Contactin-1/F3 Regulates Neuronal Migration and Morphogenesis Through Modulating RhoA Activity.

Yi-An Chen,I-Ling Lu,Jin-Wu Tsai

doi:10.3389/fnmol.2018.00422

Abstract

During neocortical development, newborn neurons migrate along radial fibers from the germinal ventricular zone (VZ) toward the cortical plate (CP) to populate the cerebral cortex. This radial migration requires adhesion activities between neurons and radial fibers; however, past research has identified only a limited number of adhesion molecules involved in this process. Contactin-1/F3 (Cntn1), a cell adhesion molecule expressed in the developing nervous system is essential for many key developmental events including neural cell adhesion, neurite outgrowth, axon guidance and myelination. However, the potential role of Cntn1 in neuronal migration during cortical development has not been investigated. Here we used in utero electroporation to introduce short hairpin RNA (shRNA) to knock down (KD) Cntn1 in neural stem cells in vivo. We found that Cntn1 KD led to a delay in neuronal migration. The arrested cells presented abnormal morphology in their leading process and more multipolar cells were observed in the deep layers of the brain, suggestive of dysregulation in process formation. Intriguingly, Cntn1 KD also resulted in upregulation of RhoA, a negative regulator for neuronal migration. Interference of RhoA by expression of the dominant-negative RhoAN19 partially rescued the neuronal migration defects caused by Cntn1 KD. Our results showed that Cntn1 is a novel adhesion protein that is essential for neuronal migration and regulates process formation of newborn cortical neurons through modulating RhoA signaling pathway.

Highlights

In the cerebral cortex,the highly organized pyramidal neurons originate directly or indirectly from radial glial cell (RGC) located in the deep proliferative germinal region, known as the ventricular zone (VZ) (Kriegstein and Noctor, 2004; Molyneaux et al, 2007)
Neuronal Migration Delay Resulting From Cntn1 knock down (KD)
We found that Cntn1 short hairpin RNA (shRNA) (shCntn1)-018 showed ∼90% downregulation of Cntn1 expression 2 days after transfection (Figure 1A) and selected for in utero electroporation experiments

Summary

Introduction

In the cerebral cortex,the highly organized pyramidal neurons originate directly or indirectly from RGCs located in the deep proliferative germinal region, known as the VZ (Kriegstein and Noctor, 2004; Molyneaux et al, 2007). The newborn neurons migrate along radial fiber of RGCs to the CP. A limited number of molecules have been identified to be involved in neuronal migration in the developing cortex, such as N-cadherin, integrins, and connexins (Kawauchi, 2015). Suppression of N-cadherin perturbs the attachment of migrating neurons to the radial glial fibers (Kawauchi et al, 2010). The treatment with antibodies against β1-integrin suppresses radial glial fiber-dependent neuronal migration in vitro (Anton et al, 1999). The gap junction subunits connexin 26 (Cx26) and connexin 43 (Cx43) are found to be expressed at the contact points between radial fibers and migrating neurons. Cx26 and Cx43 may provide dynamic adhesive contacts that interact with the internal cytoskeleton (Elias et al, 2007)

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