Subtype switching of vesicular glutamate transporters at parallel fibre–Purkinje cell synapses in developing mouse cerebellum

Abstract

Two subtypes of the vesicular glutamate transporter are expressed differentially in two excitatory afferents synapsing on to Purkinje cells: VGluT1 (BNPI) in axon terminals of cerebellar granule cells (i.e. parallel fibres; PFs) and VGluT2 (DNPI) in those of the inferior olivary neurons (climbing fibres; CFs). In the present study, we examined their expression in the developing mouse cerebellum. By in situ hybridization, the inferior olivary nucleus selectively expressed VGluT2 mRNA through postnatal life. In the cerebellum, both subtypes were transcribed in the external and internal granular layers during the first postnatal week. Thereafter, VGluT1 mRNA showed marked upregulation in the internal granular layer, whereas VGluT2 mRNA disappeared from the external and internal granular layers by the end of the third postnatal week. By immunohistochemistry, CF terminals consistently exhibited VGluT2 immunoreactivity in the postnatal cerebellum. By contrast, in the first 10 days of postnatal life, VGluT2 predominated in PF terminals, despite the transcription of both transporters in developing granule cells. During the second 10 days, VGluT2 in PF terminals was replaced with VGluT1 from deep regions of the molecular layer upwards, correlating with dendritic translocation of CFs. This replacement was accomplished by postnatal day 30. Taking that late-borne PFs are laid down successively on earlier ones in the molecular layer, the deep-to-superficial replacement represents maturation-linked switching from VGluT2 to VGluT1 in individual PFs, and is likely to be regulated at both the transcription and translation levels.

The Etv1/Er81 transcription factor orchestrates activity-dependent gene regulation in the terminal maturation program of cerebellar granule cells

“…The testican gene turned out to be expressed mainly in stellate cells of the cerebellum. We selected 14 genes from the previous study and three additional TTXsuppressive genes which were identified in this study and expressed in the mature cerebellum (10)(11)(12). PCR analysis confirmed that the expression of all 17 genes was inhibited by TTX to different degrees, ranging from 15-85% ( Fig.…”

An essential role for vesicular glutamate transporter 1 (VGLUT1) in postnatal development and control of quantal size

“…The VGLUT1 KO mice die at the age when a strong upregulation of VGLUT1 through newly emerging VGLUT1 synapses as well as a replacement of the previously predominant VGLUT2 isoform in cerebellar, hippocampal, and cortical neurons occur (19,26). This down-regulation of VGLUT2 is independent of VGLUT1 up-regulation and biological activity, given that it occurs in VGLUT1 KO mice.…”

“…However, none of these brain regions exclusively express one isoform, and although the majority of glutamatergic neurons express either VGLUT1 or VGLUT2, several studies describe coexpression of both isoforms, for example, in cerebellar mossy fiber terminals (16,17) and cerebellar unipolar brush cells (18). Most remarkably, a developmental switch from VGLUT2 to VGLUT1 occurs in the hippocampus, cortex, and cerebellum (19). The third isoform, VGLUT3, is less widely expressed than the other two.…”

A pivotal role of calcineurin signaling in development and maturation of postnatal cerebellar granule cells

“…In contrast, doublecortin, Homer2, MARCKS-like protein, caspase-3, and VGluT2 genes, which are all FK-down genes, have been reported to be significantly expressed in the EGL during the postnatal period (26)(27)(28)(29)(30). We performed in situ hybridization of cerebellar sections at P8 and The numbers and proportions of the Depo-down genes and Depo-up genes (a total of 87 genes) (C) and those of the FK-up genes and FK-down genes (a total of 77 genes) (D) are indicated in each group of the Dev-up genes, Dev-down genes, and non-Dev genes.…”