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

Objective: To localize the chromosomal position of a novel cataract mutatio n (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). F-1 females were backcrossed to albino MH males with catar acts. Results: The results were consistent with a model of a single autosom al recessive gene [153 cataract, 169 wild-type; chi (2) = 0.8, 1 degree of freedom (d.f.), p > 0.35]. Linkage with the albino (tyrosinase; Tyr) locus was evident (chi (2) = 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 mappi ng determined that the most likely order of these loci is D7Mit340 - jrc D7 Mit227 - D7Mit270 - Tyr. Although animals with the mutant phenotype appeare d 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 us eful in the study of the genetics of cataracts in other animal species, inc luding humans. Copyright (C) 2001 S. Karger AG, Basel.