This work was supported by Alexander disease research grants from the Intractable Disease Research Grants, from the Ministry of Health, Labour and Welfare of the government of Japan. We are very grateful to Dr. Merle Ruberg for critical reading of this manuscript. Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.