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Background Hippocampal demyelination, a common feature of postmortem multiple sclerosis (MS) brains, reduces neuronal gene expression and is a likely contributor to the memory impairment that is found in greater than 40% of individuals with (MS). How demyelination alters neuronal gene expression is unknown. Methods To explore if loss of hippocampal myelin alters expression of neuronal microRNAs (miRNA), we compared miRNA profiles from myelinated and demyelinated hippocampi from postmortem MS brains and performed validation studies. Findings A network-based interaction analysis depicts a correlation between increased neuronal miRNAs and decreased neuronal genes identified in our previous study. The neuronal miRNA miR-124, was increased in demyelinated MS hippocampi and targets mRNAs encoding 26 neuronal proteins that were decreased in demyelinated hippocampus, including the ionotrophic glutamate receptors, AMPA 2 and AMPA3. Hippocampal demyelination in mice also increased miR-124, reduced expression of AMPA receptors and decreased memory performance in water maze tests. Remyelination of the mouse hippocampus reversed these changes. Conclusion We establish here that myelin alters neuronal gene expression and function by modulating the levels of the neuronal miRNA miR-124. Inhibition of miR-124 in hippocampal neurons may provide a therapeutic approach to improve memory performance in MS patients.

Used in combination with immunomodulatory therapies, remyelinating therapies are a viable therapeutic approach for treating individuals with multiple sclerosis. Studies of postmortem MS brains identified greater remyelination in demyelinated cerebral cortex than in demyelinated brain white matter and implicated reactive astrocytes as an inhibitor of white matter remyelination. An animal model that recapitulates these phenotypes would benefit the development of remyelination therapeutics. We have used a modified cuprizone protocol that causes a consistent and robust demyelination of mouse white matter and cerebral cortex. Spontaneous remyelination occurred significantly faster in the cerebral cortex than in white matter and reactive astrocytes were more abundant in white matter lesions. Remyelination of white matter and cerebral cortex was therapeutically enhanced by daily injections of thyroid hormone triiodothronine (T3). In summary, we describe an in vivo demyelination/remyelination paradigm that can be powered to determine efficacy of therapies that enhance white matter and cortical remyelination.

Purpose-Human remyelination promoting IgM mAbs target oligodendrocytes (OLs) and function in animal models of multiple sclerosis (MS). However, their mechanism of action is unknown. This study seeks to identify the cellular mechanism of action of a recombinant human IgM on OL survival.Methods-Binding of rHIgM22 to the surface of rat OLs was studied by co-localization with various markers. RHIgM22-mediated effects on apoptotic signaling in OLs, differentiation markers and signaling molecules were detected by Western blotting and immunoprecipitation.Results-RHIgM22 co-localized with integrin β3 but not other integrin β-chains in OLs. Downstream of integrin β3 we identified Src family kinase (SFK) Lyn as a key player of rHIgM22-mediated actions in OLs. Lyn immunoprecipitated in a complex together with integrin αvβ3 and PDGFαR. Lyn expression was 9 fold up-regulated and Lyn activation was 3 fold higher in rHIgM22-treated OL cultures compared to controls. RHIgM22 inhibited apoptotic signaling by greater than 10 fold reduction of caspase-3 and capsase-9 cleavage and reduced by 4 fold expression of differentiation markers MBP and MOG in OLs. SFK inhibitors PP2 and SU6656 inhibited Lyn activity and restored caspase-cleavage in OLs. A human IgM that did not promote remyelination and medium were used as controls.Conclusions-rHIgM22 prevented apoptotic signaling and inhibited OL differentiation by Lyn implying that IgM-mediated remyelination is due to protection of OPC and OLs rather than promotion of OPC differentiation.

The high mobility group (HMG) proteins are important modulators of chromatin structure and gene transcription. Overexpression of HMGA1 proteins in vivo induces neoplastic transformation and promotes a highly metastatic cellular phenotype. This study focuses on characterization of HMGA1a in vivo posttranslational modification (PTM) patterns found in a nonmetastatic and two metastatic lines of MCF-7 human breast cancer cells of differing tumorigenic potential. PTM types and the amino acids on which they occur were identified by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. Mass analysis was restricted to MALDI peaks having less than +/-150 parts per million (ppm) error, thereby holding our analysis to a more stringent criterion than previously published work with the HMG proteins. Validation of MALDI-TOF MS analysis was accomplished utilizing electrospray ionization tandem mass spectrometry (ESI MS/MS) and manual analysis of ion fragmentation spectra. Patterns and sites of PTMs identified in this study suggest that HMGA1a proteins, like the histones, exhibit a biochemical modification "code" that relates to cellular function. For example, both increased levels of acetylation and a previously unidentified dimethylation of both lysine and arginine residues were found on HMGA1a proteins from metastatic cells compared to proteins found in their nonmetastatic precursors. Additionally, the types of modification present on lysine-45 (e.g., unmodified, acetylation, or dimethylation) varied, depending on the metastatic potential of cells. These findings suggest that examination of the PTM patterns on HMGA1 proteins may provide valuable information concerning the physiological and phenotypic state of mammalian cells.