First published online April 10, 2009
Development 136, 905e (2009)
© The Company of Biologists Limited
Nodal fishes out brain asymmetries
Left-right asymmetries in the nervous system are common among animals, and
their importance is obvious in phenomena such as human language processing,
which occurs mainly in the brain's left hemisphere. Now, Myriam
Roussigné and colleagues reveal that Nodal signalling regulates
asymmetric neurogenesis in zebrafish
(p. 1549). The
elaboration of asymmetries between the bilateral habenular nuclei, a group of
nuclei located in the diencephalon, largely depends on the parapineal, a
nucleus that sits on the brain's left side owing to unilateral, left-sided
Nodal signalling. Here, the authors identify the chemokine receptor gene
cxcr4b as an early marker of habenular neurons. They show that
neurogenesis begins earlier in the left than in the right habenula, and that
this asymmetry is independent of the parapineal. Disrupting the asymmetric
activity of Nodal, however, leads to the symmetric onset of habenular
neurogenesis. These results indicate that asymmetric Nodal signalling acts not
just to bias the laterality of the parapineal but also has an early role in
asymmetric habenular neurogenesis.

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Related articles in Development:
- Nodal signalling imposes left-right asymmetry upon neurogenesis in the habenular nuclei
- Myriam Roussigné, Isaac H. Bianco, Stephen W. Wilson, and Patrick Blader
Development 2009 136: 1549-1557.
[Abstract]
[Full Text]