First published online April 25, 2008
Development 135, 105e (2008)
© The Company of Biologists Limited
Crossing a line in axon guidance
In bilaterally symmetric animals, the central nervous system is divided
into two halves, and, during development, the proper formation of neuronal
circuitry sometimes requires that axons choose whether they should project to
the same side (ipsilateral) or to the opposite side (contralateral) of the
embryonic midline. Many axon guidance molecules contribute to this decision,
but little is known of their transcriptional regulation. Now in their study of
the optic chiasm - the neuronal structure required for binocular vision -
Eloísa Herrera and colleagues
(p. 1833) report, for
the first time, a link between a transcription factor (Zic2) and an axon
guidance molecule (EphB1) in controlling axonal laterality. By manipulating
Zic2 expression in EphB1-expressing and EphB1-null
mice, they show that Zic2 is sufficient to switch the contralateral trajectory
of retinal axons to an ipsilateral one. Zic2 can do this via both
EphB1-dependent and -independent mechanisms. From their findings, the authors
propose that transcription factors can directly and sequentially activate
different guidance receptors throughout an axon's journey.

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Related articles in Development:
- Zic2 promotes axonal divergence at the optic chiasm midline by EphB1-dependent and -independent mechanisms
- Cristina García-Frigola, Maria Isabel Carreres, Celia Vegar, Carol Mason, and Eloísa Herrera
Development 2008 135: 1833-1841.
[Abstract]
[Full Text]