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

Highlight
• TGFβR I regulates alpaca hair growth and may inhibit coat hair elongation.
• TGFβR I is one of the target genes of let-7b and is downregulated by let-7b through transcription repression.
• TGFβR I expression may also be inhibited by let-7b expression in the dorsal skin of alpaca; thereby affecting alpaca hair follicles and hair growth cycle.

The young male alpaca ear and the back skins were used to investigate the effect of transforming growth factor receptor-β I (TGFβR I) on alpaca hair follicles and hair growth. The expression level and location of TGFβR 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 TGFβR 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 TGFβR I, which showed a significant target relationship between let-7b and TGFβR I. After transfection with let-7b eukaryotic expression vector, the relative mRNA expression of TGFβR I in alpaca skin fibroblasts did not differ, while the relative protein level was significantly decreased. In summary, a higher TGFβR I expression level in the ear skin suggests that TGFβR I may inhibit coat hair elongation. Further studies showed TGFβR I protein was downregulated by let-7b through transcriptional repression.