42-LB: A New Laminopathy Caused by an Arg133/leu Mutation in Lamin A/C and the Effects thereof on Adipocyte Differentiation and the Transcriptome

Mutations in LMNA trigger changes in nuclear architecture, signal transduction, and gene regulation, associated with a group of multisystem diseases termed laminopathies. Here we report a new laminopathy in a 26-year-old female, characterized by generalized lipoatrophy, insulin-resistant diabetes, micrognathia, symptoms of premature aging, hypertension, and biopsy-proven focal segmental glomerulosclerosis. The de novo heterozygous mutation R133L lamin A/C gene (LMNA) was found in the patient and inherited to her son who has not (yet) developed a lipodystrophic phenotype. We analyzed the nuclear morphology and laminar distribution of both 3T3-L1 pre-adipocytes and mouse glomerular mesangial cells overexpressing human wild type lamin A/C (LMNA WT) or lamin A/C with the R133L mutation (LMNA R133L) that causes the new laminopathy. We found that nuclear morphology was abnormal; the nuclei evidenced hypertrophy, nuclear membrane invagination or blebbing, and a disorganized A-type lamin meshwork in both cell lines overexpressing LMNA R133L. The differentiation from 3T3-L1 pre-adipocyte into adipocytes was impaired in cells expressing LMNA R133L; the expression levels of genes associated with adipose tissue self-renewal, including adipogenesis and angiogenesis were downregulated. Furthermore, the insulin-signaling pathway was inhibited in LMNA R133L adipocytes. Microarray gene expression profiling showed that the most prominent differences between 3T3-L1 cells expressing LMNA WT and LMNA R133L were in genes implicated in metabolic pathways, the cellular response to DNA damage, DNA repair, and RNA binding. We thus expanded the clinical spectrum of laminopathy and concluded that the LMNA R133L mutation associated with lipodystrophic features, multisystem disorders and the repairation of DNA damage.