Retinoic Acid Treatment Alters the Pattern of Retinoic Acid Receptor Beta Expression in the Embryonic Chick Limb

Abstract

Local application of retinoic acid (RA) to the anterior margin of the chick wing bud can affect patterning in both the developing limb and face, and there is evidence that RA may be a natural signalling substance in the limb (reviewed in Eichele, 1989; Brickell and Tickle, 1990, and Wedden et al, 1988). In the limb, local application of RA produces a mirror image duplication of structures across its anterior-posterior (A-P) axis. A second effect of RA application to the bud is inhibition of outgrowth of the upper beak primordium (the frontonasal mass), resulting in clefting of the primary palate.