SMAD4 and hereditary hemorrhagic telangiectasia: In mice, injection of antibodies blocking both BMP9 and BMP10 has been shown to phenocopy endothelial Eng, Acvrl1, and Smad4 mutant mice to some degree, with AVM formation in the retina and the gastrointestinal tract, suggesting that it could be a model of HHT (Table 1; Baeyens et al., 2016; Ola et al., 2016; Ruiz et al., 2016, 2020).