The objective of this project is to study the mechanisms responsible for heritable lens dysfunction resulting in anophthalmia or cataract formation in mice. To facilitate our studies of mouse eye mutants, we have been searching among inbred strains for genetic variation in lens crystallin genes using cDNA probes for Alpha-, Beta- and Gamma-crystallins. Southern blot analysis of AlphaA-crystallin sequences has detected eight restriction fragment size classes among 42 inbred strains of mice. The polymorphisms are due, in large part to insertions or deletions, in non-coding regions in or near the AlphaA-crystallin gene. Gene mapping experiments have located the AlphaA gene (designated Acry-1) to chromosome 17, very close to the mouse major histocompatibility region, H-2K. Striking linkage disequilibrium is observed between Acry-1 alleles and H-2 haplotypes among inbred strains, leading to the hypothesis that Acry-1 should be included as a component of the MHC. Similar experiments conducted on inbred strains of rats have confirmed the conservation of Acry-1 - MHC in this species. Conservation of other genes in the MHC region of mice and humans implies that the human Acry-1 gene is linked to HLA on chromosome 6. Analysis of a Beta-crystallin sequence (Bcry-1) by 17 endonucleases has failed to detect restriction fragment polymorphisms among inbred strains. Analysis of DNA from mouse x hamster somatic cell hybrid clones located Bcry-1 to chromosome 11. In contrast to the lack of variation in Bcry-1, Gamma-crystallin sequences (Gcry-1,-2,-3,-4) have demonstrated restriction polymorphism with all endonuclease so far employed. In gene mapping experiments, we have found no recombination between Gcry and a Gamma-crystallin protein variant (LEN-1) on chromosome 1 very near to the mutant gene, Elo, which produces anophthalmia in mice.
