title: Expression of silicatein and collagen genes in the marine sponge Suberites domuncula is controlled by silicate and myotrophin.
abstract: The major skeletal elements in the (Porifera) sponges, are spicules formed from inorganic material. The spicules in the Demospongiae class are composed of hydrated, amorphous silica. Recently an enzyme, silicatein, which polymerizes alkoxide substrates to silica was described from the sponge Tethya aurantia. In the present study the cDNA encoding silicatein was isolated from the sponge Suberites domuncula. The deduced polypeptide comprises 331 amino acids and has a calculated size of Mr 36 306. This cDNA was used as a probe to study the potential role of silicate on the expression of the silicatein gene. For these studies, primmorphs, a special form of aggregates composed of proliferating cells, have been used. It was found that after increasing the concentration of soluble silicate in the seawater medium from around 1 microM to approximately 60 microM, this gene is strongly upregulated. Without additional silicate only a very weak expression could be measured. Because silica as well as collagen are required for the formation of spicules, the expression of the gene encoding collagen was measured in parallel. It was also found that the level of transcripts for collagen strongly increases in the presence of 60 microM soluble silicate. In addition, it is demonstrated that the expression of collagen is also upregulated in those primmorphs which were treated with recombinant myotrophin obtained from the same sponge. Myotrophin, however, had no effect on the expression of silicatein. From these data we conclude that silicate influences the expression of the enzyme silicatein and also the expression of collagen, (via the mediator myotrophin).
authors.affiliation: Institut für Physiologische Chemie, Abteilung für Angewandte Molekularbiologie, Universität Mainz, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Krasko
authors.forename: B
authors.initials: B
authors.lastname: Lorenz
authors.forename: R
authors.initials: R
authors.lastname: Batel
authors.forename: H C
authors.initials: HC
authors.lastname: Schröder
authors.forename: I M
authors.initials: IM
authors.lastname: Müller
authors.forename: W E
authors.initials: WE
authors.lastname: Müller
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D002403:Cathepsins / Q000096:biosynthesis* / Q000235:genetics; D003001:Cloning, Molecular; D003094:Collagen / Q000096:biosynthesis* / Q000235:genetics; D018076:DNA, Complementary / Q000378:metabolism; D005786:Gene Expression Regulation; D015723:Gene Library; D005857:Germanium / Q000494:pharmacology; D006133:Growth Substances / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D011161:Porifera / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D017640:Silicates / Q000378:metabolism*; D014158:Transcription, Genetic; D015854:Up-Regulation
chemical_list: D000596:Amino Acids; D018076:DNA, Complementary; D006133:Growth Substances; D036341:Intercellular Signaling Peptides and Proteins; D017640:Silicates; C065700:myotrophin; C112571:silicatein alpha; D005857:Germanium; D003094:Collagen; D002403:Cathepsins