Molluscan engrailed expression, serial organization, and shell evolution

  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},
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.


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.



Expression of engrailed proteins in arthropods, annelids, and chordates.

Radical alterations in the roles of homeobox genes during echinoderm evolution

The expression domains in echinoderms of three important developmental regulatory genes ( distal-less, engrailed and orthodenticle ), all of which encode transcription factors that contain a homeodomain are reported, demonstrating the evolutionary lability of regulatory genes that are widely viewed as conservative.

Sequence and embryonic expression of the amphioxus engrailed gene (AmphiEn): the metameric pattern of transcription resembles that of its segment-polarity homolog in Drosophila.

The segmental expression of AmphiEn in forming somites suggests that the functions of engrailed homologs in establishing and maintaining a metameric body plan may have arisen only once during animal evolution.

Expression of engrailed during segmentation in grasshopper and crayfish.

The A/P axis in echinoderm ontogeny and evolution: evidence from fossils and molecules

SUMMARY Even though echinoderms are members of the Bilateria, the location of their anterior/posterior axis has remained enigmatic. Here we propose a novel solution to the problem employing three

Engrailed Expression during Development of a Lamprey, Lampetra japonica: A Possible Clue to Homologies between Agnathan and Gnathostome Muscles of the Mandibular Arch

It is suggested that the velothyroideus muscles of lampreys may be homologous to certain jaw muscles of teleosts–namely, the levator arcus palatini and the dilator operculi, which express en continuously while differentiating from the myogenic mesoderm into identifiable muscle types.

Shell differentiation and engrailed expression in the Ilyanassa embryo

In situ hybridization and immunocytochemistry is used to study the expression of the engrailed-related gene, Ily-en in embryos of the marine mud snail Ilyanassa obsoleta to find that Ily- en is only expressed in shell gland cells.

Homologues of the engrailed gene from five molluscan classes

The first molluscs ‐ small animals

Based on recent fine‐structure work the evolutionary history of the Mollusca is reconsidered and some alternative ideas are presented to explain the origin of the mantle cavity, ctenidia, coelom, and pecularities of the alimentary tract.

Morphogenesis: The Analysis of Molluscan Development