PATTERN REGULATION IN THE CHICK AUTOPODIUM AT ADVANCED STAGES OF EMBRYONIC-DEVELOPMENT

In previous studies we have observed that the interdigital tissue of t he chick. embryo leg bud during the stages previous to interdigital ce ll death exhibits a considerable chondrogenic potentiality both in viv o and in vitro. In the present investigation we have carried out a var iety of experimental manipulations of the chick leg bud at stage 29 to discover possible mechanisms accounting for interdigital ectopic chon drogenesis and extradigit formation. Our results show that the interdi gital tissue is capable of forming an extradigit when temporarily isol ated microsurgically and regrafted in its original location and after deletion of one of the adjacent digital primordia, suggesting that dev eloping phalangeal cartilages exercise an inhibitory effect on chondri fication in adjoining tissues. Furthermore, and of greater importance, ablation of the primordium of a digit is followed by normal developme nt of the definitive digit if the wound surfaces are suitably apposed. These results reveal a considerable regulatory potential in the autop odium at advanced stages of development. (C) 1994 Wiley-Liss, Inc.