Attractive and permissive activities of semaphorin 5A toward dorsal root ganglion axons in higher vertebrate embryos

Abstract

Elongation of the efferent fibers of dorsal root ganglion (DRG) neurons toward their peripheral targets occurs during development. Attractive or permissive systems may be involved in this elongation. However, the molecular mechanisms that control it are largely unknown. Here we show that class 5 semaphorin Sema5A had attractive/permissive effects on DRG axons. In mouse embryos, Sema5A was expressed in and around the path of DRG efferent fibers, and cell aggregates secreting Sema5A attracted DRG axons in vitro. We also found that ectopic Sema5A expression in the spinal cord attracted DRG axons. Together, these findings suggest that Sema5A functions as an attractant to elongate DRG fibers and contributes to the formation of the early sensory network.

Keywords:

• axonal guidance
• attractant
• chick embryo
• dorsal root ganglion
• mouse embryo
• semaphorin

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Funding

This work was supported by grant no. 24590256 from the program Grants-in-Aid for Scientific Research of the MEXT, Japan to T.M., and by a grant from the Naito Foundation, Japan to T.M.

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