Identification of a New Mutation p.P88L in Connexin 50 Associated with Dominant Congenital Cataract.
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SUBMITTER: Jin A
PROVIDER: S-EPMC9068895 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:PurposeTo identify the genetic cause responsible for the autosomal dominant hereditary cataract in a Chinese family.MethodsA whole family of a proband who has a dominant congenital pulverulent nuclear cataract was recruited into Zhongnan Hospital. The lenses of patients were observed by a slit-lamp microscope, and the lenses of the proband's mother were analyzed by scanning electron microscopy. Mutation screening was performed in the cataract candidate genes coding for crystallins and connexin 50 by sequencing of polymerase chain reaction (PCR) products amplified from blood leukocyte DNA samples of eight family members. The identified mutation was then investigated in other participated family members, 200 normal controls, and 40 senile cataract patients by the restriction fragment length polymorphism (RFLP) method.ResultsThe structure of the lens opacities of the proband's mother is puffy, and the fibers are tangled under a scanning electron microscope. A novel C>T transition at nucleotide position 827 was determined in the connexin 50 (GJA8) gene. This mutation led to a serine (S) to phenylalanine (F) amino acid substitution in amino acid position 276 where the secondary structure prediction suggested a helix replaced by a sheet. And the mutation was neither found in the 200 controls nor in the 40 senile cataract patients.ConclusionsA novel GJA8 gene mutation was found to be associated with hereditary cataract in a Chinese congenital cataract family.
| S-EPMC2268715 | biostudies-literature
Project description:PURPOSE: To characterize the disease-causing mutations in four generations of a Chinese family affected with bilateral congenital nuclear and zonular pulverulent cataract. METHODS: Detailed family history and clinical data were recorded. The phenotype was documented using slit-lamp photography. Candidate genes were amplified using PCR and screened for mutations using bidirectional sequencing. RESULTS: Affected individuals had nuclear and zonular pulverulent cataract with Y-sutural opacities. Sequencing of the candidate genes revealed a heterozygous c. 139G>C change in the coding sequence of the connexin 50 gene (gap junction protein, alpha 8 [GJA8]), which results in the substitution of a wild-type aspartic acid with a histidine (D47H). This mutation cosegregated with all affected individuals in the family and was not found in unaffected family members or in 100 unrelated controls. CONCLUSIONS: Our study has identified a novel connexin 50 gene (GJA8) mutation, resulting in the amino substitution p. D47H in a Chinese family with nuclear and zonular pulverulent congenital cataracts. This mutation is probably the causative lesion for the observed phenotype in this family.
| S-EPMC3626375 | biostudies-literature
Project description:Autosomal dominant congenital cataracts (ADCC) are clinically and genetically heterogeneous diseases. The present study recruited two Chinese families with bilateral nuclear cataract or zonular pulverulent phenotype. Direct sequencing of candidate genes identified two novel missense mutations of Cx50, Cx50P59A (c.175C > G) and Cx50R76H (c.227G > A), both co-segregated well with all affected individuals. Bioinformatics analysis predicted deleterious for both mutations. Functional and cellular behaviors of wild type and mutant Cx50 examined by stably transfecting recombinant systems revealed similar protein expression levels. Protein distribution pattern by fluorescence microscopy showed that Cx50R76H localized at appositional membranes forming gap junctions with enormous cytoplasmic protein accumulation, whereas the Cx50P59A mutation was found inefficient at forming detectable plaques. Cell growth test by MTT assay showed that induction of Cx50P59A decreased cell viability. Our study constitutes the first report that the Cx50P59A and Cx50R76H mutations are associated with ADCC and expands the mutation spectrum of Cx50 in association with congenital cataracts. The genetic, cellular, and functional data suggest that the altered intercellular communication governed by mutated Cx50 proteins may act as the molecular mechanism underlying ADCC, which further confirms the role of Cx50 in the maintenance of human lens transparency.
| S-EPMC4877569 | biostudies-other
Project description:To identify the mutation and the underlying mechanism of cataractogenesis in a five-generation autosomal dominant congenital lamellar cataract family.Nineteen mutation hot spots associated with autosomal dominant congenital cataract have been screened by PCR-based DNA sequencing. Recombinant wild-type and mutant human alphaB-crystallin were expressed in Escherichia coli and purified to homogeneity. The recombinant proteins were characterized by far UV circular dichroism, intrinsic tryptophan fluorescence, Bis-ANS fluorescence, multiangle light-scattering, and the measurement of chaperone activity.A novel missense mutation in the third exon of the alphaB-crystallin gene (CRYAB) was found to cosegregate with the disease phenotype in a five-generation autosomal dominant congenital lamellar cataract family. The single-base substitution (G-->A) results in the replacement of the aspartic acid residue by asparagine at codon 140. Far UV circular dichroism spectra indicated that the mutation did not significantly alter the secondary structure. However, intrinsic tryptophan fluorescence spectra and Bis-ANS fluorescence spectra indicated that the mutation resulted in alterations in tertiary and/or quaternary structures and surface hydrophobicity of alphaB-crystallin. Multiangle light-scattering measurement showed that the mutant alphaB-crystallin tended to aggregate into a larger complex than did the wild-type. The mutant alphaB-crystallin was more susceptible than wild-type to thermal denaturation. Furthermore, the mutant alphaB-crystallin not only lost its chaperone-like activity, it also behaved as a dominant negative which inhibited the chaperone-like activity of wild-type alphaB-crystallin.These data indicate that the altered tertiary and/or quaternary structures and the dominant negative effect of D140N mutant alphaB-crystallin underlie the molecular mechanism of cataractogenesis of this pedigree.
| S-EPMC2078606 | biostudies-literature
Project description:PURPOSE: To identify the molecular defect underlying an autosomal dominant congenital nuclear cataract in a Chinese family. METHODS: Twenty-two members of a three-generation pedigree were recruited, clinical examinations were performed, and genomic DNA was extracted from peripheral blood leukocytes. All members were genotyped with polymorphic microsatellite markers adjacent to each of the known cataract-related genes. Linkage analysis was performed after genotyping. Candidate genes were screened for mutation using direct sequencing. Individuals were screened for presence of a mutation by restriction fragment length polymorphism (RFLP) analysis. RESULTS: Linkage analysis identified a maximum LOD score of 3.31 (recombination fraction [theta]=0.0) with marker D22S1167 on chromosome 22, which flanks the beta-crystallin gene cluster (CRYBB3, CRYBB2, CRYBB1, and CRYBA4). Sequencing the coding regions and the flanking intronic sequences of these four candidate genes identified a novel, heterozygous C-->T transition in exon 6 of CRYBB1 in the affected individuals of the family. This single nucleotide change introduced a novel BfaI site and was predicted to result in a nonsense mutation at codon 223 that changed a phylogenetically conserved amino acid to a stop codon (p.Q223X). RFLP analysis confirmed that this mutation co-segregated with the disease phenotype in all available family members and was not found in 100 normal unrelated individuals from the same ethnic background. CONCLUSIONS: This study has identified a novel nonsense mutation in CRYBB1 (p.Q223X) associated with autosomal dominant congenital nuclear cataract.
| S-EPMC2324115 | biostudies-literature
Project description:PurposeTo identify the genetic defect in a Chinese family with bilateral congenital cataract.MethodsA three-generation family was recruited in this study. Detailed family history and clinical data were recorded. Ten candidate genes were screened for causative mutations. Direct sequencing was performed to analyze the cosegregation of the genotype with the disease phenotype.ResultsAffected individuals presented embryonal nuclear opacities in the lens. Sequencing of the candidate genes showed a heterozygous c. 616T>A variation in the connexin 46 (Cx46) gene, which resulted in the replacement of a highly conserved phenylalanine by isoleucine at codon 206 (p. F206I). This mutation co-segregated with all affected individuals and was not observed in unaffected family members or ethnically matched controls.ConclusionsWe report a novel mutation (p.F206I) in the fourth transmembrane domain of connexin 46. These findings thus expand the mutation spectrum of Cx46 in association with congenital cataract.
| S-EPMC3339038 | biostudies-literature
Project description:PURPOSE: To identify the genetic defect associated with autosomal dominant congenital cataract (ADCC) in a Chinese family, in which 11 individuals across four generations are affected with coralliform cataract. METHODS: Exome sequencing was performed in two of the ADCC-affected family members to scan for potential genetic defects. Sanger sequencing was used to verify these defects in the whole family. RESULTS: By combining whole exome sequencing and Sanger sequencing, the genetic defect was revealed to be a insertion of a cytosine after coding nucleotide 1,361 (1361insC) in the gap junction alpha 3 (GJA3) gene, causing a frameshift at codon 397 (p.Ala397Glyfs×71). This frameshift mutation cosegregates with the ADCC-affected pedigree members, but is absent in unaffected relatives and 100 normal individuals. CONCLUSIONS: A 1361 insC mutation in the C-terminus of GJA3 is found to be associated with autosomal dominant congenital coralliform cataract. This finding is similar to that of a previous publication, thus providing further evidence that the GJA3 C-terminal domain is also its mutation area, and further expanding the mutation spectrum of GJA3 in association with congenital cataract.
| S-EPMC3626289 | biostudies-other
Project description:PURPOSE: We isolated an autosomal semi-dominant cataract from our inbred SHR/OlaIpcv rat colony. Heterozygotes express pulverulent cataract with smaller eyes; homozygotes express marked microphthalmia with hypoplastic lens. We call this mutation Dca (for dominant cataract). In this study, we focus on the identification of the responsible gene. METHODS: We performed linkage mapping using 93 F2(SHR-Dca x PD) hybrids and a panel of microsatellite markers. In a separate group of animals with a SHR genetic background, we examined the lenses histologically using Epon semi-thin sections and toluidine blue staining. We also assessed the weight of the eyes as an immediate measure for microphthalmia. RESULTS: We mapped the Dca gene to chromosome 2, spanning 8.6 Mbp between markers D2Rat134 and D2Rat186. By sequencing the most plausible candidate gene, Gja8 (coding for connexin 50), we found a T to A transversion at codon 7, leading to a substitution of glutamine for leucin (L7Q). L7Q lies within the NH(2)-terminal cytosolic domain, presumably involved in voltage gating. Histology revealed disturbances in cell to cell contacts in the lens. CONCLUSIONS: L7Q is a novel mutation in connexin 50 (Gja8), causing semi-dominant pulverulent cataracts. Dca rats can serve as a model for cataract development. A study on the properties of the mutant protein may offer an insight into the connexin channel function.
| S-EPMC2373795 | biostudies-literature
Project description:To identify the potential candidate genes for a large Chinese family with autosomal dominant congenital cataract (ADCC) and nystagmus, and investigate the possible molecular mechanism underlying the role of the candidate genes in cataractogenesis.We combined the linkage analysis and direct sequencing for the candidate genes in the linkage regions to identify the causative mutation. The molecular and bio-functional properties of the proteins encoded by the candidate genes was further explored with biophysical and biochemical studies of the recombinant wild-type and mutant proteins.We identified a c. C749T (p.Q227X) transversion in exon 6 of CRYBB1, a cataract-causative gene. This nonsense mutation changes a phylogenetically conserved glutamine to a stop codon and is predicted to truncate the C-terminus of the wild-type protein by 26 amino acids. Comparison of the biophysical and biochemical properties of the recombinant full-length and truncated ?B1-crystallins revealed that the mutation led to the insolubility and the phase separation phenomenon of the truncated protein with a changed conformation. Meanwhile, the thermal stability of the truncated ?B1-crystallin was significantly decreased, and the mutation diminished the chaperoning ability of ?A-crystallin with the mutant under heating stress.Our findings highlight the importance of the C-terminus in ?B1-crystallin in maintaining the crystalline function and stability, and provide a novel insight into the molecular mechanism underlying the pathogenesis of human autosomal dominant congenital cataract.
| S-EPMC5595272 | biostudies-literature
Project description:PurposeTo identify the pathogenic gene mutation in a Chinese family with autosomal dominant inherited nuclear cataract.MethodsAfter obtained informed consent, detailed ophthalmic examinations were performed, genomic DNAs were obtained from eighteen family members in a four-generation Chinese family with five affected. All exons of candidate genes were amplified by polymerase chain reaction (PCR) and were sequenced performed by bidirectional sequencing. The stability of mutation was predicted with Prediction of Protein Mutant Stability changes (PoPMuSiC). The structure homology modeling of the mutant protein was based on Swiss-Model Serve, and its structure was displayed and compared with human connexin26 using the RasMol software.ResultsBy sequencing the encoding regions of the candidate genes, a missence mutation (c.139G>A) was detected in gap junction protein alpha 8 (GJA8) gene, which resulted in the substitution of highly conserved aspartic acid by asparagine at codon 47 (p.D47N). The mutation co-segregated with all patients and was absent in 100 normal Chinese controls. PoPMuSiC analysis showed the change in folding free energy upon mutation (ΔΔG) is 0.31 kcal/mol and the mutation p.D47N is destabilizing. The homology modeling showed that the structure of the mutant protein was different with that of human connexin26.ConclusionsThe study identified a missence mutation (c.139G>A) in GJA8 gene associated with autosomal dominant congenital cataract in a Chinese family. It gave further evidence for GJA8 associated with congenital cataract.
| S-EPMC3171490 | biostudies-literature