Developmental localization of semaphorin H messenger RNA acting as a collapsing factor on sensory axons in the mouse brain

Semaphorins/collapsins, a family of genes with a semaphorin domain conserve d from insects through to mammals, are believed to be involved in axon guid ance during neuronal development. We report the expression patterns of mous e semaphorin messenger RNAs. Among secreted semaphorins, mouse semaphorin H is structurally most similar to semaphorin III/D, the first semaphorin ide ntified as a collapsing factor for sensory axons. However, its expression p atterns apparently differ from those of semaphorin III/D. The messenger RNA s are distributed in the brain widely but unevenly during development, in p articular, in the main olfactory bulb, hippocampus and pontine nucleus. In the trunk, the expression level is high in mesodermal tissues surrounding t he dorsal root ganglia, while it is low in the spinal cord. Moreover, we ex amined whether this molecule has activity to collapse growth cones of senso ry neurons, as well as semaphorin III/D. Mouse semaphorin H collapsed growt h cones of sensory neurons of the dorsal root ganglion in a dose-dependent manner, and anti-neuropilin antibodies inhibited this activity. Taken together, these results suggest that mouse semaphorin H can function as a chemorepellent to guide sensory peripheral nerves, most likely via neu ropilin as a receptor. (C) 1999 IBRO. Published by Elsevier Science Ltd.