Rabbit Anti-Human LMNA (Phospho-Ser392) polyclonal antibody

Context: Familial partial lipodystrophy, Dunnigan variety (FPLD2) is a rare autosomal-dominant disorder due to heterozygous missense lamin A/C (LMNA) mutations. Subjects with FPLD2 gradually lose fat from the upper and lower extremities but gain fat in the face and neck around puberty. However, the precise onset of body fat changes and metabolic complications during childhood remains unknown. Objective: To compare metabolic parameters and regional body fat in children with FPLD2 with the sex- and age-matched controls from the National Health and Nutrition Examination Survey (NHANES) 2005 to 2010. Methods: We measured fasting serum triglycerides, glucose, and skinfold thicknesses in all children (aged 1 to 18 years) harboring FPLD2-causing LMNA mutations and determined regional body fat by dual-energy X-ray absorptiometry in those aged >= 8 years. Results: Thirty-two affected females and 14 males participated. The lower limb fat in all affected females, except one, was below or equal to the first percentile and in two affected males was below the fifth percentile for NHANES. One female subject with FPLD2 followed from age 6 to 16 years revealed marked loss of extremity fat much before thelarche. Serum triglycerides were higher in females with FPLD2 aged 7 to 18 years compared with controls (median 208 vs 70 mg/dL; P < 0.0001) and showed inverse correlation with extremity skinfolds. Serum triglycerides in males with FPLD2 were not significantly different than controls. Conclusions: The onset of fat loss from the extremities, especially in girls with FPLD2, occurs well before the onset of puberty. High serum triglycerides are seen in young females with FPLD2 with severe loss of fat from the extremities.

Rationale: Mutations in the LMNA gene, encoding LMNA (lamin A/C), are responsible for laminopathies. Dilated cardiomyopathy (DCM) is a major cause of mortality and morbidity in laminopathies. Objective: To gain insights into the molecular pathogenesis of DCM in laminopathies. Methods and Results: We generated a tet-off bigenic mice expressing either a WT (wild type) or a mutant LMNA (D300N) protein in cardiac myocytes. LMNA(D300N) mutation is associated with DCM in progeroid syndromes. Expression of LMNA(D300N) led to severe myocardial fibrosis, apoptosis, cardiac dysfunction, and premature death. Administration of doxycycline suppressed LMNA(D300N) expression and prevented the phenotype. Whole-heart RNA sequencing in 2-week-old WT and LMNA(D300N) mice led to identification of approximate to 6000 differentially expressed genes. Gene Set Enrichment and Hallmark Pathway analyses predicted activation of E2F (E2F transcription factor), DNA damage response, TP53 (tumor protein 53), NF kappa B (nuclear factor kappa B), and TGF beta (transforming growth factor-beta) pathways, which were validated by Western blotting, quantitative polymerase chain reaction of selected targets, and immunofluorescence staining. Differentially expressed genes involved cell death, cell cycle regulation, inflammation, and epithelial-mesenchymal differentiation. RNA sequencing of human hearts with DCM associated with defined LMNA pathogenic variants corroborated activation of the DNA damage response/TP53 pathway in the heart. Increased expression of CDKN2A (cyclin-dependent kinase inhibitor 2A)-a downstream target of E2F pathway and an activator of TP53-provided a plausible mechanism for activation of the TP53 pathway. To determine pathogenic role of TP53 pathway in DCM, Tp53 gene was conditionally deleted in cardiac myocytes in mice expressing the LMNA(D300N) protein. Deletion of Tp53 partially rescued myocardial fibrosis, apoptosis, proliferation of nonmyocyte cells, left ventricular dilatation and dysfunction, and slightly improved survival. Conclusions: Cardiac myocyte-specific expression of LMNA(D300N), associated with DCM, led to pathogenic activation of the E2F/DNA damage response/TP53 pathway in the heart and induction of myocardial fibrosis, apoptosis, cardiac dysfunction, and premature death. The findings denote the E2F/DNA damage response/TP53 axis as a responsible mechanism for DCM in laminopathies and as a potential intervention target.