CRISPR/Cas9‐mediated loss of FGF5 function increases wool staple length in sheep

Fibroblast growth factor 5 (FGF5) regulates hair length in humans and a variety of other animals. To investigate whether FGF5 has similar effects in sheep, we used CRISPR/Cas9 to generate loss-of-function mutations with the FGF5 gene in Chinese Merino sheep. A total of 16 lambs were identified with genetic mutations within the targeting locus: 13 lambs had biallelic modifications and 3 lambs had monoallelic modifications. Characterization of the modifications revealed that 13 were frame shift mutations that led to premature termination; the other 3 were in-frame deletions. Thus, CRISPR/Cas9 efficiently generated loss-of-function mutations in the sheep FGF5 gene. We then investigated the effect of loss of FGF5 function on wool traits in 12 lambs, and found that the wool staple length and stretched length of genetically modified yearling sheep were significantly longer than that of wild-type control animals. The greasy fleece weight of genetically modified yearling sheep was also significantly greater than that of wild-type sheep. Moreover, the mean fiber diameter in the genetically modified versus wild type sheep showed no significant difference, suggesting that the increase of greasy fleece weight was likely attributed to the increase in wool length. Our work suggests that CRISPR/Cas9-mediated loss of FGF5 activity could promote wool growth, and consequently increase wool length and yield. This article is protected by copyright. All rights reserved.