THE AVIAN EMBRYO - A POWERFUL MODEL SYSTEM FOR STUDYING NEURAL INDUCTION

Neural induction is the process during early embryonic development whereby the mesoderm of the embryo elicits a change of fate in cells of the overlying ectoderm, from epidermal to neural. Since its discovery in 1924 by Spemann and Mangold, who used newt embryos, most research on this developmental event has been conducted with urodelean and anuran amphibians. This is because of the ease with which they can be manipulated and because of the recent availability of cell type- and region-specific molecular markers. With the recent isolation and characterization of suitable markers in the chick embryo, and the equal ease with which it can be manipulated, the way is now open for amniote embryos to join amphibians as an experimental system for neural induction studies. Another advantage of the avian embryo is that it possesses a peripheral extraembryonic region, which although it does not contribute to embryonic tissues at all, is competent to respond to neural-inducing signals, thereby providing developmentally naive cells for in vivo and in vitro assays. Here, I review recent advances that make the chick embryo a system uniquely suited for the study of neural induction at both the cellular and the molecular level.