Filament-forming cytoskeletal GTPase (Probable). Involved in the migration of cortical neurons and the formation of neuron leading processes during embryonic development (By similarity). Plays a role in sperm head formation during spermiogenesis, potentially via facilitating localization of ACTN4 to cell filaments (PubMed:33228246). Septins polymerize into heterooligomeric protein complexes that form filaments, and can associate with cellular membranes, actin filaments and microtubules. GTPase activity is required for filament formation. Interacts with ACTN4 (PubMed:33228246). Interacts with SEPTIN9 (PubMed:17922164). Interacts (via C-terminus) with SEPTIN4 (By similarity). Colocalizes with actin stress fibers (PubMed:17922164). Expressed in the perinuclear rim and manchette structure in early elongating spermatids during spermiogenesis (By similarity). Testis-specific (at protein level). Expressed in all cell stages of spermatogenesis. Belongs to the TRAFAC class TrmE-Era-EngA-EngB-Septin-like GTPase superfamily. Septin GTPase family.