Xenbase Image ID: 180084

Figure 2. Novel insights into specification, morphogenesis and function of the frog LRO. Induction of foxj1 in central LRO precursor cells requires canonical Wnt signaling as well as signaling through Fgfr1. The latter is activated by the unconventional FGF ligand Nodal3, synergizing with Polycystin-2, whereas the former requires rapgef5, which presumably regulates nuclear import of ß-catenin (Ctnnb1). Lateral flow-sensing LRO cells depend on FGF signaling through receptor 4, which activates myf5 and myod1 in these cells that are fated to integrate into the somites. Accessibility of the foxj1 promoter is regulated by methylation of histone H3 (H3K4me3); for assembly of the methyltransferase enzyme complex, Wdr5 constitutes a central scaffolding component. Mechanical strain (red arrows) exerted on the involuting LRO precursor causes PCP-dependent posterior polarization of LRO cilia, which become motile in a strain-dependent and foxj1-dependent manner. The foxj1 gradient of gene expression (cf. Figure 1) is reflected by a medial-lateral gradient of cilia lengths and polarization. PCP is acted upon as well by the unconventional myosin Myo1d. Novel ciliary factors acting on cilia include Wdr5 (at the ciliary base) and Ccdc11 as well as Enkur (in the ciliary axoneme). These factors await detailed functional characterization. Image published in: Blum M and Ott T (2019) Copyright © 2019. This image is 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

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