ISOLATION OF 3,4-DIDEHYDRORETINOIC ACID, A NOVEL MORPHOGENETIC SIGNAL IN THE CHICK WING BUD

THERE is increasing evidence that retinoic acid is a morphogen involved in vertebrate development1,2. This evidence comes in part from studies of the chick wing bud, in which local application of all-trans-retinoic acid results in a duplication of the digit pattern along the anteroposterior axis3-5. Retinoic acid may be only one of several morphogenetic signalling compounds required for limb pattern formation. To identify novel morphogenetically active compounds, fractionated extracts of whole chick embryos were tested for their ability to induce digit pattern duplications. We describe here the isolation of a new activity present in the limb bud, which we have identified as all-trans-3,4-didehydroretinoic acid. The 3,4-didehydroretinoic acid is generated in situ from retinol through a 3,4-didehydroretinol intermediate. We show that 3,4-didehydroretinoic acid and retinoic acid are equipotent in evoking digit duplications. These findings suggest that there are at least two endogenous retinoids with morphogenetic properties in the chick limb. © 1990 Nature Publishing Group.