Project description:Bergmann glia (BG) are important in the inward type of radial migration of cerebellar granule neurons (CGNs). However, details regarding the functions of Cdc42 and Rac in BG for radial migration of CGN are unknown. To examine the roles of Cdc42 and Rac in BG during cerebellar corticogenesis, mice with a single deletion of Cdc42 or Rac1 and those with double deletions of Cdc42 and Rac1 under control of the glial fibrillary acidic protein (GFAP) promoter: GFAP-Cre;Cdc42flox/flox (Cdc42-KO), GFAP–Cre;Rac1flox/flox (Rac1-KO), and GFAP-Cre;Cdc42 flox/flox;Rac1flox/flox (Cdc42/Rac1-DKO) mice, were generated. Both Cdc42-KO and Rac1-KO mice, but more obviously Cdc42-KO mice, had disturbed alignment of BG in the Purkinje cell layer (PCL). We found that Cdc42-KO, but not Rac1-KO, induced impaired radial migration of CGNs in the late phase of radial migration, leading to retention of CGNs in the inferior half of the molecular layer (ML). Cdc42-KO, but not Rac1-KO, mice also showed aberrantly aligned Purkinje cells (PCs). These phenotypes were exacerbated in Cdc42/Rac1-DKO mice. Alignment of BG radial fibers in the ML and BG endfeet at the pial surface of the cerebellum evaluated by GFAP staining was disturbed and weak in Cdc42/Rac1-DKO mice, respectively. Our data indicate that that Cdc42 and Rac, but predominantly Cdc42, in BG play important roles during the late phase of radial migration of CGNs. We also report here that Cdc42 is involved in gliophilic migration of CGNs, in contrast to Rac, which is more closely connected to regulating neurophilic migration.
Project description:Bergmann glia (BG) are important in the inward type of radial migration of cerebellar granule neurons (CGNs). However, details regarding the functions of Cdc42 and Rac in BG for radial migration of CGN are unknown. To examine the roles of Cdc42 and Rac in BG during cerebellar corticogenesis, mice with a single deletion of Cdc42 or Rac1 and those with double deletions of Cdc42 and Rac1 under control of the glial fibrillary acidic protein (GFAP) promoter: GFAP-Cre;Cdc42flox/flox (Cdc42-KO), GFAP–Cre;Rac1flox/flox (Rac1-KO), and GFAP-Cre;Cdc42 flox/flox;Rac1flox/flox (Cdc42/Rac1-DKO) mice, were generated. Both Cdc42-KO and Rac1-KO mice, but more obviously Cdc42-KO mice, had disturbed alignment of BG in the Purkinje cell layer (PCL). We found that Cdc42-KO, but not Rac1-KO, induced impaired radial migration of CGNs in the late phase of radial migration, leading to retention of CGNs in the inferior half of the molecular layer (ML). Cdc42-KO, but not Rac1-KO, mice also showed aberrantly aligned Purkinje cells (PCs). These phenotypes were exacerbated in Cdc42/Rac1-DKO mice. Alignment of BG radial fibers in the ML and BG endfeet at the pial surface of the cerebellum evaluated by GFAP staining was disturbed and weak in Cdc42/Rac1-DKO mice, respectively. Our data indicate that that Cdc42 and Rac, but predominantly Cdc42, in BG play important roles during the late phase of radial migration of CGNs. We also report here that Cdc42 is involved in gliophilic migration of CGNs, in contrast to Rac, which is more closely connected to regulating neurophilic migration.
Project description:Cerebellar circuitry is critical for balance and motor control among a wide array of functions and largely consists of granule and Purkinje neurons. Bergmann glia in the cerebellum form distinct morphological structures that facilitate granule neuron migration during development and that maintain the cerebellar organization and functional integrity. At present, molecular control of the formation and morphogenesis of Bergmann glia remains obscure. In this study, we found that Zeb2 (a.k.a. Sip1 or Zfhx1b), a Mowat-Wilson syndrome-associated transcriptional regulator, is highly restricted to Bergmann glia and is essential for their development and maturation. The mice with Zeb2 ablation in the cerebellar neural progenitor exhibit dysgenesis of cerebellar cortical lamination and locomotion defects. Deletion of Zeb2 markedly reduced Bergmann glial proliferation, differentiation and the establishment of the normal radial scaffold, disrupting migration of granule cell progenitors from external to internal granular layers. Transcriptome profiling indicated that Zeb2 regulates multiple pathways including FGF and Notch signaling as well as axonal guidance cues including Netrin G2 and Gdf10 to control Bergmann glial development. Our data reveal that Zeb2 acts as a transcriptional integrator of diverse signaling pathways to regulate the formation and morphogenesis of Bergmann glia ensuring maintenance of cerebellar integrity, suggesting that Zeb2 dysfunction in Bergmann glia might contribute to motor deficits in Mowat-Wilson syndrome.
Project description:Neocortical basal radial glia (bRG) and cerebellar Bergmann glia (BG) are basal progenitors derived from ventricular apical radial glia (aRG) that selectively lose their apical processes. bRG and BG have been implicated in the expansion and folding of the cerebrum and cerebellum, respectively. Here, we analyzed the molecular characteristics and development of bRG and BG. Transcriptomic comparison revealed striking similarity of the molecular features of bRG and BG. We found that heightened ERK signaling activity in aRG is tightly linked to the temporal formation and the relative abundance of bRG in human and mouse cortices. Forced activation of an FGF-ERK-ETV axis that is crucial to BG induction specifically induced bRG with canonical human bRG features in mice. Therefore, our data point to a common mechanism of bRG and BG generation, bearing implications to the role for these basal progenitors in the evolution of cortical folding of the cerebrum and cerebellum.
Project description:Cortical lamination is crucial for the assembly of cerebellar circuitry. In this process, granule neurons (GNs) migrate along Bergmann glia (BG), which are specialized astroglial cells, from the external granule layer to the internal granule layer. However, the molecular mechanisms underlying BG development are not well understood. Here, we show that GFAP::Cre;Erbb3(F/F) mice, which lack Erbb3 in both radial glia and neurons, exhibit impairments in balance and motor coordination. Cerebellar lamination is aberrant, with misplaced Purkinje neurons and GN clusters. These phenotypes were not observed in Math1::CreER(T2);Erbb3(F/F) mice, where the Erbb3 gene was deleted in GNs, suggesting involvement of non-neuronal Erbb3 in cerebellar lamination. Mechanistic studies indicate that ERBB3 is crucial for the proliferation of BG, which are required for GN migration. These observations identify a crucial role for ERBB3 in cerebellar lamination and reveal a novel mechanism that regulates BG development.
Project description:Bergmann glial cells of the vertebrate cerebellum play essential roles in the development and maintenance of cerebellar structure and function. During development, Bergmann glia provide structural support to the expanding cerebellar anlage and also serve as guides for migrating neurons (granule cells). As the cerebellum matures, Bergmann glia become important in dendritic arborization, synapse maintenance and synaptic function. The molecular mechanisms underlying these diverse and important functions of Bergmann glia remain largely unknown. We used microarray analysis to examine global gene expression in individual Bergmann glial cells derived at P6 (a time of extensive neuronal migration and cerebellar growth) and at P30 (when cerebellar development is complete and Bergmann glia play important roles at synapses). After gentle dissociation of cerebellar tissue derived from mice expressing GFP under the GFAP gene promoter (GFAP-GFP mice) (Zhuo, L., et al., 1997, Developmental biology), single GFP-positive Bergmann glial cells were aspirated into microcapillary tubes. Amplified cDNAs were prepared from single cells using RT-PCR and hybridized to Affymetrix GeneChip Mouse Genome 430 2.0 expression arrays (one array per cell). Five P6 cells and five P30 cells were used to generate the data presented in this study.
Project description:Govek et al. demonstrate conditional loss of Cdc42 in cerebellar granule cell progenitors (GCPs) perturbs GCP polarity and impairs axon patterning, glial-guided migration, and cerebellar foliation. Phospho-proteomic analysis identified polarity and cytoskeletal proteins as affected targets in Cdc42 deficient GCPs.