Normal ontogenic observations on the expression of Eph receptor tyrosine kinase, Cek8, in chick embryos.

The spatio-temporal pattern of expression for the Eph receptor tyrosine kinase, Cek8, was observed in normal chick embryos from H-H stage 6 to 23 by immunohistochemical techniques. Expression of Cek8 was already present in embryos at H-H stage 6, where it was located in the neural plate of the brain region, paraxial mesoderm, and the primitive streak. Regions expressing Cek8 subsequently increased during development to include the neural folds of the brain, rhombomeres 3 and 5, the caudal part of the neural plate, neural crest cells related to the formation of glossopharyngeal nerve ganglia, invaginated cells throughout the primitive groove and the epithelium of the rudiment of the gall bladder. Cek8 was also expressed in the mesenchymal cells of the pharyngeal arches, allantoic stalk and limb buds as well as in the areas surrounding the eye vesicles and nasal pits. Furthermore, cells in the tail bud progressing to the secondary neurulation expressed Cek8. Thus, the spatiotemporal patterns of Cek8 expression appears to have intimate relationships with tissue rebuilding, the maturation of differentiated cells, and the spatial organization of tissues. Consequently, it appears that Cek8 plays an integral role in the developmental events leading to the formation of a wide--though not inclusive--variety of tissues and organ systems.