsorption. Nat Commun 2018; 9:5204. [PMID: 30523278 PMCID: PMC6283879 DOI: 10.1038/s41467-018-07468-4] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Accepted: 11/01/2018] [Indexed: 11/08/2022] Open
Abstract
The endocytic receptor cubam formed by the 460-kDa protein cubilin and the 45-kDa transmembrane protein amnionless (AMN), is essential for intestinal vitamin B12 (B12) uptake and for protein (e.g. albumin) reabsorption from the kidney filtrate. Loss of function of any of the two components ultimately leads to serious B12 deficiency and urinary protein loss in humans (Imerslund-Gräsbeck’s syndrome, IGS). Here, we present the crystal structure of AMN in complex with the amino-terminal region of cubilin, revealing a sophisticated assembly of three cubilin subunits combining into a single intertwined β-helix domain that docks to a corresponding three-faced β-helix domain in AMN. This β-helix-β-helix association thereby anchors three ligand-binding cubilin subunits to the transmembrane AMN. Electron microscopy of full-length cubam reveals a 700–800 Å long tree-like structure with the potential of dimerization into an even larger complex. Furthermore, effects of known human mutations causing IGS are explained by the structural information. Cubilin and the transmembrane protein amnionless (AMN) form the endocytic receptor cubam that is essential for intestinal vitamin B12 uptake. Here the authors present the 2.3 Å crystal structure of AMN in complex with the amino-terminal region of cubilin and discuss cubam architecture and disease causing mutations.
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17
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Kozyraki R, Cases O. Cubilin, the Intrinsic Factor-Vitamin B12 Receptor in Development and Disease. Curr Med Chem 2018; 27:3123-3150. [PMID: 30295181 DOI: 10.2174/0929867325666181008143945] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 08/11/2018] [Accepted: 08/21/2018] [Indexed: 12/29/2022]
Abstract
Gp280/Intrinsic factor-vitamin B12 receptor/Cubilin (CUBN) is a large endocytic receptor serving multiple functions in vitamin B12 homeostasis, renal reabsorption of protein or toxic substances including albumin, vitamin D-binding protein or cadmium. Cubilin is a peripheral membrane protein consisting of 8 Epidermal Growth Factor (EGF)-like repeats and 27 CUB (defined as Complement C1r/C1s, Uegf, BMP1) domains. This structurally unique protein interacts with at least two molecular partners, Amnionless (AMN) and Lrp2/Megalin. AMN is involved in appropriate plasma membrane transport of Cubilin whereas Lrp2 is essential for efficient internalization of Cubilin and its ligands. Observations gleaned from animal models with Cubn deficiency or human diseases demonstrate the importance of this protein. In this review addressed to basic research and medical scientists, we summarize currently available data on Cubilin and its implication in renal and intestinal biology. We also discuss the role of Cubilin as a modulator of Fgf8 signaling during embryonic development and propose that the Cubilin-Fgf8 interaction may be relevant in human pathology, including in cancer progression, heart or neural tube defects. We finally provide experimental elements suggesting that some aspects of Cubilin physiology might be relevant in drug design.
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Affiliation(s)
- Renata Kozyraki
- INSERM UMRS 1138, Centre de Recherche des Cordeliers, Paris-Diderot University, Paris, France
| | - Olivier Cases
- INSERM UMRS 1138, Centre de Recherche des Cordeliers, Paris-Diderot University, Paris, France
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18
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Amnionless-mediated glycosylation is crucial for cell surface targeting of cubilin in renal and intestinal cells. Sci Rep 2018; 8:2351. [PMID: 29402915 PMCID: PMC5799345 DOI: 10.1038/s41598-018-20731-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 01/23/2018] [Indexed: 11/10/2022] Open
Abstract
Mutations in either cubilin (CUBN) or amnionless (AMN) genes cause Imerslund–Gräsbeck syndrome (IGS), a hereditary disease characterised by anaemia attributed to selective intestinal malabsorption of cobalamin and low-molecular weight proteinuria. Although cubilin protein does not have a transmembrane segment, it functions as a multi-ligand receptor by binding to the transmembrane protein, amnionless. We established a system to quantitatively analyse membrane targeting of the protein complex in cultured renal and intestinal cells and analysed the pathogenic mechanisms of mutations found in IGS patients. A novel CUBN mutation, several previously reported CUBN missense mutations and all previously reported AMN missense mutations resulted in endoplasmic reticulum (ER) retention and completely inhibited amnionless-dependent plasma membrane expression of cubilin. The ER retention of cubilin and amnionless was confirmed in renal proximal tubular cells of a patient with IGS. Notably, the interaction between cubilin and amnionless was not sufficient, but amnionless-mediated glycosylation of cubilin was necessary for their surface expression. Quantitative mass spectrometry and mutagenesis demonstrated that N-linked glycosylation of at least 4 residues of cubilin protein was required for its surface targeting. These results delineated the molecular mechanisms of membrane trafficking of cubilin in renal and intestinal cells.
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Pannérec A, Migliavacca E, De Castro A, Michaud J, Karaz S, Goulet L, Rezzi S, Ng TP, Bosco N, Larbi A, Feige JN. Vitamin B12 deficiency and impaired expression of amnionless during aging. J Cachexia Sarcopenia Muscle 2018; 9:41-52. [PMID: 29159972 PMCID: PMC5803611 DOI: 10.1002/jcsm.12260] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 09/01/2017] [Accepted: 10/02/2017] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Physical frailty and loss of mobility in elderly individuals lead to reduced independence, quality of life, and increased mortality. Vitamin B12 deficiency has been linked to several age-related chronic diseases, including in the musculo-skeletal system, where vitamin B12 deficiency is generally believed to be linked to poor nutritional intake. In the present study, we asked whether aging and frailty associate with altered vitamin B12 homeostasis in humans and investigated the underlying molecular mechanisms using preclinical models. METHODS We analysed a subset of the Singapore Longitudinal Aging Study and stratified 238 participants based on age and Fried frailty criteria. Levels of methyl-malonic acid (MMA), a marker for vitamin B12 deficiency, and amnionless, the vitamin B12 co-receptor that anchors the vitamin B12 transport complex to the membrane of epithelial cells, were measured in plasma. In addition, vitamin B12 levels and the molecular mechanisms of vitamin B12 uptake and excretion were analysed in ileum, kidney, liver, and blood using a rat model of natural aging where nutritional intake is fully controlled. RESULTS We demonstrate that aging and frailty are associated with a higher prevalence of functional vitamin B12 deficiency that can be detected by increased levels of MMA in blood (ρ = 0.25; P = 0.00013). The decline in circulating vitamin B12 levels is recapitulated in a rat model of natural aging where food composition and intake are stable. At the molecular level, these perturbations involve altered expression of amnionless in the ileum and kidney. Interestingly, we demonstrate that amnionless can be detected in serum where its levels increase during aging in both rodents and human (P = 3.3e-07 and 9.2e-07, respectively). Blood amnionless levels negatively correlate with vitamin B12 in rats (r2 = 0.305; P = 0.0042) and positively correlate with the vitamin B12 deficiency marker MMA in humans (ρ = 0.22; P = 0.00068). CONCLUSIONS Our results demonstrate that aging and frailty cause intrinsic vitamin B12 deficiencies, which can occur independently of nutritional intake. Mechanistically, vitamin B12 deficiency involves the physio-pathological decline of both the intestinal uptake and the renal reabsorption system for vitamin B12. Finally, amnionless is a novel biomarker which can detect perturbed vitamin B12 bioavailability during aging and physical frailty.
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Affiliation(s)
- Alice Pannérec
- Nestlé Institute of Health Sciences, EPFL Innovation Park, Building H, 1015, Lausanne, Switzerland
| | - Eugenia Migliavacca
- Nestlé Institute of Health Sciences, EPFL Innovation Park, Building H, 1015, Lausanne, Switzerland
| | | | - Joris Michaud
- Nestlé Institute of Health Sciences, EPFL Innovation Park, Building H, 1015, Lausanne, Switzerland
| | - Sonia Karaz
- Nestlé Institute of Health Sciences, EPFL Innovation Park, Building H, 1015, Lausanne, Switzerland
| | - Laurence Goulet
- Nestlé Institute of Health Sciences, EPFL Innovation Park, Building H, 1015, Lausanne, Switzerland
| | - Serge Rezzi
- Nestlé Institute of Health Sciences, EPFL Innovation Park, Building H, 1015, Lausanne, Switzerland
| | - Tze Pin Ng
- Gerontology Research Programme, Department of Psychological Medicine, Young Loo Lin School of Medicine, National University of Singapore, Singapore.,Geriatric Education and Research Institute, Ministry of Health, Singapore
| | | | - Anis Larbi
- Singapore Immunology Network, Biopolis, Agency for Science, Technology and Research, Singapore
| | - Jerome N Feige
- Nestlé Institute of Health Sciences, EPFL Innovation Park, Building H, 1015, Lausanne, Switzerland
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20
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Green R, Allen LH, Bjørke-Monsen AL, Brito A, Guéant JL, Miller JW, Molloy AM, Nexo E, Stabler S, Toh BH, Ueland PM, Yajnik C. Vitamin B 12 deficiency. Nat Rev Dis Primers 2017; 3:17040. [PMID: 28660890 DOI: 10.1038/nrdp.2017.40] [Citation(s) in RCA: 434] [Impact Index Per Article: 62.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Vitamin B12 (B12; also known as cobalamin) is a B vitamin that has an important role in cellular metabolism, especially in DNA synthesis, methylation and mitochondrial metabolism. Clinical B12 deficiency with classic haematological and neurological manifestations is relatively uncommon. However, subclinical deficiency affects between 2.5% and 26% of the general population depending on the definition used, although the clinical relevance is unclear. B12 deficiency can affect individuals at all ages, but most particularly elderly individuals. Infants, children, adolescents and women of reproductive age are also at high risk of deficiency in populations where dietary intake of B12-containing animal-derived foods is restricted. Deficiency is caused by either inadequate intake, inadequate bioavailability or malabsorption. Disruption of B12 transport in the blood, or impaired cellular uptake or metabolism causes an intracellular deficiency. Diagnostic biomarkers for B12 status include decreased levels of circulating total B12 and transcobalamin-bound B12, and abnormally increased levels of homocysteine and methylmalonic acid. However, the exact cut-offs to classify clinical and subclinical deficiency remain debated. Management depends on B12 supplementation, either via high-dose oral routes or via parenteral administration. This Primer describes the current knowledge surrounding B12 deficiency, and highlights improvements in diagnostic methods as well as shifting concepts about the prevalence, causes and manifestations of B12 deficiency.
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Affiliation(s)
- Ralph Green
- Department of Pathology and Laboratory Medicine, University of California Davis, 4400 V Street, PATH Building, Davis, California 95817, USA
| | - Lindsay H Allen
- USDA, ARS Western Human Nutrition Research Center, University of California Davis, Davis, California, USA
| | | | - Alex Brito
- USDA, ARS Western Human Nutrition Research Center, University of California Davis, Davis, California, USA
| | - Jean-Louis Guéant
- Inserm UMRS 954 N-GERE (Nutrition Génétique et Exposition aux Risques Environnementaux), University of Lorraine and INSERM, Nancy, France
| | - Joshua W Miller
- School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey, USA
| | - Anne M Molloy
- School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, University of Dublin, Dublin, Ireland
| | - Ebba Nexo
- Department of Clinical Medicine, Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
| | - Sally Stabler
- Department of Medicine, University of Colorado Denver, Denver, Colorado, USA
| | - Ban-Hock Toh
- Centre for Inflammatory Diseases, Monash Institute of Medical Research, Clayton, Victoria, Australia
| | - Per Magne Ueland
- Laboratory of Clinical Biochemistry, Haukeland University Hospital, Bergen, Norway.,Section for Pharmacology, Department of Clinical Science, University of Bergen, Bergen, Norway
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21
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Nielsen R, Christensen EI, Birn H. Megalin and cubilin in proximal tubule protein reabsorption: from experimental models to human disease. Kidney Int 2017; 89:58-67. [PMID: 26759048 DOI: 10.1016/j.kint.2015.11.007] [Citation(s) in RCA: 298] [Impact Index Per Article: 42.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 08/17/2015] [Accepted: 08/19/2015] [Indexed: 01/19/2023]
Abstract
Proximal tubule protein uptake is mediated by 2 receptors, megalin and cubilin. These receptors rescue a variety of filtered ligands, including biomarkers, essential vitamins, and hormones. Receptor gene knockout animal models have identified important functions of the receptors and have established their essential role in modulating urinary protein excretion. Rare genetic syndromes associated with dysfunction of these receptors have been identified and characterized, providing additional information on the importance of these receptors in humans. Using various disease models in combination with receptor gene knockout, the implications of receptor dysfunction in acute and chronic kidney injury have been explored and have pointed to potential new roles of these receptors. Based on data from animal models, this paper will review current knowledge on proximal tubule endocytic receptor function and regulation, and their role in renal development, protein reabsorption, albumin uptake, and normal renal physiology. These findings have implications for the pathophysiology and diagnosis of proteinuric renal diseases. We will examine the limitations of the different models and compare the findings to phenotypic observations in inherited human disorders associated with receptor dysfunction. Furthermore, evidence from receptor knockout mouse models as well as human observations suggesting a role of protein receptors for renal disease will be discussed in light of conditions such as chronic kidney disease, diabetes, and hypertension.
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Affiliation(s)
- Rikke Nielsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | | - Henrik Birn
- Department of Biomedicine, Aarhus University, Aarhus, Denmark; Department of Renal Medicine, Aarhus University Hospital, Aarhus, Denmark.
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22
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Helmstädter M, Huber TB, Hermle T. Using the Drosophila Nephrocyte to Model Podocyte Function and Disease. Front Pediatr 2017; 5:262. [PMID: 29270398 PMCID: PMC5725439 DOI: 10.3389/fped.2017.00262] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 11/24/2017] [Indexed: 12/19/2022] Open
Abstract
Glomerular disorders are a major cause of end-stage renal disease and effective therapies are often lacking. Nephrocytes are considered to be part of the Drosophila excretory system and form slit diaphragms across cellular membrane invaginations. Nehphrocytes have been shown to share functional, morphological, and molecular features with podocytes, which form the glomerular filter in vertebrates. Here, we report the progress and the evolving tool-set of this model system. Combining a functional, accessible slit diaphragm with the power of the genetic tool-kit in Drosophila, the nephrocyte has the potential to greatly advance our understanding of the glomerular filtration barrier in health and disease.
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Affiliation(s)
- Martin Helmstädter
- Renal Division, University Medical Center Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Tobias B Huber
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tobias Hermle
- Renal Division, University Medical Center Freiburg, Freiburg, Germany.,Faculty of Medicine, University of Freiburg, Freiburg, Germany
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23
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Buers I, Pennekamp P, Nitschke Y, Lowe C, Skryabin BV, Rutsch F. Lmbrd1 expression is essential for the initiation of gastrulation. J Cell Mol Med 2016; 20:1523-33. [PMID: 27061115 PMCID: PMC4956942 DOI: 10.1111/jcmm.12844] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 02/24/2016] [Indexed: 01/06/2023] Open
Abstract
The rare inborn cblF defect of cobalamin metabolism is caused by mutations in the limb region 1 (LMBR1) domain containing 1 gene (LMBRD1). This defect is characterized by massive accumulation of free cobalamin in lysosomes and loss of mitochondrial succinyl‐CoA synthesis and cytosolic methionine synthesis. Affected children suffer from heart defects, developmental delay and megaloblastic anemia. LMBRD1 encodes for LMBD1, a predicted lysosomal cobalamin transport protein. In this study, we determine the physiological function of LMBRD1 during embryogenesis by generating Lmbrd1 deficient mice using the Cre/LoxP system. Complete loss of Lmbrd1 function is accompanied by early embryonic death in mice. Whole mount in situ hybridization studies against bone morphogenetic protein 4 and Nodal show that initial formation of the proximal–distal axis is unaffected in early embryonic stages whereas the initiation of gastrulation is disturbed shown by the expression pattern of even skipped homeotic gene 1 and fibroblast growth factor 8 in Lmbrd1 deficient mice. We conclude that intact function of LMBD1 is essential for the initiation of gastrulation.
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Affiliation(s)
- Insa Buers
- Department of General Pediatrics, Müenster University Children's Hospital, Müenster, Germany
| | - Petra Pennekamp
- Department of General Pediatrics, Müenster University Children's Hospital, Müenster, Germany
| | - Yvonne Nitschke
- Department of General Pediatrics, Müenster University Children's Hospital, Müenster, Germany
| | - Chrishanthi Lowe
- Department of General Pediatrics, Müenster University Children's Hospital, Müenster, Germany
| | - Boris V Skryabin
- Institute of Experimental Pathology, Müenster University, Müenster, Germany.,Department of Medicine (TRAM), University Hospital of Müenster, Münster, Germany
| | - Frank Rutsch
- Department of General Pediatrics, Müenster University Children's Hospital, Müenster, Germany
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24
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Montgomery E, Sayer JA, Baines LA, Hynes AM, Vega-Warner V, Johnson S, Goodship JA, Otto EA. Novel compound heterozygous mutations in AMN cause Imerslund-Gräsbeck syndrome in two half-sisters: a case report. BMC MEDICAL GENETICS 2015; 16:35. [PMID: 26040326 PMCID: PMC4630879 DOI: 10.1186/s12881-015-0181-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 05/29/2015] [Indexed: 11/25/2022]
Abstract
Background Imerslund-Gräsbeck Syndrome (IGS) is a rare autosomal recessive disease characterized by intestinal vitamin B12 malabsorption. Clinical features include megaloblastic anemia, recurrent infections, failure to thrive, and proteinuria. Recessive mutations in cubilin (CUBN) and in amnionless (AMN) have been shown to cause IGS. To date, there are only about 300 cases described worldwide with only 37 different mutations found in CUBN and 30 different in the AMN gene. Case presentation We collected pedigree structure, clinical data, and DNA samples from 2 Caucasian English half-sisters with IGS. Molecular diagnostics was performed by direct Sanger sequencing of all 62 exons of the CUBN gene and 12 exons of the AMN gene. Because of lack of parental DNA, cloning, and sequencing of multiple plasmid clones was performed to assess the allele of identified mutations. Genetic characterization revealed 2 novel compound heterozygous AMN mutations in both half-sisters with IGS. Trans-configuration of the mutations was confirmed. Conclusion We have identified novel compound heterozygous mutations in AMN in a family from the United Kingdom with clinical features of Imerslund-Gräsbeck Syndrome.
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Affiliation(s)
- Emma Montgomery
- Renal Services Centre, Freeman Hospital, Newcastle upon Tyne NHS Hospitals Foundation Trust Newcastle upon Tyne, Newcastle upon Tyne, NE7 7DN, UK.
| | - John A Sayer
- Renal Services Centre, Freeman Hospital, Newcastle upon Tyne NHS Hospitals Foundation Trust Newcastle upon Tyne, Newcastle upon Tyne, NE7 7DN, UK. .,Institute of Genetic Medicine, Centre for Life, Newcastle Upon Tyne, UK.
| | - Laura A Baines
- Renal Services Centre, Freeman Hospital, Newcastle upon Tyne NHS Hospitals Foundation Trust Newcastle upon Tyne, Newcastle upon Tyne, NE7 7DN, UK.
| | - Ann Marie Hynes
- Institute of Genetic Medicine, Centre for Life, Newcastle Upon Tyne, UK.
| | | | - Sally Johnson
- Paediatric Nephrology, Royal Victoria Infirmary, Newcastle upon Tyne NHS Hospitals Foundation Trust, Newcastle upon Tyne, N1 4LP, UK.
| | - Judith A Goodship
- Institute of Genetic Medicine, Centre for Life, Newcastle Upon Tyne, UK.
| | - Edgar A Otto
- Department of Pediatrics, University of Michigan, Ann Arbor, MI, USA.
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25
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Vázquez-Carretero MD, Palomo M, García-Miranda P, Sánchez-Aguayo I, Peral MJ, Calonge ML, Ilundain AA. Dab2, megalin, cubilin and amnionless receptor complex might mediate intestinal endocytosis in the suckling rat. J Cell Biochem 2014; 115:510-22. [PMID: 24122887 DOI: 10.1002/jcb.24685] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 09/26/2013] [Indexed: 01/12/2023]
Abstract
We previously proposed that Dab2 participates in the endocytosis of milk macromolecules in rat small intestine. Here we investigate the receptors that may mediate this endocytosis by studying the effects of age and diet on megalin, VLDLR, and ApoER2 expression, and that of age on the expression of cubilin and amnionless. Of megalin, VLDLR and ApoER2, only the megalin expression pattern resembles that of Dab2 previously reported. Thus the mRNA and protein levels of megalin and Dab2 are high in the intestine of the suckling rat, down-regulated by age and up-regulated by milk diet, mainly in the ileum. Neither age nor diet affect ApoER2 mRNA levels. The effect of age on VLDLR mRNA levels depends on the epithelial cell tested but they are down-regulated by milk diet. In the suckling rat, the intestinal expressions of both cubilin and amnionless are similar to that of megalin and megalin, cubilin, amnionless and Dab2 co-localize at the microvilli and in the apical endocytic apparatus. Co-localization of Dab2 with ApoER2 and VLDLR at the microvilli and in the apical endocytic apparatus is also observed. This is the first report showing intestinal co-localization of: megalin/cubilin/amnionless/Dab2, VLDLR/Dab2 and ApoER2/Dab2. We conclude that the megalin/cubilin/amnionless/Dab2 complex/es participate in intestinal processes, mainly during the lactation period and that Dab2 may act as an adaptor in intestinal processes mediated by ApoER2 and VLDLR.
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26
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Keene KL, Chen WM, Chen F, Williams SR, Elkhatib SD, Hsu FC, Mychaleckyj JC, Doheny KF, Pugh EW, Ling H, Laurie CC, Gogarten SM, Madden EB, Worrall BB, Sale MM. Genetic Associations with Plasma B12, B6, and Folate Levels in an Ischemic Stroke Population from the Vitamin Intervention for Stroke Prevention (VISP) Trial. Front Public Health 2014; 2:112. [PMID: 25147783 PMCID: PMC4123605 DOI: 10.3389/fpubh.2014.00112] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 07/21/2014] [Indexed: 11/13/2022] Open
Abstract
Background: B vitamins play an important role in homocysteine metabolism, with vitamin deficiencies resulting in increased levels of homocysteine and increased risk for stroke. We performed a genome-wide association study (GWAS) in 2,100 stroke patients from the Vitamin Intervention for Stroke Prevention (VISP) trial, a clinical trial designed to determine whether the daily intake of high-dose folic acid, vitamins B6, and B12 reduce recurrent cerebral infarction. Methods: Extensive quality control (QC) measures resulted in a total of 737,081 SNPs for analysis. Genome-wide association analyses for baseline quantitative measures of folate, Vitamins B12, and B6 were completed using linear regression approaches, implemented in PLINK. Results: Six associations met or exceeded genome-wide significance (P ≤ 5 × 10−08). For baseline Vitamin B12, the strongest association was observed with a non-synonymous SNP (nsSNP) located in the CUBN gene (P = 1.76 × 10−13). Two additional CUBN intronic SNPs demonstrated strong associations with B12 (P = 2.92 × 10−10 and 4.11 × 10−10), while a second nsSNP, located in the TCN1 gene, also reached genome-wide significance (P = 5.14 × 10−11). For baseline measures of Vitamin B6, we identified genome-wide significant associations for SNPs at the ALPL locus (rs1697421; P = 7.06 × 10−10 and rs1780316; P = 2.25 × 10−08). In addition to the six genome-wide significant associations, nine SNPs (two for Vitamin B6, six for Vitamin B12, and one for folate measures) provided suggestive evidence for association (P ≤ 10−07). Conclusion: Our GWAS study has identified six genome-wide significant associations, nine suggestive associations, and successfully replicated 5 of 16 SNPs previously reported to be associated with measures of B vitamins. The six genome-wide significant associations are located in gene regions that have shown previous associations with measures of B vitamins; however, four of the nine suggestive associations represent novel finding and warrant further investigation in additional populations.
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Affiliation(s)
- Keith L Keene
- Center for Public Health Genomics, University of Virginia , Charlottesville, VA , USA ; Department of Biology, Center for Health Disparities, East Carolina University , Greenville, NC , USA
| | - Wei-Min Chen
- Center for Public Health Genomics, University of Virginia , Charlottesville, VA , USA ; Department of Public Health Sciences, University of Virginia , Charlottesville, VA , USA
| | - Fang Chen
- Center for Public Health Genomics, University of Virginia , Charlottesville, VA , USA
| | - Stephen R Williams
- Center for Public Health Genomics, University of Virginia , Charlottesville, VA , USA
| | - Stacey D Elkhatib
- Center for Public Health Genomics, University of Virginia , Charlottesville, VA , USA
| | - Fang-Chi Hsu
- Department of Biostatistical Sciences, Wake Forest School of Medicine , Winston Salem, NC , USA
| | - Josyf C Mychaleckyj
- Center for Public Health Genomics, University of Virginia , Charlottesville, VA , USA ; Department of Public Health Sciences, University of Virginia , Charlottesville, VA , USA
| | - Kimberly F Doheny
- Center for Inherited Disease Research, Johns Hopkins University School of Medicine , Baltimore, MD , USA
| | - Elizabeth W Pugh
- Center for Inherited Disease Research, Johns Hopkins University School of Medicine , Baltimore, MD , USA
| | - Hua Ling
- Center for Inherited Disease Research, Johns Hopkins University School of Medicine , Baltimore, MD , USA
| | - Cathy C Laurie
- Department of Biostatistics, University of Washington , Seattle, WA , USA
| | | | - Ebony B Madden
- National Human Genome Research Institute, National Institutes of Health , Bethesda, MD , USA
| | - Bradford B Worrall
- Department of Public Health Sciences, University of Virginia , Charlottesville, VA , USA ; Department of Neurology, University of Virginia , Charlottesville, VA , USA
| | - Michele M Sale
- Center for Public Health Genomics, University of Virginia , Charlottesville, VA , USA ; Department of Public Health Sciences, University of Virginia , Charlottesville, VA , USA ; Department of Biochemistry & Molecular Genetics, University of Virginia , Charlottesville, VA , USA
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27
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Jensen LL, Andersen RK, Hager H, Madsen M. Lack of megalin expression in adult human terminal ileum suggests megalin-independent cubilin/amnionless activity during vitamin B12 absorption. Physiol Rep 2014; 2:2/7/e12086. [PMID: 25052491 PMCID: PMC4187553 DOI: 10.14814/phy2.12086] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Cubilin plays an essential role in terminal ileum and renal proximal tubules during absorption of vitamin B12 and ligands from the glomerular ultrafiltrate. Cubilin is coexpressed with amnionless, and cubilin and amnionless are mutually dependent on each other for correct processing to the plasma membrane upon synthesis. Patients with defects in either protein suffer from vitamin B12‐malabsorption and in some cases proteinuria. Cubilin lacks a transmembrane region and signals for endocytosis and is dependent on a transmembrane coreceptor during internalization. Amnionless has been shown to be able to mediate internalization of cubilin in a cell‐based model system. Cubilin has additionally been suggested to function together with megalin, and a recent study of megalin‐deficient patients indicates that uptake of cubilin ligands in the kidney is critically dependent on megalin. To further investigate the potential role of amnionless and megalin in relation to cubilin function in terminal ileum and vitamin B12 uptake, we initiated a study of CUBN/cubilin, AMN/amnionless, and LRP2/megalin expression in adult human terminal ileum. Our study is the first to reveal the expression pattern of cubilin, amnionless, and megalin in adult human terminal ileum, where cubilin and amnionless localize to the epithelial cells. Surprisingly, we did not detect any megalin protein in adult terminal ileum and consistently, only extremely low amounts of LRP2 mRNA. Our data therefore advocate that cubilin and amnionless act independently of megalin in adult terminal ileum and that the cubilin‐megalin interdependency accordingly should be considered as tissue and ligand specific. e12086 Studies of human terminal ileum samples demonstrate lack of LRP2/megalin expression in adult terminal ileum and point to a megalin‐independent cubilin‐amnionless‐driven uptake mechanism for vitamin B12.
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Affiliation(s)
- Louise L Jensen
- Department of Biomedicine, University of Aarhus, 8000 Aarhus C., Denmark
| | - Rikke K Andersen
- Department of Biomedicine, University of Aarhus, 8000 Aarhus C., Denmark
| | - Henrik Hager
- Department of Pathology, Aarhus University Hospital, 8000 Aarhus C., Denmark
| | - Mette Madsen
- Department of Biomedicine, University of Aarhus, 8000 Aarhus C., Denmark
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28
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Fyfe JC, Hemker SL, Venta PJ, Stebbing B, Giger U. Selective intestinal cobalamin malabsorption with proteinuria (Imerslund-Gräsbeck syndrome) in juvenile Beagles. J Vet Intern Med 2014; 28:356-62. [PMID: 24433284 PMCID: PMC3959579 DOI: 10.1111/jvim.12284] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 11/04/2013] [Accepted: 11/19/2013] [Indexed: 01/17/2023] Open
Abstract
Background Selective intestinal cobalamin malabsorption with mild proteinuria (Imerslund‐Gräsbeck syndrome; I‐GS), is an autosomal recessive disorder of dogs caused by mutations in AMN or CUBN that disrupt cubam function and which can present as a medical emergency. Objectives To describe the clinical, metabolic, and genetic bases of I‐GS in Beagles. Animals Four cobalamin‐deficient and 43 clinically normal Beagles and 5 dogs of other breeds. Methods Clinical description and candidate gene genetic study. Urinary organic acid and protein excretion were determined by gas‐chromatography and SDS‐PAGE, respectively. Renal cubilin protein expression was assessed on immunoblots. Mutation discovery was carried out by PCR amplification and DNA sequencing of exons with flanking splice sites and cDNA of CUBN and AMN. Genotyping was performed by restriction enzyme digestion of PCR amplicons. Results Juvenile‐affected Beagles exhibited failure to thrive, dyshematopoiesis with neutropenia, serum cobalamin deficiency, methylmalonic aciduria, hyperammonemia, and proteinuria. Affected dogs' kidneys lacked detectable cubilin protein. All affected dogs were homozygous for a single‐base deletion in CUBN exon 8 (CUBN c.786delC), predicting a translational frameshift, and the 2 parents tested were heterozygous. Conclusions The CUBN mutation in juvenile I‐GS Beagles causes a more severe cobalamin malabsorption than in Border Collies with a different CUBN defect, but is similar to I‐GS caused by AMN mutations in Giant Schnauzers and Australian Shepherds. Awareness of the disorder and breed predispositions to I‐GS is crucial to precisely diagnose and promptly treat hereditary cobalamin malabsorption and to prevent disease in those dogs at risk in future generations.
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Affiliation(s)
- J C Fyfe
- Laboratory of Comparative Medical Genetics, College of Veterinary Medicine, Michigan State University, East Lansing, MI; Department of Microbiology & Molecular Genetics, College of Veterinary Medicine, Michigan State University, East Lansing, MI
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Abstract
Optimal functioning of the central and peripheral nervous system is dependent on a constant supply of appropriate nutrients. Particularly important for optimal functioning of the nervous system is cobalamin (vitamin B12). Cobalamin deficiency is particularly common in the elderly and after gastric surgery. Many patients with clinically expressed cobalamin deficiency have intrinsic factor-related malabsorption such as that seen in pernicious anemia. The commonly recognized neurological manifestations of cobalamin deficiency include a myelopathy with or without an associated neuropathy. This review deals with neurological aspects of vitamin B12 deficiency and attempts to highlight recent developments.
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Affiliation(s)
- Neeraj Kumar
- Department of Neurology, Mayo Clinic, Rochester, MN, USA.
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Drögemüller M, Jagannathan V, Howard J, Bruggmann R, Drögemüller C, Ruetten M, Leeb T, Kook PH. A frameshift mutation in the cubilin gene (CUBN) in Beagles with Imerslund-Gräsbeck syndrome (selective cobalamin malabsorption). Anim Genet 2013; 45:148-50. [DOI: 10.1111/age.12094] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/24/2013] [Indexed: 12/23/2022]
Affiliation(s)
- Michaela Drögemüller
- Institute of Genetics; Vetsuisse Faculty; University of Bern; 3001 Bern Switzerland
| | - Vidhya Jagannathan
- Institute of Genetics; Vetsuisse Faculty; University of Bern; 3001 Bern Switzerland
| | - Judith Howard
- Department of Clinical Veterinary Medicine; University of Bern; 3001 Bern Switzerland
| | - Rémy Bruggmann
- Interfaculty Bioinformatics Unit; University of Bern; 3001 Bern Switzerland
| | - Cord Drögemüller
- Institute of Genetics; Vetsuisse Faculty; University of Bern; 3001 Bern Switzerland
| | - Maja Ruetten
- Institute of Veterinary Pathology; Vetsuisse Faculty; University of Zurich; 8057 Zurich Switzerland
| | - Tosso Leeb
- Institute of Genetics; Vetsuisse Faculty; University of Bern; 3001 Bern Switzerland
| | - Peter H. Kook
- Clinic for Small Animal Internal Medicine; Vetsuisse Faculty; University of Zurich; 8057 Zurich Switzerland
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31
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Storm T, Zeitz C, Cases O, Amsellem S, Verroust PJ, Madsen M, Benoist JF, Passemard S, Lebon S, Jønsson IM, Emma F, Koldsø H, Hertz JM, Nielsen R, Christensen EI, Kozyraki R. Detailed investigations of proximal tubular function in Imerslund-Gräsbeck syndrome. BMC MEDICAL GENETICS 2013; 14:111. [PMID: 24156255 PMCID: PMC3826550 DOI: 10.1186/1471-2350-14-111] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 10/18/2013] [Indexed: 11/10/2022]
Abstract
BACKGROUND Imerslund-Gräsbeck Syndrome (IGS) is a rare genetic disorder characterised by juvenile megaloblastic anaemia. IGS is caused by mutations in either of the genes encoding the intestinal intrinsic factor-vitamin B12 receptor complex, cubam. The cubam receptor proteins cubilin and amnionless are both expressed in the small intestine as well as the proximal tubules of the kidney and exhibit an interdependent relationship for post-translational processing and trafficking. In the proximal tubules cubilin is involved in the reabsorption of several filtered plasma proteins including vitamin carriers and lipoproteins. Consistent with this, low-molecular-weight proteinuria has been observed in most patients with IGS. The aim of this study was to characterise novel disease-causing mutations and correlate novel and previously reported mutations with the presence of low-molecular-weight proteinuria. METHODS Genetic screening was performed by direct sequencing of the CUBN and AMN genes and novel identified mutations were characterised by in silico and/or in vitro investigations. Urinary protein excretion was analysed by immunoblotting and high-resolution gel electrophoresis of collected urines from patients and healthy controls to determine renal phenotype. RESULTS Genetic characterisation of nine IGS patients identified two novel AMN frameshift mutations alongside a frequently reported AMN splice site mutation and two CUBN missense mutations; one novel and one previously reported in Finnish patients. The novel AMN mutations were predicted to result in functionally null AMN alleles with no cell-surface expression of cubilin. Also, the novel CUBN missense mutation was predicted to affect structural integrity of the IF-B12 binding site of cubilin and hereby most likely cubilin cell-surface expression. Analysis of urinary protein excretion in the patients and 20 healthy controls revealed increased urinary excretion of cubilin ligands including apolipoprotein A-I, transferrin, vitamin D-binding protein, and albumin. This was, however, only observed in patients where plasma membrane expression of cubilin was predicted to be perturbed. CONCLUSIONS In the present study, mutational characterisation of nine IGS patients coupled with analyses of urinary protein excretion provide additional evidence for a correlation between mutation type and presence of the characteristic low-molecular-weight proteinuria.
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Imerslund-Gräsbeck syndrome in a 25-month-old Italian girl caused by a homozygous mutation in AMN. Ital J Pediatr 2013; 39:58. [PMID: 24044590 PMCID: PMC3848621 DOI: 10.1186/1824-7288-39-58] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 09/15/2013] [Indexed: 11/23/2022] Open
Abstract
Imerslund-Gräsbeck syndrome is a rare autosomal recessive disorder, characterized by vitamin B12 deficiency due to selective malabsorption of the vitamin and usually results in megaloblastic anemia appearing in childhood. It is responsive to parenteral vitamin B12 therapy. The estimated prevalence (calculated based on Scandinavian data) is less than 6:1,000,000. However, many cases may be misdiagnosed. When there is reasonable evidence to suspect that a patient suffers from IGS, a new and straightforward approach to diagnosis is mutational analysis of the appropriate genes. We report for the first time the case of a girl of Italian ancestry with IGS genetically confirmed by the detection of a homozygous missense mutation in the AMN gene (c.208-2 A > G).
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Moreno-Garcia MA, Rosenblatt DS, Jerome-Majewska LA. Vitamin B(12) metabolism during pregnancy and in embryonic mouse models. Nutrients 2013; 5:3531-50. [PMID: 24025485 PMCID: PMC3798919 DOI: 10.3390/nu5093531] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 08/10/2013] [Accepted: 08/23/2013] [Indexed: 11/16/2022] Open
Abstract
Vitamin B(12) (cobalamin, Cbl) is required for cellular metabolism. It is an essential coenzyme in mammals for two reactions: the conversion of homocysteine to methionine by the enzyme methionine synthase and the conversion of methylmalonyl-CoA to succinyl-CoA by the enzyme methylmalonyl-CoA mutase. Symptoms of Cbl deficiency are hematological, neurological and cognitive, including megaloblastic anaemia, tingling and numbness of the extremities, gait abnormalities, visual disturbances, memory loss and dementia. During pregnancy Cbl is essential, presumably because of its role in DNA synthesis and methionine synthesis; however, there are conflicting studies regarding an association between early pregnancy loss and Cbl deficiency. We here review the literature about the requirement for Cbl during pregnancy, and summarized what is known of the expression pattern and function of genes required for Cbl metabolism in embryonic mouse models.
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Affiliation(s)
- Maira A. Moreno-Garcia
- Department of Human Genetics, McGill University, 1205 Avenue Docteur Penfield, N5/13,Montreal, Quebec, Canada H3A 1B1; E-Mails: (M.A.M.-G.); (D.S.R.)
| | - David S. Rosenblatt
- Department of Human Genetics, McGill University, 1205 Avenue Docteur Penfield, N5/13,Montreal, Quebec, Canada H3A 1B1; E-Mails: (M.A.M.-G.); (D.S.R.)
- Department of Pediatrics, McGill University, Montreal, Quebec, Canada H3H 1P3
| | - Loydie A. Jerome-Majewska
- Department of Human Genetics, McGill University, 1205 Avenue Docteur Penfield, N5/13,Montreal, Quebec, Canada H3A 1B1; E-Mails: (M.A.M.-G.); (D.S.R.)
- Department of Pediatrics, McGill University, Montreal, Quebec, Canada H3H 1P3
- McGill University Health Centre, 4060 Ste. Catherine West, PT 420, Montreal, Quebec, Canada H3Z 2Z3
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-514-412-4400 (ext. 23279); Fax: +1-514-412-4331
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Fyfe JC, Hemker SL, Venta PJ, Fitzgerald CA, Outerbridge CA, Myers SL, Giger U. An exon 53 frameshift mutation in CUBN abrogates cubam function and causes Imerslund-Gräsbeck syndrome in dogs. Mol Genet Metab 2013; 109:390-6. [PMID: 23746554 PMCID: PMC3729882 DOI: 10.1016/j.ymgme.2013.05.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 05/13/2013] [Accepted: 05/13/2013] [Indexed: 12/18/2022]
Abstract
Cobalamin malabsorption accompanied by selective proteinuria is an autosomal recessive disorder known as Imerslund-Gräsbeck syndrome in humans and was previously described in dogs due to amnionless (AMN) mutations. The resultant vitamin B12 deficiency causes dyshematopoiesis, lethargy, failure to thrive, and life-threatening metabolic disruption in the juvenile period. We studied 3 kindreds of border collies with cobalamin malabsorption and mapped the disease locus in affected dogs to a 2.9Mb region of homozygosity on canine chromosome 2. The region included CUBN, the locus encoding cubilin, a peripheral membrane protein that in concert with AMN forms the functional intrinsic factor-cobalamin receptor expressed in ileum and a multi-ligand receptor in renal proximal tubules. Cobalamin malabsorption and proteinuria comprising CUBN ligands were demonstrated by radiolabeled cobalamin uptake studies and SDS-PAGE, respectively. CUBN mRNA and protein expression were reduced ~10 fold and ~20 fold, respectively, in both ileum and kidney of affected dogs. DNA sequencing demonstrated a single base deletion in exon 53 predicting a translational frameshift and early termination codon likely triggering nonsense mediated mRNA decay. The mutant allele segregated with the disease in the border collie kindred. The border collie disorder indicates that a CUBN mutation far C-terminal from the intrinsic factor-cobalamin binding site can abrogate receptor expression and cause Imerslund-Gräsbeck syndrome.
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Affiliation(s)
- John C Fyfe
- Laboratory of Comparative Medical Genetics, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA.
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35
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Abstract
Hypercobalaminemia (high serum vitamin B12 levels) is a frequent and underestimated anomaly. Clinically, it can be paradoxically accompanied by signs of deficiency, reflecting a functional deficiency linked to qualitative abnormalities, which are related to defects in tissue uptake and action of vitamin B12. The aetiological profile of high serum cobalamin predominantly encompasses severe disease entities for which early diagnosis is critical for prognosis. These entities are essentially comprised of solid neoplasms, haematological malignancies and liver and kidney diseases. This review reflects the potential importance of the vitamin B12 assay as an early diagnostic marker of these diseases. A codified approach is needed to determine the potential indications of a search for high serum cobalamin and the practical clinical strategy to adopt upon discovery of elevated cobalamin levels. While low serum cobalamin levels do not necessarily imply deficiency, an abnormally high serum cobalamin level forms a warning sign requiring exclusion of a number of serious underlying pathologies. Functional cobalamin deficiency can thus occur at any serum level.
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Affiliation(s)
- E Andrès
- Service de Médecine Interne, Diabète et Maladies Métaboliques, Clinique Médicale B, Hôpital Civil, Hôpitaux Universitaires de Strasbourg, 1 porte de l'Hôpital, 67091 Strasbourg Cedex, France.
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Gräsbeck R. Hooked to vitamin B12 since 1955: A historical perspective. Biochimie 2013; 95:970-5. [DOI: 10.1016/j.biochi.2012.12.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Accepted: 12/11/2012] [Indexed: 11/28/2022]
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37
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Owczarek-Lipska M, Jagannathan V, Drögemüller C, Lutz S, Glanemann B, Leeb T, Kook PH. A frameshift mutation in the cubilin gene (CUBN) in Border Collies with Imerslund-Gräsbeck syndrome (selective cobalamin malabsorption). PLoS One 2013; 8:e61144. [PMID: 23613799 PMCID: PMC3628801 DOI: 10.1371/journal.pone.0061144] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 03/05/2013] [Indexed: 01/24/2023] Open
Abstract
Imerslund-Gräsbeck syndrome (IGS) or selective cobalamin malabsorption has been described in humans and dogs. IGS occurs in Border Collies and is inherited as a monogenic autosomal recessive trait in this breed. Using 7 IGS cases and 7 non-affected controls we mapped the causative mutation by genome-wide association and homozygosity mapping to a 3.53 Mb interval on chromosome 2. We re-sequenced the genome of one affected dog at ∼10× coverage and detected 17 non-synonymous variants in the critical interval. Two of these non-synonymous variants were in the cubilin gene (CUBN), which is known to play an essential role in cobalamin uptake from the ileum. We tested these two CUBN variants for association with IGS in larger cohorts of dogs and found that only one of them was perfectly associated with the phenotype. This variant, a single base pair deletion (c.8392delC), is predicted to cause a frameshift and premature stop codon in the CUBN gene. The resulting mutant open reading frame is 821 codons shorter than the wildtype open reading frame (p.Q2798Rfs*3). Interestingly, we observed an additional nonsense mutation in the MRC1 gene encoding the mannose receptor, C type 1, which was in perfect linkage disequilibrium with the CUBN frameshift mutation. Based on our genetic data and the known role of CUBN for cobalamin uptake we conclude that the identified CUBN frameshift mutation is most likely causative for IGS in Border Collies.
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Affiliation(s)
| | - Vidhya Jagannathan
- Institute of Genetics, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Cord Drögemüller
- Institute of Genetics, Vetsuisse Faculty, University of Bern, Bern, Switzerland
| | - Sabina Lutz
- Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Barbara Glanemann
- Department of Veterinary Clinical Science, The Royal Veterinary College, University of London, North Mymms, Hertfordshire, United Kingdom
| | - Tosso Leeb
- Institute of Genetics, Vetsuisse Faculty, University of Bern, Bern, Switzerland
- * E-mail:
| | - Peter H. Kook
- Clinic for Small Animal Internal Medicine, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
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38
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Christensen EI, Nielsen R, Birn H. From bowel to kidneys: the role of cubilin in physiology and disease. Nephrol Dial Transplant 2013; 28:274-81. [DOI: 10.1093/ndt/gfs565] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Boina Abdallah A, Ogier de Baulny H, Kozyraki R, Passemard S, Fenneteau O, Lebon S, Rigal O, Mesples B, Yacouben K, Giraudier S, Benoist JF, Schiff M. How can cobalamin injections be spaced in long-term therapy for inborn errors of vitamin B(12) absorption? Mol Genet Metab 2012; 107:66-71. [PMID: 22854512 DOI: 10.1016/j.ymgme.2012.07.007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 07/11/2012] [Accepted: 07/11/2012] [Indexed: 11/21/2022]
Abstract
Inborn errors of cobalamin (Cbl, vitamin B(12)) absorption include hereditary intrinsic factor deficiency (HIFD) and Imerslund-Gräsbeck disease (IGD). HIFD is secondary to mutations in the HIF gene while IGD is due to mutations in one of the 2 subunits of the intrinsic factor receptor that is cubilin (CUBN) or amnionless (AMN). These disorders lead to intracellular Cbl depletion which in turn causes megaloblastic bone marrow failure, accumulation of homocysteine and methylmalonic acid (MMA), and methionine depletion. The clinical presentation reflects Cbl deficiency, with gastrointestinal symptoms, pancytopenia, and megaloblastic anemia. Mixed proteinuria, when it is present is strongly suggestive of IGD. Accurate diagnosis is always an emergency because early detection and treatment with life-long parenteral pharmacological doses of hydroxocobalamin are life saving and prevent further deterioration. However, the optimal frequency for cobalamin injections as a maintenance therapy is poorly reported. In order to evaluate the optimal maintenance schedule of cobalamin injections, we retrospectively collected clinical, biological, molecular and treatment data on 7 patients affected with congenital Cbl malabsorption. Unlike previous recommendations, we showed that a maintenance dosage of 1 mg cobalamin twice a year was enough to ensure a normal clinical status and keep the hematological and metabolic parameters in the normal range. These data suggest that patients affected with inborn errors of cobalamin absorption may be safely long-term treated with cobalamin injections every 6 months with careful follow-up of hematological and metabolic parameters. This maintenance regime is beneficial because the patients' quality of life improves.
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Affiliation(s)
- Amina Boina Abdallah
- APHP, Reference Center for Inherited Metabolic Disease, Hôpital Robert Debré, F-75019 Paris, France
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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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41
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Christensen EI, Birn H, Storm T, Weyer K, Nielsen R. Endocytic Receptors in the Renal Proximal Tubule. Physiology (Bethesda) 2012; 27:223-36. [DOI: 10.1152/physiol.00022.2012] [Citation(s) in RCA: 170] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Protein reabsorption is a predominant feature of the renal proximal tubule. Animal studies show that the ability to rescue plasma proteins relies on the endocytic receptors megalin and cubilin. Recently, studies of patients with syndromes caused by dysfunctional receptors have supported the importance of these for protein clearance of human ultrafiltrate. This review focuses on the molecular biology and physiology of the receptors and their involvement in renal pathological conditions.
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Affiliation(s)
- Erik I. Christensen
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
| | - Henrik Birn
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
| | - Tina Storm
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
| | - Kathrin Weyer
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
| | - Rikke Nielsen
- Department of Biomedicine, Faculty of Health Sciences, Aarhus University, Aarhus, Denmark
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42
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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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Abstract
We report a rare case of juvenile cobalamin deficiency who presented at the age of 17 years. He was underweight and had skin changes, normocytic anemia, and autonomic dysfunction, which led to adynamic ileus and acute postrenal failure. The expected macrocytosis was masked by an underlying alpha-thalassemia trait. The patient had an excellent response to parenteral cobalamin treatment.
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44
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Beech CM, Liyanarachchi S, Shah NP, Sturm AC, Sadiq MF, de la Chapelle A, Tanner SM. Ancient founder mutation is responsible for Imerslund-Gräsbeck Syndrome among diverse ethnicities. Orphanet J Rare Dis 2011; 6:74. [PMID: 22078000 PMCID: PMC3226546 DOI: 10.1186/1750-1172-6-74] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Accepted: 11/13/2011] [Indexed: 11/17/2022] Open
Abstract
Background Imerslund-Gräsbeck syndrome (IGS) was described just over 50 years ago by Olga Imerslund and Ralph Gräsbeck and colleagues. IGS is caused by specific malabsorption of cobalamin (Cbl) due to bi-allelic mutations in either the cubilin gene (CUBN) or the human amnionless homolog (AMN). Mutations in the two genes are commonly seen in founder populations or in societies with a high degree of consanguineous marriages. One particular mutation in AMN, c.208-2A>G, causing an out-of-frame loss of exon 4 in the mRNA, is responsible for some 15% of IGS cases globally. We present evidence that this founder mutation causes a substantial percentage of cases among diverse ethnicities and that the mutation is as old as human civilization. Methods Partial genotyping indicated a founder event but its presence in diverse peoples of Arabic, Turkish, Jewish, and Hispanic ancestry suggested that the mutation might be recurrent. We therefore studied the flanking sequence spanning 3.5 Mb to elucidate the origin of the haplotype and estimate the age of the mutation using a Bayesian inference method based on observed linkage disequilibrium. Results The mutation's distribution, the size of the shared haplotype, and estimates of growth rate and carrier frequency indicated that the mutation was a single prehistoric event. Dating back to the ancient Middle East around 11,600 BC, the mutation predates the advent of writing, farming, and the monotheistic religions of the region. Conclusions This mutation causes over 50% of the IGS cases among Arabic, Turkish, and Sephardic Jewish families, making it a primary target for genetic screening among diverse IGS cases originating from the Middle East. Thus, rare founder mutations may cause a substantial number of cases, even among diverse ethnicities not usually thought to be related.
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Affiliation(s)
- Cameron M Beech
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210, USA.
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Ovunc B, Otto EA, Vega-Warner V, Saisawat P, Ashraf S, Ramaswami G, Fathy HM, Schoeb D, Chernin G, Lyons RH, Yilmaz E, Hildebrandt F. Exome sequencing reveals cubilin mutation as a single-gene cause of proteinuria. J Am Soc Nephrol 2011; 22:1815-20. [PMID: 21903995 DOI: 10.1681/asn.2011040337] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In two siblings of consanguineous parents with intermittent nephrotic-range proteinuria, we identified a homozygous deleterious frameshift mutation in the gene CUBN, which encodes cubulin, using exome capture and massively parallel re-sequencing. The mutation segregated with affected members of this family and was absent from 92 healthy individuals, thereby identifying a recessive mutation in CUBN as the single-gene cause of proteinuria in this sibship. Cubulin mutations cause a hereditary form of megaloblastic anemia secondary to vitamin B(12) deficiency, and proteinuria occurs in 50% of cases since cubilin is coreceptor for both the intestinal vitamin B(12)-intrinsic factor complex and the tubular reabsorption of protein in the proximal tubule. In summary, we report successful use of exome capture and massively parallel re-sequencing to identify a rare, single-gene cause of nephropathy.
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Affiliation(s)
- Bugsu Ovunc
- Department of Pediatrics, University of Michigan, Ann Arbor, Michigan 48109, USA
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Gräsbeck R, Tanner SM. Juvenile selective vitamin B₁₂ malabsorption: 50 years after its description-10 years of genetic testing. Pediatr Res 2011; 70:222-8. [PMID: 21623254 PMCID: PMC3152595 DOI: 10.1203/pdr.0b013e3182242124] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Fifty years have passed since the description of juvenile selective malabsorption of cobalamin (Cbl). Quality of life improvements have dramatically reduced the incidence of parasite-induced or nutritional Cbl deficiency. Consequently, inherited defects have become a leading cause of Cbl deficiency in children, which is not always expressed as anemia. Unfortunately, the gold standard for clinical diagnosis, the Schilling test, has increasingly become unavailable, and replacement tests are only in their infancy. Genetic testing is complicated by genetic heterogeneity and differential diagnosis. This review documents the history, research, and advances in genetics that have elucidated the causes of juvenile Cbl malabsorption. Genetic research has unearthed many cases in the past decade, mostly in Europe and North America, often among immigrants from the Middle East or North Africa. Lack of suitable clinical testing potentially leaves many patients inadequately diagnosed. The consequences of suboptimal Cbl levels for neurological development are well documented. By raising awareness, we wish to push for fast track development of better clinical tools and suitable genetic testing. Clinical awareness must include attention to ethnicity, a sensitive topic but effective for fast diagnosis. The treatment with monthly parenteral Cbl for life offers a simple and cost-effective solution once proper diagnosis is made.
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Affiliation(s)
- Ralph Gräsbeck
- Minerva Foundation Institute for Medical Research, Biomedicum Helsinki 2U, Helsinki 00290, Finland
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Pereira PNG, Dobreva MP, Graham L, Huylebroeck D, Lawson KA, Zwijsen AN. Amnion formation in the mouse embryo: the single amniochorionic fold model. BMC DEVELOPMENTAL BIOLOGY 2011; 11:48. [PMID: 21806820 PMCID: PMC3163621 DOI: 10.1186/1471-213x-11-48] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Accepted: 08/01/2011] [Indexed: 12/16/2022]
Abstract
BACKGROUND Despite the detailed knowledge obtained over the last decade on the molecular regulation of gastrulation in amniotes, the process of amnion development has been poorly described and illustrated in mice, and conflicting descriptions exist. Understanding the morphogenesis and development not only of the early mouse embryo, but also of its extraembryonic tissues, is crucial for correctly interpreting fate-mapping data and mouse mutants with gastrulation defects. Moreover, the recent isolation from amnion of cells with stem cell features further argues for a better understanding of the process of amnion formation. Here, we revisit the highly dynamic process of amnion formation in the mouse. Amnion development starts early during gastrulation and is intimately related to the formation of the exocoelom and the expansion of the amniotic fold. The authoritative description involves the fusion of two amniotic folds, a big posterior and a smaller anterior fold. We challenged this 'two amniotic folds' model by performing detailed histomorphological analyses of dissected, staged embryos and 3D reconstructions using historical sections. RESULTS A posterior fold of extraembryonic ectoderm and associated epiblast is formed early during gastrulation by accumulation of extraembryonic mesoderm posterior to the primitive streak. Previously called the "posterior amniotic fold", we rename it the "amniochorionic fold" (ACF) because it forms both amnion and chorion. Exocoelom formation within the ACF seems not to involve apoptosis within the mesoderm. The ACF and exocoelom expand without disrupting the anterior junction of epiblast, extraembryonic ectoderm and visceral endoderm. No separate anterior fold is formed; its absence was confirmed in 3D reconstructions. Amnion and chorion closure is eccentric, close to the anterior margin of the egg cylinder: we name it the "anterior separation point". CONCLUSIONS Here, we reconcile previous descriptions of amnion formation and provide new nomenclature, as well as an animation, that clarify and emphasize the arrangement of the tissues that contribute to amnion development and the dynamics of the process. According to our data, the amnion and the chorion are formed by a single amniochorionic fold initiated posteriorly. Finally, we give an overview on mutant mouse models with impaired amnion development.
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Affiliation(s)
- Paulo N G Pereira
- Laboratory of Developmental Signaling of the Department of Molecular and Developmental Genetics, VIB, Leuven, Belgium.
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Namour F, Dobrovoljski G, Chery C, Audonnet S, Feillet F, Sperl W, Gueant JL. Luminal expression of cubilin is impaired in Imerslund-Grasbeck syndrome with compound AMN mutations in intron 3 and exon 7. Haematologica 2011; 96:1715-9. [PMID: 21750092 DOI: 10.3324/haematol.2011.043984] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Juvenile megaloblastic anaemia 1 (OMIM # 261100) is a rare autosomic disorder characterized by selective cobalamin mal-absorption and inconstant proteinuria produced by mutations in either CUBN or AMN genes. Amnionless, the gene product of AMN, is a transmembrane protein that binds tightly to the N-terminal end of cubilin, the gene product of CUBN. Cubilin binds to intrinsic factor-cobalamin complex and is expressed in the distal intestine and the proximal renal tubule. We report a compound AMN heterozygosity with c.742C>T, p.Gln248X and c.208-2A>G mutations in 2 siblings that led to premature termination codon in exon 7 and exon 6, respectively. It produced a dramatic decrease in receptor activity in urine, despite absence of CUBN mutation and normal affinity of the receptor for intrinsic factor binding. Heterozygous carriers for c.742T and c.208-2G had no pathological signs. These results indicate that amnionless is essential for the correct luminal expression of cubilin in humans.
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Affiliation(s)
- Fares Namour
- Faculté de Médecine, INSERM U954 Nutrition, Genetics, and Environmental Risk Exposure, Vandoeuvre Les Nancy, France.
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Investigation of the ABC transporter MRP1 in selected patients with presumed defects in vitamin B12 absorption. Blood 2011; 117:4397-8. [DOI: 10.1182/blood-2010-12-322750] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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O'Toole JF, Sedor JR. Are cubilin (CUBN) variants at the heart of urinary albumin excretion? J Am Soc Nephrol 2011; 22:404-6. [PMID: 21372212 DOI: 10.1681/asn.2011010097] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
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