Epigenetic control of neural precursor cell fate during development

The temporally and spatially restricted nature of the differentiation capacity of cells in the neural lineage has been studied extensively in recent years. Epigenetic control of developmental genes, which is heritable through cell divisions, has emerged as a key mechanism defining the differentiation potential of cells. Short-term or reversible repression of developmental genes puts them in a 'poised state', ready to be activated in response to differentiation-inducing cues, whereas long-term or permanent repression of developmental genes restricts the cell fates they regulate. Here, the authors review the molecular mechanisms that underlie the establishment and regulation of differentiation potential along the neural lineage during development.

Yusuke Hirabayashi & Yukiko Gotoh

Nature Reviews Neuroscience 11, 377-388 (June 2010) | doi:10.1038/nrn2810

XENON100 announced the new results

The XENON100 collaboration submitted a paper with the first results of a 11.2 days background analysis to PRL, excluding previously unexplored parameter space and questioning the light WIMP interpretation of the DAMA and CoGeNT results.

The preprint can be found here:

arXiv:1005.0380.

These results are also covered in the media:
The New York Times
New Scientist
Nature Blog
Discover Magazine Blog
Scientific American

Wired - XENON100August 6, 2009: An article about the hunt for Dark Matter and XENON100 appeared in the UK version of the Wired magazine.

The evolutionary significance of ancient genome duplications

Many organisms are currently polyploid, or have a polyploid ancestry and now have secondarily 'diploidized' genomes. This finding is surprising because retained whole-genome duplications (WGDs) are exceedingly rare, suggesting that polyploidy is usually an evolutionary dead end. We argue that ancient genome doublings could probably have survived only under very specific conditions, but that, whenever established, they might have had a pronounced impact on species diversification, and led to an increase in biological complexity and the origin of evolutionary novelties.

Yves Van de Peer, et al.
Nature Reviews Genetics 10, 725-732 (October 2009) | doi:10.1038/nrg2600

'Junk' DNA Proves To Be Highly Valuable

What was once thought of as DNA with zero value in plants--dubbed "junk" DNA--may turn out to be key in helping scientists improve the control of gene expression in transgenic crops.  For more than 30 years, scientists have been perplexed by the workings of intergenic DNA, which is located between genes. Scientists have since found that, among other functions, some intergenic DNA plays a physical role in protecting and linking chromosomes. But after subtracting intergenic DNA, there was still leftover or "junk" DNA which seemed to have no purpose.  Cooper and collaborators investigated "junk" DNA in the model plant Arabidopsis thaliana, using a computer program to find short segments of DNA that appeared as molecular patterns. When comparing these patterns to genes, Cooper's team found that 50 percent of the genes had the exact same sequences as the molecular patterns. This discovery showed a sequence pattern link between "junk" and coding DNA. These linked patterns are called pyknons, which Cooper and his team believe might be evidence of something important that drives genome expansion in plants.

The researchers found that pyknons are also the same in sequence and size as small segments of RNA that regulate gene expression through a method known as gene silencing. This evidence suggests that these RNA segments are converted back into DNA and are integrated into the intergenic space. Over time, these sequences repeatedly accumulate. Prior to this discovery, pyknons were only known to exist in the human genome. Thus, this discovery in plants illustrates that the link between coding DNA and junk DNA crosses higher orders of biology and suggests a universal genetic mechanism at play that is not yet fully understood.  The data suggest that scientists might be able to use this information to determine which genes are regulated by gene silencing, and that there may be some application for the improvement of transgenic plants by using the pyknon information.

Science Daily - June 12, 2009
Feng et al. 

Coding DNA repeated throughout intergenic regions of the Arabidopsis thaliana genome: evolutionary footprints of RNA silencing. 

Molecular BioSystems, 2009; DOI: 10.1039/b903031j