A NEW HEREDITARY CATARACT MOUSE WITH LENS RUPTURE

A new cataract model originated in a recombinant inbred (RI) strain, C XS4 or CXSD (D), between BALB/cHeA(BALB/c or C) and STS/A(STS or S) mi ce. Opacity appeared as a white pinpoint focus in unpigmented eyes of albino mice from 5 weeks old. All the mice were bilaterally affected b y 14 weeks old. They were fully viable and fertile. There was no sex d ifference in incidence of cataract. Histologically, the 3-4 months old mice showed vacuoles in the lens cortex. The vacuoles were spread all over the lens cortex in advanced cases. Ruptures of the lens nucleus to the vitreous chamber was a typical occurrence. For elucidation of t he mode of inheritance, F-1 hybrids (CXD and SXD) and backcross progen ies [(CXD)F1XD and (SXD)F1XD] were analysed. No affected mice were obs erved in Fl hybrids. In backcross progenies, the segregation ratio of affected and normal mice was close to 1:1 in both matings. We conclude that the cataract is inherited by an autosomal single recessive gene. This mutant gene is provisionally named 'lens rupture 2' (gene symbol Ir2, Mouse Genome Database Accession No. MGD-JNUM-37399). The new cat aract model mouse will be a good tool for the genetic analysis and mol ecular biological study of cataractogenesis.