title: Neuron navigator 3a regulates liver organogenesis during zebrafish embryogenesis.
abstract: Endodermal organogenesis requires a precise orchestration of cell fate specification and cell movements, collectively coordinating organ size and shape. In Caenorhabditis elegans, uncoordinated-53 (unc-53) encodes a neural guidance molecule that directs axonal growth. One of the vertebrate homologs of unc-53 is neuron navigator 3 (Nav3). Here, we identified a novel vertebrate neuron navigator 3 isoform in zebrafish, nav3a, and we provide genetic evidence in loss- and gain-of-function experiments showing its functional role in endodermal organogenesis during zebrafish embryogenesis. In zebrafish embryos, nav3a expression was initiated at 22 hpf in the gut endoderm and at 40 hpf expanded to the newly formed liver bud. Endodermal nav3a expression was controlled by Wnt2bb signaling and was independent of FGF and BMP signaling. Morpholino-mediated knockdown of nav3a resulted in a significantly reduced liver size, and impaired development of pancreas and swim bladder. In vivo time-lapse imaging of liver development in nav3a morphants revealed a failure of hepatoblast movement out from the gut endoderm during the liver budding stage, with hepatoblasts being retained in the intestinal endoderm. In hepatocytes in vitro, nav3a acts as a positive modulator of actin assembly in lamellipodia and filipodia extensions, allowing cellular movement. Knockdown of nav3a in vitro impeded hepatocyte movement. Endodermal-specific overexpression of nav3a in vivo resulted in additional ectopic endodermal budding beyond the normal liver and pancreatic budding sites. We conclude that nav3a is required for directing endodermal organogenesis involving coordination of endodermal cell behavior.
authors.affiliation: Department of Angiogenesis and Cardiovascular Pathology, Max-Delbrueck-Center for Molecular Medicine (MDC), Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Klein
authors.forename: Janine
authors.initials: J
authors.lastname: Mikutta
authors.forename: Janna
authors.initials: J
authors.lastname: Krueger
authors.forename: Katja
authors.initials: K
authors.lastname: Scholz
authors.forename: Joep
authors.initials: J
authors.lastname: Brinkmann
authors.forename: Dong
authors.initials: D
authors.lastname: Liu
authors.forename: Justus
authors.initials: J
authors.lastname: Veerkamp
authors.forename: Doreen
authors.initials: D
authors.lastname: Siegel
authors.forename: Salim
authors.initials: S
authors.lastname: Abdelilah-Seyfried
authors.forename: Ferdinand
authors.initials: F
authors.lastname: le Noble
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D004707:Endoderm / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D017403:In Situ Hybridization; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000196:embryology; D008099:Liver / Q000002:abnormalities / Q000196:embryology* / Q000294:innervation / Q000378:metabolism*; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D038081:Organogenesis / Q000235:genetics / Q000502:physiology; D016372:RNA, Antisense / Q000235:genetics; D015398:Signal Transduction; D051153:Wnt Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D009419:Nerve Tissue Proteins; D016372:RNA, Antisense; D051153:Wnt Proteins; D029961:Zebrafish Proteins; C492033:wnt2ba protein, zebrafish