Small Genome-wide association study of insect bite hypersensitivity in Hucul horses.

Insect bite hypersensitivity (IBH) is a prevalent allergic skin disease in horses that significantly affects animal welfare and shows evidence of genetic predisposition. Understanding the genetic basis of IBH can improve management and breeding strategies. The Equine80K BeadChip microarray was used to identify genomic regions associated with the occurrence of IBH in Hucul horses. Hair samples were collected from 127 Hucul horses, including both affected individuals and controls. DNA was extracted and genotyped. A genome-wide association study (GWAS) was performed to identify loci associated with IBH susceptibility. No genome-wide significant SNPs were detected; however, five loci showed suggestive associations on ECA5, ECA15, and ECA20. The strongest signal was on ECA20, with three SNPs located within a ∼5.32 Mb region upstream of the DST gene, suggesting potential regulatory effects. DST encodes dystonin, a cytoskeletal linker protein with an epidermal isoform expressed in keratinocytes and localized to hemidesmosomes at the dermal-epidermal junction, supporting its biological relevance to skin integrity and hypersensitivity-related pathology. Additionally, several additional genes in this interval (COL21A1, KIAA1586, ZNF451, PRIM2, BAG2, RAB23, KHDRBS2, LGSN, PTP4A1, PHF3, BEND6) may contribute to IBH susceptibility. These findings support a genetic component in IBH susceptibility and highlight potential regulatory variants on chromosome 20 as key contributors. Further functional studies and fine mapping are needed to identify causal mutations and validate candidate gene involvement, which could guide future breeding and management practices to reduce IBH prevalence in Hucul horses.