Heterochronic Expression of Purkinje Cell Antigens in the Embryonic Chick Cerebellum

Despite numerous studies characterizing the organization and protein expression within the developing and adult mammalian cerebellum, there is little detail on the development of Purkinje cells and the protein expression patterns that emerge during cerebellar development in an avian species. We used western blot analysis and immunohistochemistry to characterize the expression of three cerebellar antigens to investigate cerebellar morphology and development in the domestic chicken, an important and emerging model for neurobiological studies. The 28kDa calcium binding protein, Calbindin, which is believed to be expressed in all developing and mature Purkinje cells, was first seen in cell clusters at embryonic day 10 (E10). The expression of the cerebellar patterning antigen Zebrin II was used to examine parasagittal banding and transverse zonal boundaries and was expressed beginning at E10. The expression of Calretinin was also examined and appears to be dynamically regulated during embryonic development, with initial expression in scattered interneurons, mossy fiber terminals in folia II‐IX and a subset of Purkinje cells in folia IX, X beginning at E12.5. We also characterized the development of Purkinje cell clusters separated by distinct raphes to their arrangement in a uniform monolayer. We conclude that the developmental sequence and pattern of expression in chicks closely resembles that seen in mice but appears to be accelerated. This is consistent with chicks and mice representing opposite ends of the precocial‐altricial spectrum and provides an important framework for future studies on cerebellar development and motor coordination. This work was supported by an NSERC Discovery grant 400101