Evidence of very early neuronal migration from the olfactory placode of the chick embryo.

Cell migration from the olfactory neuroepithelium is a very peculiar phenomenon in the development of the nervous system. In this paper, we provide evidence that, in the chick embryo, migration of cells from the olfactory neuroepithelium begins earlier than previously reported, namely at the same time as the first olfactory placode differentiation, that occurs several hours before the superficial ectodermal invagination that gives rise to the olfactory pit. Moreover, we provide evidence that very early migrating cells express the HuC/D RNA-binding protein antigen, a specific neuronal marker. These observations refocus our knowledge on the very first developmental stages of olfactory neuroepithelium.