Studying brain development with quail-chick neural chimeras.

Avian embryonic neural chimeras are constructed by substituting defined areas of the neural epithelium of a chick embryo by their exact counterpart obtained from a quail embryo at the same developmental stage. The experiment can also be performed using the quail as a host and the chick as a graft donor. The stages elected are either the late neurula (0 to 3 somites) or the stage after cephalic vesicles formation (10 to 14 somites) but in all cases before the onset of vascularization of the neural primordium. Quail and chick territories can be recognized in the chimeras any time after the graft owing to the particular structure of the quail nucleus or by means of species-specific antibodies. Quail-chick chimeras have been instrumental in the study of the ontogeny of the medulla oblongata and of the cerebellum. The complex morphogenetic movements and cell migrations which occur during the development of this part of the brain have been worked out by this method. The main results obtained are described in the article.