The Rho GEF Trio is transported by microtubule plus-ends and involved in focal adhesion formation in migrating neural crest cells

Directed cell migration depends on cytoskeletal rearrangements, protrusion formation, cell contraction and focal adhesion turnover. These processes are regulated by spatiotemporal fine-tuning of Rho GTPase activity. The Rho guanine nucleotide exchange factor (GEF) Trio is well suited to control R...

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Bibliographic Details
Main Author: Gossen, Stefanie
Contributors: Borchers, Annette (Prof. Dr.) (Thesis advisor)
Format: Doctoral Thesis
Language:English
Published: Philipps-Universität Marburg 2023
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Summary:Directed cell migration depends on cytoskeletal rearrangements, protrusion formation, cell contraction and focal adhesion turnover. These processes are regulated by spatiotemporal fine-tuning of Rho GTPase activity. The Rho guanine nucleotide exchange factor (GEF) Trio is well suited to control Rho GTPase activity by merging two catalytic GEF domains, allowing control over Rac1 and RhoA within a single protein. However, strict spatiotemporal control of the activity of the Trio GEF domains at the cellular level is necessary. We recently demonstrated that Trio is required for Xenopus neural crest (NC) cell protrusion formation and migration. Here, we examine the dynamic localization of Trio and its impact on Trio's role in NC cell migration. Live-cell imaging revealed that the Trio GEF2 domain co-localizes with EB3 at microtubule plus-ends. Microtubule trafficking of Trio appears to be important for its function, as a mutant GEF2 construct lacking the SxIP amino acid motif responsible for microtubule plus-end binding, was unable to rescue the Trio loss-of-function induced NC migration defects in vivo and in vitro. In addition, our analysis of microtubule dynamics in migrating neural crest cells revealed that Trio knockdown results in the stabilization of microtubules at cell-cell contacts, while destabilizing them at the leading edge compared to the control. Furthermore, our findings indicate that Trio is involved in focal adhesion dynamics, as analyzed by live-cell imaging of focal adhesion assembly and disassembly. Our data suggest that Trio is transported by microtubules to specific subcellular locations, where it has distinct functions in controlling microtubule stability, protrusion formation and adhesive functions during directed NC cell migration. Furthermore, TRIO gene mutations have been shown to cause neurodevelopmental disorders and facial dysmorphisms in patients, possibly by inhibiting the migration of neural crest cells. Similar clinical features were observed in individuals with mutations in the MAPRE2 and TUBB genes. We successfully induced Mapre2 and Tubb loss-of-function in Xenopus embryos by injecting specific translation-blocking morpholinos and demonstrate, comparable to patient data, that this knockdown results in NC migration defects and craniofacial malformations. These experiments will serve as a starting point to analyze whether Trio, Mapre2 and Tubb operate within the same signaling pathways to regulate microtubule dynamics, focal adhesion turnover and, thereby, cell motility.
DOI:10.17192/z2024.0075