Nuclear Smooth Muscle α-actin in Vascular Smooth Muscle Cell Differentiation.

Missense variants throughout , encoding smooth muscle α-actin (αSMA), predispose to adult onset thoracic aortic disease, but variants disrupting arginine 179 (R179) lead to Smooth Muscle Dysfunction Syndrome (SMDS) characterized by childhood-onset diverse vascular diseases. Our data indicate that αSMA localizes to the nucleus in wildtype (WT) smooth muscle cells (SMCs), enriches in the nucleus with SMC differentiation, and associates with chromatin remodeling complexes and SMC contractile gene promotors, and the p.R179 variant decreases nuclear localization of αSMA. SMCs explanted from a SMC-specific conditional knockin mouse model, , are less differentiated than WT SMCs, both and , and have global changes in chromatin accessibility. Induced pluripotent stem cells from patients with p.R179 variants fail to fully differentiate from neural crest cells to SMCs, and single cell transcriptomic analyses of an p.R179H patient's aortic tissue shows increased SMC plasticity. Thus, nuclear αSMA participates in SMC differentiation and loss of this nuclear activity occurs with p.R179 pathogenic variants.