| Objective Two Chinese families with autosomal dominant congenital cataract were screened to identify the pathogenic genes,and study their clinical phenotypes.Then we analyze the correlation between their genotypes and phenotypes.To identify the causes of congenital cataract and expand the mutation spectrum of pathogenic genes.To provide true and reliable molecular genetic basis for prenatal diagnosis and early detection,diagnosis and treatment of congenital cataract in children.Then take effective measures to prevent birth defects and improve the quality of birth.Methods Two families diagnosed as congenital cataract were recruited from Linyi people’s hospital.All family members were examined in detail for eyes and other systemic examinations to eliminate systemic diseases.In addition,slit lamp microscope was used to observe the types of lens opacity in patients with congenital cataract.After informed consent of patients and their families,genomic DNAs were extracted from 3?ml of peripheral blood.By polymerase chain reaction(PCR)to amplify the target fragment of the candidate gene.The amplified products were analyzed for high-throughput sequencing to screen the mutation sites of candidate genes.The Sanger sequencing was used to verify the separation of the family members.Furthermore,the relevant bioinformatics software polyphosphen-2,SIFT,PROVEAN and Mutation taster are applied to analyze the mutations and predict the pathogenicity of the protein.Results It was found that the lens presented posterior polar opacity and the phenotype was posterior polar cataract in the first family.In all patients,we found a splicing mutation c.2826-9G>A in intron 16 of tyrosine kinase receptor gene EPHA2.The mutation was not found in normal family members and normal controls.It was separated from cataractous phenotyp.It was also found that the pathogenic mutation of the protein could affect the splicing of exon,lead to the early termination of amino acid chain,and affect the function of the protein,which is the cause of congenital posterior polar cataract in the first family.Before that,the mutation has been reported at home and abroad.It was found that the lens showed central nuclear opacification and the cataract phenotype was nuclear cataract in the second family.In all patients,we found a point mutation A>C in the 209 th base of exon 3 of crystallin gene CRYBB1(c.209A>C).The 70 th amino acid of the corresponding coding product crystallin βB1 was mutated from glutamine(Q)to proline(P).The mutation was not found in normal family members and normal controls.It was separated from cataractous phenotype.Bioinformatics protein function prediction software predicted that the mutation was harmful.This site was not found in the Human Gene Mutation Database,which is a novel mutation that has not been reported.Conclusion In this study,we find a splicing mutation c.2826-9G > A in the intron 16 region of EPHA2 gene in the first family with congenital posterior polar cataract.A novel missense mutation c.209A>C of the CRYBB1 gene is found in the second family with congenital nuclear cataract.The 209 th base A of the exon 3 region is replaced by C,resulting in the 70 th amino acid of the translated βB1 protein from glutamine to proline(p.Q70P).It is the first report that this mutation leads to congenital nuclear cataract.The above two mutations not only identify the pathogenic genes and sites of congenital cataract patients,but also broaden the mutation spectrum of CRYBB1 gene.It provides scientific basis for early detection,early diagnosis and treatment of congenital cataract children. |
