Disturbed Ovarian Differentiation in XX;SRY-Negative Dogs

Abstract

In a mammal, at the beginning of its development, the gonad is bipotential. The shift into a male or female pathway is coordinated by the sex chromosomal complement, which triggers a series of genetic pathways signaling the developmental pattern of the gonadal anlage. Being mutually exclusive, the differentiated gonad should be either a testis or an ovary. In females, the absence of SRY, a testis-determining gene, drives the signaling cascades controlling the ovarian differentiation. Albeit rare, disorders of the gonadal differentiation may occur in men and domestic animals and may cause infertility or sterility. In dogs, the XX;SRY-negative disorder of sexual development (DSD) is the most frequent condition. The disorder typically presents a wide spectrum of developmental conditions of the gonad and variable virilization of the genital phenotype, that may be accompanied by hypospadias. This condition may be inherited as a sex–limited autosomal recessive trait; however, the mechanism explaining its occurrence remains poorly understood. This review intends to present an overview of the morphologic features of XX;SRY-negative syndrome in dogs, while addressing the current knowledge regarding the genetic mechanism underlying this condition.