Pseudoauthosomal región as a key factor for the molecular detection of Turner´s syndrome in horses

YAMILA PIROSANTO; NORA LASECA; FLORENCIA AZCONA; ANTONIO MOLINA ALCALÁ; MERCEDES VALERA; SEBASTIÁN DEMYDA-PEYRÁS

Davos

Conferencia; 72nd Annual Meeting of the European Federation of Animal Science; 2021

The monosomy of the sex chromosome pair (known as Turner´s syndrome) is a frequent cause of infertility in the horse. This disease, characterized by individuals showing a mare phenotype with gonadal dysgenesis, was reported across breeds mosty commonly in two different forms: pure (63, X63,X) and mosaic (63,X/64,XX). Nowadays, its diagnosis is made by direct observation using classical or molecular (FISH) karyotyping. In this study, we analyzed 6 horses previously diagnosed as carriers of Turner´s syndrome (3 pure and 3 mosaic) using a chromosomal number aberration approach based on medium density SNP genotyping. Individuals were genotyped using a 65K GGP array for horses. Copy number aberrations (CNA) were detected based on LRR intensity and heterozygosity (HET) values in two regions of the ECAX: 1:1,850,000bp (Pseudoautosomal region PAR) and 1,850,001:128,200,000bp (NON-PAR). Results were compared among groups using an ANOVA (LRR) and a Z-proportion test (HET). All the mares showed LRR abnd HET values close to 0 and 25%, respectively, in both regions (PAR and NON-PAR), indicating the presence of two ECAX. Stallions showed the same pattern in PAR, since this chromosome region is present in ECAY and ECAX. However, LRR and HET means decreased to -0.41 and 2% in NON-PAR, a pattern consistent with the presence of only one chromosome, since only one ECAX is present in stallions. Only 63,X individuals showed a single chromosome pattern (LRR=-0.42 and HET=1%) in PAR and NON-PAR, indicating absence of ECAY, and thus allowing its detection. In the case of 63,X/64,XX, PAR, and NON-PAR showed intermediate values of LRR (-0.23) and normal values of HET (21%), consistent with the coexistence of two cell lines with different chromosomal complements. In conclusion, the use of SNP genotyping seems to be a valid methodology for CAN screening in horses. In addition, the PAR region is the key to detect the ECAX monosomy. Further studies with larger datasets are necessary to validate this approach as a reliable methodology before including it in the genomic toolbox.