title: Disrupted dorsal neural tube BMP signaling in the cilia mutant Arl13b hnn stems from abnormal Shh signaling.
abstract: In the embryonic neural tube, multiple signaling pathways work in concert to create functional neuronal circuits in the adult spinal cord. In the ventral neural tube, Sonic hedgehog (Shh) acts as a graded morphogen to specify neurons necessary for movement. In the dorsal neural tube, bone morphogenetic protein (BMP) and Wnt signals cooperate to specify neurons involved in sensation. Several signaling pathways, including Shh, rely on primary cilia in vertebrates. In this study, we used a mouse mutant with abnormal cilia, Arl13b(hnn), to study the relationship between cilia, cell signaling, and neural tube patterning. Arl13b(hnn) mutants have abnormal ventral neural tube patterning due to disrupted Shh signaling; in addition, dorsal patterning defects occur, but the cause of these is unknown. Here we show that the Arl13b(hnn) dorsal patterning defects result from abnormal BMP signaling. In addition, we find that Wnt ligands are abnormally expressed in Arl13b(hnn) mutants; surprisingly, however, downstream Wnt signaling is normal. We demonstrate that Arl13b is required non-autonomously for BMP signaling and Wnt ligand expression, indicating that the abnormal Shh signaling environment in Arl13b(hnn) embryos indirectly causes dorsal defects.
authors.affiliation: Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA.
authors.forename: Vanessa L
authors.initials: VL
authors.lastname: Horner
authors.forename: Tamara
authors.initials: T
authors.lastname: Caspary
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics; D000818:Animals; D019521:Body Patterning / Q000235:genetics; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D002923:Cilia / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic / Q000254:growth & development*; D054259:Neural Tube / Q000254:growth & development* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D013116:Spinal Cord / Q000196:embryology / Q000254:growth & development / Q000378:metabolism; D051153:Wnt Proteins / Q000378:metabolism
chemical_list: C560093:Arl13b protein, mouse; D019485:Bone Morphogenetic Proteins; D053823:Hedgehog Proteins; C465570:Shh protein, mouse; D051153:Wnt Proteins; D020727:ADP-Ribosylation Factors