Widmanstaetten patterns in josephinite, a metal-bearing terrestrial rock

Widmanstaetten patterns have been found in several specimens of josephinite, a complex, metamorphosed, metal-bearing rock from placers on serpentinized peridotite in southwest Oregon. The patterns, in interior less-altered regions of the specimens, are typical of exsolution textures produced during slow cooling of a homogeneous metal. The bulk composition of the metal phases indicates that the homogeneous metal must have existed at temperatures above 500 degrees C. Josephinite Widmanstaetten patterns are the first known in terrestrial rock. We interpret them as further evidence that josephinite was derived from the mantle.     

Selective sparing of a class of striatal neurons in Huntington's disease

A distinct subpopulation of striatal aspiny neurons, containing the enzyme nicotinamide adenine dinucleotide phosphate diaphorase, is preserved in the caudate nucleus in Huntington's disease. Biochemical assays confirmed a significant increase in the activity of this enzyme in both the caudate nucleus and putamen in postmortem brain tissue from patients with this disease. The resistance of these neurons suggests that the gene defect in Huntington's disease may be modifiable by the local biochemical environment. This finding may provide insight into the nature of the genetically programmed cell death that is a characteristic of the disease.     

Reversal of neurological defects in a mouse model of Rett syndrome

Rett syndrome is an autism spectrum disorder caused by mosaic expression of mutant copies of the X-linked MECP2 gene in neurons. However, neurons do not die, which suggests that this is not a neurodegenerative disorder. An important question for future therapeutic approaches to this and related disorders concerns phenotypic reversibility. Can viable but defective neurons be repaired, or is the damage done during development without normal MeCP2 irrevocable? Using a mouse model, we demonstrate robust phenotypic reversal, as activation of MeCP2 expression leads to striking loss of advanced neurological symptoms in both immature and mature adult animals.     

Nonmethylated transposable elements and methylated genes in a chordate genome

The genome of the invertebrate chordate Ciona intestinalis was found to be a stable mosaic of methylated and nonmethylated domains. Multiple copies of an apparently active long terminal repeat retrotransposon and a long interspersed element are nonmethylated and a large fraction of abundant short interspersed elements are also methylation free. Genes, by contrast, are predominantly methylated. These data are incompatible with the genome defense model, which proposes that DNA methylation in animals is primarily targeted to endogenous transposable elements. Cytosine methylation in this urochordate may be preferentially directed to genes.