RAD51 knockout in murine liver (11-week)
RAD51 is a highly conserved DNA repair protein and is indispensable for the execution of homologous recombination, thereby participating in maintaining genomic stability. Since constitutive Rad51 knockout mice exhibit embryonic lethality, the physiological functions of RAD51, and the consequences of lacking it, are largely unknown. We herein demonstrated a critical role of RAD51 in postnatal liver development and regeneration. RAD51 is highly expressed during liver development and during regeneration following hepatectomy and hepatic injury, and is also elevated in liver-related diseases. We generated hepatocyte-specific Rad51 deletion mouse model (Rad51-CKO) to evaluate the function of RAD51 in liver development and regeneration.RAD51 deletion in postnatal hepatocytes results in aborted mitosis, global polyploidization, oxidative stress and cellular senescence. Remarkable liver fibrosis occurs as early as in 3-month-old Rad51fl/fl; Alb-Cre+/+ mice.The senescence-associated secretory phenotype in the livers of Rad51-CKO mice creates a niche that favors the activation and propagation of hepatic progenitor cells (HPCs) in which Rad51 is spared due to lack of Alb-Cre expression. The Rad51 functional HPCs and immature hepatocytes can thus proliferate vigorously, acquire increased malignancy, and eventually give rise to HCC. Our results thus demonstrate a novel function of RAD51 in liver development, homeostasis and tumorigenesis. The RAD51-CKO mice represent a unique genetic model for premature liver senescence, fibrosis, impaired regeneration and hepatocellular carcinogenesis. Overall design: Liver tissue samples taken from three independent hepatocyte-specific Rad51 deletion mice and three wild-type  littermate controls (11-week-old) were used for RNA-Seq.