TRANSIENT EXPRESSION OF CALRETININ DURING DEVELOPMENT OF CHICK CEREBELLUM - COMPARISON WITH CALBINDIN-D28K

Calcium ions play a critical role in neural development. Insights into the ontogeny of Ca2+ homeostasis were gained by investigating the dev elopmental expression of two E-F hand calcium-binding proteins. Calret inin and calbindin were monitored through their immunoreactivity in th e developing chick cerebellum (from E6 to E20). Calbindin was detected from E13 and in Purkinje cells only. Intensity of labelling increased with Purkinje cell development. Calretinin presented a transitory imm unoreactivity between Ell and E20 in the internal granular cell layer. This cell layer contains cells which will differentiate into Golgi an d granular cells which are calretinin-negative in adult chick cerebell um. Calretinin immunoreactivity presented a peak (both in number of ce lls and in intensity) at E15 and fell dramatically after E20 while cal bindin immunoreactivity was restricted to the Purkinje cells and incre ased with the development of these cells.