Subcellular localization and function of mouse radial spoke protein 3 in mammalian cells and central nervous system

Radial spoke protein 3 (RSP3) was first identified in Chlamydomonas as a component of the radial spoke. The mammalian homologue of the Chlamydomonas RSP3 gene is mainly expressed in testis and developing central nervous system (CNS). However, the subcellular localization and function of mammalian RSP3 in the developing brain and mammalian cells remain poorly understood. Here we show that the mouse RSP3 accumulates at the perinuclear region of Chinese hamster ovary (CHO) and 293T cells. Detailed analysis shows that the mouse RSP3 is not co-localized with the endoplasmic reticulum or Golgi apparatus markers in CHO cells. Using in utero electroporation, we found that over-expression of mammalian RSP3 increases the percentage of neurons reaching the upper cortical plate. In vivo analysis shows that the mouse RSP3 mainly accumulates in the proximal cytoplasmic dilation of the leading process of the migrating cortical neurons. Furthermore, we find that the mammalian RSP3 concentrates in the ependymal cilia as a component of the cilia. Thus, our data provide the first evidence for the subcellular localization and function of mammalian RSP3 in mammalian cells and developing CNS.