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Date
2025-10-21
Authors
Publisher
Philipps-Universität Marburg
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Abstract
Neural crest (NC) cells are highly migratory cells that give rise to a variety of vertebrate tissues and their migratory behavior resembles cancer cell migration and invasion. Directed NC cell migration is controlled by several mechanisms, including contact inhibition of locomotion (CIL), a phenomenon in which migrating cells change the polarity and directionality upon collision with another cell. During CIL, the formation of transient cell-cell contacts locally activates the small Rho GTPase RhoA, leading to protrusion collapse at the contact sites and a change in migration direction. Previously, we have shown that Ptk7 (protein tyrosine kinase 7), an evolutionary conserved Wnt/PCP co-receptor, is dynamically localized at Xenopus NC cell-cell contacts and mediates homophilic binding via its extracellular domains. Loss of Ptk7 function inhibits Xenopus NC cell migration and induces a blebbing phenotype in explanted NC cells. However, the precise molecular mechanisms by which Ptk7 regulates NC migration remain unclear. Interestingly, depletion of the Rho guanine exchange factor (GEF) Trio results in a phenotype, similar to that observed in Ptk7 morphants. Trio is particularly well suited to relay signals to the cytoskeleton as it contains a GEF1 domain that activates Rac1, but also a GEF2 domain that specifically activates RhoA. Here, we analyze the functional and physical interplay of Ptk7 and Trio during NC migration. We show that both Ptk7 and Trio are required for CIL. Using Ptk7 deletion constructs, we found that the extracellular domain of Ptk7 is not only necessary for CIL but also sufficient to protect non-NC tissue from NC cell invasion. In comparison, Trio controls the change in migration direction after collision presumably by transmitting the cell contact information to the cytoskeleton. Consistent with their role in CIL, Trio interacts with Ptk7 at cell-cell contact sites in NC explants. Moreover, rescue experiments showed that Trio acts downstream of Ptk7 during NC migration and protrusion formation. Thereby, Trio’s GEF2 domain, which specifically activates RhoA, but not the GEF1 domain, restored NC migration in Ptk7 morphants. In explanted NC cells, we observed that a loss of Ptk7 function leads to an increase in Rac1 activity but a decrease in RhoA. In addition, overexpression of either a dominant negative Rac1 or a constitutively active RhoA restored NC migration in Ptk7 morphant embryos. Thus, our data suggest that Ptk7 inhibits Trio GEF1-mediated Rac1 activity at cell-cell contact sites, thereby limiting Trio’s function to the activation of RhoA and thus mediating CIL.
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Dates
Created: 2024Issued: 2025-10-21Updated: 2025-10-21
Faculty
Fachbereich Biologie
Language
eng
Data types
DoctoralThesis
DFG-subjects
contact inhibition of locomotionTrioXenopusPtk7neural crest
DDC-Numbers
500
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Till, Katharina Maria: Analyzing the role of Ptk7/Trio-signaling in Xenopus neural crest cell migration. : Philipps-Universität Marburg 2025-10-21. DOI: https://doi.org/10.17192/z2024.0102.