Superconductivity phase diagram of Na(x)CoO2*1.3H2O

The microscopic origin of superconductivity in the high-transition-temperature (high-T(c)) copper oxides remains the subject of active inquiry; several of their electronic characteristics are well established as universal to all the known materials, forming the experimental foundation that all theories must address. The most fundamental of those characteristics, for both the copper oxides and other superconductors, is the dependence of the superconducting T(c) on the degree of electronic band filling. The recent report of superconductivity near 4 K in the layered sodium cobalt oxyhydrate, Na(0.35)CoO2*1.3H2O, is of interest owing to both its triangular cobalt-oxygen lattice and its generally analogous chemical and structural relationships to the copper oxide superconductors. Here we show that the superconducting T(c) of this compound displays the same kind of behaviour on chemical doping that is observed in the high-T(c) copper oxides. Specifically, the optimal superconducting T(c) occurs in a narrow range of sodium concentrations (and therefore electron concentrations) and decreases for both underdoped and overdoped materials, as observed in the phase diagram of the copper oxide superconductors. The analogy is not perfect, however, suggesting that Na(x)CoO2*1.3H2O, with its triangular lattice geometry and special magnetic characteristics, may provide insights into systems where coupled charge and spin dynamics play an essential role in leading to superconductivity.     

The identification of norlobariol,a new lichen constituent fromXanthoparmelia scabrosa (Tayl.) Hale

Summary Norlobariol (I) previously described as a synthetic product derived from norlobaridone (II) was isolated as a new metabolite fromXanthoparmelia scabrosa (Tayl.) Hale.Acknowledgment. The authors wish to acknowledge the assistance of Dr D. Galloway in identifying the lichen sample and Dr A.W. Campbell for the microanalytical data.     

Astrocyte glypicans 4 and 6 promote formation of excitatory synapses via GluA1 AMPA receptors

In the developing central nervous system (CNS), the control of synapse number and function is critical to the formation of neural circuits. We previously demonstrated that astrocyte-secreted factors powerfully induce the formation of functional excitatory synapses between CNS neurons. Astrocyte-secreted thrombospondins induce the formation of structural synapses, but these synapses are postsynaptically silent. Here we use biochemical fractionation of astrocyte-conditioned medium to identify glypican 4 (Gpc4) and glypican 6 (Gpc6) as astrocyte-secreted signals sufficient to induce functional synapses between purified retinal ganglion cell neurons, and show that depletion of these molecules from astrocyte-conditioned medium significantly reduces its ability to induce postsynaptic activity. Application of Gpc4 to purified neurons is sufficient to increase the frequency and amplitude of glutamatergic synaptic events. This is achieved by increasing the surface level and clustering, but not overall cellular protein level, of the GluA1 subunit of the AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) glutamate receptor (AMPAR). Gpc4 and Gpc6 are expressed by astrocytes in vivo in the developing CNS, with Gpc4 expression enriched in the hippocampus and Gpc6 enriched in the cerebellum. Finally, we demonstrate that Gpc4-deficient mice have defective synapse formation, with decreased amplitude of excitatory synaptic currents in the developing hippocampus and reduced recruitment of AMPARs to synapses. These data identify glypicans as a family of novel astrocyte-derived molecules that are necessary and sufficient to promote glutamate receptor clustering and receptivity and to induce the formation of postsynaptically functioning CNS synapses.     

A genome-wide association study in Han Chinese identifies multiple susceptibility loci for IgA nephropathy

We performed a two-stage genome-wide association study of IgA nephropathy (IgAN) in Han Chinese, with 1,434 affected individuals (cases) and 4,270 controls in the discovery phase and follow-up of the top 61 SNPs in an additional 2,703 cases and 3,464 controls. We identified associations at 17p13 (rs3803800, P = 9.40 × 10(-11), OR = 1.21; rs4227, P = 4.31 × 10(-10), OR = 1.23) and 8p23 (rs2738048, P = 3.18 × 10(-14), OR = 0.79) that implicated the genes encoding tumor necrosis factor (TNFSF13) and α-defensin (DEFA) as susceptibility genes. In addition, we found multiple associations in the major histocompatibility complex (MHC) region (rs660895, P = 4.13 × 10(-20), OR = 1.34; rs1794275, P = 3.43 × 10(-13), OR = 1.30; rs2523946, P = 1.74 × 10(-11), OR = 1.21) and confirmed a previously reported association at 22q12 (rs12537, P = 1.17 × 10(-11), OR = 0.78). We also found that rs660895 was associated with clinical subtypes of IgAN (P = 0.003), proteinuria (P = 0.025) and IgA levels (P = 0.047). Our findings show that IgAN is associated with variants near genes involved in innate immunity and inflammation.     

Rare independent mutations in renal salt handling genes contribute to blood pressure variation

The effects of alleles in many genes are believed to contribute to common complex diseases such as hypertension. Whether risk alleles comprise a small number of common variants or many rare independent mutations at trait loci is largely unknown. We screened members of the Framingham Heart Study (FHS) for variation in three genes-SLC12A3 (NCCT), SLC12A1 (NKCC2) and KCNJ1 (ROMK)-causing rare recessive diseases featuring large reductions in blood pressure. Using comparative genomics, genetics and biochemistry, we identified subjects with mutations proven or inferred to be functional. These mutations, all heterozygous and rare, produce clinically significant blood pressure reduction and protect from development of hypertension. Our findings implicate many rare alleles that alter renal salt handling in blood pressure variation in the general population, and identify alleles with health benefit that are nonetheless under purifying selection. These findings have implications for the genetic architecture of hypertension and other common complex traits.     

Isolation of chrysotalunin,a red pigment from a New Zealand soil

Summary Benzene extraction of Te Kopuru sand, a podzol located in the subtropical region of New Zealand, yielded a high melting pigment. Spectroscopic data showed it to be the bianthraquinone chrysotalunin. This is the first report of its occurrence in the Southern hemisphere soil.Acknowledgment. The authors wish to thank Dr B. K. G. Theng, Soil Bureau, D.S.I.R., Lower Hutt, for the sample of the Te Kopuru sand podzol humus B horizon and Dr D. J. Wright of the Chemistry Department, University of Canterbury, for the high resolution mass spectral data.     

The Medicago genome provides insight into the evolution of rhizobial symbioses

Legumes (Fabaceae or Leguminosae) are unique among cultivated plants for their ability to carry out endosymbiotic nitrogen fixation with rhizobial bacteria, a process that takes place in a specialized structure known as the nodule. Legumes belong to one of the two main groups of eurosids, the Fabidae, which includes most species capable of endosymbiotic nitrogen fixation. Legumes comprise several evolutionary lineages derived from a common ancestor 60 million years ago (Myr ago). Papilionoids are the largest clade, dating nearly to the origin of legumes and containing most cultivated species. Medicago truncatula is a long-established model for the study of legume biology. Here we describe the draft sequence of the M. truncatula euchromatin based on a recently completed BAC assembly supplemented with Illumina shotgun sequence, together capturing ～94% of all M. truncatula genes. A whole-genome duplication (WGD) approximately 58 Myr ago had a major role in shaping the M. truncatula genome and thereby contributed to the evolution of endosymbiotic nitrogen fixation. Subsequent to the WGD, the M. truncatula genome experienced higher levels of rearrangement than two other sequenced legumes, Glycine max and Lotus japonicus. M. truncatula is a close relative of alfalfa (Medicago sativa), a widely cultivated crop with limited genomics tools and complex autotetraploid genetics. As such, the M. truncatula genome sequence provides significant opportunities to expand alfalfa's genomic toolbox.