Arthropod-like expression patterns of engrailed and wingless in the annelid Platynereis dumerilii suggest a role in segment formation.
The origin of animal segmentation, the periodic repetition of anatomical structures along the anteroposterior axis, is a long-standing issue that has been recently revived by comparative developmental genetics. In particular, a similar extensive morphological segmentation (or metamerism) is commonly recognized in annelids and arthropods. Mostly based on this supposedly homologous segmentation, these phyla have been united for a long time into the clade Articulata. However, recent phylogenetic analysis dismissed the Articulata and thus challenged the segmentation homology hypothesis. Here, we report the expression patterns of genes orthologous to the arthropod segmentation genes engrailed and wingless in the annelid Platynereis dumerilii. In Platynereis, engrailed and wingless are expressed in continuous ectodermal stripes on either side of the segmental boundary before, during, and after its formation; this expression pattern suggests that these genes are involved in segment formation. The striking similarities of engrailed and wingless expressions in Platynereis and arthropods may be due to evolutionary convergence or common heritage. In agreement with similarities in segment ontogeny and morphological organization in arthropods and annelids, we interpret our results as molecular evidence of a segmented ancestor of protostomes.
Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, UPR 2167, 1 avenue de la terrasse, 91190 Gif sur Yvette, France.
Benjamin
B
Prud'homme
Renaud
R
de Rosa
Detlev
D
Arendt
Jean-François
JF
Julien
Rafael
R
Pajaziti
Adriaan W C
AW
Dorresteijn
André
A
Adoutte
Joachim
J
Wittbrodt
Guillaume
G
Balavoine
D000818:Animals; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics*; D004475:Ectoderm / Q000502:physiology; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology*; D007814:Larva / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D011077:Polychaeta / Q000235:genetics* / Q000502:physiology*; D012038:Regeneration / Q000502:physiology; D016415:Sequence Alignment; D014157:Transcription Factors
D018398:Homeodomain Proteins; D014157:Transcription Factors; C106185:engrailed homeobox proteins