A novel mutation of p.F32I in GJA8 in human dominant congenital cataracts.

AIM: To identify a causative mutation in a three-generation family with autosomal dominant congenital total cataract and dissect the molecular consequence of the identified mutation. METHODS: Clinical and ophthalmological examinations were performed on the affected and unaffected family members. Mutation were screened in recruited family members by polymerase chain reaction (PCR) of the two reported genes (CRYAA and GJA8) which were linked to human total cataracts and direct sequencing of the PCR product. The molecular consequences of the identified mutation was dissected. The plasmids carrying wild-type and mutant mouse ORF of Gja8, coding for connexin 50 (Cx50), were generated and ectopic expressed in 293 cells. Recombinant protein expression and cellular localization of recombinated Cx50 were assessed by confocal microscopy. RESULTS: Clinical and ophthalmological examinations were performed on the affected and unaffected family members. Mutation were screened in recruited family members by PCR of the two reported genes (CRYAA and GJA8) which were linked to human total cataracts and direct sequencing of the PCR product. The molecular consequences of the identified mutation was dissected. The plasmids carrying wild-type and mutant mouse ORF of Gja8, coding for Cx50, were generated and ectopic expressed in 293 cells. Recombinant protein expression and cellular localization of recombinated Cx50 were assessed by confocal microscopy. CONCLUSION: This study has identified a novel cataract mutation in GJA8, which adds a novel mutation to the existing spectrum of Cx50 mutations with cataract. The molecular consequences of p.F32I mutation in GJA8 exclude instability and the mislocalization of mutant Cx50 protein.

Novel mutations in PDE6B causing human retinitis pigmentosa.

AIM: To identify the genetic defects of a Chinese patient with sporadic retinitis pigmentosa (RP). METHODS: Ophthalmologic examinations were performed on the sporadic RP patient, 144 genes associated with retinal diseases were scanned with capture next generation sequencing (CNGS) approach. Two heterozygous mutations in PDE6B were confirmed in the pedigree by Sanger sequencing subsequently. The carrier frequency of PDE6B mutations of reported PDE6B mutations based on the available two public exome databases (1000 Genomes Project and ESP6500 Genomes Project) and one in-house exome database was investigated. RESULTS: We identified compound heterozygosity of two novel nonsense mutations c.1133G>A (p.W378X) and c.2395C>T (p.R799X) in PDE6B, one reported causative gene for RP. Neither of the two mutations in our study was presented in three exome databases. Two mutations (p.R74C and p.T604I) in PDE6B have relatively high frequencies in the ESP6500 and in-house databases, respectively, while no common dominant mutation in each of the database or across all databases. CONCLUSION: We demonstrates that compound heterozygosity of two novel nonsense mutations in PDE6B could lead to RP. These results collectively point to enormous potential of next-generation sequencing in determining the genetic etiology of RP and how various mutations in PDE6B contribute to the genetic heterogeneity of RP.

Identification of a novel GJA8 (Cx50) point mutation causes human dominant congenital cataracts.

Hereditary cataracts are clinically and genetically heterogeneous lens diseases that cause a significant proportion of visual impairment and blindness in children. Human cataracts have been linked with mutations in two genes, GJA3 and GJA8, respectively. To identify the causative mutation in a family with hereditary cataracts, family members were screened for mutations by PCR for both genes. Sequencing the coding regions of GJA8, coding for connexin 50, revealed a C > A transversion at nucleotide 264, which caused p.P88T mutation. To dissect the molecular consequences of this mutation, plasmids carrying wild-type and mutant mouse ORFs of Gja8 were generated and ectopically expressed in HEK293 cells and human lens epithelial cells, respectively. The recombinant proteins were assessed by confocal microscopy and Western blotting. The results demonstrate that the molecular consequences of the p.P88T mutation in GJA8 include changes in connexin 50 protein localization patterns, accumulation of mutant protein, and increased cell growth.