Chapter 2 Quail–Chick Transplantations

This chapter provides methods for quail–chick transplantations. The method is based on the observation that all embryonic and adult cells of the quail possess condensed heterochromatin in one large mass in the center of the nucleus, associated with the nucleolus. When combined with chick cells, quail cells can readily be recognized by the structure of their nucleus, thus providing a permanent genetic marker. The transformation from the early neural ectoderm to the mature brain involves an enormous complexity that comes about via differential growth of various regions of the neuroepithelium, extensive cell migrations, and assembly of the very complicated wiring taking place between the neurons of the central nervous system. Quail–chick chimeras provide a means to unveil some of the mechanisms underlying these complex processes. Quail and chick are closely related in taxonomy, although they differ by their size at birth and by the duration of their incubation period. For many years, analysis of chimeras relied on the differential staining of the nucleus by either the Feulgen–Rossenbeck reaction or other DNA staining methods, such as acridine orange or bizbenzimide, which could be combined with immunocytochemistry. Subsequently, species-specific antibodies that recognize either quail or chick cells have been developed. In addition, cell type-specific reagents are available either as monoclonal antibodies or as nuclear probes that distinguish, at the single resolution, whether a cell produces a particular product and if it belongs to the host or the donor.