Filament-forming cytoskeletal GTPase (Probable). Involved in the migration of cortical neurons and the formation of neuron leading processes during embryonic development (PubMed:20181826). Plays a role in sperm head formation during spermiogenesis, potentially via facilitating localization of ACTN4 to cell filaments (By similarity). 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 (By similarity). Interacts (via C-terminus) with SEPTIN4 (PubMed:20181826). Colocalizes with actin stress fibers (By similarity). Expressed in the perinuclear rim and manchette structure in early elongating spermatids during spermiogenesis (PubMed:33228246). Expressed in the testis and brain including the cerebrum, hippocampus and cerebellum (at protein level). Expressed in the cerebral cortex from 15.5 dpc reaching maximum expression at 17.5 dpc, expression remains robust until P30 (PubMed:20181826). Expressed in early elongating spermatids during spermiogenesis (PubMed:33228246). Belongs to the TRAFAC class TrmE-Era-EngA-EngB-Septin-like GTPase superfamily. Septin GTPase family. Intron retention.