Sex chromosomal abnormalities associated with equine infertility: validation of a simple molecular screening tool in the Purebred Spanish Horse

Abstract

Chromosomal abnormalities in the sex chromosome pair (ECAX and ECAY) are widely associated with reproductive problems in horses. However, a large proportion of these abnormalities remains undiagnosed due to the lack of an affordable diagnostic tool that allows for avoiding karyotyping tests. Hereby, we developed an STR (single-tandem-repeat)-based molecular method to determine the presence of the main sex chromosomal abnormalities in horses in a fast, cheap and reliable way. The frequency of five ECAX-linked (LEX026, LEX003, TKY38, TKY270 and UCDEQ502) and two ECAY-linked (EcaYH12 and SRY) markers was characterized in 261 Purebred Spanish Horses to determine the efficiency of the methodology developed to be used as a chromosomal diagnostic tool. All the microsatellites analyzed were highly polymorphic, with a sizeable number of alleles (polymorphic information content > 0.5). Based on this variability, the methodology showed 100% sensitivity and 99.82% specificity to detect the most important sex chromosomal abnormalities reported in horses (chimerism, Turner's syndrome and sex reversal syndromes). The method was also validated with 100% efficiency in 10 individuals previously diagnosed as chromosomally aberrant. This STR screening panel is an efficient and reliable molecular-cytogenetic tool for the early detection of sex chromosomal abnormalities in equines that could be included in breeding programs to save money, effort and time of veterinary practitioners and breeders.

A new molecular screening tool for the detection of chromosomal abnormalities in donkeys

“…On the contrary, sensitivity was 100%, since there was no possibility for an animal with only one EASX to obtain a diallelic result. Similar values had been previously in horses (Anaya et al, ), thus validating the robustness of the technique.…”

“…The analysis by sex showed an increased variability in females according to A n , with 22 alleles represented only in jennies (198, 202, 204, 206 and 208 in LEX003 ; 306 in LEX026 ; 152, 160, 168 and 170 in TKY270 ; 119, 137, 145, 149, 157 and 159 in TKY38 ; and 152, 156, 160, 162, 166 and 174 in UCEDQ502 ). Interestingly, some of the alleles detected in jennies had not been described previously in mares (Anaya et al, ), confirming the increased variability of this species. The analysis by breed showed very similar X n results in Andalusian and Moroccan jennies (7.6 and 8.0, respectively), but with several breed‐specific (Table ).…”

“…Concerning A n per loci, it ranged from 5 ( LEX026 ) to 14 ( UCEDQ502 ) with an average of 9.6 ( X n ), including a wide variety of homozygous and heterozygous genotypes in all the markers studied. This allele variability was higher than that previously described in horses ( X n = 8.4) (Anaya et al, ). The analysis by sex showed an increased variability in females according to A n , with 22 alleles represented only in jennies (198, 202, 204, 206 and 208 in LEX003 ; 306 in LEX026 ; 152, 160, 168 and 170 in TKY270 ; 119, 137, 145, 149, 157 and 159 in TKY38 ; and 152, 156, 160, 162, 166 and 174 in UCEDQ502 ).…”

“…Five X‐linked microsatellite markers ( LEX003 , LEX026 , TKY270 , TKY38 and UCEDQ502 ) and two Y‐linked markers ( ECAYM2 microsatellite and SRY gene) previously described in horses (Anaya et al, ) were amplified by PCR using the same primer pairs (Table ) and protocols described for horses (Anaya et al, ). The PCR products were genotyped by capillary electrophoresis at the Central Service for Research Support of the University of Córdoba using a 3130 xl DNA sequencer (Applied Biosystems, CA, USA).…”

“…Although diagnosis of these anomalies has usually accomplished by karyotyping, the use of molecular methodologies has been more recently proposed as an interesting alternative (Demyda‐Peyras, Bugno‐Poniewierska, Pawlina, Anaya, & Moreno‐Millán, ; Gamo et al, ). In this sense, our group validated a new diagnostic tool based on short‐tandem‐repeat (STR) markers (Anaya et al, ) able to detect seven kinds of karyotype aberrations associated with the sexual pair, such as Turner syndrome, four kinds of intersex syndromes and two kinds of chimerism. Therefore, the aim of this study was to evaluate the use of such methodology in two diverse breeds of domestic donkeys, the Spanish Andalusian, and the African Moroccan breeds.…”