Jamil A Hashmi1, Fatima Fadhli2, Ahmed Almatrafi3, Sibtain Afzal4, Khushnooda Ramzan5, Holger Thiele6, Peter Nürnberg6, Sulman Basit7. 1. Center for Genetics and Inherited Diseases, Taibah University Almadinah Almunawwarah, Saudi Arabia. 2. Department of Genetic Diseases, King Abdulla Medical City-Madinah Maternity and Children Hospital, Almadinah Almunawwarah, Saudi Arabia. 3. Department of Biology, College of Science, Taibah University, Almadinah Almunawwarah, Saudi Arabia. 4. Faculty of Allied & Health Sciences, Imperial College of Business Studies, Lahore, Pakistan. 5. Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia. 6. Cologne Center for Genomics (CCG), University of Cologne, Weyertal 115 b, 50931 Cologne, Germany. 7. Center for Genetics and Inherited Diseases, Taibah University Almadinah Almunawwarah, Saudi Arabia. Electronic address: sbasit.phd@gmail.com.
Abstract
BACKGROUND: Cohen syndrome (CS) is a rare multi-system autosomal recessive disorder with a high prevalence in the Finnish population. Clinical features of Finnish-type CS are homogeneous, however, in non-Finnish populations, CS diagnosis is challenging due to broad phenotypic variability. METHODS: We studied a consanguineous family having three affected individuals with clinical features of severe intellectual disability and global developmental delay. Clinical diagnosis of the phenotype could not be established based on the features. Therefore, whole genome SNP genotyping and whole exome sequencing (WES) were performed on DNA samples from affected and unaffected family members. RESULTS: Homozygosity mapping identified a shared loss of heterozygosity region on chromosome 8q22.1-q22.3 and WES data analysis revealed an insertion-deletion (indel) mutation (c.11519_11521delCAAinsT) in the VPS13B gene. The indel is predicted to cause a frameshift resulting in a premature termination of the VPS13B protein (NP_060360.3:p.Pro3840Leufs*2). CONCLUSION: VPS13B encodes a giant transmembrane protein called vacuolar protein sorting 13 homolog B. VPS13B is known to play a role in the glycosylation of Golgi proteins and in endosomal-lysosomal trafficking. Moreover, it is thought to function in vesicle mediated transport and sorting of proteins within the cell. The mechanism by which abnormalities of the VPS13B protein lead to the phenotype of CS is currently unknown. Here, in this study, we successfully established a clinical diagnosis of CS cases from a family using genomic analyses. Clinical re-examination of the patients revealed characteristic ocular abnormalities.
BACKGROUND:Cohen syndrome (CS) is a rare multi-system autosomal recessive disorder with a high prevalence in the Finnish population. Clinical features of Finnish-type CS are homogeneous, however, in non-Finnish populations, CS diagnosis is challenging due to broad phenotypic variability. METHODS: We studied a consanguineous family having three affected individuals with clinical features of severe intellectual disability and global developmental delay. Clinical diagnosis of the phenotype could not be established based on the features. Therefore, whole genome SNP genotyping and whole exome sequencing (WES) were performed on DNA samples from affected and unaffected family members. RESULTS: Homozygosity mapping identified a shared loss of heterozygosity region on chromosome 8q22.1-q22.3 and WES data analysis revealed an insertion-deletion (indel) mutation (c.11519_11521delCAAinsT) in the VPS13B gene. The indel is predicted to cause a frameshift resulting in a premature termination of the VPS13B protein (NP_060360.3:p.Pro3840Leufs*2). CONCLUSION:VPS13B encodes a giant transmembrane protein called vacuolar protein sorting 13 homolog B. VPS13B is known to play a role in the glycosylation of Golgi proteins and in endosomal-lysosomal trafficking. Moreover, it is thought to function in vesicle mediated transport and sorting of proteins within the cell. The mechanism by which abnormalities of the VPS13B protein lead to the phenotype of CS is currently unknown. Here, in this study, we successfully established a clinical diagnosis of CS cases from a family using genomic analyses. Clinical re-examination of the patients revealed characteristic ocular abnormalities.