Deletion of the Nucleotide Exchange Factor Vav3 Enhances Axonal Complexity and Synapse Formation but Tampers Activity of Hippocampal Neuronal Networks In Vitro.

David Wegrzyn,Kerry Tedford,Christine Wegrzyn,Andreas Faissner,Klaus-Dieter Fischer

doi:10.3390/ijms21030856

David Wegrzyn, Kerry Tedford + Show 3 more

Open Access

https://doi.org/10.3390/ijms21030856

Copy DOI

Abstract

Vav proteins activate GTPases of the RhoA subfamily that regulate the cytoskeleton and are involved in adhesion, migration, differentiation, polarity and the cell cycle. While the importance of RhoA GTPases for neuronal morphology is undisputed, their regulation is less well understood. In this perspective, we studied the consequences of the deletion of Vav2, Vav3 and Vav2 and 3 (Vav2−/−, Vav3−/−, Vav2−/−/3−/−) for the development of embryonic hippocampal neurons in vitro. Using an indirect co-culture system of hippocampal neurons with primary wild-type (WT) cortical astrocytes, we analysed axonal and dendritic parameters, structural synapse numbers and the spontaneous network activity via immunocytochemistry and multielectrode array analysis (MEA). Here, we observed a higher process complexity in Vav3−/−, but not in Vav2−/− neurons after three and five days in vitro (DIV). Furthermore, an enhanced synapse formation was observed in Vav3−/− after 14 days in culture. Remarkably, Vav2−/−/3−/− double knockout neurons did not display synergistic effects. Interestingly, these differences were transient and compensated after a cultivation period of 21 days. Network analysis revealed a diminished number of spontaneously occurring action potentials in Vav3−/− neurons after 21 DIV. Based on these results, it appears that Vav3 participates in key events of neuronal differentiation.

Highlights

The Vav subfamily of guanine nucleotide exchange factors (GEFs) is composed of the three members Vav1, Vav2 and Vav3 [1]
In view of the importance of small GTPases of the RhoA family for neuronal differentiation, we sought to determine the impact of the guanine nucleotide exchange factors Vav2 and Vav3 on neuronal morphology
While the expression of MAP2 is limited to the dendritic compartment [33], Tau proteins highly accumulate in the axon and take part in its stabilization [34]

Summary

Introduction

The Vav subfamily of guanine nucleotide exchange factors (GEFs) is composed of the three members Vav, Vav and Vav3 [1]. Vav proteins are regulated by receptor tyrosine kinases and activate their target proteins by catalysing the exchange of GDP by GTP [6,7]. In this way Vav proteins can activate members of the Rho GTPase family. GDP/GTP binding experiments could show that Vav proteins activate RhoA, RhoG and Rac but not Cdc42 [8]. There are indications that Cdc is influenced by Vav and Vav through an accumulation of phosphatidylinositol 3,4,5-trisphosphate [9]

Methods

Results

Conclusion