Xenbase Image ID: 147739

Fig. 8. Model for the spatial restriction of FGF signaling by PN1 in germ layer and primary axis development. (A,B) Feedback regulation of FGF/Erk signaling by the transcription factor Xbra and the secreted proteins HtrA1 and PN1 in early gastrula (lateral view, A) and early neurula (dorsal view, B) Xenopus embryo. Unbroken lines indicate biochemical interaction and dashed lines transcriptional regulation. Red bars represent inhibition of ectoderm and head development by mesodermal FGF signals. (C) Summary of the observations reported here and by Hou et al. (2007) of how the HtrA1 protease cleaves cell surface proteoglycans to mobilize FGF/proteoglycan messages that activate FGF receptors at a distance. As described by Kim et al. (2012), HtrA1 can also degrade non-bound FGF proteins. PN1, which binds to heparan sulfate (HS) (Li and Huntington, 2012), regulates paracrine FGF signaling by binding to and inhibiting HtrA1. Image published in: Acosta H et al. (2015) Copyright © 2015. Image reproduced with permission of the publisher and the copyright holder. This is an Open Access article distributed under the terms of the Creative Commons Attribution License. Larger Image Printer Friendly View

Return to previous page