Mutations in WDR62, encoding a centrosomal and nuclear protein, in Indian primary microcephaly families with cortical malformations

Primary microcephaly is an autosomal recessive disorder characterized by smaller than normal brain size and mental retardation. It is genetically heterogeneous with seven loci: MCPH1-MCPH7. We have previously reported genetic analysis of 35 families, including the identification of the MCPH7 gene STIL. Of the 35 families, three families showed linkage to the MCPH2 locus. Recent whole-exome sequencing studies have shown that the WDR62 gene, located in the MCPH2 candidate region, is mutated in patients with severe brain malformations. We therefore sequenced the WDR62 gene in our MCPH2 families and identified two novel homozygous protein truncating mutations in two families. Affected individuals in the two families had pachygyria, microlissencephaly, band heterotopias, gyral thickening, and dysplastic cortex. Using immunofluorescence study, we showed that, as with other MCPH proteins, WDR62 localizes to centrosomes in A549, HepG2, and HaCaT cells. In addition, WDR62 was also localized to nucleoli. Bioinformatics analysis predicted two overlapping nuclear localization signals and multiple WD-40 repeats in WDR62. Two other groups have also recently identified WDR62 mutations in MCPH2 families. Our results therefore add further evidence that WDR62 is the MCPH2 gene. The present findings will be helpful in genetic diagnosis of patients linked to the MCPH2 locus

Analysis of rare variants in the CFH gene in patients with the cuticular drusen subtype of age-related macular degeneration

Purpose: Age-related macular degeneration (AMD) and cuticular drusen (CD), a clinical subtype of AMD, have been linked to genetic variants in the complement factor H (CFH) gene. In this study, we aimed to investigate the frequency of rare variants in the CFH gene in 180 cases with CD. In addition, we aimed to determine the frequency of a previously reported rare, highly penetrant CFH variant (p. Arg1210Cys) in a Dutch-German non-CD-type AMD case-control cohort, and to describe the phenotype of patients carrying the p. Arg1210Cys variant. Methods: Study subjects were selected from the European Genetic Database (EUGENDA), a joint AMD database of the Radboud University Medical Centre and the University Hospital of Cologne, and graded at the Cologne Image Reading Centre and Laboratory (CIRCL). Additionally, two CD cases were recruited from the VU Medical Centre in Amsterdam. The CFH gene was analyzed in 180 CD cases with Sanger sequencing. All identified variants were analyzed for potential damaging effects with prediction software tools Sorting Intolerant from Tolerant (SIFT) and Polymorphism Phenotyping (PolyPhen). In addition, we genotyped the p. Arg1210Cys variant in 813 non-CD type AMD cases and 1175 controls. Results: Sequencing identified 11 rare, heterozygous missense variants, one frameshift variant, and one splice acceptor site variant in 16 CD cases. The p. Arg1210Cys variant was identified in two CD cases but was not identified in our Dutch-German non-CD-type AMD case-control cohort. Conclusions: The present study identified the presence of rare variants in the CFH gene in 16 (8.8%) of 180 patients with the CD subtype of AMD. The carriers of rare CFH variants displayed a significantly earlier age at onset than non-carriers (p=0.016). The rare missense variant p. Arg1210Cys was identified in two CD cases, but was not detected in 813 non-CD type AMD cases or in the 1,175 controls of our Dutch-German cohort. The current study suggests that the p. Arg1210Cys variant may be restricted to a subset of patients with the CD subtype of AMD. Detailed clinical pheno-typing, including fluorescein angiography, of patients with AMD carrying the p. Arg1210Cys variant in other cohorts is required to confirm this finding

Whole Exome Sequencing in Patients with the Cuticular Drusen Subtype of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in elderly people worldwide. Cuticular drusen (CD) is a clinical subtype of AMD, which typically displays an earlier age at onset, and has a strong genetic component. Genetic studies support a role for rare sequence variants in CD susceptibility, and rare sequence variants in the CFH gene have been identified in 8.8% of CD cases. To further explore the role of rare variants in CD, we performed whole exome sequencing (WES) in 14 affected members of six families and 12 sporadic cases with CD. We detected rare sequence variants in CFH and FBLN5, which previously were shown to harbor rare variants in patients with CD. In addition, we detected heterozygous rare sequence variants in several genes encoding components of the extracellular matrix (ECM), including FBLN1, FBLN3/EFEMP1, FBLN5, FBLN6/HMCN1, FBN2, and COL15A1. Two rare pathogenic variants were identified in the COL15A1 gene: one in a sporadic case and another was found to segregate in a family with six affected individuals with CD. In addition, two rare pathogenic variants were identified in the FGL1 gene in three unrelated CD cases. These findings suggest that alterations in the ECM and in the coagulation pathway may play a role in the pathogenesis of CD. The identified candidate genes require further analyses in larger cohorts to confirm their role in the CD subtype of AMD. No evidence was found of rare sequence variants in a single gene that segregate with CD in the six families, suggesting that the disease is genetically heterogeneous