The mouse radial spoke protein 3 is a nucleocytoplasmic shuttling protein that promotes neurogenesis

Radial spoke protein 3 (RSP3) was first identified in Chlamydomonas as a component of radial spoke, which is important for flagellar motility. The mammalian homolog of the Chlamydomonas RSP3 protein is found to be a mammalian protein kinase A-anchoring protein that binds ERK1/2. Here we show that mouse RSP3 is a nucleocytoplasmic shuttling protein. The full-length RSP3–EGFP fusion protein is mainly located in the cytoplasm of Chinese hamster ovary cells. However, by using deletion mutants of RSP3, we identified two nuclear localization signals and a nuclear export signal in RSP3. Moreover, using in utero electroporation, we found that overexpression of RSP3 in the developing cerebral cortex promotes neurogenesis. The layer II/III of the neocortex was much thicker in the RSP3-transfected region than that of the untransfected region in the neocortex. We also show that RSP3 is specifically located in the primary cilia of the radial glial cells, where it acts as a signaling mediator that regulates neurogenesis. Thus, our results suggest that RSP3 is a nucleocytoplasmic shuttling protein and plays an essential role in neurogenesis.