RESUMO
Neural crest (NC) cells are highly migratory cells that contribute to various vertebrate tissues, and whose migratory behaviors resemble cancer cell migration and invasion. Information exchange via dynamic NC cell-cell contact is one mechanism by which the directionality of migrating NC cells is controlled. One transmembrane protein that is most likely involved in this process is protein tyrosine kinase 7 (PTK7), an evolutionary conserved Wnt co-receptor that is expressed in cranial NC cells and several tumor cells. In Xenopus, Ptk7 is required for NC migration. In this study, we show that the Ptk7 protein is dynamically localized at cell-cell contact zones of migrating Xenopus NC cells and required for contact inhibition of locomotion (CIL). Using deletion constructs of Ptk7, we determined that the extracellular immunoglobulin domains of Ptk7 are important for its transient accumulation and that they mediate homophilic binding. Conversely, we found that ectopic expression of Ptk7 in non-NC cells was able to prevent NC cell invasion. However, deletion of the extracellular domains of Ptk7 abolished this effect. Thus, Ptk7 is sufficient at protecting non-NC tissue from NC cell invasion, suggesting a common role of PTK7 in contact inhibition, cell invasion, and tissue integrity.
Assuntos
Moléculas de Adesão Celular/metabolismo , Diferenciação Celular , Movimento Celular , Inibição de Contato , Neoplasias Pulmonares/metabolismo , Crista Neural/metabolismo , Receptores Proteína Tirosina Quinases/metabolismo , Animais , Polaridade Celular , Humanos , Neoplasias Pulmonares/patologia , Xenopus laevisRESUMO
Directional migration during embryogenesis and tumor progression faces the challenge that numerous external signals need to converge to precisely control cell movement. The Rho guanine exchange factor (GEF) Trio is especially well suited to relay signals, as it features distinct catalytic domains to activate Rho GTPases. Here, we show that Trio is required for Xenopus cranial neural crest (NC) cell migration and cartilage formation. Trio cell-autonomously controls protrusion formation of NC cells and Trio morphant NC cells show a blebbing phenotype. Interestingly, the Trio GEF2 domain is sufficient to rescue protrusion formation and migration of Trio morphant NC cells. We show that this domain interacts with the DEP/C-terminus of Dishevelled (DVL). DVL - but not a deletion construct lacking the DEP domain - is able to rescue protrusion formation and migration of Trio morphant NC cells. This is likely mediated by activation of Rac1, as we find that DVL rescues Rac1 activity in Trio morphant embryos. Thus, our data provide evidence for a novel signaling pathway, whereby Trio controls protrusion formation of cranial NC cells by interacting with DVL to activate Rac1.
Assuntos
Movimento Celular/genética , Proteínas Desgrenhadas/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Crista Neural/citologia , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais/genética , Proteínas de Xenopus/metabolismo , Xenopus laevis/embriologia , Animais , Proteínas Desgrenhadas/genética , Fatores de Troca do Nucleotídeo Guanina/genética , Células HEK293 , Humanos , Crista Neural/embriologia , Fenótipo , Plasmídeos/genética , Ligação Proteica/genética , Domínios Proteicos , Proteínas Serina-Treonina Quinases/genética , Transfecção , Proteínas de Xenopus/genética , Proteínas rac1 de Ligação ao GTP/metabolismo , Proteína rhoA de Ligação ao GTP/metabolismoRESUMO
Canonical Wnt signaling plays a dominant role in the development of the neural crest (NC), a highly migratory cell population that generates a vast array of cell types. Canonical Wnt signaling is required for NC induction as well as differentiation, however its role in NC migration remains largely unknown. Analyzing nuclear localization of ß-catenin as readout for canonical Wnt activity, we detect nuclear ß-catenin in premigratory but not migratory Xenopus NC cells suggesting that canonical Wnt activity has to decrease to basal levels to enable NC migration. To define a possible function of canonical Wnt signaling in Xenopus NC migration, canonical Wnt signaling was modulated at different time points after NC induction. This was accomplished using either chemical modulators affecting ß-catenin stability or inducible glucocorticoid fusion constructs of Lef/Tcf transcription factors. In vivo analysis of NC migration by whole mount in situ hybridization demonstrates that ectopic activation of canonical Wnt signaling inhibits cranial NC migration. Further, NC transplantation experiments confirm that this effect is tissue-autonomous. In addition, live-cell imaging in combination with biophysical data analysis of explanted NC cells confirms the in vivo findings and demonstrates that modulation of canonical Wnt signaling affects the ability of NC cells to perform single cell migration. Thus, our data support the hypothesis that canonical Wnt signaling needs to be tightly controlled to enable migration of NC cells.
Assuntos
Movimento Celular/fisiologia , Crista Neural/citologia , Fatores de Transcrição TCF/metabolismo , Fator 3 de Transcrição/metabolismo , Proteínas Wnt/metabolismo , Via de Sinalização Wnt/fisiologia , Proteínas de Xenopus/metabolismo , Xenopus laevis/embriologia , Animais , Hibridização In Situ , Indóis/farmacologia , Organogênese/fisiologia , Oximas/farmacologia , Crânio/embriologia , beta Catenina/metabolismoRESUMO
Neural crest cells are a highly migratory pluripotent cell population that generates a wide array of different cell types and failure in their migration can result in severe birth defects and malformation syndromes. Neural crest migration is controlled by various means including chemotaxis, repellent guidance cues and cell-cell interaction. Non-canonical Wnt PCP (planar cell polarity) signaling has previously been shown to control cell-contact mediated neural crest cell guidance. PTK7 (protein tyrosine kinase 7) is a transmembrane pseudokinase and a known regulator of Wnt/PCP signaling, which is expressed in Xenopus neural crest cells and required for their migration. PTK7 functions as a Wnt co-receptor; however, it remains unclear by which means PTK7 affects neural crest migration. Expressing fluorescently labeled proteins in Xenopus neural crest cells we find that PTK7 co-localizes with the Ror2 Wnt-receptor. Further, co-immunoprecipitation experiments demonstrate that PTK7 interacts with Ror2. The PTK7/Ror2 interaction is likely relevant for neural crest migration, because Ror2 expression can rescue the PTK7 loss of function migration defect. Live cell imaging of explanted neural crest cells shows that PTK7 loss of function affects the formation of cell protrusions as well as cell motility. Co-expression of Ror2 can rescue these defects. In vivo analysis demonstrates that a kinase dead Ror2 mutant cannot rescue PTK7 loss of function. Thus, our data suggest that Ror2 can substitute for PTK7 and that the signaling function of its kinase domain is required for this effect.