Molecular characterization of 64,XY SRY-negative intersex horses

SEBASTIÁN DEMYDA PEYRÁS

Woods Hole, Massachusets

Conferencia; 19th Annual FIR symposium; 2016

Marine Biology Laboratory

Chromosomal abnormalities are one of the most underestimated causes of non-explained infertility in the horse. Among them, sex reversal syndrome is a genetic disease characterized by inconsistencies between genetic and morphological sex. It is normally associated with morphological abnormalities in the reproductive tract and infertility in mares. The most common presentation observed is the 64,XY SRY (sex determining region)-negative DSD in which individuals always show the presence of the Y chromosome (ECAY, Equus caballus Y) and the absence of a functional SRY gene. Previously, Raudsepp et al. (2010) described two possible presentations of this syndrome: an extensive ECAY deletion which included a substantial portion of the ECAY, or a 21 kb deletion surrounding the SRY region . Here we present preliminary results of 16 new mares diagnosed as 64,XY SRY(-) DSD showing classical morphological symptoms (sterility and a slight gonadal dysgenesis) associated with this disease. We determined the absence of SRY and performed a genome walking of its surrounding region in order to characterize the deletion observed. An extra 30 kb region was covered by 11 primer pairs specifically designed for this experiment. Our results showed the presence of 5 different deletion ranges not previously described (size range between 38.7 and 50.7 kb; Figure 1). These deletions were at least 16 kb bigger than those reported earlier, showing that sex reversal mares have a variable molecular background. Although molecular differences were remarkable between animals and even compared with previous studies, morphological symptoms and individual behavior were similar. Our results suggest that inactivation of the SRY gene is enough to produce this genetic syndrome. Unfortunately, the lack of ECAY reference genome do not allowed to clarify the extension of the deletion by aCGH or next generation sequencing.