The regulatory roles of TGF-β1 in formation of the cerebellar primordium during early developmental stages

Abstract

Coordinated production of the multiple neural cell types within the cerebellar primordium is critical during cerebellum development. All the GABAergic and Glutamatergic neurons are derived from the cerebellar ventricular zone and rhombic lip, respectively. Purkinje cells (PCs) and Cerebellar nuclei (CN) neurons are among the earliest neurons born approximately between embryonic days (E) 9 to 13. Before embryonic day 14.5, postmitotic and differentiated PCs and CN neurons migrate towards the PC plate (PCP) and nuclear transitory zone (NTZ) of the cerebellar primordium. The cellular and molecular mechanisms underlying the early cerebellar neurogenesis, migration/differentiation, and connectivity establishment are unclear. Macroautophagy (hereafter autophagy) plays an essential role in regulating cellular phenotype, including epithelial to mesenchymal transition and endothelial to mesenchymal transition. Transforming growth factor-beta 1 (TGF-β1) is also involved in regulating cellular phenotype via several mechanisms, including autophagy. It is a key player in pre-and postnatal development. Therefore, we hypothesis that TGF-β1 may control early cerebellar development by modulating the levels of cell adhesion molecules (CAMs) and autophagy pathway in the mouse cerebellar primordium. To better understand the role of TGF-β1, we used mouse embryonic cerebellar tissues derived from embryonic days 9 to 13, performed RT-qPCR, western blotting, and analyzed in situ hybridization (ISH) data; from “Allen Developing Mouse Brain Atlas.” In this study, I showed the activation of the Canonical TGF-β signaling pathway at the time window that coincides with the formation of the PCP and NTZ. In addition, my data demonstrate that activated TGF-β signaling pathway sequentially and temporally could upregulate the expression of N-cadherin and β-catenin with maximum expression at E11/E12, with subsequent upregulation of the Cdh8 and NCAM expression at E12 and E13. My data also showed activated TGF-β signaling occurs concurrently with inhibition of autophagic-flux at E11/E12. However, basal autophagy occurs during earlier developmental stages from E9 to E10. This study identified a crucial role of the TGF-β signaling pathway and its regulatory effects on Cadherins expression and autophagic flux during cerebellar development, which all together potentially contribute to the proliferation, migration/differentiation, and positioning of the cerebellar nuclei neurons and Purkinje cells within their domains.