PresentationNeuroscience

Wnt-Induced Calcium Signaling Mediates Axon Growth and Guidance in the Developing Corpus Callosum

Science Signaling  10 Jan 2012:
Vol. 5, Issue 206, pp. pt1
DOI: 10.1126/scisignal.2002523

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A presentation from Neuroscience 2009, the Society for Neuroscience annual meeting, in Chicago, IL, 17 to 21 October 2009.

Abstract

Wnt5a gradients guide callosal axons by repulsion through Ryk receptors in vivo. We recently found that Wnt5a repels cortical axons and promotes axon outgrowth through calcium signaling in vitro. Here, using cortical slices, we show that Wnt5a signals through Ryk to guide and promote outgrowth of callosal axons after they cross the midline. Calcium transient frequencies in callosal growth cones positively correlate with axon outgrowth rates in vitro. In cortical slices, calcium release through inositol 1,4,5-trisphosphate (IP3) receptors and calcium entry through transientreceptor potential channels modulate axon growth and guidance. Knocking down Ryk inhibits calcium signaling in cortical axons, reduces rates of axon outgrowth subsequent to midline crossing, and causes axon guidance defects. Calcium- and calmodulin-dependent protein kinase II (CaMKII) is required downstream of Wnt-induced calcium signaling for postcrossing callosal axon growth and guidance. Taken together, these results suggest that growth and guidance of postcrossing callosal axons by Wnt-Ryk-calcium signaling involves axon repulsion through CaMKII.

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