The use of a novel combination of diagnostic molecular and cytogenetic approaches in horses with sexual karyotype abnormalities: A rare case with an abnormal cellular chimerism

Abstract

Sexual chromosomal aberrations are known to cause congenital abnormalities and unexplained infertility in horses. Most of these anomalies remain undiagnosed because of the complexity of the horse karyotype and the lack of specialized laboratories that can perform such diagnoses. On the other hand, the utilization of microsatellite markers is a technique widely spread in horse breeding, mostly due to their usage in parentage tests. We studied the usage of a novel combination of diagnostic approaches 25 in the evaluation of a very uncommon case of chromosomal abnormalities in a Spanish Purebred colt, primarily detected using a commercial panel of short tandem repeat (STR) makers. Based on these results we performed a full cytogenetical analysis using conventional and fluorescent in situ hybridization (FISH) techniques with individual ECAX (Equus caballus chromosome X) and ECAY (Equus caballus chromosome Y) painting probes. We also tested the presence of two genes associated with the sexual development in horses and an extra novel panel of 8 microsatellite markers specifically located in the sex chromosome pair. This is the first case reported of a leukocyte chimerism between a chromosomally normal (64,XY) and abnormal (63,X0) cell lines in horses. Our results indicate that the use of the STR markers as a screening technique and as a confirmation utilizing cytogenetic techniques can be used as a very interesting easy and non-expensive diagnostic approach to detect chromosomal abnormalities in the domestic horse.