A combination of Wnt and growth factor signaling induces Arl4c expression to form epithelial tubular structures

Growth factor‐dependent epithelial morphological changes and proliferation are essential for the formation of tubular structures, but the underlying molecular mechanisms are poorly understood. Co‐stimulation with Wnt3a and epidermal growth factor (Wnt3a/EGF) induced development of tubes consisting of intestinal epithelial cells by inducing expression of Arl4c, an Arf‐like small GTP‐binding protein, in three‐dimensional culture, while stimulation with Wnt3a or EGF alone did not. Arl4c expression resulted in rearrangement of the cytoskeleton through activation of Rac and inactivation of Rho properly, which promoted cell growth by inducing nuclear translocation of Yes‐associated protein and transcriptional co‐activator with PDZ‐binding motif (YAP/TAZ) in leading cells. Arl4c was expressed in ureteric bud tips and pretubular structures in the embryonic kidney. In an organoid culture assay, Wnt and fibroblast growth factor signaling simultaneously induced elongation and budding of kidney ureteric buds through Arl4c expression. YAP/TAZ was observed in the nucleus of extending ureteric bud tips. Thus, Arl4c expression induced by a combination of growth factor signaling mechanisms is involved in tube formation. Synopsis Wnt and EGF signals jointly induce the small GTP‐binding protein Arl4c in epithelial cells, which form tubules. Arl4c regulates actin cytoskeleton dynamics through RhoGTPases, and the resulting cell shape changes activate the transcription factor YAP/TAZ, promoting cell proliferation. Co‐stimulation of epithelial cells with Wnt3a and EGF activates Arl4c, which induces tubule formation. Arl4c regulates actin cytoskeleton dynamics through the ARNO‐Arf6‐Rac1‐RhoA axis. Actin cytoskeleton changes activate YAP/TAZ signaling and cell proliferation. This mechanism is involved in the morphogenesis of kidney ureteric buds. Graphical Abstract Wnt and EGF signals jointly induce the small GTP‐binding protein Arl4c in epithelial cells, which form tubules. Arl4c regulates actin cytoskeleton dynamics through RhoGTPases, and the resulting cell shape changes activate the transcription factor YAP/TAZ, promoting cell proliferation.