The chick/quail chimeric system: a model for early cerebellar development.

The chick/quail chimeric system is now extensively used to study the development of the central nervous system. Here we discuss data obtained by this powerful experimental approach by which to study several issues of the cerebellar ontogenesis. We first discuss experiments which have allowed redefinition of the localization of the cerebellar primordium in the early neural tube and which suggest that the cerebellum could originate from different morphogenetic units. Then, we discuss experiments testing the possible role of the homeobox containing gene En-2 in cerebellar specification and showing that the En-2 expressing cerebellar neuroepithelium can act as an organizer. Finally we discuss data obtained in chimeric embryos with partial cerebellar grafts used to reexamine the origin and settling of several types of cortical cerebellar cells, in particular granule cells, molecular layer interneurons and Purkinje cells.