Mutation Identification And Functional Analysis Of Disease Gene In A Family With Congenital Cataract

Congenital cataract is defined as an opacification of the eye lens which appear atbirth or shortly after. It is the main cause of blindness in children all over the world.About one third infant lose their sight is caused by congenital cataract, and50%of themare inherited. Congenital cataract is inherited as autosomal dominant traits which is themost common inherited form. Congenital cataract is a heterogeneous lens disorder inclinically and genetically. So far, more than40genetic loci have been linked tocongenital cataracts, and at least26genes have been cloned, although these numbers arecontinually growing.To identify the disease-causing gene of a Chinese autosomal dominant congenitalcataract(ADCC), candidate genes were analyzed and direct DNA sequencing was used toidentify the mutation in this article. The purpose of this study is to explore the moleculargenetic mechanism of autosomal dominant congenital cataract, and provide the effectivetheoretical basis for clinical prenatal diagnosis, prevention and treatment of this disease.Slit lamp examination showed nuclear cataract. Autosomal dominant inheritancepattern was confirmed in this family through pedigree analysis. Direct DNA sequenceanalysis identified a novel splicing mutation in intron3(IVS3+1G>A) of MIP gene.The mutation is co-segregated with the affected family members, and don’t carry themutation in the unaffected individuals in the family and110unrelated normal controls. Toinvestigate how the donor splice-site mutation affect the mRNA splicing, WT and mutantMIP minigene were construct into pcDNA3.1(+) vector, constructs were transientlytransfected into HeLa cells, RT-PCR analysis, the donor splice-site mutation leads todeletion of exon3in mRNA coding by MIP gene.This study identified a novel donor splice-site mutation(c.606+1G>A) in MIP genein a Chinese congenital cataract family, in vitro RT-PCR analysis show that the splicingmutation result in the deletion of exon3in mRNA coding by MIP gene, this is the firstreport that donor splice-site mutation in MIP gene(IVS3+1G>A) causing autosomaldominant congenital cataract(ADCC), and expands the spectrum of mutations that causingADCC.