Figure 2.

Contribution of endothelial Cx40 and Cx37 to developmental retinal angiogenesis. (A) Immunostaining of whole-mounted retinas from P5 wild-type (WT) mice shows the dual labeling of endothelial cells (ECs) for Cx40 (red) and the EC marker vascular endothelial (VE)-cadherin (green) (left panels), and for Cx37 (green) and VE-cadherin (red) (right panels). (B) Labeling of retina whole-mounts for the EC marker IB4 (black) reveals reduced extension of the vascular network in P5 Cx40^−/− and Cx37^−/− mice, compared to WT. Strikingly, the density of angiogenic vessels was reduced in the retinas of Cx40^−/− mice, but increased in those of Cx37^−/− animals (upper panels). Immunostaining shows increased coverage of neovessels identified by IB4 (purple) with α-smooth muscle actin (αSMA, green)-positive cells in the retina of a Cx40^−/− mouse. In contrast, Cx37^−/− animals display a reduced coverage of retinal neovessels by αSMA-positive mural cells (middle panels). The lower panel summarizes the main angiogenesis defects of the developing retinas of Cx40^−/− and Cx37^−/− mice.