Let-7b promotes alpaca hair growth via transcriptional repression of TGFßR I.

The young male alpaca ear and the back skins were used to investigate the effect of transforming growth factor receptor-ß I (TGFßR I) on alpaca hair follicles and hair growth. The expression level and location of TGFßR I in alpaca ear and dorsal skin were detected through real-time quantitative PCR (RT-PCR) and paraffin section immunohistochemical technique (ICC-P). The results shown TGFßR I was lower expression in back skin compared to ear skin and the mean density of the positive reaction in ear skin was significantly higher than back skin. The targeted relationship with let-7b was detected using the dual-luciferase reporter vector of TGFßR I, which showed a significant target relationship between let-7b and TGFßR I. After transfection with let-7b eukaryotic expression vector, the relative mRNA expression of TGFßR I in alpaca skin fibroblasts did not differ, while the relative protein level was significantly decreased. In summary, a higher TGFßR I expression level in the ear skin suggests that TGFßR I may inhibit coat hair elongation. Further studies showed TGFßR I protein was downregulated by let-7b through transcriptional repression.