Helium solubility in olivine and implications for high 3He/4He in ocean island basalts

High 3He/4He ratios found in ocean island basalts are the main evidence for the existence of an undegassed mantle reservoir. However, models of helium isotope evolution depend critically on the chemical behaviour of helium during mantle melting. It is generally assumed that helium is strongly enriched in mantle melts relative to uranium and thorium, yet estimates of helium partitioning in mantle minerals have produced conflicting results. Here we present experimental measurements of helium solubility in olivine at atmospheric pressure. Natural and synthetic olivines were equilibrated with a 50% helium atmosphere and analysed by crushing in vacuo followed by melting, and yield a minimum olivine-melt partition coefficient of 0.0025 +/- 0.0005 (s.d.) and a maximum of 0.0060 +/- 0.0007 (s.d.). The results indicate that helium might be more compatible than uranium and thorium during mantle melting and that high 3He/4He ratios can be preserved in depleted residues of melting. A depleted source for high 3He/4He ocean island basalts would resolve the apparent discrepancy in the relative helium concentrations of ocean island and mid-ocean-ridge basalts.     

North Pacific seasonality and the glaciation of North America 2.7 million years ago

In the context of gradual Cenozoic cooling, the timing of the onset of significant Northern Hemisphere glaciation 2.7 million years ago is consistent with Milankovitch's orbital theory, which posited that ice sheets grow when polar summertime insolation and temperature are low. However, the role of moisture supply in the initiation of large Northern Hemisphere ice sheets has remained unclear. The subarctic Pacific Ocean represents a significant source of water vapour to boreal North America, but it has been largely overlooked in efforts to explain Northern Hemisphere glaciation. Here we present alkenone unsaturation ratios and diatom oxygen isotope ratios from a sediment core in the western subarctic Pacific Ocean, indicating that 2.7 million years ago late-summer sea surface temperatures in this ocean region rose in response to an increase in stratification. At the same time, winter sea surface temperatures cooled, winter floating ice became more abundant and global climate descended into glacial conditions. We suggest that the observed summer warming extended into the autumn, providing water vapour to northern North America, where it precipitated and accumulated as snow, and thus allowed the initiation of Northern Hemisphere glaciation.     

STIM1 is a Ca2+ sensor that activates CRAC channels and migrates from the Ca2+ store to the plasma membrane

As the sole Ca2+ entry mechanism in a variety of non-excitable cells, store-operated calcium (SOC) influx is important in Ca2+ signalling and many other cellular processes. A calcium-release-activated calcium (CRAC) channel in T lymphocytes is the best-characterized SOC influx channel and is essential to the immune response, sustained activity of CRAC channels being required for gene expression and proliferation. The molecular identity and the gating mechanism of SOC and CRAC channels have remained elusive. Previously we identified Stim and the mammalian homologue STIM1 as essential components of CRAC channel activation in Drosophila S2 cells and human T lymphocytes. Here we show that the expression of EF-hand mutants of Stim or STIM1 activates CRAC channels constitutively without changing Ca2+ store content. By immunofluorescence, EM localization and surface biotinylation we show that STIM1 migrates from endoplasmic-reticulum-like sites to the plasma membrane upon depletion of the Ca2+ store. We propose that STIM1 functions as the missing link between Ca2+ store depletion and SOC influx, serving as a Ca2+ sensor that translocates upon store depletion to the plasma membrane to activate CRAC channels.     

A genome-wide scalable SNP genotyping assay using microarray technology

Oligonucleotide probe arrays have enabled massively parallel analysis of gene expression levels from a single cDNA sample. Application of microarray technology to analyzing genomic DNA has been stymied by the sequence complexity of the entire human genome. A robust, single base-resolution direct genomic assay would extend the reach of microarray technology. We developed an array-based whole-genome genotyping assay that does not require PCR and enables effectively unlimited multiplexing. The assay achieves a high signal-to-noise ratio by combining specific hybridization of picomolar concentrations of whole genome-amplified DNA to arrayed probes with allele-specific primer extension and signal amplification. As proof of principle, we genotyped several hundred previously characterized SNPs. The conversion rate, call rate and accuracy were comparable to those of high-performance PCR-based genotyping assays.     

Identification of a ferrireductase required for efficient transferrin-dependent iron uptake in erythroid cells

The reduction of iron is an essential step in the transferrin (Tf) cycle, which is the dominant pathway for iron uptake by red blood cell precursors. A deficiency in iron acquisition by red blood cells leads to hypochromic, microcytic anemia. Using a positional cloning strategy, we identified a gene, six-transmembrane epithelial antigen of the prostate 3 (Steap3), responsible for the iron deficiency anemia in the mouse mutant nm1054. Steap3 is expressed highly in hematopoietic tissues, colocalizes with the Tf cycle endosome and facilitates Tf-bound iron uptake. Steap3 shares homology with F(420)H(2):NADP(+) oxidoreductases found in archaea and bacteria, as well as with the yeast FRE family of metalloreductases. Overexpression of Steap3 stimulates the reduction of iron, and mice lacking Steap3 are deficient in erythroid ferrireductase activity. Taken together, these findings indicate that Steap3 is an endosomal ferrireductase required for efficient Tf-dependent iron uptake in erythroid cells.     

Genetic variation in laboratory mice

Characterizing the patterns of genetic variation in an organism provides fundamental insight into the evolutionary history of the organism and defines the scope and nature of studies that must be designed to correlate genotype to phenotype. Given the pre-eminent role of the inbred mouse in biomedical research, considerable effort has been undertaken in recent years to describe more fully the nature and amount of genetic variation among the numerous strains of mice that are in widest use. Here, we discuss recent studies that have contributed to an emerging understanding of the unique variation patterns found in inbred strains of mice and how they have arisen through a combination of natural evolution and human-directed breeding. These preliminary results have ramifications for genetic research into complex biomedical traits and are the basis for the development of future variation resources.     

Seasonal prediction of hurricane activity reaching the coast of the United States

Much of the property damage from natural hazards in the United States is caused by landfalling hurricanes--strong tropical cyclones that reach the coast. For the southeastern Atlantic coast of the US, a statistical method for forecasting the occurrence of landfalling hurricanes for the season ahead has been reported, but the physical mechanisms linking the predictor variables to the frequency of hurricanes remain unclear. Here we present a statistical model that uses July wind anomalies between 1950 and 2003 to predict with significant and useful skill the wind energy of US landfalling hurricanes for the following main hurricane season (August to October). We have identified six regions over North America and over the east Pacific and North Atlantic oceans where July wind anomalies, averaged between heights of 925 and 400 mbar, exhibit a stationary and significant link to the energy of landfalling hurricanes during the subsequent hurricane season. The wind anomalies in these regions are indicative of atmospheric circulation patterns that either favour or hinder evolving hurricanes from reaching US shores.