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). {ECO:0000250|UniProtKB:Q9DA97, ECO:0000269|PubMed:33228246, ECO:0000305}. This is the function of SEPTIN14 (septin 14, ENSG00000154997).