Let-7b regulates alpaca hair growth by downregulating ectodysplasin A.

Hypohidrotic ectodermal dysplasia (HED), also known as anhidrotic ectodermal dysplasia, is characterized by the clinical manifestations of less sweat or no sweat, sparse or no hair, tooth agenesis and/or abnormal tooth morphology. The characteristics of alpaca ear hair differ from the back hair. The ectodysplasin A (EDA) signaling pathway has a regulatory effect on skin development and hair growth. The aim of the present study was to study the effects of EDA on alpaca hair growth by examining the mRNA and protein expression levels of EDA in alpaca ear and back skin by reverse transcription­quantitative polymerase chain reaction and western blot analysis, respectively. Results indicated that EDA expression was higher in the ear skin compared with the back skin. The expression levels of let­7b in the skin of healthy alpacas varies; the difference between let­7b expression levels of the ear and back have been reported to be >2­fold, suggesting a role for let­7b in the development of adult alpaca skin and hair follicles. A dual­luciferase reporter vector was constructed to verify the targeting relationship between microRNA let­7b and EDA, and the results revealed that EDA was a target gene of let­7b. Alpaca skin fibroblasts were transfected with a let­7b eukaryotic expression vector to investigate the regulatory relationship between let­7b and EDA. The expression of EDA was decreased in the transfected group; immunocytochemical results demonstrated that the EDA protein was abundantly expressed in the fibroblast cytoplasm. EDA protein expression was weaker in the transfected cells than in the untransfected cells. These results suggested that EDA may serve a role in alpaca hair growth and is probably a target gene of let­7b; let­7b downregulated EDA mRNA and protein expressions, which suggested that let­7b may regulate alpaca hair growth. These conclusions suggested that let­7b may be associated with HED.