Novel mutations identified in Chinese families with autosomal dominant congenital cataracts by targeted next-generation sequencing

Abstract

BackgroundCongenital cataract is a clinically and genetically heterogeneous visual impairment. The aim of this study was to identify causative mutations in five unrelated Chinese families diagnosed with congenital cataracts.MethodsDetailed family history and clinical data were collected, and ophthalmological examinations were performed using slit-lamp photography. Genomic DNA was extracted from peripheral blood of all available members. Thirty-eight genes associated with cataract were captured and sequenced in 5 typical nonsyndromic congenital cataract probands by targeted next-generation sequencing (NGS), and the results were confirmed by Sanger sequencing. Bioinformatics analysis was performed to predict the functional effect of mutant genes.ResultsResults from the DNA sequencing revealed five potential causative mutations: c.154 T > C(p.F52 L) in GJA8 of Family 1, c.1152_1153insG(p.S385Efs*83) in GJA3 of Family 2, c.1804 G > C(p.G602R) in BFSP1 of Family 3, c.1532C > T(p.T511 M) in EPHA2 of Family 4 and c.356G > A(p.R119H) in HSF4 of Family 5. These mutations co-segregated with all affected individuals in the families and were not found in unaffected family members nor in 50 controls. Bioinformatics analysis from several prediction tools supported the possible pathogenicity of these mutations.ConclusionsIn this study, we identified five novel mutations (c.154 T > C in GJA8, c.1152_1153insG in GJA3, c.1804G > C in BFSP1, c.1532C > T in EPHA2, c.356G > A in HSF4) in five Chinese families with hereditary cataracts, respectively. NGS can be used as an effective tool for molecular diagnosis of genetically heterogeneous disorders such as congenital cataract, and the results can provide more effective clinical diagnosis and genetic counseling for the five families.

A novel missense mutation in the HSF4 gene of giant pandas with senile congenital cataracts

“…This residue lies downstream of the region specific isoform HSF4b, the main splice variant expressed in the lens, and within a highly-conserved segment just before the downstream hydrophobic region. The equivalent human mutation (R371W) has not been reported to our knowledge, although multiple studies have described pathogenic mutations in other parts of the human protein caused by the replacement of arginine residues, including R73H 9 , 15 , R73L 28 , R110C 32 , R119C 5 , 33 , R119H 30 , and R175P 11 . Almost all of these mutations affect the DNA-binding domain, with only R175P found in the oligomerization domain 11 .…”

“…However, no disease-causing mutations have been reported in the isoform-specific region unique to HSF4b, or in the large conserved block of amino acids between the isoform-specific region and the downstream hydrophobic repeat. Additional disease-causing mutations have been found in reports published after the literature survey, but these are also located primarily in the DNA-binding domain 28 – 30 and one very near to the C-terminus of the protein 31 . The discovery of a pathogenic mutation between the isoform-specific and downstream hydrophobic regions of the giant panda HSF4 protein therefore indicates a potential novel disease mechanism.…”

Whole Exome Sequencing Reveals Novel and Recurrent Disease-Causing Variants in Lens Specific Gap Junctional Protein Encoding Genes Causing Congenital Cataract

“…The novel p.Ser258GlnfsTer68 frameshift variant identified in family C resulted from a cytosine insertion that introduced a premature translation stop codon, located in the cytoplasmic carboxy-terminal region of Cx46 protein. Four other disease-causing variants, c.1137dupC, c.1189dupG, c.1200dupC, c.1152insG, in GJA3 have previously been localised to the same region of the protein with all causing cataract [33][34][35][36]. Several missense or truncated carboxy-terminal Cx32 mutants linked to CMTX have also been shown to cause loss or reduction in function [37,38].…”

Abnormal function of EPHA2/p.R957P mutant in congenital cataract

“…The c.2870G>C transversion leads to the substitution of a nonpolar and hydrophobic proline residue for a positive charge and highly conserved arginine residue at codon 957 (p.R957P) which located at the SAM domain of EPHA2. Since human EPHA2 was first identified as the causative gene responsible for cataracts that map to 1p36 in 2008 [9] , twentyfive variants were reported in different populations so far (https://cat-map.wustl.edu/; Table 2) [1,4,9,21,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] . These variants are located in different domains of EPHA2, including CRD, FN III, JMS, TK, SAM and PDZ domains.…”