Developmental changes in expression and distribution of the glutamate receptor channel delta 2 subunit according to the Purkinje cell maturation

Abstract

The glutamate receptor (GluR) channel delta 2 subunit is considered to be a functional molecule involved in motor coordination, Purkinje cell synapse formation and cerebellar long-term depression. We examined developmental changes in expression and distribution of the GluR delta 2 in the mouse cerebellum by in situ hybridization and immunohistochemistry. The GluR delta 2 mRNA was detected as early as embryonic day 15 (E15) in a cell mass consisting of Purkinje neuroblasts in the posterior cerebellum. During late embryonic and postnatal periods, the GluR delta 2 mRNA was expressed abundantly and specifically in Purkinje cells. By immunohistochemistry, immunoreactivity of the GluR delta 2 was found in both shafts and spines of Purkinje dendrites at early postnatal period. By P21, however, the intense immunoreactivity became restricted to the dendritic spines, especially along the postsynaptic membrane in contact with parallel fiber terminals. These findings suggested that the transcription of the GluR delta 2 subunit occurs in the Purkinje cells from fetal through adult stage, but the intracellular localization of the protein products undergoes an alteration from non-synaptic to synaptic site when active synaptogenesis takes place.