7H). These results indicate that NS depletion predisposes proliferating hepatocytes to replication-dependent DNA damage by perturbing RAD51 recruitment to DNA damage foci. The importance of NS in liver development is shown by the increase of spontaneous DNA damage, apoptosis, BDH, and fibrosis in albNScko livers. DNA damage appears first in albNScko livers during the first to second postnatal week, followed by an increase of apoptotic cells that peaks at 3 weeks of age and the appearance of necrotic foci and regenerative

hepatic nodules. Complete loss of NS proteins by albNScko occurs within Epigenetics Compound Library the first week after birth and mainly affects developing hepatocytes. Although we cannot exclude the possibility that the Alb-Cre transgene is expressed in subsets of BECs, our data indicate that most BECs do not show Alb-Cre activity. AZD1208 This may explain why biliary hyperplasia becomes a prominent feature in adult albNScko livers. Newly generated hepatocytes in albNScko livers form small nodules and display basophilic cytoplasm and multiple small nucleoli. These cells also show higher mitotic activity and NS-positive expression and are less developmentally mature (as evidenced

by their AFP-positive and PAS-negative staining), compared to nonregenerative hepatocytes outside the nodule. The close spatial association between the regenerative nodules and periportal areas suggests that newly generated hepatocytes may be derived from non-NS-deficient medchemexpress BECs or HSPCs. In support of this, albNScko livers display increased HSPC-related proteins and the expansion of A6 and CK19 double-positive cells. These findings suggest that HSPCs may be activated by albNScko-induced liver damage. To date, only

a handful of mouse genetic models exhibit the phenotype of robust HSPC activation.[22-25] Compared to those published, the albNScko model has the unique features of an early-onset expansion of HSPCs (within 4 weeks of age) and long-term survival (over 1 year). The role of NS in liver regeneration is shown by the increased NS expression and the response of albNScko livers to CCl4 and PHx. In addition to the phenotypes of acute pericentral necrosis and leukocyte infiltration observed in NSflx/flx livers, CCl4 triggers severe hydropic degeneration in NS-deleted nonregenerative hepatocytes. In contrast, hepatocytes within the regenerative nodules are relatively resistant to the acute necrosis caused by CCl4, which may be explained by their less-differentiated features and lower expression of CYP2E1. Subsequent to CCl4-induced damage, mitotic cells are increased in the BDE, regenerative nodules, and nonregenerative hepatocytes of albNScko livers.