Abstract
The LMNA gene encodes for the nuclear envelope proteins lamin A and C (lamin A/C). A novel R133L heterozygous mutation in the LMNA gene causes atypical progeria syndrome (APS). However, the underlying mechanism remains unclear. Here, we used transgenic mice (LmnaR133L/+ mice) that expressed a heterozygous LMNA R133L mutation and 3T3-L1 cell lines with stable overexpression of LMNA R133L (by lentiviral transduction) as in vivo and in vitro models to investigate the mechanisms of LMNA R133L mutations that mediate the APS phenotype. We found that a heterozygous R133L mutation in LMNA induced most of the metabolic disturbances seen in patients with this mutation, including ectopic lipid accumulation, limited subcutaneous adipose tissue (SAT) expansion, and insulin resistance. Mitochondrial dysfunction and senescence promote ectopic lipid accumulation and insulin resistance. In addition, the FLAG-mediated pull-down capture followed by mass spectrometry assay showed that p160 Myb-binding protein (P160 MBP; Mybbp1 aa $$ a $$<math> <semantics><mrow><mi>a</mi></mrow> <annotation>$$ a $$</annotation></semantics> </math> ), the critical transcriptional repressor of PGC-1α, was bound to lamin A/C. Increased Mybbp1 aa $$ a $$<math> <semantics><mrow><mi>a</mi></mrow> <annotation>$$ a $$</annotation></semantics> </math> levels in tissues and greater Mybbp1 aa $$ a $$<math> <semantics><mrow><mi>a</mi></mrow> <annotation>$$ a $$</annotation></semantics> </math> -lamin A/C binding in nuclear inhibit PGC-1α activity and promotes mitochondrial dysfunction. Our findings confirm that the novel R133L heterozygous mutation in the LMNA gene caused APS are associated with marked mitochondrial respiratory chain impairment, which were induced by decreased PGC-1α levels correlating with increased Mybbp1a levels in nuclear, and a senescence phenotype of the subcutaneous fat.