title: Unc-5/netrin-mediated axonal projection during larval serotonergic nervous system formation in the sea urchin, Hemicentrotus pulcherrimus.
abstract: The molecular structure and role of two splice-isoforms of Unc-5 (Hp-Unc-5v1 and v2) in Unc-5/netrin interaction during serotonergic axonal projection were elucidated in this study. Hp-Unc-5v1 was found to be comprised of two immunoglobulin-like domains, two thrombospondin domains in the extracellular region, and ZU-5, DB, and Death domains in the cytoplasmic region, whereas Hp-Unc-5v2 lacked one thrombospondin domain, the transmembrane domain, and all cytoplasmic domains. Hp-Unc-5v1 was transcribed in unfertilized eggs, which continued until the 3-day post-fertilization (-dpf) 2-arm pluteus stage, but was suspended at the mesenchyme blastula stage (mB1), whereas Hp-Unc-5v2 was not transcribed in unfertilized eggs, but was from after fertilization to the same developmental stage of mB1 as Hp-Unc-5v1. Relative accumulation of transcripts of both splice-isoforms peaked at the prism stage and declined thereafter, and they were localized at the vegetal pole region of early gastrulae, around the blastopore in mid- to late gastrulae, at fore- and mid-gut regions and on the basal side of dorsal ectoderm in 28-hour post-fertilization prism larvae, and within axons at and after the 2-dpf pluteus stage. Hp-Unc-5v2:GFP was detected in the entire serotonergic cell body and extracellularly on the basal surface of oral ectoderm in 2-dpf plutei and exclusively within axons in 4-dpf plutei. Overexpression of Hp-Unc-5v2 resulted in decreased axonal projection in plutei. Knockdown of Hp-Unc-5v1 by morpholino antisense oligonucleotide resulted in severe deficiency of axonal projection. Interference of Unc-5/netrin interaction using an exogenous synthetic SQDFGKTW peptide from the VI domain in Hp-netrin inhibited axonal projection and larval swimming.
authors.affiliation: Research Center for Marine Biology, Tohoku University, Asamushi, Aomori, Japan.
authors.forename: Kouki
authors.initials: K
authors.lastname: Abe
authors.forename: Tomoko
authors.initials: T
authors.lastname: Katow
authors.forename: Shioh
authors.initials: S
authors.lastname: Ooka
authors.forename: Hideki
authors.initials: H
authors.lastname: Katow
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000502:physiology; D001483:Base Sequence; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D047330:Hemicentrotus / Q000196:embryology / Q000235:genetics* / Q000254:growth & development; D015151:Immunoblotting; D017403:In Situ Hybridization; D007814:Larva / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009420:Nervous System / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D059326:Serotonergic Neurons / Q000378:metabolism
chemical_list: D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D049452:Green Fluorescent Proteins