XPA and Cowden syndrome 1: The main goal of the present study was to determine the extent to which XPG deficiency in mice results in multisystem progeroid degenerative changes as observed in CS and XP/CS patients, as well as in other NER-deficient mouse models including Xpa/Csb, Xpd, and Ercc1 mutants [48], [51], [68], [69], [72], [77], [107].