Localization of a recessive juvenile cataract mutation to proximal chromosome 7 in mice

Objective: To localize the chromosomal position of a novel cataract mutation (juvenile recessive cataract; jrc) in mice. Methods: A mapping population was developed by crossing cataract males (albino MH) to wild-type (females (black C57BL/6J). F₁ (females were backcrossed) to albino MH males with cataracts. Results: The results were consistent with a model of a single autosomal recessive gene [153 cataract, 169 wild-type; Χ²= 0.8, 1 degree of freedom (d.f.), p>0.35]. Linkage with the albino (tyrosinase; Tyr) locus was evident (Χ² = 61.5, 1 d.f., p<0.0001), implicating chromosome 7 as the location of jrc. Recombination percentages (± SE) between jrc and D7Mit340 (1.2 cM location), D7Mit227 (16.0 cM) and D7Mit270 (18.0 cM) were 17.1 ± 2.1, 3.7 ± 1.1 and 6.2 ± 1.3%, respectively. Multi-point mapping determined that the most likely order of these loci is D7Mit340 - jrc -D7Mit227 - D7Mit270 - Tyr. Although animals with the mutant phenotype appeared to have little or no sense of sight, their growth was not different (p>0.20) from that of normal mice. Conclusion: The jrc mutation model may be useful in the study of the genetics of cataracts in other animal species, including humans.