Research ArticleNeuroscience

Local Application of Neurotrophins Specifies Axons Through Inositol 1,4,5-Trisphosphate, Calcium, and Ca2+/Calmodulin–Dependent Protein Kinases

Science Signaling  15 Nov 2011:
Vol. 4, Issue 199, pp. ra76
DOI: 10.1126/scisignal.2002011

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Trking a Calcium Signal to Axon Specification

Neurons are polar cells with structurally and functionally distinct processes that are specialized to receive information (the dendrites) or to pass it along to other cells (the axon). Nakamuta et al. investigated the extracellular and intracellular signals involved in axon specification—the process whereby one immature neurite is “chosen” to become an axon, whereas the others become dendrites—a process that occurs in vitro in the absence of directional cues. Blocking neurotrophin signaling through Trk receptors inhibited the loss of neurite symmetry in cultured hippocampal neurons, suggesting that the autocrine or paracrine release of neurotrophins was crucial for axonal specification. Local application of neurotrophin to a given neurite induced axon specification in that neurite, enabling the authors to determine that calcium signaling was crucial to axonal specification in response to the neurotrophin NT-3 in vitro. Moreover, they used an electroporation system to confirm a role for neurotrophin and calcium signaling in axonal specification of cortical neurons in vivo.