title: FGF-mediated mesoderm induction involves the Src-family kinase Laloo.
abstract: During embryogenesis, inductive interactions underlie the development of much of the body plan. In Xenopus laevis, factors secreted from the vegetal pole induce mesoderm in the adjacent marginal zone; members of both the transforming growth factor-beta (TGF-beta) and fibroblast growth factor (FGF) ligand families seem to have critical roles in this process. Here we report the identification and characterization of laloo, a novel participant in the signal transduction cascade linking extracellular, mesoderm-inducing signals to the nucleus, where alteration of cell fate is driven by changes in gene expression. Overexpression of laloo, a member of the Src-related gene family, in Xenopus embryos gives rise to ectopic posterior structures that frequently contain axial tissue. Laloo induces mesoderm in Xenopus ectodermal explants; this induction is blocked by reagents that disrupt the FGF signalling pathway. Conversely, expression of a dominant-inhibitory Laloo mutant blocks mesoderm induction by FGF and causes severe posterior truncations in vivo. This work provides the first evidence that a Src-related kinase is involved in vertebrate mesoderm induction.
authors.affiliation: Department of Molecular Vertebrate Embryology, The Rockefeller University, New York, New York 10021, USA.
authors.forename: D C
authors.initials: DC
authors.lastname: Weinstein
authors.forename: J
authors.initials: J
authors.lastname: Marden
authors.forename: F
authors.initials: F
authors.lastname: Carnevali
authors.forename: A
authors.initials: A
authors.lastname: Hemmati-Brivanlou
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D046508:Culture Techniques; D018076:DNA, Complementary; D004627:Embryonic Induction; D005346:Fibroblast Growth Factors / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental; D008648:Mesoderm / Q000502:physiology*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D015398:Signal Transduction; D014981:Xenopus; D029867:Xenopus Proteins; D018631:ras Proteins / Q000502:physiology; D019061:src-Family Kinases / Q000302:isolation & purification / Q000502:physiology*
chemical_list: D018076:DNA, Complementary; C114358:HCK protein, Xenopus; D029867:Xenopus Proteins; D005346:Fibroblast Growth Factors; D019061:src-Family Kinases; D018631:ras Proteins