PTK7 recruits dsh to regulate neural crest migration

Abstract

PTK7 regulates planar cell polarity (PCP) signaling during vertebrate neural tube closure and establishment of inner ear hair cell polarity; however, its signaling mechanism is unknown. Here, we demonstrate a new function for PTK7 in Xenopus neural crest migration and use this system in combination with in vitro assays to define the intersection of PTK7 with the non-canonical Wnt signaling pathway that regulates PCP. In vitro, using Xenopus ectodermal explants, we show that PTK7 recruits dishevelled (dsh) to the plasma membrane, a function that is dependent on the PDZ domain of dsh, as well as on the conserved kinase domain of PTK7. Furthermore, endogenous PTK7 is required for frizzled7-mediated dsh localization. Immunoprecipitation experiments confirm that PTK7 can be found in a complex with dsh and frizzled7, suggesting that it cooperates with frizzled to localize dsh. To evaluate the in vivo relevance of the PTK7-mediated dsh localization, we analyzed Xenopus neural crest migration, as loss-of-function of PTK7 inhibits neural crest migration in whole embryos as well as in transplanted neural crest cells. Supporting the in vivo role of PTK7 in the localization of dsh, a PTK7 deletion construct deficient in dsh binding inhibits neural crest migration. Furthermore, the PTK7-mediated membrane localization of a dsh deletion mutant lacking PCP activity inhibits neural crest migration. Thus, PTK7 regulates neural crest migration by recruiting dsh, providing molecular evidence of how PTK7 intersects with the PCP signaling pathway to regulate vertebrate cell movements.

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

“…In Xenopus and mice, expression of 'core PCP' components including Stbm/Vang, Prickle and DAAM was observed in the cranial NC (Bekman and Henrique, 2002;Darken et al, 2002;Goto and Keller, 2002;Nakaya et al, 2004). In Xenopus, PTK7 which has been shown to modulate PCP signaling in many developmental processes is expressed in premigratory and migratory cranial NC (Shnitsar and Borchers, 2008). Taken together these data confirm a requirement of PCP signaling in the migration of NC cells.…”

Cell polarity

“…46,81 However, it remains to be determined whether important roles exist for Ryk or for the PCP-associated tyrosine kinase Ptk7 in modulating the non-canonical Wnt signal during limb development. 96,97 Is cell polarity in the limb regulated by Wnt5a gradients? As a secreted signaling molecule, Wnt5a may regulate cell polarity by generating morphogen gradients in the developing skeleton.…”

Mechanisms driving neural crest induction and migration in the zebrafish andXenopus laevis

“…149,175 Loss of function studies have implicated Wnt11r in crest migration. 176 A component of the non-canonical Wnt signaling pathway PTK7 is required for normal neural crest migration, 177 while pescadillo, which appears to be regulated by non-canonical Wnt4 signaling, is also involved in crest migration. endomesoderm of late blastula/early gastrula stage embryos, and appears to regulate expression of the secreted BMP-Nodal-Wnt inhibitor Cerberus; 200 expression of a "dominant-negative" form of XBlimp1 leads to the loss of embryonic head.…”