Sex reversal syndrome in two Spanish Purebred mares: genetic and molecular studies

SEBASTIÁN DEMYDA PEYRÁS; GABRIEL ANAYA; SARA NEGRO RAMA; MANUEL HIDALGO; MERCEDES VALERA; ALBERTO MEMBRILLO; MIGUEL MORENO MILLÁN

Helsinki

Congreso; . 18th annual European Society for Domestic Animals Reproduction Conference; 2014

18th annual European Society for Domestic Animals Reproduction

Sex chromosomal abnormalities are more common among horses thanis generally thought. Most of these cases are associated withmorphological abnormalities of the reproductive tract. However, somecases are also associated with unexplained infertility, and from these ahigher percentage remains undiagnosed. We studied two SpanishPurebred mares submitted to our laboratory due to the lack of cyclicityand the abnormal external appearance. First mare (C1) was morphologicallynormal, showing a slightly reduced ovarian size and nocyclicity over 3 reproductive seasons. Second mare (C2) showed majormorphological abnormalities including the absence of the uterus andovaries and the presence of two inguinal ?testicle-like? structures. Bothcases were karyotyped using conventional cytogenetic techniques (Gand C-Banding) showing a a 64, XY male complement. SRY, AMYand ZFY genes, located in the Equus caballus Y chromosome; ECAY)were assessed by PCR in both animals. Results were positive with theexception of the SRY gene in C1. ECAX (Equus caballus Xchromosome) and ECAY copy number were analyzed using a panelof eight specific microsatellite markers (five in the ECAX and three inthe ECAY). All the results were mono-allellic for both blood and hairDNA samples determining the presence of only one differentchromosomal copy, discarding the occurrence of blood cellularchimerism. We determined that both animals were sex reversal mares.However, the large morphological differences between them arenoteworthy, probably related to the differences observed in the SRYgene. To conclude, the use of molecular markers is an efficient assistanttool to detect the presence of chromosomal abnormalities, animportant but poorly studied cause of reproductive failures amonghorses.