Novel copy number variation of the TGFβ3 gene is associated with TGFβ3 gene expression and duration of fertility traits in hens

Improvements in the duration of fertility (DF) could increase the interval between successive artificial inseminations, thereby decreasing the cost associated with production of hatching eggs. The molecular mechanisms involved in DF in hens remains under-explored. In this study, expression levels of the transforming growth factor-β genes (TGFβs: TGFβ1, TGFβ2, TGFβ3) were investigated in utero-vaginal junctions (UVJs) of hens with long DF (Group L, n = 10) and short DF (Group S, n = 10). TGFβ1 and 2 tended to exhibit higher expression levels in UVJs from Group L hens. The expression levels of TGFβ3 mRNA and protein were significantly increased in UVJs of hens from Group L compared to hens in Group S. Consistently, six TGFβs downstream genes (DAXX, MEKK1, T-BET, GATA-3, TAK1, and FOXP3) associated with the immune response were found to be significantly differentially expressed in UVJs of Group L than Group S hens. In addition, four SNPs were identified in intron 1 of TGFβ3, and these SNPs were significantly associated with DF traits (P < 0.05). Furthermore, we identified multi-copy and copy number variants (CNVs) in chicken TGFβ3 and later determined significant associations between TGFβ3 CNVs and DF traits in hens. Specifically, TGFβ3 copy number exhibited a significant positive correlation with its expression (P < 0.05). Collectively, our results suggest that chicken DF traits may be regulated by the expression of TGFβ3 in UVJ. Meanwhile, the copy number variation in the TGFβ3 gene identified in this study seems to be one marker for DF traits.