Left-right asymmetry in the sea urchin embryo is regulated by nodal signaling on the right side.
The asymmetric positioning of internal organs on the left or right side of the body is highly conserved in vertebrates and relies on a Nodal signaling pathway acting on the left side of the embryo. Whether the same pathway also regulates left-right asymmetry in invertebrates and what is the evolutionary origin of the mechanisms controlling left-right determination are not known. Here, we show that nodal regulates left-right asymmetry in the sea urchin but that, intriguingly, its expression is reversed compared to vertebrates. Nodal signals emitted from the right side of the larva prevent the right coelomic pouch from forming the imaginal rudiment. Inhibition of Nodal signaling after gastrulation causes formation of an ectopic rudiment on the right side, leading to twinned urchins after metamorphosis. In contrast, ectopic activation of the pathway prevents formation of the rudiment. Our results show that the mechanisms responsible for left-right determination are conserved within basal deuterostomes.
UMR 7009 CNRS, Université de Paris VI, Biologie du Développement, Observatoire Oceanologique, 06230 Villefranche-sur-Mer, France.
Véronique
V
Duboc
Eric
E
Röttinger
François
F
Lapraz
Lydia
L
Besnardeau
Thierry
T
Lepage
D028341:Activins / Q000378:metabolism; D000818:Animals; D019521:Body Patterning; D004475:Ectoderm / Q000502:physiology; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism; D005775:Gastrula / Q000502:physiology; D018398:Homeodomain Proteins / Q000378:metabolism; D055458:Left-Right Determination Factors; D008969:Molecular Sequence Data; D055457:Nodal Protein; D012617:Sea Urchins / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000502:physiology*; D000097577:Homeobox Protein PITX2
D028341:Activins; D018398:Homeodomain Proteins; D055458:Left-Right Determination Factors; D055457:Nodal Protein; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D000097577:Homeobox Protein PITX2