A myelin protein fraction extracted with thioethanol

Epigenetic mechanisms facilitating oligodendrocyte development, maturation, and aging

The process of oligodendrocyte differentiation is regulated by a dynamic interaction between a genetic and an epigenetic program. Recent studies, addressing nucleosomal histone modifications have considerably increased our knowledge regarding epigenetic regulation of gene expression during oligodendrocyte development and aging. These results have generated new hypotheses regarding the mechanisms underlying the decreased efficiency of endogenous remyelination in response to demyelinating injuries with increasing age. In this review, we present an overview of the epigenetic mechanisms regulating gene expression at specific stages of oligodendrocyte differentiation and maturation as well as the changes that occur with aging.

Evaluating epigenetic landmarks in the brain of multiple sclerosis patients: a contribution to the current debate on disease pathogenesis

The evidence suggesting a role of epigenetics in the definition of complex trait diseases is rapidly increasing. The gender prevalence of multiple sclerosis, the low level concordance in homozygous twins and the linkage to several genetic loci, suggest an epigenetic component to the definition of this demyelinating disorder. While the immune etio-pathogenetic mechanism of disease progression has been well characterized, still relatively little is known about the initial events contributing to onset and progression of the demyelinating lesion. This article addresses the challenging question of whether loss of the mechanisms of epigenetic regulation of gene expression in the myelinating cells may contribute to the pathogenesis of multiple sclerosis, by affecting the repair process and by modulating the levels of enzymes involved in neo-epitope formation. The role of altered post-translational modifications of nucleosomal histones and DNA methylation in white matter oligodendroglial cells are presented in terms of pathogenetic concepts and the relevance to therapeutic intervention is then discussed.

Tentative identification of a second central nervous system myelin membrane autoantigen (M2) by a biochemical comparison with the basic protein (BP)

Two central nervous system myelin autoantigens, M2 and basic protein (BP), were examined, using complement-fixing antibodies against each autoantigen as markers on myelin. M2 activity was very labile and very insoluble, PB activity was very resistant. Trypsin reduced both activities an this reduction was greater after phospholipase treatment. Both activities were slightly solubilized in 8 M urea. It is known that BP is not present on the surface of myelin and is considered a peripheral membrane protein. M2 appears to be a surface and integral membrane protein, and as such resembles Folch Pi proteolipid protein. The relationship between M2 and BP requires further study.

A comparison of composition and fluidity of multiple sclerosis and normal myelin

Myelin was isolated from normal-appearing white matter from the brains of 11 multiple sclerosis (MS) patients, 11 normal individuals, and 1 patient with subacute sclerosing panencephalitis (SSPE). Ratios of protein, cholesterol, and phospholipid content, total fatty acid content, and total amino acid content were determined. The lipid bilayer fluidity of the myelin was measured using electron spin resonance and fluorescence polarization spectroscopy. The protein-to-phospholipid ratio was higher than normal, the cholesterol-to-protein ratio was lower than normal while the cholesterol-to-phospholipid ratio was normal in MS myelin. This suggested a relative increase of protein to lipid content in MS myelin. Of the fatty acid content of a total lipid extract, MS myelin had relatively more 16:0, less 18:3, and less 22:3, 24:1 than normal. The total amino acid content of MS myelin was altered in a way which suggested a decreased percentage of basic protein and an increased percentage of proteolipids. SSPE myelin had similar changes in amino acid content but not in protein-to-cholesterol or -phospholipid ratios or fatty acid content as MS myelin. There was no significant difference in myelin fluidity, however, between MS and normal myelin using fatty acid spin labels or fluorescent probes. A correlation was found between the fluidity and the cholesterol-to-phospholipid ratio but the MS and normal samples varied over a similar range. Although these alterations in lipid and protein composition had no effect on fluidity, they may nevertheless have serious consequences for myelin structure.