Genomic screening of allelic and genotypic transmission ratio distortion in horse.
Authors: Laseca Nora, Cánovas Ángela, Valera Mercedes, Id-Lahoucine Samir, Perdomo-González Davinia I, Fonseca Pablo A S, Demyda-Peyrás Sebastián, Molina Antonio
Journal: PloS one
Summary
# Editorial Summary: Transmission Ratio Distortion in Equine Genetics When inheritance patterns deviate from Mendelian expectations—a phenomenon termed transmission ratio distortion (TRD)—it signals underlying biological mechanisms affecting fertility, embryonic viability, or gamete production. Laseca and colleagues screened 277 Pura Raza Español horses (genotyped across 554,634 SNPs in family trios) for evidence of such distortion using SNP-by-SNP analysis, identifying 140 SNPs displaying allelic TRD and 42 showing genotypic patterns; notably, 63 variants exhibited stallion-specific distortion whilst 41 were mare-specific. Functional annotation revealed that genes harbouring these distorted loci cluster around spermatogenesis, oocytogenesis, embryonic development, and hormonal regulation, with ten genes emerging as plausible candidates influencing reproductive performance. For breeding programmes and stud management, these findings provide a genomic framework for identifying potentially subfertile breeding stock and understanding why certain crosses or individuals underperform reproductively despite apparent health. Practitioners working with breeding animals should recognise that poor conception rates or reduced viable offspring numbers may reflect inherited genetic factors affecting gamete transmission rather than conventional management or veterinary issues alone.
Read the full abstract on PubMed
Practical Takeaways
- •Genomic screening can identify specific alleles that deviate from normal Mendelian inheritance and may affect reproductive success in breeding programs
- •Breeders can use TRD markers to improve stallion and mare selection by identifying carriers of distorted alleles affecting fertility and embryonic viability
- •Understanding parent-of-origin effects (stallion vs. mare TRD) allows for targeted breeding decisions to optimize reproductive outcomes
Key Findings
- •140 SNPs with allelic TRD patterns and 42 with genotypic patterns were identified across 277 horse trios
- •63 SNPs showed stallion-TRD, 41 showed mare-TRD, and 36 exhibited overall TRD affecting inheritance patterns
- •10 functional candidate genes related to fertility were identified, associated with spermatogenesis, oocyte division, embryonic development, and hormonal activity
- •42 SNPs exhibited heterosis patterns suggesting potential advantages in heterozygous carriers