ALL-TRANS 3,4-DIDEHYDRORETINOIC ACID EQUALS ALL-TRANS-RETINOIC ACID IN SUPPORT OF CHICK NEURONAL DEVELOPMENT

All-trans 3,4-didehydroretinoic acid (at-ddRA) has been identified as a biologically important retinoid in avian, but not mammalian, embryon ic development, In this report, we show that at-ddRA, like ah-trans re tinoic acid (atRA), supports the survival and differentiation of sympa thetic neurons of the embryonic chick, Furthermore, the expression of the retinoid-responsive gene RAR beta 2 is increased in neurons expose d to either at-ddRA or atRA, The mechanism whereby at-ddRA exerts its effects in chick neurons may involve binding to and activation of nucl ear retinoid receptors, For this reason, the binding of recombinant ch ick RAR beta 2 to at-ddRA and to receptor-specific DNA response elemen ts was examined and compared with the binding characteristics of recom binant murine RAR beta 2, Tile chick RAR beta 2, like the mammalian RA R, binds to [H-3]atRA with high affinity (k(d) = 0.7-2 nM), Furthermor e, both chick and murine RAR beta 2 bind equally web to at-ddRA, atRA, and 9-cis RA, but neither receptor shows appreciable binding to 13-ci s RA, The chick RAR beta 2 recognizes previously described retinoic: a cid response elements of mammalian gene promoters and, Like mammalian RAR beta 2, shows enhanced binding in the presence of RXR, This study provides evidence that at-ddRA., like atRA, supports neuronal developm ent in the thick by its interaction with nuclear retinoid receptors.