Sox2 controls Schwann cell self-organization through fibronectin fibrillogenesis

Elen Torres-Mejía,Charlotte Kleeberger,Sabrina C Desbordes,Theresa Bäcker,Dietrich Trümbach,Kamyar Hadian,Tanja Orschmann,Wolfgang Wurst,Ulf Dornseifer,Hernán López-Schier,Jara Kerstin Brenke

doi:10.1038/s41598-019-56877-y

Abstract

The extracellular matrix is known to modulate cell adhesion and migration during tissue regeneration. However, the molecular mechanisms that fine-tune cells to extra-cellular matrix dynamics during regeneration of the peripheral nervous system remain poorly understood. Using the RSC96 Schwann cell line, we show that Sox2 directly controls fibronectin fibrillogenesis in Schwann cells in culture, to provide a highly oriented fibronectin matrix, which supports their organization and directional migration. We demonstrate that Sox2 regulates Schwann cell behaviour through the upregulation of multiple extracellular matrix and migration genes as well as the formation of focal adhesions during cell movement. We find that mouse primary sensory neurons and human induced pluripotent stem cell-derived motoneurons require the Sox2-dependent fibronectin matrix in order to migrate along the oriented Schwann cells. Direct loss of fibronectin in Schwann cells impairs their directional migration affecting the alignment of the axons in vitro. Furthermore, we show that Sox2 and fibronectin are co-expressed in proregenerative Schwann cells in vivo in a time-dependent manner during sciatic nerve regeneration. Taken together, our results provide new insights into the mechanisms by which Schwann cells regulate their own extracellular microenvironment in a Sox2-dependent manner to ensure the proper migration of neurons.

Highlights

The extracellular matrix is known to modulate cell adhesion and migration during tissue regeneration
To understand the crosstalk between the extra cellular matrix (ECM) and pro-regenerative Schwann cells mediated by Sox[2], we established an in vitro model system using the rat Schwann cell line RSC96 (SCwt)
In agreement with a previous study[6], we observed a change in the behaviour of the Sox2-overexpressing cells, characterized by increased clustering as shown in Fig. 1b for one example clone, SCSox2/Cl2 (Fig. 1c and Supplementary Fig. 1a; full-length blots are presented in Supplementary Fig. 1b)

Summary

Introduction

The extracellular matrix is known to modulate cell adhesion and migration during tissue regeneration. After PNS injury, Schwann cells reprogram to a proregenerative state[4], proliferate and migrate to form the bands of Büngner, which are cellular channels made of glial basal lamina that guide the axons to their original targets[5]. During regeneration of the PNS, Sox[2] expression in Schwann cells is important for their maintenance in a dedifferentiated stage as well as their sorting, mediated by the cell-cell adhesion protein N-cadherin[6]. Whether Sox[2] directly regulates Schwann cell behaviour through integrin-mediated cell-ECM adhesion is unexplored. After PNS injury, FN fibrillogenesis, a process by which FN assembles into fibrils, is increased at the injury site, supporting cellular adhesion and inducing the migration and proliferation of the Schwann cells, which in turn favours axonal growth[15,16]

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Results

Conclusion