title: LvDelta is a mesoderm-inducing signal in the sea urchin embryo and can endow blastomeres with organizer-like properties.
abstract: Signals from micromere descendants play a critical role in patterning the early sea urchin embryo. Previous work demonstrated a link between the induction of mesoderm by micromere descendants and the Notch signaling pathway. In this study, we demonstrate that these micromere descendants express LvDelta, a ligand for the Notch receptor. LvDelta is expressed by micromere descendants during the blastula stage, a time when signaling has been shown to occur. By a combination of embryo microsurgery, mRNA injection and antisense morpholino experiments, we show that expression of LvDelta by micromere descendants is both necessary and sufficient for the development of two mesodermal cell types, pigment cells and blastocoelar cells. We also demonstrate that LvDelta is expressed by macromere descendants during mesenchyme blastula and early gastrula stages. Macromere-derived LvDelta is necessary for blastocoelar cell and muscle cell development. Finally, we find that expression of LvDelta is sufficient to endow blastomeres with the ability to function as a vegetal organizing center and to coordinate the development of a complete pluteus larva.
authors.affiliation: Department of Biological Sciences, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA. hxssbi@rit.edu
authors.forename: Hyla C
authors.initials: HC
authors.lastname: Sweet
authors.forename: Michael
authors.initials: M
authors.lastname: Gehring
authors.forename: Charles A
authors.initials: CA
authors.lastname: Ettensohn
mesh_terms: D000818:Animals; D001483:Base Sequence; D001755:Blastocyst / Q000502:physiology; D001757:Blastomeres / Q000378:metabolism / Q000502:physiology*; D003001:Cloning, Molecular; D015870:Gene Expression; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism*; D008648:Mesoderm / Q000502:physiology*; D008969:Molecular Sequence Data; D051880:Receptors, Notch; D012617:Sea Urchins / Q000196:embryology / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction
chemical_list: D008024:Ligands; D008565:Membrane Proteins; D051880:Receptors, Notch