RBP4 and vitamin A deficiency: Accordingly, the phenotype of the Bco2−/−Rbp4−/− embryos from dams on the VAD diet during pregnancy was more severe than that of Rbp4−/− embryos from dams on a similar dietary regimen, as in addition to eye defects and peripheral edemas (the hallmarks of embryonic vitamin A deficiency in the Rbp4−/− mice12), they displayed other congenital malformations (Figs 2 and 3A).