Abbreviated exposure to cuprizone is sufficient to induce demyelination and oligodendrocyte loss.

Cuprizone intoxication is one of several animal models used to study demyelination and remyelination. Early treatment protocols exposed mice to cuprizone for 6 weeks to induce demyelination; however, more recent reports have varied exposure times from 4 to 5 weeks. The goal of this study was to determine the minimal exposure of cuprizone in C57BL/6 mice that would induce a pathology of robust demyelination and gliosis similar to that described for a 5- or 6-week treatment. We found that an abbreviated insult of only 2 weeks of exposure to cuprizone induced significant demyelination 3 weeks later (5-week time point) but was somewhat variable. Three weeks of exposure to cuprizone produced extensive demyelination by week 5, equivalent to that observed with 5 weeks of exposure. The depletion of mature oligodendrocytes, as well as microglia and astrocyte accumulation, showed trends similar to those with 5-week exposure to cuprizone. Once mature oligodendrocytes are perturbed after a 3-week treatment, the progression to demyelination occurs without requiring further exposure. Furthermore, the early removal of cuprizone did not accelerate remyelination, suggesting that other sequences of events must follow before repair can occur. Thus, a short, "hit and run" CNS insult triggers a cascade of events leading to demyelination 2-3 weeks later.

A locus for generalized tonic-clonic seizure susceptibility maps to chromosome 10q25-q26.

Inheritance patterns in twins and multiplex families led us to hypothesize that two loci were segregating in subjects with juvenile myoclonic epilepsy (JME), one predisposing to generalized tonic-clonic seizures (GTCS) and a second to myoclonic seizures. We tested this hypothesis by performing genome-wide scan of a large family (Family 01) and used the results to guide analyses of additional families. A locus was identified in Family 01 that was linked to GTCS (10q25-q26). Model-based multipoint analysis of the 10q25-q26 locus showed a logarithm of odds (LOD) score of 2.85; similar results were obtained with model-free analyses (maximum nonparametric linkage [NPL] of 2.71; p = 0.0019). Analyses of the 10q25-q26 locus in 10 additional families assuming heterogeneity revealed evidence for linkage in four families; model-based and model-free analyses showed a heterogeneity LOD (HLOD) of 2.01 (alpha = 0.41) and maximum NPL of 2.56 (p = 0.0027), respectively, when all subjects with GTCS were designated to be affected. Combined analyses of all 11 families showed an HLOD of 4.04 (alpha = 0.51) and maximum NPL score of 4.20 (p = 0.000065). Fine mapping of the locus defined an interval of 4.45Mb. These findings identify a novel locus for GTCS on 10q25-q26 and support the idea that distinct loci underlie distinct seizure types within an epilepsy syndrome such as JME.

Alterations in metabolism and gene expression in brain regions during cuprizone-induced demyelination and remyelination.

Exposure of mice to the copper chelator, cuprizone, results in CNS demyelination. There is remyelination after removal of the metabolic insult. We present brain regional studies identifying corpus callosum as particularly severely affected; 65% of cerebroside is lost after 6 weeks of exposure. We examined recovery of cerebroside and ability to synthesize cerebroside and cholesterol following removal of the toxicant. The temporal pattern for concentration of myelin basic protein resembled that of cerebroside. We applied Affymetrix GeneChip technology to corpus callosum to identify temporal changes in levels of mRNAs during demyelination and remyelination. Genes coding for myelin structural components were greatly down-regulated during demyelination and up-regulated during remyelination. Genes related to microglia/macrophages appeared in a time-course (peaking at 6 weeks) correlating with phagocytosis of myelin and repair of lesions. mRNAs coding for many cytokines had peak expression at 4 weeks, compatible with intercellular signaling roles. Of interest were other genes with temporal patterns correlating with one of the three above patterns, but of function not obviously related to demyelination/remyelination. The ability to correlate gene expression with known pathophysiological events should help in elucidating further function of such genes as related to demyelination/remyelination.