XY sex-reversal syndrome in the domestic horse

Abstract

The XY sex-reversal syndrome occurs when a phenotypic mare is born that has the karyotype of a stallion. The syndrome is manifested by both genotypic and phenotypic heterogeneity. The sex-reversed genetic condition occurs frequently within certain pedigrees where XY females have been found and can be readily detected by chromosome karyotyping. The phenotypic spectrum ranges from the feminine mare with a reproductive tract that is within normal limits to the greatly masculinized mare. Pedigree analysis suggests that there are two modes of inheritance: (1) an X-linked recessive or autosomal sex-limited dominant transmitted through the female and (2) an autosomal sex-limited dominant or a Y chromosomal mutation with variable expression transmitted through the male.

Classical and Molecular Cytogenetics of Disorders of Sex Development in Domestic Animals

“…Equine sex reversal syndrome is a concept that covers, analogously to those of humans, different disorders of sex development in which a level of disagreement between the genetic, gonadal and phenotypic sex is noticed. Phenotypically normal horse mares and horse mares with different degrees of masculinization and virilization have been found with a normal stallion karyotype [Kent et al, 1986;Long, 1988]. Primary infertility of XY mares appeared to be due to gonadal dysgenesis (i.e.…”

Equine clinical cytogenetics: the past and future

“…The differences in phenotype may reflect the type of genetic abnormality that is present. Familial patterns of inheritance have been described, particularly in certain Arabian horse sire lines (Kieffer et al, 1976;Kent et al, 1986;Bowling et al, 1987). Molecular testing of these horses may identify a deletion of or a non-functional SRY gene (Pailhoux et al, 1995;Abe et al, 1999;Mäkinen et al, 1999;Bugno et al, 2003).…”

Equine Disorders of Sexual Development in 17 Mares Including XX, <i>SRY</i>-Negative, XY, <i>SRY</i>-Negative and XY, <i>SRY</i>-Positive Genotypes

“…Equine sex reversal represents a syndrome lacking a specific phenotype. There is a continuum of masculinized phenotypes that range from normal females to females with conspicuous ambiguous external genitalia [Kent et al, 1986]. Genetically they fall into 4 broad categories: XX karyotype, SRYnegative genotype with ovotestis or testis; XY, SRY -negative with gonadal dysgenesis; and XY, SRY -positive with testis or gonadal dysgenesis [Pailhoux et al, 1995;Mäki-nen et al, 1999;Bugno et al, 2003;Switonski et al, 2005;Kuiper and Distl, 2007].…”