Controlled levels of canonical Wnt signaling are required for neural crest migration

Controlled levels of canonical Wnt signaling are required for neural crest migration

Maj, Ewa Anna

Dissertation

Angenommen am: 2015-12-03

Erschienen: 2016-01-22

Betreuer: Borchers, Annette Prof. Dr.

Gutachter: Borchers, Annette Prof. Dr.

Gutachter: Hahn, Heidi Prof. Dr.

Zum Verlinken/Zitieren: http://hdl.handle.net/11858/00-1735-0000-0028-86A0-1

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Zusammenfassung

Englisch

Canonical Wnt signaling has been shown to orchestrate the development of the neural crest (NC), a transient population of multipotent, migratory cells that generate 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 elusive. Conversely, ß-catenin independent, non-canonical Wnt pathways have been shown to be required in the migration of NC cells. To delineate a possible function of canonical Wnt-signaling in Xenopus NC migration, canonical Wnt signaling was activated or inhibited at different time points after NC induction using chemical modulators affecting ß-catenin stability and inducible glucocorticoid fusion-constructs of Lef/Tcf transcription factors. Modulation of non-canonical Wnt pathways was performed using chemical inhibitors and provided a comparision to migration defects observed upon dysregulation of canonical Wnt signaling. In each case, alternations in NC migration were analyzed either in vivo using whole mount in situ hybridization or in vitro by life-cell imaging of explanted NC cells. Ectopic activation of canonical Wnt signaling caused predominantly a strong inhibition of cranial NC migration. Less frequently patterning defects of the cranial NC streams were observed. Intriguingly, inhibition of canonical Wnt signaling phenocopies NC migration defects already observed upon activation. Furthermore, modulation of canonical Wnt caused differences in expression of NC-marker genes. Inhibition of non-canonical Wnt signaling results mostly in formation of unstructured NC branches, however, changes in expression of NC-markers were not observed. Additionally, life-cell imaging in combination with biophysical data analysis of explanted NC cells confirmed the in vivo findings and demonstrated that modulation of both canonical and non-canonical Wnt signalings affect cell mobility and the ability to perform single cell migration. Furthermore, it has been shown that endogenous ß-catenin is present in the nucleus at premigratory stages, but starts to be removed in the progress of migration, suggesting that canonical Wnt activity has to decrease to basal levels at the onset of NC migration. Thus, the data confirms necessity of non-canonical Wnt signaling for proper NC cells migration and support the hypothesis that canonical Wnt signaling needs to be tightly controlled to enable migration of NC cells.

Keywords: Developmental Biology