Krt5, also known as keratin 5, is a protein-coding gene. Keratins are intermediate filament proteins that play a crucial role in providing mechanical stability to epithelial cells. Krt5 is expressed in basal epithelial cells and is involved in maintaining the integrity of epithelial tissues. It may also be associated with signaling pathways, though specific pathways are context-dependent, and its overall biological importance lies in tissue development, homeostasis, and response to injury [2,3,4,5,6,7,8]. Genetic models, such as knockout (KO) and conditional knockout (CKO) mouse models, can be valuable in studying its function.

In lung-related studies, p63(+)Krt5(+) distal airway stem cells are essential for lung regeneration. Selective ablation of these cells in vivo prevents lung regeneration after influenza-induced damage, leading to pre-fibrotic lesions and deficient oxygen exchange, indicating the importance of Krt5-expressing cells in lung repair processes [1]. In melanoma, knockdown of Krt5 using siRNAs significantly promoted the proliferation, migration, and invasion of A375 cells, suggesting that Krt5 plays inhibitory roles in melanoma metastasis [4]. In the kidney, Krt5+ urothelial cells act as developmental and tissue repair progenitors. Fate mapping analysis showed that adult uroplakin-positive renal urothelial cells derive from embryonic and neonatal Krt5+ cells, and in response to congenital urinary tract obstruction, postnatal Krt5+ cells can differentiate into uroplakin-positive cells [8].

In conclusion, Krt5 is crucial for maintaining the integrity of epithelial tissues. Model-based research, especially KO/CKO mouse models, has revealed its significance in lung regeneration, melanoma metastasis, and kidney urothelial development and repair. Understanding Krt5's function provides insights into the mechanisms of these biological processes and related disease conditions.