A Non-Synonymous HMGA2 Variant Decreases Height in Shetland Ponies and Other Small Horses.
Authors: Frischknecht Mirjam, Jagannathan Vidhya, Plattet Philippe, Neuditschko Markus, Signer-Hasler Heidi, Bachmann Iris, Pacholewska Alicja, Drögemüller Cord, Dietschi Elisabeth, Flury Christine, Rieder Stefan, Leeb Tosso
Journal: PloS one
Summary
# Editorial Summary Researchers conducted a genome-wide association study on just 48 Shetland ponies to identify genetic variants controlling height at withers, successfully mapping a quantitative trait locus to equine chromosome 6 using the Illumina SNP70 BeadChip. Through fine-mapping and targeted sequencing, they pinpointed a non-synonymous mutation in the HMGA2 gene (c.83G>A; p.G28E) that alters the first AT-hook DNA-binding domain of the protein—a functionally critical region—and demonstrated via electrophoretic mobility shift assay that this variant significantly impairs DNA binding capacity. This mutation segregates across several pony breeds but remains absent in standard-sized horse breeds, suggesting it represents a breed-specific quantitative trait nucleotide that reduces growth potential and final stature. The findings provide mechanistic insight into how a single genetic variant can exert substantial effects on height in horses, unlike the polygenic architecture seen in humans where hundreds of loci with modest individual effects control this trait. For breeding programmes and selection decisions, this work offers a clear molecular marker that could be used to predict mature height in Shetland and other small pony breeds, potentially informing breeding strategies for size-specific demands.
Read the full abstract on PubMed
Practical Takeaways
- •Understanding the genetic basis of height variation can inform breeding decisions in pony breeds and help identify animals carrying size-determining variants.
- •This variant explains a major portion of heritable height differences in Shetland ponies and related small breeds, providing a molecular marker for selective breeding programs.
- •The HMGA2 gene represents a validated target for height selection in equine breeding; genetic testing could help breeders maintain or modify size traits predictably.
Key Findings
- •A non-synonymous HMGA2 variant (c.83G>A; p.G28E) in the first exon significantly decreases height at withers in Shetland ponies and other small horse breeds.
- •The variant impairs DNA binding of the first AT-hook domain of HMGA2 protein, as demonstrated by electrophoretic mobility shift assay.
- •The variant segregates in multiple pony breeds but is absent in regular-sized horse breeds, suggesting breed-specific selection for small stature.
- •Genome-wide association mapping successfully identified a quantitative trait nucleotide with large effect on height using only 48 animals.