Krt71, encoding a type II keratin, is specifically expressed in the inner root sheath (IRS) of the hair follicle. It plays a crucial role in determining hair structure and coat phenotypes in various mammals [3]. Mutations in Krt71 have been linked to hair-related phenotypes, such as curly hair, hypotrichosis, and follicular dysplasia, indicating its importance in hair development and maintenance. Genetic models, including KO mouse models, are valuable for studying its function [4].

In dogs, a missense variant (c.451C>T) in exon 2 of Krt71 is known to cause curly fur in some breeds. However, in Curly Coated Retrievers, a novel structural variant in exon 7 (c.1266_1273delinsACA) was identified, which is predicted to result in a frameshift and stop-loss, significantly affecting the protein structure if translated. This variant was also found in other breeds with curly or wavy coats [1,2]. In Hereford cattle, a loss-of-function variant in Krt71 (c.281delTGTGCCCA; p.Met94AsnfsX14) leads to inner root sheath dysplasia and recessive congenital hypotrichosis [3]. In rats, the Rex (Re) mutation, a 7-bp deletion at the splicing acceptor site of intron 1 of Krt71, causes curly hair in Re/+ rats and hair loss in Re/Re rats, with the deletion provoking an in-frame deletion in the alpha-helical rod domain of the KRT71 protein [5]. In mice, Krt71-knockout (KO) mice display curly hair and a new phenomenon of complete hair shedding at 3-5 weeks, mimicking woolly hair and hairlessness, providing a valuable model for hair disorder studies [4].

In conclusion, Krt71 is essential for maintaining normal hair structure and development in multiple species. Studies using KO mouse models and other genetic models in different animals have revealed its role in hair-related phenotypes and disorders, such as curly hair, hypotrichosis, and follicular dysplasia. These findings contribute to our understanding of the molecular mechanisms underlying hair development and related diseases, potentially guiding future research and therapeutic strategies in hair-related conditions.

References:

1. Salmela, E, Niskanen, J, Arumilli, M, Lohi, H, Hytönen, M K. 2018. A novel KRT71 variant in curly-coated dogs. In Animal genetics, 50, 101-104. doi:10.1111/age.12746. https://pubmed.ncbi.nlm.nih.gov/30456859/

2. Bauer, A, Hadji Rasouliha, S, Brunner, M T, Roosje, P, Leeb, T. 2018. A second KRT71 allele in curly coated dogs. In Animal genetics, 50, 97-100. doi:10.1111/age.12743. https://pubmed.ncbi.nlm.nih.gov/30444027/

3. Jacinto, Joana G P, Markey, Alysta D, Veiga, Inês M B, Beever, Jonathan E, Drögemüller, Cord. 2021. A KRT71 Loss-of-Function Variant Results in Inner Root Sheath Dysplasia and Recessive Congenital Hypotrichosis of Hereford Cattle. In Genes, 12, . doi:10.3390/genes12071038. https://pubmed.ncbi.nlm.nih.gov/34356054/

4. Zhang, Tao, Yao, Hongwu, Wang, Hejun, Sui, Tingting. 2023. Development of Woolly Hair and Hairlessness in a CRISPR-Engineered Mutant Mouse Model with KRT71 Mutations. In Cells, 12, . doi:10.3390/cells12131781. https://pubmed.ncbi.nlm.nih.gov/37443815/

5. Kuramoto, Takashi, Hirano, Ryuji, Kuwamura, Mitsuru, Serikawa, Tadao. 2010. Identification of the rat Rex mutation as a 7-bp deletion at splicing acceptor site of the Krt71 gene. In The Journal of veterinary medical science, 72, 909-12. doi:. https://pubmed.ncbi.nlm.nih.gov/20179389/