Diagram of GFAP mutations in relation to protein domains and clinical classification Location of Alexander disease-associated mutations in GFAP in relation to protein domain structure of intermediate filaments.  The boxes indicate the four a-helical sub-domains within the central rod domain, separated by non-helical linkers. Each symbol represents the standard single letter code for the mutated amino acid for an individual patient or family (in the case of familial patients or identical twins). Multiple independent occurrences of a mutation are indicated by the number of symbols.  Only one symbol is shown for twins or familial patients.  A boxed symbol indicates that this mutation was inherited and found in multiple familial members.  A circle around a mutation indicates that the patient was asymptomatic at the time of diagnosis.  Symbols are color coded for clinical category based on age of onset (infantile, juvenile, adult). Mutations that are considered “disease-causing” are on the right – variants that are presently considered innocuous and not responsible for disease are shown on the left.  The diagram includes all patients who have been published as of the date shown, as well as some unpublished patients.