Schematic model of lamin polymers. Lamin dimers form from monomers that associate in a parallel, head-to-head manner, forming a coiled coil though the central α-helical domain. Lamin polymers then assemble by association of dimers in a polar head-to-tail manner through a staggered 2 to 4 nm overlap of the highly conserved amino- and carboxy-terminal rod domain ends. Protofilaments are finally produced through anti-parallel association of two lamin polymers. Between three and four protofilaments associate laterally to form an intermediate filament about 10 nm in diameter.