Fibroblast growth factor 5 (FGF5) is a famous dominant inhibitor of anagen phase of hair cycle. Mutations of FGF5 gene result in a longer wool in mice, donkeys, dogs, cats, and even in human eyelashes. Sheep is an important source of wool production. How to improve the production of wool quickly and effectively is an urgent problem to be solved. In this study, we generated five FGF5-knockout Dorper sheep by the CRISPR/Cas9 system. The expression level of FGF5 mRNA in knockout (KO) sheep decreased significantly, and all FGF5 proteins were dysfunctional. The KO sheep displayed a significant increase in fine-wool and active hair-follicle density. The crosstalk between androgen and Wnt/ β-catenin signaling downstream of FGF5 gene plays a key role. We established downstream signaling cascades for the first time, including FGF5, FGFR1, androgen, AR, Wnt/β-catenin, Shh/Gli2, c-MYC, and KRTs. These findings further improved the function of FGF5 gene, and provided therapeutic ideas for androgen alopecia. including cats (Felis catus) 7,8 , dogs (Canis lupus familiaris) 9,10 , donkeys (Equus africanus asinus) 11 , Syrian hamster (Mesocricetus auratus) 12 , domestic guinea pigs (Cavia porcellus) 13 , and even human (Homo sapiens) 14. Sheep are one of the most important wool animals. However, traditional breeding limits the genetic improvement of sheep breeding in the short term. Current results indicate that the CRISPR-Cas9 system can be successfully employed in a broad range of organisms 15-21. In the previous study, we had successfully generated FGF5-knockout heterozygous sheep using the CRISPR/ Cas9 system by direct one-step cytoplasmic injection of Cas9 mRNA and sgRNA into zygotes, and the relationship
