Study on the expression patterns of inner root sheath-specific genes in Tan sheep hair follicle during different developmental stages.

By analyzing the expression patterns of inner root sheath (IRS) specific genes during different developmental stages of hair follicle (HF) in Tan sheep embryos and at birth, this study aims to reveal the influence of the IRS on crimped wool. Skin tissues from the scapular region of male Tan sheep were collected at 85 days (E85) and 120 days (E120) of fetal development, and at 0 days (D0), 35 days (D35), and 60 days (D60) after birth, with four samples at each stage. Real-time quantitative polymerase chain reaction (RT-qPCR) was employed to determine the relative expression levels of IRS type I keratin genes (KRT25, KRT26, KRT27, KRT28), type II keratin genes (KRT71, KRT72, KRT73, KRT74), and the trichohyalin gene (TCHH) in the skin of Tan sheep at different stages. Results showed that the expression levels of all IRS-specific genes peaked at D0, with the expression of all genes significantly higher than at E85 (P < 0.01), except for KRT73 and TCHH. The expression levels of KRT25, KRT26, and KRT72 were also significantly higher than at E120 (P < 0.01). Furthermore, the expression levels of KRT27, KRT28, KRT71, and KRT74 were significantly higher than both at E120 and D35 (P < 0.01). The expression levels of other genes at different stages showed no significant difference (P > 0.05). Conclusion: The IRS-specific genes exhibit the highest expression levels in Tan sheep at the neonatal stage. The expression levels of KRT71, KRT72, and TCHH, which are consistent with the pattern of wool crimp, may influence the morphology of the IRS and thereby affect the crimp of Tan sheep wool.