LOCALIZATION OF THE MOUSE GENE RELEASING SEX-LIMITED EXPRESSION OF SLP

To probe genetic variation in the regulation of sexual dimorphism, we have characterized the mouse protein Sip, coded by the gene sex-limite d protein (Slp). Slp expression in many strains is limited to males an d is androgen-dependent. However, female expression is also observed i n rare strains, due to nonlinked gene(s) termed regulator of sex-limit ation (rsl). In this report we demonstrate that female expression of S lp results from homozygous recessive allele(s) at a single autosomal l ocus that maps to a 2.2-centimorgan interval on chromosome 13. This co nclusion was supported by extensive genetic analyses including the use of polymorphic microsatellites to type numerous backcross progeny and a recombinant inbred series and to identify the congenic interval in three independently derived congenic strains. Four attractive candidat e genes were identified by the localization of rsl. Interestingly, rsl was found not only to enable expression in females but to also increa se expression in males. The findings suggest that the expression of Sl p and perhaps other sexually dimorphic proteins is regulated by two pa thways, one that is dependent upon rsl but not androgens and another t hat is rsl-independent hut requires androgens.