A novel donor splice-site mutation of major intrinsic protein gene associated with congenital cataract in a Chinese family.

PURPOSE: To identify the disease-causing gene in a Chinese family with autosomal dominant congenital cataract.

METHODS

Clinical and ophthalmologic examinations were performed on all members of a Chinese family with congenital cataract. Nine genes associated with congenital cataract were screened using direct DNA sequencing. Mutations were confirmed using restriction fragment length polymorphism (RFLP) analysis. The mutated multi-intronic plasmid (MIP) minigene, which carries the disease-causing splice-site mutation, and the wild-type (WT) MIP minigene were constructed using the pcDNA3.1 expression vector. Wild-type and mutant MIP minigene constructs were transiently transfected into HeLa cells. After 48 h of incubation at 37 °C, total RNA isolation and reverse transcription (RT)-PCR analysis were performed, and PCR products were separated and confirmed with sequencing.

RESULTS

Direct DNA sequence analysis identified a novel splice-site mutation in intron 3 (c.606+1 G>A) of the MIP gene. To investigate the manner in which the splice donor mutation could affect mRNA splicing, WT and mutant MIP minigenes were inserted in the pcDNA3.1 (+) vector. Constructs were transfected into HeLa cells. RT-PCR analysis showed that the donor splice site mutation led to deletion of exon 3 in the mRNA encoded by the MIP gene.

CONCLUSIONS

The present study identified a novel donor splice-site mutation (c.606+1G>A) in the MIP gene in a Chinese family with congenital cataract. In vitro RT-PCR analysis showed that this splice-site mutation resulted in the deletion of exon 3 from mRNA encoded by the MIP gene. This is the first report to show that donor splice-site mutation in MIP genes can cause autosomal dominant congenital cataract.