septin

Septins are a family of GTP-binding cytoskeletal proteins that assemble into hetero-oligomeric complexes and polymerize into filaments, rings, and girdles that organize cellular membranes. They are conserved across fungi and animals, and in humans there are multiple SEPT genes (for example SEPT2, SEPT7, SEPT9) that encode proteins with a central GTPase domain flanked by variable N- and C-terminal regions often containing coiled-coil motifs. GTP binding and hydrolysis regulate their assembly and disassembly.

Septins form ordered cytoskeletal structures that can act as scaffolds and diffusion barriers, helping to compartmentalize membranes and coordinate cytoskeletal dynamics. In yeast they assemble at the mother–bud neck to form a collar that constrains the diffusion of membrane proteins during division. In animal cells they localize to the cleavage furrow during cytokinesis and to the base of cilia, where they contribute to membrane organization and vesicle trafficking. Septins interact with actin filaments, microtubules and with kinases and motor proteins, integrating signals controlling cell shape, polarity, and division.

Functions and roles include cytokinesis, cell polarity, vesicle trafficking, ciliogenesis, and organelle morphology. They also participate in the formation of diffusion barriers that segregate membrane domains during cell division and differentiation.

Clinical and research notes: Dysregulation or mutations in septin genes have been associated with human disease in various contexts, including hereditary neuralgic amyotrophy linked to SEPT9 and connections to cancer and ciliopathies in some studies. In model organisms, septin disruption often leads to defects in cytokinesis and tissue development, underscoring their essential roles in cell biology.

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