Hedgehog signaling patterns mesoderm in the sea urchin.
The Hedgehog (Hh) signaling pathway is essential for patterning many structures in vertebrates including the nervous system, chordamesoderm, limb and endodermal organs. In the sea urchin, a basal deuterostome, Hh signaling is shown to participate in organizing the mesoderm. At gastrulation the Hh ligand is expressed by the endoderm downstream of the Brachyury and FoxA transcription factors in the endomesoderm gene regulatory network. The co-receptors Patched (Ptc) and Smoothened (Smo) are expressed by the neighboring skeletogenic and non-skeletogenic mesoderm. Perturbations of Hh, Ptc and Smo cause embryos to develop with skeletal defects and inappropriate non-skeletogenic mesoderm patterning, although initial specification of mesoderm occurs without detectable abnormalities. Perturbations of the pathway caused late defects in skeletogenesis and in the non-skeletogenic mesoderm, including altered numbers of pigment and blastocoelar cells, randomized left-right asymmetry of coelomic pouches, and disorganized circumesophageal muscle causing an inability to swallow. Together the data support the requirement of Hh signaling in patterning each of the mesoderm subtypes in the sea urchin embryo.
Walton
Katherine D
KD
Department of Biology, Duke University, Box 90338, Durham, NC 27708, USA.
Warner
Jacob
J
Hertzler
Philip H
PH
McClay
David R
DR
D000818:Animals; D004330:Drosophila / Q000254:growth & development / Q000502:physiology; D029721:Drosophila Proteins / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000502:physiology; D005326:Fetal Proteins / Q000235:genetics / Q000502:physiology*; D005784:Gene Amplification; D005786:Gene Expression Regulation; D053823:Hedgehog Proteins / Q000235:genetics / Q000502:physiology*; D008648:Mesoderm / Q000502:physiology*; D016296:Mutagenesis; D009693:Nucleic Acid Hybridization; D016133:Polymerase Chain Reaction; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D011995:Recombination, Genetic; D012617:Sea Urchins / Q000196:embryology* / Q000235:genetics / Q000254:growth & development; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000235:genetics / Q000502:physiology*; D000098908:Brachyury Protein
D029721:Drosophila Proteins; D005326:Fetal Proteins; D053823:Hedgehog Proteins; D012313:RNA; D020825:T-Box Domain Proteins; D000098908:Brachyury Protein