RETINOID SIGNALING IN THE VERTEBRATE EMBRYO

Many findings indicate that active retinoids (vitamin A metabolites, w hich are known to be hormone-like ligands), are regulatory signals dur ing embryogenesis. Treating early vertebrate embryos with retinoids ca n cause teratogenesis. Notably, it generates specific defects in the m ain body axis. Considering other data showing that Early vertebrate em bryos contain physiolocally relevant concentrations of endogenous acti ve retinoids and express retinoid binding proteins and receptors, it i s not unlikely that retinoids act as developmental signals, which regu late axial patterning in the early vertebrate embryo. The purpose of t his review is to discuss this point, referring to retinoid teratogenes is, and to the availabilities and functions of retinoid ligands, bidin g proteins and receptors in the early embryo.