Molluscan engrailed expression, serial organization, and shell evolution

@article{Jacobs2000MolluscanEE,
  title={Molluscan engrailed expression, serial organization, and shell evolution},
  author={David K Jacobs and Charles Gregory Wray and Cathy J. Wedeen and Richard Kostriken and Robert DeSalle and Joseph L. Staton and Ruth D. Gates and David R. Lindberg},
  journal={Evolution \& Development},
  year={2000},
  volume={2}
}
SUMMARY Whether the serial features found in some molluscs are ancestral or derived is considered controversial. Here, in situ hybridization and antibody studies show iterated engrailed‐gene expression in transverse rows of ectodermal cells bounding plate field development and spicule formation in the chiton, Lepidochitona caverna, as well as in cells surrounding the valves and in the early development of the shell hinge in the clam, Transennella tantilla. Ectodermal expression of engrailed is… 

Engrailed in cephalopods: a key gene related to the emergence of morphological novelties

An engrailed cognate is identified in the squid Loligo, which provides new evidence that engrailing in molluscs is not restricted to a ‘shell function’ and has been recruited in the mollusc lineage for the emergence of morphological novelties in cephalopods.

Expression of segment polarity genes in brachiopods supports a non-segmental ancestral role of engrailed for bilaterians

Findings suggest that bilaterians might share an ancestral, non-segmental domain of engrailed expression during early embryogenesis, and suggest the role of “segmentation genes” in organisms that lack a segmented body.

The expression of an engrailed protein during embryonic shell formation of the tusk‐shell, Antalis entalis (Mollusca, Scaphopoda)

The single anlage of the scaphopod protoconch contradicts earlier hypotheses of a monophyletic taxon Diasoma (Scaphopoda + Bivalvia), which has been mainly based on the assumption of a primarily bilobed shell in both taxa.

Ancestral Patterning of Tergite Formation in a Centipede Suggests Derived Mode of Trunk Segmentation in Trilobites

The centipede Strigamia maritima is utilized to study the correspondence between the expression of engrailed during late embryonic to postembryonic stages, and the development of the dorsal exoskeletal plates, and it is suggested that this association represents a symplesiomorphy within Euarthropoda.

Dynamic expression of ancient and novel molluscan shell genes during ecological transitions

These expression data reflect the regulatory complexity that underlies molluscan shell construction from larval stages to adulthood, and serves to highlight the different ecological demands placed on each stage.

Expression of Patella vulgata orthologs of engrailed and dpp-BMP2/4 in adjacent domains during molluscan shell development suggests a conserved compartment boundary mechanism.

It is concluded that engrailed and dpp are most likely involved in setting up a compartment boundary between these cells, very similar to the situation in, for example, the developing wing imaginal disc in Drosophila.

Possible co-option of engrailed during brachiopod and mollusc shell development

The results suggest that en and mpox are possibly involved in brachiopod embryonic shell development and the evolutionary developmental origin of lophotrochozoan biomineralization through independent gene co-option is discussed.

MICROMORPHOLOGY AND GENE EXPRESSION IN MUSCLE AND SHELL DEVELOPMENT OF THE MOLLUSCA

This work comprises detailed studies by scanning electron microscope, fluorescence staining combined with confocal laser scanning microscopy, as well as serial sectioning analyses and reconstruction techniques to elucidate the development of the larval and adult musculature of several basal representatives of the molluscan classes Polyplacophora, Bivalvia, Scaphopoda, and Gastropoda.
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