The building of the skeleton in the indirectdeveloping sea urchin embryo is a complexmorphogenetic process that is executed by thePrimary Mesenchyme Cells or PMCs (Ettensohn etal, 1997; Wilt 2002). It is well known that thePMCs acquire most of the positional and temporalinformation from the overlying ectoderm forskeletal initiation and growth (Armstrong 1993;Cavalieri et al, 2003; Röttinger et al, 2008). In thisstudy, we analyze the function of a novel gene,encoding for a tripartite motif-containing (TRIM)protein denoted strim1, that adds up to the list ofgenes constituting the epithelial-mesenchymalsignaling network.We show that strim1 is expressed in ectodermregions adjacent to the bilateral clusters of PMCs.Strim1 misexpression causes the number of PMCsto double and leads to skeletal abnormalities. Bymicromere transplantations, we establish thatskeletal defects depend upon strim1 misexpressionin ectoderm cells. Reciprocally, knock-down ofstrim1 function abrogates PMC migration andblocks skeletogenesis. Identical phenotype isshown by chimeras in which strim1 function isblocked selectively in the ectoderm. We also showthat clonal expression of strim1 into ectoderm cellsfrom knocked-down embryos restores the correctskeletogenic program. Finally, we report thatstrim1 triggers the expression of the ectodermspecificgene pax2/5/8, and the PMC marker sm30(an ectoderm signaling dependent gene).We conclude that strim1 function is able to elicitspecific gene expression both in ectoderm cells andPMCs to guide the biomineralization duringmorphogenesis.ReferencesArmstrong, N, Hardin, J and McClay, DR (1993). Cell-cellinteractions regulate skeleton formation in the sea urchin embryo.Development 119, 833-40.Cavalieri, V, Spinelli, G and Di Bernardo, M (2003). Impairing Otphomeodomain function in oral ectoderm cells affects skeletogenesisin sea urchin embryos. Dev Biol 262, 107-18.Ettensohn, CA, Guss, KA, Hodor, PG, and Malinda, KM (1997).The morphogenesis of the skeletal system of the sea urchin embryo,in: Collier JR (Ed.), Reproductive Biology of Invertebrates, vol. VII:Progress in Developmental Biology, Oxford & IBH publishing Co.Pvt. Ltd. New Delhi, Calcutta. 225-265.Röttinger, E, Saudemont, A, Duboc, V, Besnardeau, L, McClay, Dand Lepage, T (2008). FGF signals guide migration of mesenchymalcells, control skeletal morphogenesis and regulate gastrulationduring sea urchin development. Development 135, 353-65.Wilt, FH (2002). Biomineralization of the spicules of sea urchinembryos. Zoolog Sci 19, 253-61.
|Number of pages||0|
|Publication status||Published - 2011|