GPT and Decreased liver function: Modestly increased levels of both ALT and AST activity were seen in the plasma of 10-d induced RosaCreER; Mdm2I438K/I438K mice compared with control mice (Supplemental Fig. S3H,I), although these levels normalized over the longer term, suggesting that any liver dysfunction was mild and transient and consistent with the recovery of restrained p21 expression by this time.