Exclusion of Candidate Genes for Canine SRY-Negative XX Sex Reversal

In mammals, the Y-linked SRY gene is normally responsible for testis induction, yet testis development can occur in the absence of Y-linked genes, including SRY. The canine model of SRY-negative XX sex reversal could lead to the discovery of novel genes in the mammalian sex determination pathway. The autosomal genes causing testis induction in this disorder in dogs, humans, pigs, and horses are presently unknown. In goats, a large deletion is responsible for sex reversal linked to the polled (hornless) phenotype. However, this region has been excluded as being causative of the canine disorder, as have WT1 and DMRT1 in more recent studies. The purpose of this study was to determine whether microsatellite marker alleles near or within five candidate genes (GATA4, FOG2, LHX1, SF1, SOX9) are associated with the affected phenotype in a pedigree of canine SRY-negative XX sex reversal. Primer sequences flanking nucleotide repeats were designed within genomic sequences of canine candidate gene homologues. Fluorescence-labeled polymorphic markers were used to screen a subset of the mul-tigenerational pedigree, and marker alleles were determined by software. Our results indicate that the mutation causing canine SRY-negative XX sex reversal in this pedigree is unlikely to be located in regions containing these candidates. In mammals, the Y-linked SRY gene is normally responsible for testis induction, yet testis development can occur in the absence of SRY. Specifically, testes or ovotestes develop i