Genetic associations of INHBE gene variants with milk production traits in dairy cattle

The inhibin subunit beta E ( INHBE ) gene encodes activin E, a hepatokine belonging to the TGF-β superfamily, and plays important roles in regulating lipid metabolism, energy homeostasis and immune responses. Our previous study identified INHBE as a potential candidate gene for milk traits through liver transcriptome analysis of Holstein cows. Herein, we systematically evaluated the genetic effects of INHBE on milk yield and composition traits in 947 Chinese Holstein cattle. Two single nucleotide polymorphisms (SNPs) were identified, including 5:g.56006974C>T located in the 5′ regulatory region and 5:g.56004276G>A in the 3′ regulatory region. Phenotype-genotype association analysis indicated that the 5:g.56006974C>T locus was significantly associated with milk fat yield ( p = 0.0015; p = 0.0036) and fat percentage ( p = 0.0339; p = 0.0216) across two lactations, as well as milk protein yield in the first lactation ( p = 0.0378). The 5:g.56004276G>A variant was significantly associated with milk fat yield in the second lactation ( p = 0.0181). Linkage disequilibrium (LD) analysis showed that the two SNPs formed a haplotype block ( r 2 = 1.0), which was significantly associated with 305-day milk yield ( p = 0.0049; p = 0.0220), milk fat yield ( p = 0.0002; p < 0.0001), milk fat percentage ( p = 0.0249, the second lactation), milk protein yield ( p = 0.0009, the first lactation) and milk protein percentage ( p = 0.0464, the second lactation). Furthermore, JASPAR analysis indicated that the T allele at the 5:g.56006974C>T locus may introduce a predicted binding motif for the transcription factor ZNF341. Notably, dual-luciferase reporter assays showed that this variant significantly reduced the transcriptional activity of the INHBE promoter ( p = 0.0005). These findings suggest that INHBE is a promising candidate gene associated with milk yield and composition traits, and its regulatory variants may serve as useful genetic markers for future genomic selection programs in dairy cattle breeding.