Cilia-driven leftward flow determines laterality in Xenopus.
Curr Biol
; 17(1): 60-6, 2007 Jan 09.
Article
em En
| MEDLINE
| ID: mdl-17208188
ABSTRACT
Determination of the vertebrate left-right body axis during embryogenesis results in asymmetric development and placement of most inner organs. Although the asymmetric Nodal cascade is conserved in all vertebrates, the mechanism of symmetry breakage has remained controversial. In mammalian and fish embryos, a cilia-driven leftward flow of extracellular fluid is required for initiation of the Nodal cascade. This flow is localized at the posterior notochord ("node") and Kupffer's vesicle, respectively. In frog and chick embryos, however, molecular asymmetries are required earlier, from cleavage stages through gastrulation. The validity of a cilia-based mechanism for all vertebrates therefore has been questioned. Here we show that a cilia-driven leftward flow precedes asymmetric nodal expression in the frog Xenopus. Motile monocilia emerged on the gastrocoel roof plate during neurulation and lengthened and polarized from an initially central position to the posterior pole of cells. Concomitantly, a robust leftward fluid flow developed from stage 15 onward, significantly before asymmetric nodal transcription started in the left-lateral-plate mesoderm at stage 19. Injection of 1.5% methylcellulose into the archenteron prevented leftward flow and resulted in laterality defects, demonstrating that the flow itself was required for asymmetric gene expression and organ placement.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Xenopus
/
Cílios
/
Desenvolvimento Embrionário
/
Gástrula
Limite:
Animals
Idioma:
En
Revista:
Curr Biol
Assunto da revista:
BIOLOGIA
Ano de publicação:
2007
Tipo de documento:
Article
País de afiliação:
Alemanha