Isoform-dependent immunolocalization of 14-3-3 proteins in developing rat cerebellum

We investigated the expression of 14-3-3 protein and its 7 isoforms during postnatal development of rat cerebellum with immunoblot and immunohistochemistry with isoform-specific antibodies. The relative amounts of total 14-3-3 protein, probed by an antibody (14-3-3 COM) recognizing a sequence shared among its isoforms, exhibited no significant changes from postnatal day 2 (P2) to P100. 14-3-3 COM-like immunoreactivity (IR), initially in the apical portion of Purkinje cells at P2, extended to Purkinje cell bodies at P14 and to their dendrites (P100) with increasing intensity. Molecular layer (after P7) and cerebellar nucleus neurons (after P14) were also immunolabeled with this antibody. These chronological changes were shared with those obtained with beta, gamma, and eta isoforms. In contrast, epsilon isoform-like IR was initially identified in processes of radial and Bergmann glia at P2 prior to its appearance in the molecular layer at P7 with subsequent intensification also in Purkinje cells after P14. Zeta and tau isoform-like IR was identified in the white matter and/or in oligodendroglial cells. The sigma isoform was the only isoform exhibiting a significant quantitative change with a peak at P14. Immunolocalization of sigma isoform was initially restricted in several cells in Purkinje cell layer at P2 and shifted to nuclei of external and internal granule cells and Purkinje cells after P14, whereas its immunolabeling was markedly weaker at P100. Different immunolocalizations of the 7 isoforms suggest that 14-3-3 protein isoforms individually associate with the neuronal and glial proliferation, differentiation, migration and development during postnatal formation of rat cerebellum.