Rab34 small GTPase is required for Hedgehog signaling and an early step of ciliary vesicle formation in the mouse

Abstract

The primary cilium is a microtubule-based organelle that protrudes from the cell surface and plays essential roles in embryonic development. Ciliogenesis begins with the successive fusion of preciliary vesicles to form ciliary vesicles, which then dock onto the distal end of the mother centriole. Rab proteins have been linked to cilia formation in cultured cells, but not yet in vivo. In the present study, we demonstrate that endocytic recycling protein Rab34 localizes to cilia and that its mutation results in significant decrease in ciliogenesis in both cultured cells and mice. Rab34 is required for the successive fusion of preciliary vesicles to generate ciliary vesicles and the migration of the mother centriole from perinuclear region to plasma membrane. We also show that Rab34 mutant mice exhibit polydactyly and cleft lip and palate. These phenotypes are consistent with the observations that unciliated Rab34 mutant cells fail to respond to Hedgehog signaling and that Gli3 processing to generate a repressor is reduced in Rab34 mutant embryos. Therefore, Rab34 is required for an early step of ciliary vesicle formation and Hh signaling in vivo.