Lamin A/C impairments cause mitochondrial dysfunction by attenuating PGC1 alpha and the NAMPT-NAD(+) pathway

Mutations in the lamin A/C gene (LMNA) cause laminopathies such as the premature aging Hutchinson Gilford progeria syndrome (HGPS) and altered lamin A/C levels are found in diverse malignancies. The underlying lamin-associated mechanisms remain poorly understood. Here we report that lamin A/C-null mouse embryo fibroblasts (Lmna(-/-) MEFs) and human progerin-expressing HGPS fibroblasts both display reduced NAD(+) levels, unstable mitochondrial DNA and attenuated bioenergetics. This mitochondrial dysfunction is associated with reduced chromatin recruitment (Lmna(-/-) MEFs) or low levels (HGPS) of PGC1 alpha, the key transcription factor for mitochondrial homeostasis. Lmna(-/-) MEFs showed reduced expression of the NAD(+)-biosynthesis enzyme NAMPT and attenuated activity of the NAD(+)-dependent deacetylase SIRT1. We find high PARylation in lamin A/C-aberrant cells, further decreasing the NAD(+) pool and consistent with impaired DNA base excision repair in both cell models, a condition that fuels DNA damage-induced PARylation under oxidative stress. Further, ATAC-sequencing revealed a substantially altered chromatin landscape in Lmna(-/-) MEFs, including aberrantly reduced accessibility at the Nampt gene promoter. Thus, we identified a new role of lamin A/C as a key modulator of mitochondrial function through impairments of PGC1 alpha and the NAMPT-NAD(+) pathway, with broader implications for the aging process.