Lack of WWC2 Protein Leads to Aberrant Angiogenesis in Postnatal Mice

Abstract

The WWC protein family is an upstream regulator of the Hippo signalling pathway that is involved in many cellular processes. We examined the effect of an endothelium-specific WWC1 and/or WWC2 knock-out on ocular angiogenesis. Knock-outs were induced in C57BL/6 mice at the age of one day (P1) and evaluated at P6 (postnatal mice) or induced at the age of five weeks and evaluated at three months of age (adult mice). We analysed morphology of retinal vasculature in retinal flat mounts. In addition, in vivo imaging and functional testing by electroretinography were performed in adult mice. Adult WWC1/2 double knock-out mice differed neither functionally nor morphologically from the control group. In contrast, the retinas of the postnatal WWC knock-out mice showed a hyperproliferative phenotype with significantly enlarged areas of sprouting angiogenesis and a higher number of tip cells. The branching and end points in the peripheral plexus were significantly increased compared to the control group. The deletion of the WWC2 gene was decisive for these effects; while knocking out WWC1 showed no significant differences. The results hint strongly that WWC2 is an essential regulator of ocular angiogenesis in mice. As an activator of the Hippo signalling pathway, it prevents excessive proliferation during physiological angiogenesis. In adult animals, WWC proteins do not seem to be important for the maintenance of the mature vascular plexus.

Modulation of GABAAreceptor trafficking by WWC2 reveals class-specific mechanisms of synapse regulation by WWC family proteins

“…Substantial Wwc2 gene expression was also present in endothelial and vascular/leptomeningeal cells in the hippocampus and cortex (Fig. 1C), consistent with studies demonstrating a critical role for WWC2 in vascular development 33,34 . Many, though not all, forebrain neurons co-express KIBRA and WWC2, and their gene expression is positively correlated in excitatory hippocampal cell types (Fig.…”

WWC2 expression in the testis: Implications for spermatogenesis and male fertility

“…3,14 Due to their common structure and binding partners, WWC proteins were shown to possess a redundant function if they are expressed in the same tissue at the same time. 3,13,14 However, Wwc2 has an unique impact on murine embryonal angiogenesis 14 and postnatal ocular angiogenesis, 38 pointing to its crucial role in early embryonic development when the other Wwc family members are not or only weakly expressed.…”

Distinctive Roles of YAP and TAZ in Human Endothelial Progenitor Cells Growth and Functions

“…This process removes excess vessels from the vascular network by regulating the expression of connective tissue growth factor (CTGF) and actin polymerization [ 28 ]. Depletion of WW-and-C2-domain-containing (WWC2), an upstream regulator of the Hippo signaling pathway and inhibitor of YAP/TAZ, leads to the hyperproliferation of endothelial cells with enlarged sprouting areas and increased tip cell numbers in the ocular vessels of postnatal mice [ 8 ].…”

“…The activity of YAP and TAZ is inhibited by the large tumor suppressor (LATS) kinases which phosphorylate YAP and TAZ at specific serine residues and prevent their nuclear translocation. Although there is evidence showing that the Hippo signaling pathway controls the survival and activity of mature endothelial cells [ 7 , 8 , 9 ], the regulatory roles of YAP and TAZ in EPC functions are still largely unknown.…”