Scaffold protein SHANK3 regulates endothelial cell motility and tissue mechanics

SHANK3 is a multidomain scaffolding protein critical for neuronal function, which has been linked to neurodevelopmental disorders such as autism spectrum disorder. More recently, SHANK3 has been shown to play a role in cell survival and actin dynamics outside the nervous system. Here, we show that SHANK3 is widely expressed in endothelial cells across different tissues, where its role is not well understood. SHANK3 localised to endothelial cell-cell junctions in cultured endothelial cells, and its depletion compromised endothelial barrier function. SHANK silencing altered cell mechanics including elongated cell morphology, reduced cell-matrix traction forces and alteration of cell migration rate. It further triggered dynamic heterogeneity in endothelial monolayers, with regions of coordinated long-range migration interspersed with areas exhibiting only local velocity fluctuations, consistent with a transition toward more fluid-like tissue behaviour. This change in collective dynamics was accompanied by increased spheroid spreading and fusion, suggestive of altered tissue viscosity, and coincided with disrupted cell-cell junction morphology and mechanical forces in SHANK3-depleted cells. In vivo, SHANK3 depletion impaired endothelial cell migration, resulting in delayed sprouting of intersegmental vessels and disruption of the vascular network in zebrafish embryos. Furthermore, inducible endothelial-specific deletion of SHANK3 in postnatal mice impaired angiogenic sprouting and reduced vascular complexity in the developing retina. Overall, we demonstrate that SHANK3 plays a role in endothelial cell motility and tissue mechanics, with implications for vascular processes during development.