Altered gene expression pattern in the fatty liver dystrophy mouse reveals impaired insulin-mediated cytoskeleton dynamics.

The mouse fatty liver dystrophy (fld) mutation is characterized by transient hypertriglyceridemia and fatty liver during the neonatal period, followed by development of a peripheral neuropathy. To uncover the metabolic pathway that is disrupted by the fld mutation, we analyzed the altered pattern of gene expression in the fatty liver of fld neonates by representational difference analysis of cDNA. Differentially expressed genes detected include a novel member of the Ras superfamily of small GTP-binding proteins, a novel Ser/Thr kinase, and several actin cytoskeleton-associated proteins including actin, profilin, alpha-actinin, and myosin light chain. Because these proteins have a potential functional link in the propagation of hormone signals, we investigated cytoskeleton dynamics in fld cells in response to hormone treatment. These studies revealed that preadipocytes from fld mice exhibit impaired formation of actin membrane ruffles in response to insulin treatment. These findings suggest that the altered mRNA expression levels detected in fld tissue represent a compensatory response for the nonfunctional fld gene and that the fld gene product may be required for development of normal insulin response.