Nuclear SUN2 coordinates endothelial cell-matrix interactions to regulate blood vessel homeostasis and barrier function.

Vascular endothelial cells respond to environmental forces to remodel vessels during development and to achieve homeostasis, and mis-regulated responses lead to vascular dysfunction and disease. The nucleus participates in transmitting signals to cell-matrix junctions via the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex that resides in the nuclear envelope, but how this information is regulated and relayed is incompletely understood. We found that the LINC complex protein SUN2 is required for proper endothelial cell-matrix interactions that occur far from the nucleus and affect angiogenic expansion, vascular responses to flow, and barrier integrity. Endothelial cells lacking SUN2 had inappropriate responses to environmental cues generated under both non-flow and flow conditions as well as reduced expression of flow-mediated transcription factors in vitro and in vivo. Expression of several matrix and adhesion genes was reduced in SUN2-depleted cells and associated with defective extracellular matrix, dysmorphic focal adhesions resistant to dynamic turnover, and disturbed cell-matrix force distribution. Mechanistically, nuclear SUN2 regulated cytoskeletal microtubule dynamics upstream of effects on cell and focal adhesion morphology, barrier integrity, and flow-mediated endothelial quiescence. These findings indicate that nuclear SUN2 establishes and maintains blood vessel homeostasis by controlling microtubule-mediated effects on focal adhesion and extracellular matrix properties, with implications for cardiovascular aging and diseases such as Marfan syndrome that affect vessel wall integrity.