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  • Bruno Vellutini 18:35 on 2013/08/26 Permalink
    Tags: meetings, , ,   

    Submitted abstract to SICB2014 

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    Beyond boundaries: expression of “segment polarity” genes during larval lobe development in brachiopods

    Sars International Centre for Marine Molecular Biology, Univ. of Bergen, Norway

    Brachiopods are sessile bivalved spiralians closely related to annelids, molluscs, and nemerteans. Despite having an unsegmented adult body, the larval body of many brachiopods is divided in lobes disposed along the anterior-posterior axis. This morphology and presence of partitioned coeloms in some larvae have been treated as evidence that brachiopods evolved from a segmented ancestor. We approached this hypothesis by characterizing the development of brachiopod larval lobes and the expression of genes commonly expressed in segments of arthropods and annelids (i.e. “segment polarity” genes) in the trilobed larva of Terebratalia transversa and the bilobed larva of Novocrania anomala. We have cloned Engrailed, Wnt genes, and components of the Hedgehog pathway and analysed their expression by in situ hybridization. The three lobes of T. transversa larva were delimited by an anterior ectodermal groove and a posterior less prominent constriction. We detected adjacent stripes of wnt1 and engrailed transcripts in the ectoderm delimiting the anterior boundary. At the posterior boundary, wnt1 and engrailed were co-expressed on a ventral and a dorsal band. Genes of the Hedgehog pathway were not expressed on the larval lobes. Adjacent stripes of wnt1 and engrailed are also found at parasegment and segment boundaries of arthropods and annelids, respectively, while co-expression is observed in the chordate mid-hindbrain boundary and hemichordate collar-trunk boundary. Thus, our results suggest that engrailed and wnt1, but not hedgehog, might be involved in the development of lobe boundaries of T. transversa larvae in a similar manner as observed in other morphological boundaries.

  • Bruno Vellutini 12:50 on 2012/07/04 Permalink
    Tags: meetings   

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    Sent poster to print for the EuroEvoDevo 2012 Lisbon meeting. Here is the final art:

    EED12 poster

  • Bruno Vellutini 12:00 on 2012/04/29 Permalink
    Tags: , meetings, , , , ,   

    Abstract submitted to EuroEvoDevo 2012 

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    Germ cell development in non-spiralian lophotrochozoans: insights from a bryozoan and a brachiopod

    Bryozoa and Brachiopoda are two spiralian taxa that, unlike other spiralians, undergo non-spiral cleavage and have unique non-trochophore larvae. Previous morphological studies determined that no distinctive germline is formed during embryonic development and that germ cells first appear relatively late in larval life or after metamorphosis. These observations suggest that the specification of primordial germ cells occurs by late inductive signaling (epigenesis) rather than inheritance of maternal determinants (preformation). The molecular mechanisms involved in germ cell formation in bryozoans and brachiopods are currently unknown. We have therefore used RNASeq data to identify and then clone the conserved germline-specific genes vasa, nanos, and piwi from the bryozoan Membranipora membranacea and the brachiopod Terebratalia transversa. In situ hybridization shows that Mm-nanos transcripts are not detected in the blastomeres during early cleavage, but are localized posteriorly in the internal sac region of the late-gastrula stage and early cyphonautes larvae of M. membranacea. In addition, Mm-piwi2 mRNA is present in the cytoplasm of M. membranacea blastomeres and is broadly expressed in the larval tissues, except for the corona and apical organ. Our preliminary results suggest that the signaling related to the differentiation of bryozoan germ cells may be established earlier in ontogeny than previously thought, possibly during gastrulation. A thorough analysis of the expression patterns will provide clues for understanding the regulatory mechanisms of pluripotent and germ cell development in bryozoans and brachiopods and offer further insights about the developmental diversity of spiralians.

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