High altitude adaptation in Daghestani populations from the Caucasus

We have surveyed 15 high-altitude adaptation candidate genes for signals of positive selection in North Caucasian highlanders using targeted re-sequencing. A total of 49 unrelated Daghestani from three ethnic groups (Avars, Kubachians, and Laks) living in ancient villages located at around 2,000 m above sea level were chosen as the study population. Caucasian (Adygei living at sea level, N = 20) and CEU (CEPH Utah residents with ancestry from northern and western Europe; N = 20) were used as controls. Candidate genes were compared with 20 putatively neutral control regions resequenced in the same individuals. The regions of interest were amplified by long-PCR, pooled according to individual, indexed by adding an eight-nucleotide tag, and sequenced using the Illumina GAII platform. 1,066 SNPs were called using false discovery and false negative thresholds of ~6%. The neutral regions provided an empirical null distribution to compare with the candidate genes for signals of selection. Two genes stood out. In Laks, a non-synonymous variant within HIF1A already known to be associated with improvement in oxygen metabolism was rediscovered, and in Kubachians a cluster of 13 SNPs located in a conserved intronic region within EGLN1 showing high population differentiation was found. These variants illustrate both the common pathways of adaptation to high altitude in different populations and features specific to the Daghestani populations, showing how even a mildly hypoxic environment can lead to genetic adaptation.     

A Microfluidic Pump/Valve Inspired by Xylem Embolism and Transpiration in Plants

In plants, transpiration draws the water upward from the roots to the leaves. However, this flow can be blocked by air bubbles in the xylem conduits, which is called xylem embolism. In this research, we present the design of a biomimetic microfluidic pump/valve based on water transpiration and xylem embolism. This micropump/valve is mainly composed of three parts: the first is a silicon sheet with an array of slit-like micropores to mimic the stomata in a plant leaf; the second is a piece of agarose gel to mimic the mesophyll cells in the sub-cavities of a stoma; the third is a micro-heater which is used to mimic the xylem embolism and its self-repairing. The solution in the microchannels of a microfluidic chip can be driven by the biomimetic “leaf” composed of the silicon sheet and the agarose gel. The halting and flowing of the solution is controlled by the micro-heater. Results have shown that a steady flow rate of 1.12 µl/min can be obtained by using this micropump/valve. The time interval between the turning on/off of the micro-heater and the halt (or flow) of the fluid is only 2∼3 s. This micropump/valve can be used as a “plug and play” fluid-driven unit. It has the potential to be used in many application fields.     

同型半胱氨酸对大鼠血管平滑肌细胞增殖的作用

血中同型半胱氨酸（ｈｏｍｏｃｙｓｔｅｉｎｅ,ＨＣＹ）浓度的升高已成为动脉粥样硬化发生的一个独立危险因子．为进一步阐明ＨＣＹ促进血管平滑肌细胞（ｖａｓｃｕｌａｒｓｍｏｏｔｈｍｕｓｃｌｅｃｅｌｓ,ＶＳＭＣｓ）增殖,从而引起动脉粥样硬化发生的机理．本实验采用细胞计数、３Ｈ－ＴｄＲ参入、细胞周期分析、Ｎｏｒｔｈｅｒｎ杂交方法证明,一定剂量的ＨＣＹ可促进离体培养的ＷＫＹ大鼠血管平滑肌细胞增殖,使其ＤＮＡ合成增加,细胞周期中Ｓ期细胞所占比例增加４３％,并促进ｃ－ｍｙｃ与ｃ－ｆｏｓ原癌基因ｍＲＮＡ表达增加．提示ＨＣＹ可能通过促进ＶＳＭＣｓ增殖而诱发动脉粥样硬化     

Long-term effects of grassland management on soil microbial abundance: implications for soil carbon and nitrogen storage

Grassland management intensification can significantly affect the structure and composition of important soil microbial groups such as bacteria and fungi. Changes to these microbial communities can greatly influence carbon (C) and nitrogen (N) cycling in grassland soils. Here we specifically address how microbial abundances might shift under the effect of multiple management practices and how this in turn might relate to changes in soil C and N storage. Soil samples were collected from a 23-year-old grassland experiment and real-time quantitative Polymerase Chain Reaction (PCR) was performed to address whether and how (1) chronic nutrient additions, (2) liming (i.e., the addition of CaCO₃ to soils), and (3) grazing by rabbits might affect archaeal, bacterial and fungal microbial groups. We found that liming additions significantly increased archaeal and bacterial abundance whilst strongly reducing fungal abundance. The addition of N-only (as NH₄NO₃) significantly reduced bacterial abundance while chronic grazing by rabbits resulted in positive effects on archaeal abundance. Despite long-term grassland management significantly affecting soil microbial abundances (and Fungal-to-Bacterial ratios), microbial changes were not related to either changes in soil C or N pools. Overall, our results suggest that (1) important microbial-‘soil functioning’ relationships may only be detected at lower taxonomic levels, and (2) liming-induced increases in soil pH determined significant shifts in soil microbial abundance, which could have important consequences for the delivery of multiple soil ecosystem services (i.e., nutrient regulation, C and N sequestration) from permanent grassland.     

The Spatiotemporal Role of COX-2 in Osteogenic and Chondrogenic Differentiation of Periosteum-Derived Mesenchymal Progenitors in Fracture Repair

Periosteum provides a major source of mesenchymal progenitor cells for bone fracture repair. Combining cell-specific targeted Cox-2 gene deletion approaches with in vitro analyses of the differentiation of periosteum-derived mesenchymal progenitor cells (PDMPCs), here we demonstrate a spatial and temporal role for Cox-2 function in the modulation of osteogenic and chondrogenic differentiation of periosteal progenitors in fracture repair. Prx1Cre-targeted Cox-2 gene deletion in mesenchyme resulted in marked reduction of intramembraneous and endochondral bone repair, leading to accumulation of poorly differentiated mesenchyme and immature cartilage in periosteal callus. In contrast, Col2Cre-targeted Cox-2 gene deletion in cartilage resulted in a deficiency primarily in cartilage conversion into bone. Further cell culture analyses using Cox-2 deficient PDMPCs demonstrated reduced osteogenic differentiation in monolayer cultures, blocked chondrocyte differentiation and hypertrophy in high density micromass cultures. Gene expression microarray analyses demonstrated downregulation of a key set of genes associated with bone/cartilage formation and remodeling, namely Sox9, Runx2, Osx, MMP9, VDR and RANKL. Pathway analyses demonstrated dysregulation of the HIF-1, PI3K-AKT and Wnt pathways in Cox-2 deficient cells. Collectively, our data highlight a crucial role for Cox-2 from cells of mesenchymal lineages in modulating key pathways that control periosteal progenitor cell growth, differentiation, and angiogenesis in fracture repair.     

Post-translational Regulation of Mitogen-activated Protein Kinase Phosphatase (MKP)-1 and MKP-2 in Macrophages Following Lipopolysaccharide Stimulation: THE ROLE OF THE C TERMINI OF THE PHOSPHATASES IN DETERMINING THEIR STABILITY*

MAPK phosphatases (MKPs) are critical modulators of the innate immune response, and yet the mechanisms regulating their accumulation remain poorly understood. In the present studies, we investigated the role of post-translational modification in the accumulation of MKP-1 and MKP-2 in macrophages following LPS stimulation. We found that upon LPS stimulation, MKP-1 and MKP-2 accumulated with different kinetics: MKP-1 level peaked at ∼1 h, while MKP-2 levels continued to rise for at least 6 h. Accumulation of both MKP-1 and MKP-2 were attenuated by inhibition of the ERK cascade. Interestingly, p38 inhibition prior to LPS stimulation had little effect on MKP-1 and MKP-2 protein levels, but hindered their detection by an M-18 MKP-1 antibody. Studies of the epitope sequence recognized by the M-18 MKP-1 antibody revealed extensive phosphorylation of two serine residues in the C terminus of both MKP-1 and MKP-2 by the ERK pathway. Remarkably, the stability of both MKP-1 and MKP-2 was markedly decreased in macrophages in the presence of an ERK pathway inhibitor. Mutation of the two C-terminal serine residues in MKP-1 and MKP-2 to alanine decreased their half-lives, while mutating these residues to aspartate dramatically increased their half-lives. Deletion of the C terminus from MKP-1 and MKP-2 also considerably increased their stabilities. Surprisingly, enhanced stabilities of the MKP-1 and MKP-2 mutants were not associated with decreased ubiquitination. Degradation of both MKP-1 and MKP-2 was attenuated by proteasomal inhibitors. Our studies suggest that MKP-1 and MKP-2 stability is regulated by ERK-mediated phosphorylation through a degradation pathway independent of polyubiquitination.     

Myeloid Mineralocorticoid Receptor Deficiency Inhibits Aortic Constriction-Induced Cardiac Hypertrophy in Mice

Mineralocorticoid receptor (MR) blockade has been shown to suppress cardiac hypertrophy and remodeling in animal models of pressure overload (POL). This study aims to determine whether MR deficiency in myeloid cells modulates aortic constriction-induced cardiovascular injuries. Myeloid MR knockout (MMRKO) mice and littermate control mice were subjected to abdominal aortic constriction (AAC) or sham operation. We found that AAC-induced cardiac hypertrophy and fibrosis were significantly attenuated in MMRKO mice. Expression of genes important in generating reactive oxygen species was decreased in MMRKO mice, while that of manganese superoxide dismutase increased. Furthermore, expression of genes important in cardiac metabolism was increased in MMRKO hearts. Macrophage infiltration in the heart was inhibited and expression of inflammatory genes was decreased in MMRKO mice. In addition, aortic fibrosis and inflammation were attenuated in MMRKO mice. Taken together, our data indicated that MR deficiency in myeloid cells effectively attenuated aortic constriction-induced cardiac hypertrophy and fibrosis, as well as aortic fibrosis and inflammation.     

Mean time to resolution of gene duplication

The mean time to resolution of gene duplication (T_r) is studied in this paper under the double null recessive (DNR) and haplo-insufficient (HI) models within the same analytical and simulation framework. We show that when population size is not too small (more precisely Nμ > 0.1), T_r for unlinked duplication is usually larger than that for linked and T_r for unlinked duplication under the HI model might be greatly prolonged, which were consistent with previous observations. Furthermore, by analytical approach we here indicate the primary underlying mechanism is that the frequency of the original (or wild-type) chromosomal haplotype of the linked duplication decreases nearly exponential to zero with time while that of the unlinked decreases quickly to an quasi-equilibrium; and this phenomenon is particularly profound under the HI model, because the quasi-equilibrium frequency of the original chromosomal haplotype (x₀) under the HI model is higher than that under the DNR model. These results suggest that recombination and HI model might jointly contribute to the marked prolongation of T_r even in a modest population. The prolonged T_r and higher quasi-equilibrium frequency of the original allele at both duplicated loci might have offered more opportunities for the emergence of novel genes.     

Inhibition of JNK by overexpression of the JNL binding domain of JIP-1 prevents apoptosis in sympathetic neurons

Studies in non-neuronal cells show that c-Jun N-terminal kinases (JNK) play a key role in apoptotic cell death. In some neurons JNK is also thought to initiate cell death by the activation of c-Jun. JNK inhibition has been achieved pharmacologically by inhibiting upstream kinases, but there has been no direct demonstration that inhibition of JNK can prevent neuronal death. We have therefore examined whether the JNK binding domain (JBD) of JNK-interacting protein-1 (JIP-1, a scaffold protein and specific inhibitor of JNK) can inhibit c-Jun phosphorylation and support the survival of sympathetic neurons deprived of NGF. We show that expression of the JBD in >80% of neurons was sufficient to prevent the phosphorylation of c-Jun and its nuclear accumulation as well as abrogate neuronal cell death induced by NGF deprivation. JBD expression also preserved the capacity of mitochondria to reduce MTT. Interestingly, although the PTB domain of JIP was reported to interact with rhoGEF, expression of the JBD domain was sufficient to localize the protein to the membrane cortex and growth cones. Hence, JNK activation is a key event in apoptotic death induced by NGF withdrawal, where its point of action lies upstream of mitochondrial dysfunction.     

CXCR2 is critical to hyperoxia-induced lung injury

Hyperoxia-induced lung injury is characterized by infiltration of activated neutrophils in conjunction with endothelial and epithelial cell injury, followed by fibrogenesis. Specific mechanisms recruiting neutrophils to the lung during hyperoxia-induced lung injury have not been fully elucidated. Because CXCL1 and CXCL2/3, acting through CXCR2, are potent neutrophil chemoattractants, we investigated their role in mediating hyperoxia-induced lung injury. Under variable concentrations of oxygen, murine survival during hyperoxia-induced lung injury was dose dependent. Eighty percent oxygen was associated with 50% mortality at 6 days, while greater oxygen concentrations were more lethal. Using 80% oxygen, we found that lungs harvested at day 6 demonstrated markedly increased neutrophil sequestration and lung injury. Expression of CXCR2 ligands paralleled neutrophil recruitment to the lung and CXCR2 mRNA expression. Inhibition of CXC chemokine ligands/CXCR2 interaction using CXCR2(-/-) mice exposed to hyperoxia significantly reduced neutrophil sequestration and lung injury, and led to a significant survival advantage as compared with CXCR2(+/+) mice. These findings demonstrate that CXC chemokine ligand/CXCR2 biological axis is critical during the pathogenesis of hyperoxia-induced lung injury.