Autosomal Dominant Congenital Cataract Family Research Articles

Mutation screening in autosomal dominant congenital cataract families from North India.

Congenital cataract an opacity of the eye lens is present at birth and results in visual impairment during early childhood. If left untreated, it can lead to permanent blindness. Its prevalence is ten times higher in developing countries like India. Thus, we aimed to investigate the underlying genetic defects in three autosomal dominant congenital cataract (ADCC) families from North India. Detailed family histories were collected, pedigrees drawn followed by slit-lamp examination and lens photography. Mutation screening was performed in the candidate genes for crystallins, connexins, and membrane proteins by Sanger sequencing. Pathogenicity of novel variant was assessed bioinformatically. In an ADCC (CC-3006) family with bilateral membranous cataract and microcornea, a novel change (c.1114C>T;p.P372S) in GJA3 has been detected. In other two ADCC families affected with subcapsular (CC-286) and shrunken membranous hypermature cataract (CC-3014), a nonsense mutation (c.463C>T;p.Q155X) in CRYβB2 and a frameshift deletion (c.590_591delAG;p.E197VfsX22) in CRYβA1/A3 respectively, are observed. These variants segregated completely with the phenotypes in respective families and were absent in their unaffected family members and unrelated controls (testedfor novel variant in GJA3). Earlier p.Q155X (CRYβB2) and p.E197VfsX22 (CRYβA1/A3) are reported with entirely different phenotypes. Thus, findings in present study expand the mutation spectrum and phenotypic heterogeneity linked with GJA3, CRYβB2, and CRYβA1/A3 for congenital cataracts. Identifying underlying genetic defects is essential for disease management and appropriate genetic counseling.

Molecular diagnosis of autosomal dominant congenital cataract in two families from North India reveals a novel and a known variant in GJA8 and GJA3.

The study aims to detect the underlying genetic defect in two autosomal dominant congenital cataract (ADCC) families. A detailed family history was collected, pedigrees were drawn, and slit-lamp examination and lens photography were performed. Mutation screening was carried out in the genes for crystallins and connexins by PCR and Sanger sequencing. Ethnically matched controls were tested for the identified variants. Different bioinformatics tools were used to assess the pathogenicity of the observed variants. In an ADCC family with total cataract, a novel change (c.166A > G) (p.Thr56Ala) in GJA8 was identified. In another ADCC family with nuclear cataract, c.134G > C (p.Trp45Ser) in GJA3 has been detected. These variants co-segregated completely in patients in their respective families and were neither observed in unaffected family members nor in ethnically matched 100 controls, excluding them as polymorphisms. The present study identifies a novel variant c.166A > G (p.Thr56Ala) in GJA8 in an ADCC family having total cataract and a previously known mutation c.134G > C (p.Trp45Ser) in GJA3 in another ADCC family. Thr56 in GJA8 seems to be a mutation hotspot, as previously an ADCC Mauritanian family harbored a different substitution (p.Thr56Pro) at the same codon, although for a different phenotype (nuclear cataract). Similarly, Trp45 in GJA3 appears as a mutation hotspot, as p.Trp45Ser has previously been reported for nuclear cataract in a Chinese ADCC family. p.Thr56 (GJA8) and p.Trp45 (GJA3) are in the extracellular loop 1 (EL1) in their respective connexin proteins, which, along with EL2, are essential for gap junction formation, hemichannel docking, and regulating the voltage gating of the channels. Hence, residues in these regions seem crucial for maintaining eye lens transparency.

A novel mutation GJA8 NM_005267.5: c.124G\u2009>\u2009A, p.(E42K) causing congenital nuclear cataract

BackgroundTo identify the genetic mutation of a four-generation autosomal dominant congenital cataract family in China.MethodsTargeted region sequencing containing 778 genes associated with ocular diseases was performed to screen for the potential mutation, and Sanger sequencing was used to confirm the mutation. The homology model was constructed to identify the protein structural change, several online software were used to predict the mutation impact. CLUSTALW was used to perform multiple sequence alignment from different species.ResultsA novel heterozygous mutation, GJA8 NM_005267.5: c.124G > A, p.(E42K) was found, which cosegregated with congenital cataract phenotype in this family. Bioinformatics analysis of the mutation showed that the surface potential diagram of proteins changed. Several online programs predicted the mutation was ‘Pathogenic’, ‘Damaging’, ‘Disease causing’ or ‘Deleterious’.ConclusionsA novel mutation NM_005267.5(GJA8):c.124G > A was identified in our study. Our finding can broaden the mutation spectrum of GJA8, enrich the phenotype-genotype correlation of congenital cataract and help to better understand the genetic background of congenital cataract.

Identification and functional analysis of a novel missense mutation in GJA8, p.Ala69Thr

BackgroundTo explore the molecular genetic cause of a four-generation autosomal dominant congenital cataract family in China.MethodsTargeted region sequencing was performed to screen for the potential mutation, and Sanger sequencing was used to confirm the mutation. The homology model was constructed to identify the protein structural change, PolyPhen-2 and Provean were used to predict the mutation impact. Functional and cellular analysis of the wild and mutant GJA8 were performed in DF-1 cells by western blotting, dye uptake assay, immunofluorescence, Annexin V-FITC staining.ResultsA novel heterozygous mutation (c.205G > A; p.Ala69Thr) was identified within GJA8, which cosegregated with congenital cataract phenotype in this family. Bioinformatics analysis showed the mutation was located in a highly conserved region, and the mutation was predicted to be pathogenic. Function analysis indicated that the mutation inhibited GJA8 hemichannel activity, reduced cell tolerance to oxidative stress, changed the protein distribution pattern and inhibited the cell growth.ConclusionsWe have identified a novel missense mutation in GJA8 (c.205G > A, p.Ala69Thr) in a four-generation Chinese family and our results will further broaden the gene mutation spectrum of GJA8.

Identification of genetic mutation in a Chinese pedigree with congenital cataract by whole-exome sequencing

Background Genetic mutation remains to be the most common cause of congenital cataract.Whole exon sequencing technology is an ideal method to detect the pathogenic gene mutations. Objective This study was to identify the pathogenic gene in a Chinese autosomal dominant congenital cataract (ADCC) family by whole-exome sequencing. Methods This study complied with Helsinki Declaration and the protocol was approved by Ethic Committee of Peking University Third Hospital.Informed consent was obtained from each subject before any medical examination.A cross-sectional study was designed.A Chinese ADCC family with 4 generations and 48 members were enrolled in Peking University Third Hospital, of which Ⅰ1 and Ⅰ2 died.The periphery blood of 8-10 ml was collected from each member of Ⅱ, Ⅲ and Ⅳ generations for the high throughput sequencing of genes using whole exon trapping and new sequencing technology, and the sequencing results were compared with the data of human HA PMAP8, dbSNP130 and 1000 Genome Project database.The synonymous mutation was filtered after reported common variants, and the false positive results of explicit sequencing were finally excluded by Sanger sequencing and then the candidate genes were identified.The mutation genes were screened to determine the pathogenic gene of this ADCC family. Results Eleven ADCC patients were found in this family, and the patients distributed in each generation with an equal chance for involvement in male and female subjects, which conformed to an autosomal dominant inheritance pattern.All the patients were nuclear cataract.Genome-wide whole-exome sequencing found that major intrinsic protein (MIP) gene was known genes of ADCC in initially identified candidate genes, so the Sanger was used to verify the MIP gene.The heterozygous mutation of MIP gene (chr12: 56845250 C>T) appeared to be the pathogenic cause of this ADCC family.The mutation occurred in the splice sites of the gene, resulting in the fourth exon coded-61 amino acids are replaced by leucine, histidine and serine, which lead to the abnormal truncated proteins. Conclusions The heterozygous mutation of MIP gene is the molecular pathogenesis of this Chinese ADCC family. Key words: Pedigree; Cataract/genetics; Membrane glycoproteins/genetics; Mutation/genetics; Aquaporins/genetics; Alternative splicing/genetics; Autosomal dominant; Whole-exome sequencing; Major intrinsic protein/genetics; Chinese

Analysis of GJA3 mutation associated with a Chinese family with autosomal dominant congenital cataract by whole-exome sequencing

Congenital cataract is one of the important reasons for the blindness of children, and most congenital cataracts are genetic.At present, thirty-nine genes have been identified relating to autosomal dominant congenital cataract (ADCC). Objective This study was to identify and analyze the virulence gene of a Chinese family pedigree with ADCC by whole-exome sequencing. Methods A Chinese ADCC family was recruited in Affiliated First Hospital of Zhengzhou University from August to September in 2014.The family disease history and clinical data were recorded.The peripheral venous blood of 10 ml was collected in 14 patients with congenital cataract and 14 families with normal phenotype, and the peripheral blood samples were obtained from 100 healthy examined people as controls.The genomic DNA was extracted form all subjects using standard phenol chlorum method, and proband DNA was screened by whole-exome sequencing.Then mutation locus of the candidate gene was selected after compared with the information of database in the proband.The mutation locus of the candidate gene from 14 normal families and 100 healthy controls were amplified and sequenced by PCR technique based on the primer sequence of mutation locus of proband to verify the pathogenic gene of this ADCC family.This study protocol was approved by Ethic Committee of Affiliated First Hospital of Zhengzhou University and complied with Helsinki Declaration.Written informed consent was obtained from subjects or custodian before any medical examination. Results The family had a total of 5 generations of 68 members, in which 20 subjects were found with congenital cataract.The inheritance mode consisted with autosomal dominant inheritance.Cortical cataract was found in both eyes in the patients.Whole-exome sequencing showed that the 143rd ribonucleotide A of exon 2 explicit factor of chromosome 13 GJA3 gene mutated into G (c.143A>G) in the proband, which resulted in the 48th amino acids changed from glutamate into glycine (p.E48G). PCR amplification product sequencing displayed that the same mutation of DNA appeared in all the patients of this family, while not the same mutation was seen in the candidate genes of normal phenotype families and 100 healthy controls. Conclusions GJA3 gene c. 143A>G is a virulence mutation site in this ADCC family, it is a supplement of the mutation spectrum of GJA3 gene. Key words: Cataract/genetics; Connexins/genetics; Mutation, missense; Whole-exome sequencing; Amino Acid Sequence

A Novel CRYBB2 Stopgain Mutation Causing Congenital Autosomal Dominant Cataract in a Chinese Family.

Congenital cataract is the most common cause of the visual disability and blindness in childhood. This study aimed to identify gene mutations responsible for autosomal dominant congenital cataract (ADCC) in a Chinese family using next-generation sequencing technology. This family included eight unaffected and five affected individuals. After complete ophthalmic examinations, the blood samples of the proband and two available family members were collected. Then the whole exome sequencing was performed on the proband and Sanger sequencing was applied to validate the causal mutation in the two family members and control samples. After the whole exome sequencing data were filtered through a series of existing variation databases, a heterozygous mutation c.499T<G (p.E167X) in CRYBB2 gene was found. And the results showed that the mutation cosegregated with the disease phenotype in the family and was absolutely absent in 1000 ethnicity-matched control samples. Thus, the heterozygous mutation c.499T<G (p.E167X) in CRYBB2 was the causal mutation responsible for this ADCC family. In conclusion, our findings revealed a novel stopgain mutation c.499T<G (p.E167X) in the exon 6 of CRYBB2 which expanded the mutation spectrum of CRYBB2 in Chinese congenital cataract population and illustrated the important role of CRYBB2 in the genetics research of congenital cataract.

A recurrent mutation of CRYGD gene in a northern Chinese family with autosomal dominant congenital nuclear cataract

Background Congenital cataract is a major cause for blindness of childhood. Genetic gene mutation accounts for almost 1/3 of congenital cataract patients. The most common inheritance type is autosomal dominant congenital cataract (ADCC). Over 100 mutations in 26 genes have been found to be associated with ADCC. Objective This study was to identify the disease-causing gene mutation in a family with ADCC. Methods This study was approved by Ethic Committee of Beijing Tongren Hospital and followed Declaration of Helsinki. A northern Chinese family with autosomal dominant congenital nuclear cataract was entrolled in Beijing Tongren Hospital in January 2011. Ocular examinations were performed and periphery blood specimens were collected from each family member under the informed consent. Genomic DNA was extracted. Twenty-one microsatellite markers around 17 ADCC genes were selected for linkage analysis, and two-point LOD score was calculated. CRYGC gene and CRYGD gene were amplified and screened for mutations using direct sequencing. ProtScale software was used to analyze the changes of hydrophobicity of the mutated protein. Co-segregation of the observed change with the disease phenotype was further detected by restriction fragment length polymorphism (RFLP). Results This family included 20 members of 4 generations, and 9 patients were examined in serial 4 passages, which conformed to autosomal dominant inheritance pattern. Clinical examination revealed binocular congenital nuclear cataract in the 9 patients. Maximum two-point LOD score was 4. 68 at marker D2S325 (θ=0). A known T→C change at position 127 of cDNA sequence was found by mutations screening of CRYGD gene. ProtScale programs showed an obvious increase of the local hydrophobicity in the mutant protein. RFLP results indicated that this missense mutation co-segregated with affected members of the family, but was absent in unaffected members and 100 unrelated controls. Conclusions c. T127C mutation of CRYGD gene appears to be the molecular pathogenesis of this ADCC family. Aberrant structure of mutant CRYGD protein caused by hydrophobicity change may lead to opacification of lens. Key words: Cataract/congenital; Cataract/genetics; DNA mutational analysis; Lens nucleus, crystalline/pathology; Pedigree; gamma-Crystallin/genetics; Mutations; Chinese

A missense mutation in CRYGD linked with autosomal dominant congenital cataract of aculeiform type

To detect the underlying genetic defects in two autosomal dominant congenital cataract (ADCC) families, having respectively twenty and four members affected with bilateral congenital cataract. Detailed family history and clinical data were recorded. Mutation screening in twenty three candidate genes including crystallins (CRYAA, CRYAB, CRYBA1/A3, CRYBA2, CRYBA4, CRYBB1, CRYBB2, CRYBB3, CRYGA, CRYGB, CRYGC, CRYGD, and CRYGS), gap junctional channels; connexins (GJA8, GJA3), beaded filament chain proteins (BFSP1, BFSP2), major intrinsic protein (MIP), lens intrinsic membrane protein-2 (LIM2), transcriptional factor (MAF), and in genes encoding for membrane-associated proteins (TMEM114, CHMP4B, EPHA2) was performed by bi-directional sequence analysis of the amplified products. In family A twenty members in six generations were affected by bilateral aculeiform type cataract and in family B four affected members in three generations had granular nuclear cataract. Mutation screening in already known candidate genes by sequence analyses revealed proline to threonine substitution at codon 23 (p.Pro23Thr) in CRYGD for aculeiform type cataract in family A. The family B with four members affected by granular nuclear cataract, however, could not be linked with any of these analyzed 23 candidate genes. The present study describes identification of p.Pro23Thr mutation in CRYGD for aculeiform type cataract in an ADCC family of Indian origin. The identical mutation has previously been reported to be linked with different phenotypes; lamellar cataract, cerulean cataract, coralliform cataract, flaky silica-like nuclear cataract and fasciculiform type cataract in different ADCC families. Interestingly, a mutation of different codon, i.e., p.Arg58His in CRYGD has been reported to be linked with aculeiform cataract in four different families; two from Switzerland, one from Macedonia and in a Mexican family. The findings in present study thus expand the genetic heterogeneity for aculeiform type cataract. Further, exclusion of these twenty three known candidate genes in family B having ADCC of granular nuclear type indicates the role of some other gene apart from for crystallins, gap junction channels, beaded filaments and membrane-associated proteins, and MAF for this phenotype.