THE RETINOID-X RECEPTOR-LIGAND, 9-CIS-RETINOIC ACID, IS A POTENTIAL REGULATOR OF EARLY XENOPUS DEVELOPMENT

Endogenous retinoids are potential regulators of vertebrate embryogene sis that have been implicated in early anterior-posterior patterning a nd limb-bud development. We have characterized the temporal and spatia l distribution of 9-cis-retinoic acid in the Xenopus embryo and compar ed it to two other retinoids, all-trans-retinoic acid and all-trans-re tinoyl-beta-glucuronide. 9-cis-Retinoic acid is first detected after t he midblastula transition and by the end of gastrulation is localized primarily within the anterior and posterior dorsal regions of the embr yo. Since 9-cis-retinoic acid is a 6-fold more potent dysmorphogen tha n trans-retinoic acid, we suggest that it is involved in the early spe cification of the Xenopus anterior-posterior axis.