1
|
Hirata E, Sakata KT, Dearden GI, Noor F, Menon I, Chiduza GN, Menon AK. Molecular characterization of Rft1, an ER membrane protein associated with congenital disorder of glycosylation RFT1-CDG. J Biol Chem 2024:107584. [PMID: 39025454 DOI: 10.1016/j.jbc.2024.107584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 07/10/2024] [Accepted: 07/11/2024] [Indexed: 07/20/2024] Open
Abstract
The oligosaccharide needed for protein N-glycosylation is assembled on a lipid carrier via a multi-step pathway. Synthesis is initiated on the cytoplasmic face of the endoplasmic reticulum (ER) and completed on the luminal side after transbilayer translocation of a heptasaccharide lipid intermediate. More than 30 Congenital Disorders of Glycosylation (CDGs) are associated with this pathway, including RFT1-CDG which results from defects in the membrane protein Rft1. Rft1 is essential for the viability of yeast and mammalian cells and was proposed as the transporter needed to flip the heptasaccharide lipid intermediate across the ER membrane. However, other studies indicated that Rft1 is not required for heptasaccharide lipid flipping in microsomes or unilamellar vesicles reconstituted with ER membrane proteins, nor is it required for the viability of at least one eukaryote. It is therefore not known what essential role Rft1 plays in N-glycosylation. Here, we present a molecular characterization of human Rft1, using yeast cells as a reporter system. We show that it is a multi-spanning membrane protein located in the ER, with its N and C-termini facing the cytoplasm. It is not N-glycosylated. The majority of RFT1-CDG mutations map to highly conserved regions of the protein. We identify key residues that are important for Rft1's ability to support N-glycosylation and cell viability. Our results provide a necessary platform for future work on this enigmatic protein.
Collapse
Affiliation(s)
- Eri Hirata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Ken-Taro Sakata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Grace I Dearden
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Faria Noor
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - George N Chiduza
- Structure and Function of Biological Membranes - Chemistry Department, Université Libre de Bruxelles - Campus Plaine, 1050 Brussels, Belgium
| | - Anant K Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA.
| |
Collapse
|
2
|
Hirata E, Sakata KT, Dearden GI, Noor F, Menon I, Chiduza GN, Menon AK. Molecular characterization of Rft1, an ER membrane protein associated with congenital disorder of glycosylation RFT1-CDG. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.03.587922. [PMID: 38617304 PMCID: PMC11014557 DOI: 10.1101/2024.04.03.587922] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
The oligosaccharide needed for protein N-glycosylation is assembled on a lipid carrier via a multi-step pathway. Synthesis is initiated on the cytoplasmic face of the endoplasmic reticulum (ER) and completed on the luminal side after transbilayer translocation of a heptasaccharide lipid intermediate. More than 30 Congenital Disorders of Glycosylation (CDGs) are associated with this pathway, including RFT1-CDG which results from defects in the membrane protein Rft1. Rft1 is essential for the viability of yeast and mammalian cells and was proposed as the transporter needed to flip the heptasaccharide lipid intermediate across the ER membrane. However, other studies indicated that Rft1 is not required for heptasaccharide lipid flipping in microsomes or unilamellar vesicles reconstituted with ER membrane proteins, nor is it required for the viability of at least one eukaryote. It is therefore not known what essential role Rft1 plays in N-glycosylation. Here, we present a molecular characterization of human Rft1, using yeast cells as a reporter system. We show that it is a multi-spanning membrane protein located in the ER, with its N and C-termini facing the cytoplasm. It is not N-glycosylated. The majority of RFT1-CDG mutations map to highly conserved regions of the protein. We identify key residues that are important for Rft1's ability to support N-glycosylation and cell viability. Our results provide a necessary platform for future work on this enigmatic protein.
Collapse
Affiliation(s)
- Eri Hirata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Ken-taro Sakata
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Grace I. Dearden
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Faria Noor
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - Indu Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| | - George N. Chiduza
- Structure and Function of Biological Membranes - Chemistry Department, Université Libre de Bruxelles - Campus Plaine, 1050 Brussels, Belgium
| | - Anant K. Menon
- Department of Biochemistry, Weill Cornell Medical College, New York, NY 10065, USA
| |
Collapse
|
3
|
Toustou C, Walet-Balieu ML, Kiefer-Meyer MC, Houdou M, Lerouge P, Foulquier F, Bardor M. Towards understanding the extensive diversity of protein N-glycan structures in eukaryotes. Biol Rev Camb Philos Soc 2021; 97:732-748. [PMID: 34873817 PMCID: PMC9300197 DOI: 10.1111/brv.12820] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 11/04/2021] [Accepted: 11/24/2021] [Indexed: 12/12/2022]
Abstract
N‐glycosylation is an important post‐translational modification of proteins that has been highly conserved during evolution and is found in Eukaryota, Bacteria and Archaea. In eukaryotes, N‐glycan processing is sequential, involving multiple specific steps within the secretory pathway as proteins travel through the endoplasmic reticulum and the Golgi apparatus. In this review, we first summarize the different steps of the N‐glycan processing and further describe recent findings regarding the diversity of N‐glycan structures in eukaryotic clades. This comparison allows us to explore the different regulation mechanisms of N‐glycan processing among eukaryotic clades. Recent findings regarding the regulation of protein N‐glycosylation are highlighted, especially the regulation of the biosynthesis of complex‐type N‐glycans through manganese and calcium homeostasis and the specific role of transmembrane protein 165 (TMEM165) for which homologous sequences have been identified in several eukaryotic clades. Further research will be required to characterize the function of TMEM165 homologous sequences in different eukaryotic clades.
Collapse
Affiliation(s)
- Charlotte Toustou
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale (Glyco-MEV) EA4358, Mont-Saint-Aignan, 76821, France
| | - Marie-Laure Walet-Balieu
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale (Glyco-MEV) EA4358, Mont-Saint-Aignan, 76821, France
| | - Marie-Christine Kiefer-Meyer
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale (Glyco-MEV) EA4358, Mont-Saint-Aignan, 76821, France
| | - Marine Houdou
- Univ Lille, CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, Lille, F-59000, France.,Laboratory of Cellular Transport Systems, Department of Cellular and Molecular Medicine, KU Leuven, Herestraat 49, Box 802, Leuven, 3000, Belgium
| | - Patrice Lerouge
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale (Glyco-MEV) EA4358, Mont-Saint-Aignan, 76821, France
| | - François Foulquier
- Univ Lille, CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, Lille, F-59000, France
| | - Muriel Bardor
- Normandie Univ, UNIROUEN, Laboratoire Glycobiologie et Matrice Extracellulaire végétale (Glyco-MEV) EA4358, Mont-Saint-Aignan, 76821, France.,Univ Lille, CNRS, UMR 8576 - UGSF - Unité de Glycobiologie Structurale et Fonctionnelle, Lille, F-59000, France
| |
Collapse
|
4
|
Paprocka J, Jezela-Stanek A, Tylki-Szymańska A, Grunewald S. Congenital Disorders of Glycosylation from a Neurological Perspective. Brain Sci 2021; 11:brainsci11010088. [PMID: 33440761 PMCID: PMC7827962 DOI: 10.3390/brainsci11010088] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2020] [Revised: 01/01/2021] [Accepted: 01/04/2021] [Indexed: 12/11/2022] Open
Abstract
Most plasma proteins, cell membrane proteins and other proteins are glycoproteins with sugar chains attached to the polypeptide-glycans. Glycosylation is the main element of the post-translational transformation of most human proteins. Since glycosylation processes are necessary for many different biological processes, patients present a diverse spectrum of phenotypes and severity of symptoms. The most frequently observed neurological symptoms in congenital disorders of glycosylation (CDG) are: epilepsy, intellectual disability, myopathies, neuropathies and stroke-like episodes. Epilepsy is seen in many CDG subtypes and particularly present in the case of mutations in the following genes: ALG13, DOLK, DPAGT1, SLC35A2, ST3GAL3, PIGA, PIGW, ST3GAL5. On brain neuroimaging, atrophic changes of the cerebellum and cerebrum are frequently seen. Brain malformations particularly in the group of dystroglycanopathies are reported. Despite the growing number of CDG patients in the world and often neurological symptoms dominating in the clinical picture, the number of performed screening tests eg transferrin isoforms is systematically decreasing as broadened genetic testing is recently more favored. The aim of the review is the summary of selected neurological symptoms in CDG described in the literature in one paper. It is especially important for pediatric neurologists not experienced in the field of metabolic medicine. It may help to facilitate the diagnosis of this expanding group of disorders. Biochemically, this paper focuses on protein glycosylation abnormalities.
Collapse
Affiliation(s)
- Justyna Paprocka
- Department of Pediatric Neurology, Faculty of Medical Science in Katowice, Medical University of Silesia, 40-752 Katowice, Poland
- Correspondence: ; Tel.: +48-606-415-888
| | - Aleksandra Jezela-Stanek
- Department of Genetics and Clinical Immunology, National Institute of Tuberculosis and Lung Diseases, 01-138 Warsaw, Poland;
| | - Anna Tylki-Szymańska
- Department of Pediatrics, Nutrition and Metabolic Diseases, The Children’s Memorial Health Institute, W 04-730 Warsaw, Poland;
| | - Stephanie Grunewald
- NIHR Biomedical Research Center (BRC), Metabolic Unit, Great Ormond Street Hospital and Institute of Child Health, University College London, London SE1 9RT, UK;
| |
Collapse
|
5
|
Abiramalatha T, Arunachal G, Muthusamy K, Thomas N. A family with floppy neonates with severe respiratory insufficiency: A lethal phenotype of RFT1-CDG due to a novel mutation. Eur J Med Genet 2018; 62:248-253. [PMID: 30071302 DOI: 10.1016/j.ejmg.2018.07.023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Revised: 07/03/2018] [Accepted: 07/28/2018] [Indexed: 11/17/2022]
Abstract
Congenital disorders of glycosylation (CDG) are a rapidly expanding group of inborn errors of metabolism with around 100 types described so far. Because of the limited number of reported cases in each type except PMM2-CDG, the complete clinical picture of other types is not known. RFT1-CDG is a rare type, with ten cases reported in the literature. Our patient presented as a floppy neonate with severe respiratory insufficiency and ventilator dependence in the newborn period. He had fetal growth restriction, facial dysmorphism, high arched palate, bilateral cryptorchidism, hypoplastic pons and cerebellum and probable hearing impairment. He succumbed to the illness on day 24 of life. There was a similar history of two previous sibling deaths in the early neonatal period due to respiratory insufficiency and history of multiple neonatal and infant deaths in the extended family. Transferrin iso-electric focusing was normal. Clinical exome sequencing revealed a novel homozygous missense mutation (c.1018 G > A) in RFT1 gene [NM_052859; c.1018G > A; p.G340S; ENST00000296292] and the parents were heterozygous for the same (ClinVar SVC000778540). The pathogenic variants so far reported are all missense variants affecting the luminal loops; whereas the variant in our case is in the trans-membrane helical domain. A strong family history of neonatal deaths and similar presentations in the previous 2 siblings suggests the homogenous phenotype of this mutation. Severe respiratory insuffiency and ventilator dependence shows the lethality of the disease phenotype and incompatibility with survival beyond the neonatal period.
Collapse
Affiliation(s)
- Thangaraj Abiramalatha
- Department of Neonatology, Christian Medical College, Vellore, India; Department of Neonatology, Sri Ramachandra Medical College and Research Institute, Chennai, India
| | - Gautham Arunachal
- Department of Clinical Genetics, Christian Medical College, Vellore, India
| | - Karthik Muthusamy
- Department of Pediatric Neurology, Christian Medical College, Vellore, India
| | - Niranjan Thomas
- Department of Neonatology, Christian Medical College, Vellore, India.
| |
Collapse
|
6
|
Quelhas D, Jaeken J, Fortuna A, Azevedo L, Bandeira A, Matthijs G, Martins E. RFT1-CDG: Absence of Epilepsy and Deafness in Two Patients with Novel Pathogenic Variants. JIMD Rep 2018; 43:111-116. [PMID: 29923091 DOI: 10.1007/8904_2018_112] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 04/29/2018] [Accepted: 05/03/2018] [Indexed: 12/14/2022] Open
Abstract
This report is on two novel patients with RFT1-CDG. Their phenotype is characterized by mild psychomotor disability, behavioral problems, ataxia, and mild dysmorphism. Neither of them shows signs of epilepsy, which was observed in all RFT1-CDG patients reported to date (n = 14). Also, deafness, which is often associated with this condition, was not observed in our patients. Molecular analysis of RFT1 showed biallelic missense variants including three novel ones: c.827G > A (p.G276D), c.73C > T (p.R25W), and c.208T > C (p.C70R).
Collapse
Affiliation(s)
- D Quelhas
- Unidade de Bioquímica Genética, Centro de Genética Médica, Centro Hospitalar do Porto, Porto, Portugal. .,Unit for Multidisciplinary Research in Biomedicine, ICBAS, UP, Porto, Portugal.
| | - J Jaeken
- Center for Metabolic Diseases, KU Leuven, Leuven, Belgium
| | - A Fortuna
- Unidade de Bioquímica Genética, Centro de Genética Médica, Centro Hospitalar do Porto, Porto, Portugal.,Unit for Multidisciplinary Research in Biomedicine, ICBAS, UP, Porto, Portugal
| | - L Azevedo
- i3S-Instituto de Investigação e Inovação em Saúde, UP, Population Genetics and Evolution Group, Porto, Portugal.,IPATIMUP-Institute of Molecular Pathology and Immunology, UP, Porto, Portugal.,FCUP-Department of Biology, Faculty of Sciences, UP, Porto, Portugal
| | - A Bandeira
- Centro Referência Doenças Hereditárias do Metabolismo, Centro Hospitalar do Porto, Porto, Portugal
| | - G Matthijs
- Department of Human Genetics, KU Leuven, Leuven, Belgium
| | - E Martins
- Unit for Multidisciplinary Research in Biomedicine, ICBAS, UP, Porto, Portugal.,Centro Referência Doenças Hereditárias do Metabolismo, Centro Hospitalar do Porto, Porto, Portugal
| |
Collapse
|
7
|
Ferreira CR, Altassan R, Marques-Da-Silva D, Francisco R, Jaeken J, Morava E. Recognizable phenotypes in CDG. J Inherit Metab Dis 2018; 41:541-553. [PMID: 29654385 PMCID: PMC5960425 DOI: 10.1007/s10545-018-0156-5] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Revised: 12/23/2017] [Accepted: 02/06/2018] [Indexed: 01/06/2023]
Abstract
Pattern recognition, using a group of characteristic, or discriminating features, is a powerful tool in metabolic diagnostic. A classic example of this approach is used in biochemical analysis of urine organic acid analysis, where the reporting depends more on the correlation of pertinent positive and negative findings, rather than on the absolute values of specific markers. Similar uses of pattern recognition in the field of biochemical genetics include the interpretation of data obtained by metabolomics, like glycomics, where a recognizable pattern or the presence of a specific glycan sub-fraction can lead to the direct diagnosis of certain types of congenital disorders of glycosylation. Another indispensable tool is the use of clinical pattern recognition-or syndromology-relying on careful phenotyping. While genomics might uncover variants not essential in the final clinical expression of disease, and metabolomics could point to a mixture of primary but also secondary changes in biochemical pathways, phenomics describes the clinically relevant manifestations and the full expression of the disease. In the current review we apply phenomics to the field of congenital disorders of glycosylation, focusing on recognizable differentiating findings in glycosylation disorders, characteristic dysmorphic features and malformations in PMM2-CDG, and overlapping patterns among the currently known glycosylation disorders based on their pathophysiological basis.
Collapse
Affiliation(s)
- Carlos R Ferreira
- Medical Genetics Branch National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
- Division of Genetics and Metabolism, Children's National Medical Center, Washington, DC, USA
| | - Ruqaia Altassan
- Metabolic Center, Department of Pediatrics, University Hospitals Leuven, Herestraat 49, B-3000, Leuven, Belgium
- Department of Development and Regeneration, Faculty of Medicine, KU Leuven, Leuven, Belgium
| | - Dorinda Marques-Da-Silva
- UCIBIO, Departamento Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Lisboa, Portugal
- Portuguese Association for CDG, Lisboa, Portugal
| | - Rita Francisco
- UCIBIO, Departamento Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade NOVA de Lisboa, Lisboa, Portugal
- Portuguese Association for CDG, Lisboa, Portugal
| | - Jaak Jaeken
- Metabolic Center, Department of Pediatrics, University Hospitals Leuven, Herestraat 49, B-3000, Leuven, Belgium
- Department of Development and Regeneration, Faculty of Medicine, KU Leuven, Leuven, Belgium
| | - Eva Morava
- Metabolic Center, Department of Pediatrics, University Hospitals Leuven, Herestraat 49, B-3000, Leuven, Belgium.
- Department of Development and Regeneration, Faculty of Medicine, KU Leuven, Leuven, Belgium.
- Department of Clinical Genomics, Center for Individualized Medicine, Mayo Clinic, Rochester, MN, USA.
| |
Collapse
|
8
|
Bastaki F, Bizzari S, Hamici S, Nair P, Mohamed M, Saif F, Malik EM, Al-Ali MT, Hamzeh AR. Single-center experience of N-linked Congenital Disorders of Glycosylation with a Summary of Molecularly Characterized Cases in Arabs. Ann Hum Genet 2017; 82:35-47. [PMID: 28940310 DOI: 10.1111/ahg.12220] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 08/14/2017] [Accepted: 08/16/2017] [Indexed: 12/18/2022]
Abstract
Congenital disorders of glycosylation (CDG) represent an expanding group of conditions that result from defects in protein and lipid glycosylation. Different subgroups of CDG display considerable clinical and genetic heterogeneity due to the highly complex nature of cellular glycosylation. This is further complicated by ethno-geographic differences in the mutational landscape of each of these subgroups. Ten Arab CDG patients from Latifa Hospital in Dubai, United Arab Emirates, were assessed using biochemical (glycosylation status of transferrin) and molecular approaches (next-generation sequencing [NGS] and Sanger sequencing). In silico tools including CADD and PolyPhen-2 were used to predict the functional consequences of uncovered mutations. In our sample of patients, five novel mutations were uncovered in the genes: MPDU1, PMM2, MAN1B1, and RFT1. In total, 9 mutations were harbored by the 10 patients in 7 genes. These are missense and nonsense mutations with deleterious functional consequences. This article integrates a single-center experience within a list of reported CDG mutations in the Arab world, accompanied by full molecular and clinical details pertaining to the studied cases. It also sheds light on potential ethnic differences that were not noted before in regards to CDG in the Arab world.
Collapse
Affiliation(s)
- Fatma Bastaki
- Pediatric Department, Latifa Hospital, Dubai Health Authority, Dubai, UAE
| | | | - Sana Hamici
- Pediatric Department, Latifa Hospital, Dubai Health Authority, Dubai, UAE
| | | | - Madiha Mohamed
- Pediatric Department, Latifa Hospital, Dubai Health Authority, Dubai, UAE
| | - Fatima Saif
- Pediatric Department, Latifa Hospital, Dubai Health Authority, Dubai, UAE
| | | | | | | |
Collapse
|
9
|
Barba C, Darra F, Cusmai R, Procopio E, Dionisi Vici C, Keldermans L, Vuillaumier-Barrot S, Lefeber DJ, Guerrini R. Congenital disorders of glycosylation presenting as epileptic encephalopathy with migrating partial seizures in infancy. Dev Med Child Neurol 2016; 58:1085-91. [PMID: 27172925 DOI: 10.1111/dmcn.13141] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/22/2016] [Indexed: 11/29/2022]
Abstract
AIM Epilepsy is commonly observed in congenital disorders of glycosylation (CDG), but no distinctive electroclinical pattern has been recognized. We aimed at identifying a characteristic clinical presentation that might help targeted diagnostic work-up. METHOD Based on the initial observation of an index case with CDG and migrating partial seizures, we evaluated 16 additional children with CDG and analysed their clinical course, biochemical, genetic, electrographic, and imaging findings. RESULTS Four of 17 consecutively observed children with CDG (three females, one male) were first referred between the first and fourth month of life, after early onset of migrating partial seizures. All four patients manifested developmental delay, microcephaly, and multi-organ involvement. Magnetic resonance imaging disclosed cerebral and cerebellar atrophy. Isoelectrofocusing of transferrin, enzymatic studies, and lipid-linked oligosaccharide analysis indicated CDG-I. Genetic testing demonstrated either homozygous or compound heterozygous variants involving the ALG3 gene in patients 1 and 3, the RFT1 gene in patient 2, and the ALG1 gene in patient 4. At last follow-up, patients 1 and 2 were 5 and 3(1/2) years old. Patients 3 and 4 had died due to respiratory failure during pneumonia and refractory status epilepticus respectively. INTERPRETATION Children with migrating partial seizures and concomitant multisystem involvement should be investigated for CDG.
Collapse
Affiliation(s)
- Carmen Barba
- Pediatric Neurology Unit and Laboratories, A. Meyer Children's Hospital - University of Florence, Florence, Italy
| | - Francesca Darra
- Child Neuropsychiatry, University-Hospital of Verona, Verona, Italy
| | | | - Elena Procopio
- Metabolic Unit, A. Meyer Children's Hospital - University of Florence, Florence, Italy
| | | | | | | | - Dirk J Lefeber
- Department of Neurology, Translational Metabolic Laboratory, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Renzo Guerrini
- Pediatric Neurology Unit and Laboratories, A. Meyer Children's Hospital - University of Florence, Florence, Italy.,IRCCS Stella Maris, Pisa, Italy
| | | |
Collapse
|
10
|
A Glycosylation Mutant of Trypanosoma brucei Links Social Motility Defects In Vitro to Impaired Colonization of Tsetse Flies In Vivo. EUKARYOTIC CELL 2015; 14:588-92. [PMID: 25862152 DOI: 10.1128/ec.00023-15] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/03/2015] [Indexed: 01/10/2023]
Abstract
Transmission of African trypanosomes by tsetse flies requires that the parasites migrate out of the midgut lumen and colonize the ectoperitrophic space. Early procyclic culture forms correspond to trypanosomes in the lumen; on agarose plates they exhibit social motility, migrating en masse as radial projections from an inoculation site. We show that an Rft1(-/-) mutant needs to reach a greater threshold number before migration begins, and that it forms fewer projections than its wild-type parent. The mutant is also up to 4 times less efficient at establishing midgut infections. Ectopic expression of Rft1 rescues social motility defects and restores the ability to colonize the fly. These results are consistent with social motility reflecting movement to the ectoperitrophic space, implicate N-glycans in the signaling cascades for migration in vivo and in vitro, and provide the first evidence that parasite-parasite interactions determine the success of transmission by the insect host.
Collapse
|
11
|
Helander A, Stödberg T, Jaeken J, Matthijs G, Eriksson M, Eggertsen G. Dolichol kinase deficiency (DOLK-CDG) with a purely neurological presentation caused by a novel mutation. Mol Genet Metab 2013; 110:342-4. [PMID: 23890587 DOI: 10.1016/j.ymgme.2013.07.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 06/30/2013] [Accepted: 07/01/2013] [Indexed: 01/05/2023]
Abstract
A 4-month old boy presented with multiple epileptic seizure types including West syndrome. Screening for infectious and structural etiologies showed normal results. A metabolic investigation was undertaken to investigate the cause of his neurological disease. Screening for congenital disorders of glycosylation (CDG) by HPLC analysis of serum carbohydrate-deficient transferrin (CDT) showed a type 1 pattern with 18% disialotransferrin (reference < 2%) and 2% asialotransferrin (reference 0). An undiagnosed 10-year old sister with a similar clinical history with infantile spasms at age 4 months, intellectual disability and an autism spectrum disorder, also showed a type 1 CDT pattern. Both siblings lacked dysmorphic features and extra-cerebral symptoms. The boy had cytotoxic edema of the thalamus and mesencephalon on MRI at age 7 months, whereas the girl had normal MRI at age 8 months. Phosphomannomutase (PMM) and phosphomannose isomerase (MPI) activities in cultured fibroblasts were normal, excluding PMM2-CDG and MPI-CDG. Fibroblast lipid-linked oligosaccharide analysis was also normal, suggesting an early defect in glycan assembly. Sequence analysis of the dolichol kinase gene revealed a homozygous new missense mutation (p.M1?; c.2 T > C) in both siblings. In conclusion, two siblings were demonstrated to suffer from DOLK-CDG (MIM 610768) and to be homozygous for a new mutation. They presented with West syndrome and so far show a purely neurological phenotype.
Collapse
Affiliation(s)
- Anders Helander
- Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden; Karolinska University Laboratory, Stockholm, Sweden.
| | | | | | | | | | | |
Collapse
|
12
|
Jelk J, Gao N, Serricchio M, Signorell A, Schmidt RS, Bangs JD, Acosta-Serrano A, Lehrman MA, Bütikofer P, Menon AK. Glycoprotein biosynthesis in a eukaryote lacking the membrane protein Rft1. J Biol Chem 2013; 288:20616-23. [PMID: 23720757 PMCID: PMC3711325 DOI: 10.1074/jbc.m113.479642] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Revised: 05/21/2013] [Indexed: 12/13/2022] Open
Abstract
Mature dolichol-linked oligosaccharides (mDLOs) needed for eukaryotic protein N-glycosylation are synthesized by a multistep pathway in which the biosynthetic lipid intermediate Man5GlcNAc2-PP-dolichol (M5-DLO) flips from the cytoplasmic to the luminal face of the endoplasmic reticulum. The endoplasmic reticulum membrane protein Rft1 is intimately involved in mDLO biosynthesis. Yeast genetic analyses implicated Rft1 as the M5-DLO flippase, but because biochemical tests challenged this assignment, the function of Rft1 remains obscure. To understand the role of Rft1, we sought to analyze mDLO biosynthesis in vivo in the complete absence of the protein. Rft1 is essential for yeast viability, and no Rft1-null organisms are currently available. Here, we exploited Trypanosoma brucei (Tb), an early diverging eukaryote whose Rft1 homologue functions in yeast. We report that TbRft1-null procyclic trypanosomes grow nearly normally. They have normal steady-state levels of mDLO and significant N-glycosylation, indicating robust M5-DLO flippase activity. Remarkably, the mutant cells have 30-100-fold greater steady-state levels of M5-DLO than wild-type cells. All N-glycans in the TbRft1-null cells originate from mDLO indicating that the M5-DLO excess is not available for glycosylation. These results suggest that rather than facilitating M5-DLO flipping, Rft1 facilitates conversion of M5-DLO to mDLO by another mechanism, possibly by acting as an M5-DLO chaperone.
Collapse
Affiliation(s)
- Jennifer Jelk
- the Institute of Biochemistry and Molecular Medicine,
University of Bern, 3012 Bern, Switzerland
| | - Ningguo Gao
- the Department of Pharmacology, University of Texas
Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Mauro Serricchio
- the Institute of Biochemistry and Molecular Medicine,
University of Bern, 3012 Bern, Switzerland
| | - Aita Signorell
- From the Department of Biochemistry, Weill Cornell Medical
College, New York, New York 10065
| | - Remo S. Schmidt
- the Institute of Biochemistry and Molecular Medicine,
University of Bern, 3012 Bern, Switzerland
| | - James D. Bangs
- the Department of Microbiology and Immunology, School of
Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, New York 14214,
and
| | - Alvaro Acosta-Serrano
- the Parasitology and Vector Biology Departments,
Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
| | - Mark A. Lehrman
- the Department of Pharmacology, University of Texas
Southwestern Medical Center at Dallas, Dallas, Texas 75390
| | - Peter Bütikofer
- the Institute of Biochemistry and Molecular Medicine,
University of Bern, 3012 Bern, Switzerland
| | - Anant K. Menon
- From the Department of Biochemistry, Weill Cornell Medical
College, New York, New York 10065
| |
Collapse
|
13
|
Barone R, Aiello C, Race V, Morava E, Foulquier F, Riemersma M, Passarelli C, Concolino D, Carella M, Santorelli F, Vleugels W, Mercuri E, Garozzo D, Sturiale L, Messina S, Jaeken J, Fiumara A, Wevers RA, Bertini E, Matthijs G, Lefeber DJ. DPM2-CDG: a muscular dystrophy-dystroglycanopathy syndrome with severe epilepsy. Ann Neurol 2013; 72:550-8. [PMID: 23109149 DOI: 10.1002/ana.23632] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
OBJECTIVE Congenital disorders of glycosylation (CDG) are a group of metabolic diseases due to defects in protein and lipid glycosylation. We searched for the primary defect in 3 children from 2 families with a severe neurological phenotype, including profound developmental delay, intractable epilepsy, progressive microcephaly, severe hypotonia with elevated blood creatine kinase levels, and early fatal outcome. There was clinical evidence of a muscular dystrophy-dystroglycanopathy syndrome, supported by deficient O-mannosylation by muscle immunohistochemistry. METHODS Biochemical and molecular methods were combined to pinpoint the defect in the glycosylation pathway in the endoplasmic reticulum. RESULTS Metabolic investigations revealed CDG-I, pointing to a defect in protein N-glycosylation in the endoplasmic reticulum. Analysis of lipid-linked oligosaccharides in fibroblasts showed accumulation of Dol-PP-GlcNAc(2) -Man(5) . DNA analysis revealed mutations in DPM2, 1 of the subunits of the dolichol-phosphate-mannose (DPM) synthase; the patient in the first family is compound heterozygous for 2 mutations (c.68A>G, predicting a missense mutation p.Y23C and c.4-1G>C, a splice mutation), whereas the patients in the second family are homozygous for the same missense mutation (c.68A>G, p.Y23C). INTERPRETATION We describe a new CDG, due to a deficiency of DPM2. Hence, mutations have now been described in the genes for the 3 subunits of DPM: DPM1, DPM2, and DPM3, whereby DPM2-CDG links the congenital disorders of glycosylation to the congenital muscular dystrophies.
Collapse
Affiliation(s)
- Rita Barone
- Pediatric Neurology, Department of Pediatrics, University of Catania, Catania, Italy
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Ondruskova N, Vesela K, Hansikova H, Magner M, Zeman J, Honzik T. RFT1-CDG in adult siblings with novel mutations. Mol Genet Metab 2012; 107:760-2. [PMID: 23111317 DOI: 10.1016/j.ymgme.2012.10.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/26/2012] [Revised: 10/07/2012] [Accepted: 10/07/2012] [Indexed: 11/29/2022]
Abstract
RFT1-CDG is a rare N-glycosylation disorder. Only 6 children with RFT1-CDG have been described, all with failure to thrive, feeding problems, hypotonia, developmental delay, epilepsy, decreased vision, deafness and thrombotic complications. We report on two young adult siblings with RFT1-CDG, compound heterozygotes for the novel missense mutations c.1222A>G (p.M408V) and c.1325G>A (p.R442Q) in RFT1 gene. Similar to the previously described patients, these siblings have profound intellectual disability but no feeding problems or failure to thrive. Their epilepsy is well controlled and coagulopathy is mild without clinical consequences. In addition, visual acuity is normal in both patients and hearing impairment is present only in one. Our findings extend the phenotype associated with RFT1-CDG.
Collapse
Affiliation(s)
- Nina Ondruskova
- Department of Pediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University in Prague and General University Hospital in Prague, Prague, Czech Republic
| | | | | | | | | | | |
Collapse
|
15
|
Diseases of glycosylation beyond classical congenital disorders of glycosylation. Biochim Biophys Acta Gen Subj 2012; 1820:1306-17. [DOI: 10.1016/j.bbagen.2012.02.001] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 01/31/2012] [Accepted: 02/02/2012] [Indexed: 12/30/2022]
|
16
|
Targeted polymerase chain reaction-based enrichment and next generation sequencing for diagnostic testing of congenital disorders of glycosylation. Genet Med 2012; 13:921-32. [PMID: 21811164 DOI: 10.1097/gim.0b013e318226fbf2] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
PURPOSE Congenital disorders of glycosylation are a heterogeneous group of disorders caused by deficient glycosylation, primarily affecting the N-linked pathway. It is estimated that more than 40% of congenital disorders of glycosylation patients lack a confirmatory molecular diagnosis. The purpose of this study was to improve molecular diagnosis for congenital disorders of glycosylation by developing and validating a next generation sequencing panel for comprehensive mutation detection in 24 genes known to cause congenital disorders of glycosylation. METHODS Next generation sequencing validation was performed on 12 positive control congenital disorders of glycosylation patients. These samples were blinded as to the disease-causing mutations. Both RainDance and Fluidigm platforms were used for sequence enrichment and targeted amplification. The SOLiD platform was used for sequencing the amplified products. Bioinformatic analysis was performed using NextGENe® software. RESULTS The disease-causing mutations were identified by next generation sequencing for all 12 positive controls. Additional variants were also detected in three controls that are known or predicted to impair gene function and may contribute to the clinical phenotype. CONCLUSIONS We conclude that development of next generation sequencing panels in the diagnostic laboratory where multiple genes are implicated in a disorder is more cost-effective and will result in improved and faster patient diagnosis compared with a gene-by-gene approach. Recommendations are also provided for data analysis from the next generation sequencing-derived data in the clinical laboratory, which will be important for the widespread use of this technology.
Collapse
|
17
|
Jones MA, Ng BG, Bhide S, Chin E, Rhodenizer D, He P, Losfeld ME, He M, Raymond K, Berry G, Freeze HH, Hegde MR. DDOST mutations identified by whole-exome sequencing are implicated in congenital disorders of glycosylation. Am J Hum Genet 2012; 90:363-8. [PMID: 22305527 DOI: 10.1016/j.ajhg.2011.12.024] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 12/12/2011] [Accepted: 12/30/2011] [Indexed: 01/16/2023] Open
Abstract
Congenital disorders of glycosylation (CDG) are inherited autosomal-recessive diseases that impair N-glycosylation. Approximately 20% of patients do not survive beyond the age of 5 years old as a result of widespread organ dysfunction. Although most patients receive a CDG diagnosis based on abnormal glycosylation of transferrin, this test cannot provide a genetic diagnosis; indeed, many patients with abnormal transferrin do not have mutations in any known CDG genes. Here, we combined biochemical analysis with whole-exome sequencing (WES) to identify the genetic defect in an untyped CDG patient, and we found a 22 bp deletion and a missense mutation in DDOST, whose product is a component of the oligosaccharyltransferase complex that transfers the glycan chain from a lipid carrier to nascent proteins in the endoplasmic reticulum lumen. Biochemical analysis with three biomarkers revealed that N-glycosylation was decreased in the patient's fibroblasts. Complementation with wild-type-DDOST cDNA in patient fibroblasts restored glycosylation, indicating that the mutations were pathological. Our results highlight the power of combining WES and biochemical studies, including a glyco-complementation system, for identifying and confirming the defective gene in an untyped CDG patient. This approach will be very useful for uncovering other types of CDG as well.
Collapse
Affiliation(s)
- Melanie A Jones
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Abstract
Glycosylation is an essential process by which sugars are attached to proteins and lipids. Complete lack of glycosylation is not compatible with life. Because of the widespread function of glycosylation, inherited disorders of glycosylation are multisystemic. Since the identification of the first defect on N-linked glycosylation in the 1980s, there are over 40 different congenital protein hypoglycosylation diseases. This review will include defects of N-linked glycosylation, O-linked glycosylation and disorders of combined N- and O-linked glycosylation.
Collapse
Affiliation(s)
- Susan E Sparks
- Department of Pediatrics, Levine Children's Hospital at Carolinas Medical Center, Charlotte, NC, USA; Department of Pediatrics, University of North Carolina School of Medicine, Chapel Hill, NC, USA
| |
Collapse
|
19
|
Jaeken J. Congenital disorders of glycosylation (CDG): it's (nearly) all in it! J Inherit Metab Dis 2011; 34:853-8. [PMID: 21384229 DOI: 10.1007/s10545-011-9299-3] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 02/08/2011] [Accepted: 02/10/2011] [Indexed: 12/28/2022]
Abstract
Congenital disorders of glycosylation (CDG) is a booming class of metabolic diseases. Its number has increased nearly fourfold (to 45) since 2003, the year of the Komrower lecture, entitled 'Congenital disorders of glycosylation CDG): It's all in it!'. This paper presents an overview of recently discovered CDG and CDG phenotypes, of a diagnostic approach, of (the lack of) treatment, of CDG genetics, of a novel CDG nomenclature and classification, and of some future directions in the CDG field.
Collapse
Affiliation(s)
- Jaak Jaeken
- Universitair Ziekenhuis Gasthuisberg, Herestraat 49, 3000, Leuven, Belgium.
| |
Collapse
|
20
|
Mohamed M, Guillard M, Wortmann S, Cirak S, Marklova E, Michelakakis H, Korsch E, Adamowicz M, Koletzko B, van Spronsen F, Niezen-Koning K, Matthijs G, Gardeitchik T, Kouwenberg D, Lim BC, Zeevaert R, Wevers R, Lefeber D, Morava E. Clinical and diagnostic approach in unsolved CDG patients with a type 2 transferrin pattern. Biochim Biophys Acta Mol Basis Dis 2011; 1812:691-8. [DOI: 10.1016/j.bbadis.2011.02.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 02/18/2011] [Accepted: 02/22/2011] [Indexed: 11/29/2022]
|
21
|
Vleugels W, Duvet S, Peanne R, Mir AM, Cacan R, Michalski JC, Matthijs G, Foulquier F. Identification of phosphorylated oligosaccharides in cells of patients with a congenital disorders of glycosylation (CDG-I). Biochimie 2011; 93:823-33. [PMID: 21315133 DOI: 10.1016/j.biochi.2011.01.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 01/29/2011] [Indexed: 11/24/2022]
Abstract
Protein N-glycosylation is initiated by the dolichol cycle in which the oligosaccharide precursor Glc(3)Man(9)GlcNAc(2)-PP-dolichol is assembled in the endoplasmic reticulum (ER). One critical step in the dolichol cycle concerns the availability of Dol-P at the cytosolic face of the ER membrane. In RFT1 cells, the lipid-linked oligosaccharide (LLO) intermediate Man(5)GlcNAc(2)-PP-Dol accumulates at the cytosolic face of the ER membrane. Since Dol-P is a rate-limiting intermediate during protein N-glycosylation, continuous accumulation of Man(5)GlcNAc(2)-PP-Dol would block the dolichol cycle. Hence, we investigated the molecular mechanisms by which accumulating Man(5)GlcNAc(2)-PP-Dol could be catabolized in RFT1 cells. On the basis of metabolic labeling experiments and in comparison to human control cells, we identified phosphorylated oligosaccharides (POS), not found in human control cells and present evidence that they originate from the accumulating LLO intermediates. In addition, POS were also detected in other CDG patients' cells accumulating specific LLO intermediates at different cellular locations. Moreover, the enzymatic activity that hydrolyses oligosaccharide-PP-Dol into POS was identified in human microsomal membranes and required Mn(2+) for optimal activity. In CDG patients' cells, we thus identified and characterized POS that could result from the catabolism of accumulating LLO intermediates.
Collapse
Affiliation(s)
- Wendy Vleugels
- Laboratory for Molecular Diagnosis, Center for Human Genetics, University of Leuven, B-3000 Leuven, Belgium
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Cantagrel V, Lefeber DJ, Ng BG, Guan Z, Silhavy JL, Bielas SL, Lehle L, Hombauer H, Adamowicz M, Swiezewska E, De Brouwer AP, Blümel P, Sykut-Cegielska J, Houliston S, Swistun D, Ali BR, Dobyns WB, Babovic-Vuksanovic D, van Bokhoven H, Wevers RA, Raetz CRH, Freeze HH, Morava E, Al-Gazali L, Gleeson JG. SRD5A3 is required for converting polyprenol to dolichol and is mutated in a congenital glycosylation disorder. Cell 2010; 142:203-17. [PMID: 20637498 DOI: 10.1016/j.cell.2010.06.001] [Citation(s) in RCA: 204] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2010] [Revised: 03/26/2010] [Accepted: 05/06/2010] [Indexed: 02/08/2023]
Abstract
N-linked glycosylation is the most frequent modification of secreted and membrane-bound proteins in eukaryotic cells, disruption of which is the basis of the congenital disorders of glycosylation (CDGs). We describe a new type of CDG caused by mutations in the steroid 5alpha-reductase type 3 (SRD5A3) gene. Patients have mental retardation and ophthalmologic and cerebellar defects. We found that SRD5A3 is necessary for the reduction of the alpha-isoprene unit of polyprenols to form dolichols, required for synthesis of dolichol-linked monosaccharides, and the oligosaccharide precursor used for N-glycosylation. The presence of residual dolichol in cells depleted for this enzyme suggests the existence of an unexpected alternative pathway for dolichol de novo biosynthesis. Our results thus suggest that SRD5A3 is likely to be the long-sought polyprenol reductase and reveal the genetic basis of one of the earliest steps in protein N-linked glycosylation.
Collapse
Affiliation(s)
- Vincent Cantagrel
- Neurogenetics Laboratory, Institute for Genomic Medicine, Howard Hughes Medical Institute, Department of Neurosciences and Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Jaeken J, Vleugels W, Régal L, Corchia C, Goemans N, Haeuptle MA, Foulquier F, Hennet T, Matthijs G, Dionisi-Vici C. RFT1-CDG: deafness as a novel feature of congenital disorders of glycosylation. J Inherit Metab Dis 2009; 32 Suppl 1:S335-8. [PMID: 19856127 DOI: 10.1007/s10545-009-1297-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 09/24/2009] [Accepted: 09/25/2009] [Indexed: 10/20/2022]
Abstract
Congenital disorders of glycosylation (CDG) are genetic diseases due to defects in the synthesis of glycans and in the attachment of glycans to lipids and proteins. Actually, some 42 CDG are known including defects in protein N-glycosylation, in protein O-glycosylation, in lipid glycosylation, and in multiple and other glycosylation pathways. Most CDG are multisystem diseases and a large number of signs and symptoms have already been reported in CDG. An exception to this is deafness. This symptom has not been observed as a consistent feature in CDG. In 2008, a novel defect was identified in protein N-glycosylation, namely in RFT1. This is a defect in the assembly of N-glycans. RFT1 is involved in the transfer of Man(5)GlcNAc(2)-PP-Dol from the cytoplasmic to the luminal side of the endoplasmic reticulum. According to the novel nomenclature (non-italicized gene symbol followed by -CDG) this defect is named RFT1-CDG. Recently, three other patients with RFT1-CDG have been reported and here we report two novel patients. Remarkably, all six patients with RFT1-CDG show sensorineural deafness as part of a severe neurological syndrome. We conclude that RFT1-CDG is the first 'deafness-CDG'. CDG should be included in the work-up of congenital, particularly syndromic, hearing loss.
Collapse
Affiliation(s)
- J Jaeken
- Center for Metabolic Disease, University of Leuven, Leuven, Belgium.
| | | | | | | | | | | | | | | | | | | |
Collapse
|