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Dis Model Mech January 1, 2013; 6 (1): 261-8.

Serotonin has early, cilia-independent roles in Xenopus left-right patterning.

Consistent left-right (LR) patterning of the heart and viscera is a crucial part of normal embryogenesis. Because errors of laterality form a common class of birth defects, it is important to understand the molecular mechanisms and stage at which LR asymmetry is initiated. Frog embryos are a system uniquely suited to analysis of the mechanisms involved in orientation of the LR axis because of the many genetic and pharmacological tools available for use and the fate-map and accessibility of early blastomeres. Two major models exist for the origin of LR asymmetry and both implicate pre-nervous serotonergic signaling. In the first, the charged serotonin molecule is instructive for LR patterning; it is redistributed asymmetrically along the LR axis and signals intracellularly on the right side at cleavage stages. A second model suggests that serotonin is a permissive factor required to specify the dorsal region of the embryo containing chiral cilia that generate asymmetric fluid flow during neurulation, a much later process. We performed theory-neutral experiments designed to distinguish between these models. The results uniformly support a role for serotonin in the cleavage-stage embryo, long before the appearance of cilia, in ventral right blastomeres that do not contribute to the ciliated organ.

PubMed ID: 22899856
PMC ID: PMC3529356
Article link: Dis Model Mech
Grant support: [+]

Species referenced: Xenopus
Genes referenced: gal.2 gnao1 lefty nodal1 pitx2 rpsa tbx2

Article Images: [+] show captions
References [+] :
Adams, Early, H+-V-ATPase-dependent proton flux is necessary for consistent left-right patterning of non-mammalian vertebrates. 2006, Pubmed, Xenbase