title: Isolation of Ef silicatein and Ef lectin as molecular markers for sclerocytes and cells involved in innate immunity in the freshwater sponge Ephydatia fluviatilis.
abstract: Sponges (phylum Porifera) have remarkable regenerative and reconstitutive abilities and represent evolutionarily the oldest metazoans. To investigate sponge stem cell differentiation, we have focused on the asexual reproductive system in the freshwater sponge Ephydatia fluviatilis. During germination, thousands of stem cells proliferate and differentiate to form a fully functional sponge. As an initial step of our investigation of stem cell (archeocyte) differentiation, we isolated molecular markers for two differentiated cell types: spicule-making sclerocyte cells, and cells involved in innate immunity. Sclerocyte lineage-specific Ef silicatein shares 45% to 62% identity with other sponge silicateins. As in situ hybridization of Ef silicatein specifically detects archeocytes possibly committed to sclerocytes, as well as sclerocytes with an immature or mature spicule, therefore covering all the developmental stages, we conclude that Ef silicatein is a suitable sclerocyte lineage marker. Ef lectin, a marker for the cell type involved in innate immunity, shares 59% to 65% identity with the marine sponge Suberites domuncula galactose-binding protein (Sd GBP) and horseshoe crab Tachypleus tridentatus tachylectin1/lectinL6. Since Sd GBP and tachylectin1 are known to bind to bacterial lipopolysaccharides and inhibit the growth of bacteria, Ef lectin may have a similar function and be expressed in a specialized type of cell involved in defense against invading bacteria. Ef lectin mRNA and protein are not expressed in early stages of development, but are detected in late stages. Therefore, Ef lectin may be specifically expressed in differentiating and/or differentiated cells. We suggest Ef lectin as a marker for cells that assume innate immunity in freshwater sponges.
authors.affiliation: Group for Evolutionary Regeneration Biology, Center for Developmental Biology, RIKEN Kobe, Minatojima-Minami, Japan. funayama@cdb.riken.jp
authors.forename: Noriko
authors.initials: N
authors.lastname: Funayama
authors.forename: Mikiko
authors.initials: M
authors.lastname: Nakatsukasa
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Kuraku
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Takechi
authors.forename: Mikako
authors.initials: M
authors.lastname: Dohi
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Iwabe
authors.forename: Takashi
authors.initials: T
authors.lastname: Miyata
authors.forename: Kiyokazu
authors.initials: K
authors.lastname: Agata
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015415:Biomarkers / Q000378:metabolism; D002403:Cathepsins / Q000235:genetics / Q000302:isolation & purification*; D002454:Cell Differentiation / Q000502:physiology*; D016000:Cluster Analysis; D005618:Fresh Water; D007113:Immunity, Innate / Q000235:genetics / Q000276:immunology*; D017403:In Situ Hybridization; D007564:Japan; D037102:Lectins / Q000235:genetics / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011161:Porifera / Q000276:immunology* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D013234:Stem Cells / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D037102:Lectins; C112571:silicatein alpha; D002403:Cathepsins