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A Developmental Switch of Axon Targeting in the Continuously Regenerating Mouse Olfactory System

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Science  11 Apr 2014:
Vol. 344, Issue 6180, pp. 194-197
DOI: 10.1126/science.1248805

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Axon Routing in the Olfactory System

The olfactory system of mice entails a developmental program that wires neurons expressing similar olfactory receptors into glomeruli together. Although the adult olfactory system continues to produce and incorporate new neurons, it cannot withstand severe damage (see the Perspective by Cheetham and Belluscio). Ma et al. (p. 194) and Tsai and Barnea (p. 197) examined the difference in responses between early development and adulthood. Manipulating the expression of an odorant receptor or the activity of the olfactory neurons altered olfactory neuron axonal pathfinding. The results suggest that the guidance systems used differ between early development and adulthood: Early axons find their own way, but later-in-life axons can only follow existing pathways.

Abstract

The mammalian olfactory system has the natural capacity to regenerate throughout the animal’s life span. Despite constant neurogenesis, olfactory sensory neurons project to precise, stereotypical positions in the brain. Here, we identify a critical period of olfactory sensory axon targeting during postnatal development in mouse. Perturbing axon projection beyond postnatal day 7 permanently disrupts targeting specificity of the sensory neurons. In addition, we find that the establishment of the convergence map requires perinatal sensory neurons. Late-born neurons appear to connect with prospective glomeruli based on homotypic interactions among neurons expressing the same odorant receptor. Our results reveal a developmental switch in axon guidance and a mechanism of circuit integration of adult-born neurons.

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