Retinoic acid signaling regulates embryonic clock hairy2 gene expression in the developing chick limb

► RA induces limb hairy2 expression. ► RA promotes a short-term, transient increase of p-Erk and p-Akt in the anterior limb. ► RA enhances Gli3-A/Gli3-R in the anterior limb, in a short-term, transient manner. ► BMP4 inhibits hairy2 expression in the distal limb. ► RA shapes limb hairy2 expression pattern during limb development.