The effects of ERCC1 deficiency on mouse hepatocytes in vivo

• Main Author: Chipchase, Michael
• Published: University of Edinburgh 2003
• Subjects: 572.8
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.642812

ERCC1-XPF is a structure specific endonuclease that acts in nucleotide excision repair (NER), and is also involved in repair of DNA interstrand crosslinks and removal of non-homologous 3’ tails during recombination. The ERCC1 null mouse is runted and dies of liver failure before weaning, at about 3 weeks old. By three weeks after birth, some ERCC1 null hepatocytes have developed polyploidy. The liver phenotype of the ERCC1 null mouse is not observed in other NER deficiency models, which indicates that the loss of non-NER roles of ERCC1 are responsible for the liver phenotype. Development of liver polyploidy in the ERCC1 null hepatocytes has been tracked from before birth to death using FACS analysis and nuclear area distribution measurements. This has been compared to hepatocyte polyploidy development in wild type mice. The ERCC1 null mice undergo an accelerated development of polyploidy compared to age matched wild type mice. The cell cycle status of ERCC1 null hepatocytes has been investigated using a fluorescence immunostaining assay for centromeres. This reveals that the enlarged ERCC1 null hepatocytes are primarily in G2/M. Enlarged old wild type hepatocytes are also primarily in G2/M. However, normal ERCC1 null, old wild type and young wild type hepatocytes are primarily in G1/G0. The premature polyploidy liver phenotype of the ERCC1 null mouse is very similar to that seen in a transgenic mouse that overexpresses p21 in liver. Immunohistochemistry shows that p21 protein levels are increased in ERCC1 null liver. The increase in p21 protein levels was seen in old wild type livers when measured by immunohistochemistry and Northern blot analysis. A p53-ERCC1 double null mouse was made to test if the ERCC1 phenotype was dependent on p53. ERCC1-p53 null hepatocytes have the same accelerated polyploidy and increased p21 levels as ERCC1 null hepatocytes.