Shear stimulation of FOXC1 and FOXC2 differentially regulates cytoskeletal activity during lymphatic valve maturation.

Abstract

Mutations in the transcription factor <i>FOXC2</i> are predominately associated with lymphedema. Herein, we demonstrate a key role for related factor FOXC1, in addition to FOXC2, in regulating cytoskeletal activity in lymphatic valves. FOXC1 is induced by laminar, but not oscillatory, shear and inducible, endothelial-specific deletion impaired postnatal lymphatic valve maturation in mice. However, deletion of <i>Foxc2</i> induced valve degeneration, which is exacerbated in <i>Foxc1; Foxc2</i> mutants. <i>FOXC1</i> knockdown (KD) in human lymphatic endothelial cells increased focal adhesions and actin stress fibers whereas <i>FOXC2</i>-KD increased focal adherens and disrupted cell junctions, mediated by increased ROCK activation. ROCK inhibition rescued cytoskeletal or junctional integrity changes induced by inactivation of FOXC1 and FOXC2 <i>invitro</i> and <i>vivo</i> respectively, but only ameliorated valve degeneration in <i>Foxc2</i> mutants. These results identify both FOXC1 and FOXC2 as mediators of mechanotransduction in the postnatal lymphatic vasculature and posit cytoskeletal signaling as a therapeutic target in lymphatic pathologies.