Regulator of sex-limitation (Rs1) encodes a pair of KRAB zinc-finger genes that control sexually dimorphic liver gene expression

Abstract

Sexually dimorphic expression of a broad array of liver proteins involved in reproduction and xenobiotic metabolism is induced at puberty by sex-specific growth hormone patterns. An additional control of sex-dependent gene expression is conferred by Regulator of sex-limitation (Rs1) alleles. In variant rs1 mice, females inappropriately express the male Sex-limited protein, S1p. We recently showed that a panel of male-specific liver genes is repressed by Rs1, accentuating sex differences in a hormone-independent manner. Here we map rs1 to a region on Chromosome 13 comprised exclusively of KRAB (Kruppel-associated box) zinc-finger protein (ZFP) genes. Among eight Rs1 candidate (Rs1can) genes within the critical genetic interval, the recent duplicates Rs1can-4 and Rs1can-9 both harbor mutations in rs1 mice (partial deletion and splice-site inactivation, respectively). Transgenesis with bacterial artificial chromosome (BAC) clones encompassing Rs1can-4 restores male-specific MUP (major urinary protein) expression to rs1 mice, whereas a BAC containing Rs1can-9 rescues sex-specific expression of S1p and cytochrome P450 Cyp2d9. Thus, the Rs1can-4 and Rs1can-9 paralogs partitioned regulation of their target genes during evolution. This demonstrates the first biological role for a set of KRAB zinc-finger repressor proteins and reveals the molecular basis of a gene-silencing pathway critical for sexual dimorphism.