Retinoic acid (RA) is known as a teratogen that induces abnormalities in facial structures which are made up mainly of neural crest-derived mesenchyme. We investigated expression patterns of RA receptor (RAR) genes (subtypes α, β, γ) during mouse facial development. The expression of the rarβ gene is specific for the mesenchyme around developing eyes and nose, whereas the RARγ gene is expressed in the mesenchyme differentiating to facial cartilages and bones. In contrast, the RARα gene is expressed weakly and uniformly over the facial region. These results suggest that crucial roles of endogenous RA in facial development depend on differential functions of the RAR subtypes.
