Eph-Pak2a signaling regulates branching of the pharyngeal endoderm by inhibiting late-stage epithelial dynamics.
Branching morphogenesis depends on the precise temporal and spatial control of epithelial dynamics. In the vertebrate head, endodermal branches, called pharyngeal pouches, form through the transient stratification, collective migration and reorganization of epithelial cells into bilayers. Here, we report novel requirements for the EphrinB ligands B2a and B3b, the Ephb4a receptor and the Pak2a kinase in the development of pouches and the posterior facial skeleton that depends on pouches for its segmentation. Time-lapse imaging in zebrafish shows that EphB-Pak2a signaling is required to stabilize pouch epithelial cells at the end of branching morphogenesis. Transgenic rescue experiments further demonstrate that endodermal Eph-ephrin signaling promotes pouch integrity by targeting Pak2a to the plasma membrane, where subsequent activation by Wnt4a-Cdc42 signaling increases junctional E-cadherin in maturing pouches. Integration of Eph-ephrin and Wnt4a signaling through Pak2a thus signals the end of branching morphogenesis by increasing intercellular adhesion that blocks further epithelial rearrangements.
Broad CIRM Center, Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
Chong Pyo
CP
Choe
Broad CIRM Center, Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA gcrump@usc.edu.
J Gage
JG
Crump
D000818:Animals; D001934:Branchial Region / Q000196:embryology*; D004847:Epithelial Cells / Q000502:physiology*; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D018613:Microscopy, Confocal; D009024:Morphogenesis / Q000502:physiology*; D060172:Morpholinos / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D036224:Receptor, EphB4 / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D059008:Time-Lapse Imaging; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000378:metabolism*
D060172:Morpholinos; D029961:Zebrafish Proteins; D036224:Receptor, EphB4; C523516:Pak2a protein, zebrafish; D017346:Protein Serine-Threonine Kinases
Branching morphogenesis; Craniofacial; Eph-ephrin; PAK; Pharyngeal pouches; Zebrafish