Mouse semaphorin H inhibits neurite outgrowth from sensory neurons.

Mouse semaphorin H (M-semaH) was structurally similar to semaphorin III/D, a mammalian homologue of collapsin 1 which was identified as a collapsing factor for sensory nerves. In this study we investigated the expression patterns of M-semaH mRNA and the protein binding sites in the trunk of mouse embryos. M-semaH mRNA was expressed in the mesenchymal tissues surrounding each dorsal root ganglia. These tissues include the caudal sclerotome and perinotochordal mesenchyme, which were thought to express factors repulsive to axons. M-semaH binding was detected on the spinal nerves. We further investigated, using in vitro co-culture assay, whether M-semaH acted as a chemorepulsive molecule on sensory axons. The results suggested that M-semaH was a candidate for a chemorepellent expressed in the mesenchyme surrounding the sensory ganglia, which is involved in the axonal guidance mechanism of sensory nerves in the trunk.