Nature view

Research highlights from the NPG family of journals.

Rewriting the rules of structure

The ability of Ge₂Sb₂Te₅ to flip between two states makes it the material of choice in DVD RAM. The rewritable properties of modern optical multimedia depend on this phase-change mechanism, whose structural basis is elucidated in an advance online publication for Nature Materials. Alexander Kolobov and colleagues report that Ge₂Sb₂Te₅ does not conform to the usual nature of phase-change materials. Instead, it is a shift in the arrangement of germanium atoms between octahedral and tetrahedral states that underlies the material's valuable properties.

articles
Understanding the phase-change mechanism of rewritable optical media
A. V. KOLOBOV et al.
Nature Materials 3; September 2004
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Neuroscience: a class distinction

Hubel and Wiesel first distinguished 'simple' from 'complex' cells in the visual cortex in 1962. This provided a dominant framework for the consideration of optical processing in the mammalian visual system. The two categories are defined by the characteristics of the cells' receptive fields, which have classically been thought to reflect two distinct, hierarchical patterns of synaptic input. An advance online publication in Nature Neuroscience by Nicholas Priebe and colleagues presents an alternative model, supported by results from intracellular recordings. Their model proposes that the voltage level at which the cells fire splits them into two groups that correspond to the simple and complex categories.

articles
The contribution of spike threshold to the dichotomy of cortical simple and complex cells
N. J. PRIEBE et al.
Nature Neuroscience 7; August 2004
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Prion diseases intrigue scientists because of their unique nature — prions seem to lack nucleic acid and propagate by transmission of protein misfolding. But these properties present particular difficulties for diagnosing infection, precluding normal methods based on nucleic acid polymerase chain reaction or immune responses. In next month's Nature Reviews Microbiology, Claudio Soto considers the urgent need for an early diagnostic test and discusses the state of current research. This article will be available free online throughout October.

reviews
Diagnosing prion diseases: needs, challenges and hopes
C. SOTO
Nature Reviews Microbiology 2, 809; October 2004
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Immunology: opening up to differentiation

Immune-receptor loci in the genome are rearranged by the recombination machinery during the differentiation of T and B cells. In an advance online publication for Nature Reviews Immunology, Yehudit Bergman and Howard Cedar describe how the loci are made accessible to the machinery through a stepwise removal of gene-repression mechanisms. This process initially favours one allele in each cell — which the authors suggest could be the basis for the generation of gene diversity in other systems.

articles
A stepwise epigenetic process controls immunoglobulin allelic exclusion
Y. BERGMAN AND H. CEDAR
Nature Immunology 4; September 2004
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Sorted

One of the most powerful ways to search genomes for regions that underlie human diseases is association testing in population groups. The theory simple: on average you would expect disease alleles to be more frequent in ascertained cases than in controls. However, human populations are rarely genetically homologous, so association studies can throw up misleading markers and false results, which dilute the power of this approach. Populations should be genetically homologous for these studies to work accurately. In the European Journal of Human Genetics, Ke Hao and colleagues report dramatic results of a new method for sorting populations genotypically. They show that only a few single nucleotide polymorphisms are needed to accurately sort genetically distant populations into homologous subgroups. Association tests performed on these sorted subgroups and are more reliable and more powerful than the major alternative approach, family-based association tests.

articles
Detect and adjust for population stratification in population-based association study using genomic control markers: an application of Affymetrix Genechip® Human Mapping 10K array
K. HAO et al.
European Journal of Human Genetics; September 2004
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