First published online September 5, 2008
Development 135, 1902e (2008)
© The Company of Biologists Limited
Calcium asymmetry signals left from right
In mouse embryos, the establishment of left-right (LR) asymmetry, which
initiates the proper positioning of the internal organs, requires
intracellular calcium (Cai2+) enrichment along the left
side of the node. But does this mechanism also establish laterality in other
vertebrates? On p.
3271, Susan Smith and colleagues report that chick embryos also use a
left-side enriched Cai2+ asymmetry to establish
laterality. They show that Cai2+ is enriched along the
front edge of Hensen's node (the chick's organizer) by the definitive
primitive streak stage. Subsequent left-side enrichment of
Cai2+ requires the activity of ryanodine receptors
(intracellular calcium channels) and extracellular calcium, which suggests
that calcium-induced calcium release supplies the Cai2+.
Furthermore, the manipulation of Cai2+ across the node
randomizes heart laterality and disrupts asymmetric gene expression. Finally,
other established laterality mediators regulate LR identity by directly
affecting node Cai2+ concentrations, the authors report.
Thus, they suggest, Cai2+ asymmetry across the node may
be a conserved mechanism for establishing laterality among vertebrates,
despite differences in node architecture.

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Related articles in Development:
- A ryanodine receptor-dependent Cai2+ asymmetry at Hensen's node mediates avian lateral identity
- Ana Garic-Stankovic, Marcos Hernandez, George R. Flentke, Maija H. Zile, and Susan M. Smith
Development 2008 135: 3271-3280.
[Abstract]
[Full Text]