title: FGF-activated calcium channels control neural gene expression in Xenopus.
abstract: In vertebrates, the formation of the nervous system starts at gastrulation with a process called neural induction. This process requires, at least in part, the inhibition of BMP signalling in the ectoderm by noggin, as well as FGF receptor activation and Ca2+ signalling. Our studies with Xenopus embryos suggest that an increase in intracellular Ca2+ concentration ([Ca2+]i), via dihydropyridine-sensitive Ca2+ channels (DHP-sensitive Ca2+ channels) is necessary and sufficient to direct the ectodermal cells toward a neural fate, and that Ca2+ directly controls the expression of neural genes. The mechanism by which the DHP-sensitive Ca2+ channels are activated during neural induction remains unknown. One possible mechanism is via the activation of FGF signalling. Using isolated ectoderm tissue, here we demonstrated that FGF-4 depolarises the membrane of ectodermal cells and induces an increase in [Ca2+]i. This Ca2+ increase can be blocked by SU5402, an FGF receptor inhibitor, and by DHP-sensitive Ca2+ channel antagonists. These inhibitors also block the induction of neural genes. We discuss a possible gating mechanism for the activation of DHP-sensitive Ca2+ channels via the FGF signalling pathway, which involves arachidonic acid and TRPC1 channel activation.
authors.affiliation: Centre de biologie du développement, CNRS UMR 5547, Université Paul Sabatier, 118, route de Narbonne F 31062 Toulouse Cedex, France.
authors.forename: Karen W
authors.initials: KW
authors.lastname: Lee
authors.forename: Marc
authors.initials: M
authors.lastname: Moreau
authors.forename: Isabelle
authors.initials: I
authors.lastname: Néant
authors.forename: Anne
authors.initials: A
authors.lastname: Bibonne
authors.forename: Catherine
authors.initials: C
authors.lastname: Leclerc
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D004627:Embryonic Induction; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D011758:Pyrroles / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics; D000099176:Noggin Protein
chemical_list: D016718:Arachidonic Acid; D002118:Calcium; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002352:Carrier Proteins; D005346:Fibroblast Growth Factors; D011758:Pyrroles; D000099176:Noggin Protein; C105686:SU 5402