Krt77, a type II epithelial cell α-keratin gene family member, plays a crucial role in animal epidermal and coat formation [1]. It is involved in epidermal development and is associated with processes like keratinocyte differentiation, skin development, and epithelial cell differentiation [2].

In a study on Chinese cattle, a 30-bp insertion in the Krt77 gene was found to be associated with environmental adaptation, with the insertion frequency increasing from the northwest to the southeast population and correlated with local annual mean temperature, relative humidity, and temperature humidity index [1]. In murine studies, the loss of Krt77 did not cause fetal lethality or harm skin and appendage development, but led to an up-regulation of Krt1, suggesting functional compensation [4]. In addition, Krt77 was identified as one of the key genes in the protein-protein interaction network analysis related to wool fiber diameter variation in Angora rabbits [2]. Also, its expression levels decreased from admission to discharge in COVID-19 patients, being related to the regulation of inflammation drivers in the disease [3].

In conclusion, Krt77 is essential for epidermal and coat formation. Studies on Krt77, especially through gene-knockout models in mice, have provided insights into its role in environmental adaptation in cattle, functional compensation in murine skin, wool fiber diameter determination in rabbits, and inflammation regulation in COVID-19. These findings contribute to understanding its biological functions and its implications in different biological processes and disease conditions.

References:

1. Zhang, Mengqi, Wu, Daoyi, Ahmed, Zulfiqar, Huang, Bizhi, Lei, Chuzhao. 2023. The genetic secrets of adaptation: decoding the significance of the 30-bp insertion in the KRT77 gene for Chinese cattle. In Animal biotechnology, 34, 3847-3854. doi:10.1080/10495398.2023.2232663. https://pubmed.ncbi.nlm.nih.gov/37452660/

2. Huang, Dongwei, Ding, Haisheng, Wang, Yuanlang, Wang, Xiaofei, Zhao, Huiling. 2024. Integration Analysis of Hair Follicle Transcriptome and Proteome Reveals the Mechanisms Regulating Wool Fiber Diameter in Angora Rabbits. In International journal of molecular sciences, 25, . doi:10.3390/ijms25063260. https://pubmed.ncbi.nlm.nih.gov/38542234/

3. Gade, Inger Lise, Bodilsen, Jacob, Mariager, Theis, Bennike, Tue Bjerg, Honoré, Bent. 2025. Exhaled breath protein composition in patients hospitalized during the first wave of COVID-19. In Journal of breath research, , . doi:10.1088/1752-7163/add617. https://pubmed.ncbi.nlm.nih.gov/40341493/

4. Ghorbanalipoor, S, Hommel, T, Kolbe, T, Posch, C, Dahlhoff, M. 2024. The loss of keratin 77 in murine skin is functionally compensated by keratin 1. In Biochimica et biophysica acta. Molecular cell research, 1872, 119881. doi:10.1016/j.bbamcr.2024.119881. https://pubmed.ncbi.nlm.nih.gov/39603462/