Filament-forming cytoskeletal GTPase. Forms a filamentous structure with SEPTIN12, SEPTIN6, SEPTIN2 and probably SEPTIN4 at the sperm annulus which is required for the structural integrity and motility of the sperm tail during postmeiotic differentiation (By similarity). Required for normal organization of the actin cytoskeleton. Plays a role in the biogenesis of polarized columnar-shaped epithelium by maintaining polyglutamylated microtubules, thus facilitating efficient vesicle transport, and by impeding MAP4 binding to tubulin. Required for the progression through mitosis. Forms a scaffold at the midplane of the mitotic splindle required to maintain CENPE localization at kinetochores and consequently chromosome congression. During anaphase, may be required for chromosome segregation and spindle elongation. Plays a role in ciliogenesis and collective cell movements. 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: probably acts by regulating the assembly of the tectonic-like complex (also named B9 complex) by localizing TMEM231 protein (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. Filaments are assembled from asymmetrical heterotrimers, composed of SEPTIN2, SEPTIN6 and SEPTIN7 that associate head-to-head to form a hexameric unit (By similarity). Interaction between SEPTIN2 and SEPTIN7 seems indirect. Interacts with SEPTIN5 (By similarity). Interaction with SEPTIN4 not detected (By similarity). Interacts with SEPTIN9. Component of a septin core octomeric complex consisting of SEPTIN12, SEPTIN7, SEPTIN6 and SEPTIN2 or SEPTIN4 in the order 12-7-6-2-2-6-7-12 or 12-7-6-4-4-6-7-12 and located in the sperm annulus. Interacts with MAP4. Interacts with DZIP1L (By similarity). Accumulates near the contractile ring from anaphase through telophase, and finally condenses into the midbody. In interphase and postmitotic cells, localized to fibrous or granular structures, depending on the growth state of the cell. Localizes at the base of the cilia near the morphological distinction between the cilia and plasma membranes. Found in the sperm annulus (By similarity). Belongs to the TRAFAC class TrmE-Era-EngA-EngB-Septin-like GTPase superfamily. Septin GTPase family.