Fig 2. Drawing of the various classes and structures of intermediate filament proteins. The central rod is composed of 4 -helical sub-domains separated by nonhelical linkers. The central rods are remarkably similar among the classes, whereas the heads and tails demonstrate considerable variability and partly contribute to tissue specificity. Most of the described mutations in Alexander disease occur in the 1A and 2A subdomains of the rod. Modified from ref. 22. With permission.