Retinoic acid repatterns axolotl lateral line receptors

The effects of all-trans retinoic acid on the development of the lateral line placodes of axolotls was studied. Late gastrula and early neurula were exposed to 10(-7) to 10(-5) M retinoic acid for one hour and then reared until they would normally be feeding larvae. As in other vertebrates, the extent of the developmental abnormalities is concentration dependent. Those embryos exposed to the highest concentration of retinoic acid failed to form much of the forebrain and midbrain, including the olfactory, optic and otic organs, which were reduced or absent. Although all lateral line placodes continued to generate fully formed receptors and cranial nerves, the production of neuromasts and the organization of these receptors into lines were markedly reduced. Equally important, all of the placodes at the highest concentration of retinoic acid failed to generate ampullary organs, thereby indicating a strong posteriorizing effect of retinoic acid on these placodes.