Filament-forming cytoskeletal GTPase. Required for normal organization of the actin cytoskeleton. Plays a role in the biogenesis of polarized columnar-shaped epithelium. Required for the progression through mitosis through regulation of chromosome congression. During anaphase, may be required for chromosome segregation and spindle elongation. Plays a role in ciliogenesis and collective cell movements including convergent extension during gastrulation. In cilia, required for the integrity of the diffusion barrier at the base of the primary cilium that prevents diffusion of transmembrane proteins between the cilia and plasma membranes. Controls cell shape and not polarization of cells during convergent extension (By similarity). Septins polymerize into heterooligomeric protein complexes that form filaments, and associate with cellular membranes, actin filaments and microtubules. GTPase activity is required for filament formation. Can form heterooligomers with other family members and form filaments. Interacts with wdpcp (By similarity). Localizes at the base of the cilia near the morphological distinction between the cilia and plasma membranes. Belongs to the TRAFAC class TrmE-Era-EngA-EngB-Septin-like GTPase superfamily. Septin GTPase family.