Four loci explain 83% of size variation in the horse.
Authors: Makvandi-Nejad Shokouh, Hoffman Gabriel E, Allen Jeremy J, Chu Erin, Gu Esther, Chandler Alyssa M, Loredo Ariel I, Bellone Rebecca R, Mezey Jason G, Brooks Samantha A, Sutter Nathan B
Journal: PloS one
Summary
# Editorial Summary Selective breeding has produced remarkable variation in horse body size—from miniatures standing under one metre to Shires exceeding two metres at the withers—yet the genetic architecture underlying this diversity remained largely unknown. Using genome-wide association studies (GWAS) across horse populations, researchers identified just four genetic loci that collectively explain 83% of size variation in the species, a finding that contrasts sharply with human height genetics, which involves numerous variants each with modest effects. Three of these loci harbour genes previously linked to stature in humans (LCORL, HMGA2 and ZFAT), whilst the LCORL/NCAPG locus also influences growth in cattle, suggesting these regions represent conserved developmental pathways affecting body size across mammalian species. The concentrated genetic control of equine size reflects the intense artificial selection within breed populations, creating relatively large allelic effects at a small number of loci rather than the polygenic architecture seen in naturally reproducing populations. For equine professionals, understanding that size is controlled by a discrete set of major genes has implications for selective breeding programmes, predictive genetics in young stock assessment, and potentially for identifying size-related health or performance trade-offs linked to these specific genomic regions.
Read the full abstract on PubMed
Practical Takeaways
- •Breeders can potentially use genetic markers at four key loci to predict and select for desired size within breeds more efficiently
- •The genetic basis of extreme size variation (miniatures to draft breeds) is controlled by a surprisingly small number of genes, enabling targeted breeding strategies
- •Understanding these shared genetic mechanisms across species may inform selective breeding practices and help maintain breed standards
Key Findings
- •Four genetic loci explain 83% of size variation in horses across breeds
- •Three size loci (LCORL, HMGA2, ZFAT) are shared with human height-controlling genes
- •LCORL/NCAPG locus is implicated in both horse size and cattle growth
- •Horse size alleles show large effect sizes unlike humans, reflecting domestication selection