FGF7 Polymorphisms, Especially Chr7:57803771:C>T, Are Associated with Lambskin Traits in Hu Sheep

Lambskin quality is an economically important trait in Hu sheep (Ovis aries), with wool-pattern characteristics contributing substantially to commercial value. However, the genetic basis of lambskin variation remains incompletely understood. This study evaluated single nucleotide polymorphisms (SNPs) in four candidate genes involved in hair follicle development, FGF7, FGFR2, SMAD5, and SOSTDC1, in 384 Hu sheep using Sequenom MassARRAY® technology. Allele and genotype frequencies, heterozygosity, polymorphism information content (PIC), and Hardy–Weinberg equilibrium (HWE) were assessed, followed by association analyses with categorical and quantitative lambskin traits. A total of 18 polymorphic SNPs were successfully genotyped. Three FGF7 SNPs showed significant associations with lambskin traits, with all corresponding significant allelic associations remaining significant after false discovery rate (FDR) correction. For Oar_v4.0:Chr7:57803771:C>T, the C-allele frequency increased from 0.30 in straight-wool individuals to 0.53 in fully wavy-wool individuals, and the C allele was associated with higher odds of the fully wavy phenotype (OR = 2.70, 95% CI: 1.56–4.68). This locus was also significantly associated with pattern area and lambskin grade, whereas Oar_v4.0:Chr7:57740946:G>A and Oar_v4.0:Chr7:57741376:T>G were associated with pattern area and pattern width. SMAD5 variants showed nominal associations with some traits but did not remain significant after FDR correction, whereas FGFR2 showed no significant associations and SOSTDC1 showed a nominal genotype association with lambskin grade. Protein–protein interaction analysis further placed FGF7 within a network involving signaling proteins related to epithelial proliferation and hair follicle development. Collectively, these findings identify the FGF7 region, particularly Oar_v4.0:Chr7:57803771:C>T, as the strongest candidate signal associated with lambskin variation in Hu sheep.