title: Tsukushi controls ectodermal patterning and neural crest specification in Xenopus by direct regulation of BMP4 and X-delta-1 activity.
abstract: In Xenopus, ectodermal patterning depends on a mediolateral gradient of BMP signaling, higher in the epidermis and lower in the neuroectoderm. Neural crest cells are specified at the border between the neural plate and the epidermis, at intermediate levels of BMP signaling. We recently described a novel secreted protein, Tsukushi (TSK), which works as a BMP antagonist during chick gastrulation. Here, we report on the Xenopus TSK gene (X-TSK), and show that it is involved in neural crest specification. X-TSK expression accumulates after gastrulation at the anterior-lateral edges of the neural plate, including the presumptive neural crest region. In gain-of-function experiments, X-TSK can strongly enhance neural crest specification by the dorsolateral mesoderm or X-Wnt8 in ectodermal explants, while the electroporation of X-TSK mRNA in the lateral ectoderm of embryos after gastrulation can induce the expression of neural crest markers in vivo. By contrast, depletion of X-TSK in explants or embryos impairs neural crest specification. Similarly to its chick homolog, X-TSK works as a BMP antagonist by direct binding to BMP4. However, X-TSK can also indirectly regulate BMP4 mRNA expression at the neural plate border via modulation of the Delta-Notch signaling pathway. We show that X-TSK directly binds to the extracellular region of X-delta-1, and modulates Delta-dependent Notch activity. We propose that X-TSK plays a key role in neural crest formation by directly regulating BMP and Delta activities at the boundary between the neural and the non-neural ectoderm.
authors.affiliation: Division of Developmental Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto 860-8556, Japan.
authors.forename: Sei
authors.initials: S
authors.lastname: Kuriyama
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lupo
authors.forename: Kunimasa
authors.initials: K
authors.lastname: Ohta
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Ohnuma
authors.forename: William A
authors.initials: WA
authors.lastname: Harris
authors.forename: Hideaki
authors.initials: H
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D015153:Blotting, Western; D019521:Body Patterning / Q000502:physiology*; D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D004475:Ectoderm / Q000502:physiology*; D018274:Electroporation; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D047468:Immunoprecipitation; D017403:In Situ Hybridization; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000378:metabolism*; D009432:Neural Crest / Q000502:physiology*; D009841:Oligonucleotides; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014981:Xenopus / Q000196:embryology*; D029867:Xenopus Proteins / Q000378:metabolism / Q000502:physiology*
chemical_list: D055415:Bone Morphogenetic Protein 4; D019485:Bone Morphogenetic Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009841:Oligonucleotides; C510454:TSKU protein, Xenopus; D029867:Xenopus Proteins; C525812:bmp4 protein, Xenopus; C064045:delta protein