Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, Department of Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, Department of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, Department of Neurology, Boston University School of Medicine and Veterans Administration Boston Healthcare System, Boston, Massachusetts 02130, Department of Anatomy & Neurobiology, Boston University School of Medicine, Boston, Massachusetts 02118, Department of Neurology, University of California Los Angeles, Los Angeles, California 90095, Department of Neuroscience, University of Connecticut Medical School, Farmington, Connecticut 06030, and University of Texas Southwestern Medical Center, Dallas, Texas 75390. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
(Impact Factor: 6.34).
01/2013; 33(5):1927-1939. DOI: 10.1523/JNEUROSCI.2080-12.2013
We have previously shown that myelin abnormalities characterize the normal aging process of the brain and that an age-associated reduction in Klotho is conserved across species. Predominantly generated in brain and kidney, Klotho overexpression extends life span, whereas loss of Klotho accelerates the development of aging-like phenotypes. Although the function of Klotho in brain is unknown, loss of Klotho expression leads to cognitive deficits. We found significant effects of Klotho on oligodendrocyte functions, including induced maturation of rat primary oligodendrocytic progenitor cells (OPCs) in vitro and myelination. Phosphoprotein analysis indicated that Klotho's downstream effects involve Akt and ERK signal pathways. Klotho increased OPC maturation, and inhibition of Akt or ERK function blocked this effect on OPCs. In vivo studies of Klotho knock-out mice and control littermates revealed that knock-out mice have a significant reduction in major myelin protein and gene expression. By immunohistochemistry, the number of total and mature oligodendrocytes was significantly lower in Klotho knock-out mice. Strikingly, at the ultrastructural level, Klotho knock-out mice exhibited significantly impaired myelination of the optic nerve and corpus callosum. These mice also displayed severe abnormalities at the nodes of Ranvier. To decipher the mechanisms by which Klotho affects oligodendrocytes, we used luciferase pathway reporters to identify the transcription factors involved. Together, these studies provide novel evidence for Klotho as a key player in myelin biology, which may thus be a useful therapeutic target in efforts to protect brain myelin against age-dependent changes and promote repair in multiple sclerosis.