Mei-P26 regulates microRNAs and cell growth in the Drosophila ovarian stem cell lineage

Drosophila neuroblasts and ovarian stem cells are well characterized models for stem cell biology. In both cell types, one daughter cell self-renews continuously while the other undergoes a limited number of divisions, stops to proliferate mitotically and differentiates. Whereas neuroblasts segregate the Trim-NHL (tripartite motif and Ncl-1, HT2A and Lin-41 domain)-containing protein Brain tumour (Brat) into one of the two daughter cells, ovarian stem cells are regulated by an extracellular signal from the surrounding stem cell niche. After division, one daughter cell looses niche contact. It undergoes 4 transit-amplifying divisions to form a cyst of 16 interconnected cells that reduce their rate of growth and stop to proliferate mitotically. Here we show that the Trim-NHL protein Mei-P26 (refs 7, 8) restricts growth and proliferation in the ovarian stem cell lineage. Mei-P26 expression is low in stem cells but is strongly induced in 16-cell cysts. In mei-P26 mutants, transit-amplifying cells are larger and proliferate indefinitely leading to the formation of an ovarian tumour. Like brat, mei-P26 regulates nucleolar size and can induce differentiation in Drosophila neuroblasts, suggesting that these genes act through the same pathway. We identify Argonaute-1, a component of the RISC complex, as a common binding partner of Brat and Mei-P26, and show that Mei-P26 acts by inhibiting the microRNA pathway. Mei-P26 and Brat have a similar domain composition that is also found in other tumour suppressors and might be a defining property of a new family of microRNA regulators that act specifically in stem cell lineages.     

应用EMME／2宏语言执行道路定价模型

香港的交通拥挤非常严重,而且好像并不能通过增加道路容量来解决,考虑到大多数拥挤地区空间的限制和增加道路容量所导致的潜在需求,交通规划人员和经济专家们为解决交通拥挤问题,已经把他们的注意力从交通供方面转移交通需求上。道路定价方法可构成交通需求管理战略的一部分,为交通拥挤问题提供了一个有效、公平、灵活的解决方案。香港特共政府已指定了一个咨询机构,来调查电子道路定价系统的需求,以及执行后的社会反应,为了     

Detectable clonal mosaicism from birth to old age and its relationship to cancer

We detected clonal mosaicism for large chromosomal anomalies (duplications, deletions and uniparental disomy) using SNP microarray data from over 50,000 subjects recruited for genome-wide association studies. This detection method requires a relatively high frequency of cells with the same abnormal karyotype (>5-10%; presumably of clonal origin) in the presence of normal cells. The frequency of detectable clonal mosaicism in peripheral blood is low (<0.5%) from birth until 50 years of age, after which it rapidly rises to 2-3% in the elderly. Many of the mosaic anomalies are characteristic of those found in hematological cancers and identify common deleted regions with genes previously associated with these cancers. Although only 3% of subjects with detectable clonal mosaicism had any record of hematological cancer before DNA sampling, those without a previous diagnosis have an estimated tenfold higher risk of a subsequent hematological cancer (95% confidence interval = 6-18).     

Hereditary mixed polyposis syndrome is caused by a 40-kb upstream duplication that leads to increased and ectopic expression of the BMP antagonist GREM1

Hereditary mixed polyposis syndrome (HMPS) is characterized by apparent autosomal dominant inheritance of multiple types of colorectal polyp, with colorectal carcinoma occurring in a high proportion of affected individuals. Here, we use genetic mapping, copy-number analysis, exclusion of mutations by high-throughput sequencing, gene expression analysis and functional assays to show that HMPS is caused by a duplication spanning the 3' end of the SCG5 gene and a region upstream of the GREM1 locus. This unusual mutation is associated with increased allele-specific GREM1 expression. Whereas GREM1 is expressed in intestinal subepithelial myofibroblasts in controls, GREM1 is predominantly expressed in the epithelium of the large bowel in individuals with HMPS. The HMPS duplication contains predicted enhancer elements; some of these interact with the GREM1 promoter and can drive gene expression in vitro. Increased GREM1 expression is predicted to cause reduced bone morphogenetic protein (BMP) pathway activity, a mechanism that also underlies tumorigenesis in juvenile polyposis of the large bowel.     

Interaction between ERAP1 and HLA-B27 in ankylosing spondylitis implicates peptide handling in the mechanism for HLA-B27 in disease susceptibility

Ankylosing spondylitis is a common form of inflammatory arthritis predominantly affecting the spine and pelvis that occurs in approximately 5 out of 1,000 adults of European descent. Here we report the identification of three variants in the RUNX3, LTBR-TNFRSF1A and IL12B regions convincingly associated with ankylosing spondylitis (P < 5 × 10(-8) in the combined discovery and replication datasets) and a further four loci at PTGER4, TBKBP1, ANTXR2 and CARD9 that show strong association across all our datasets (P < 5 × 10(-6) overall, with support in each of the three datasets studied). We also show that polymorphisms of ERAP1, which encodes an endoplasmic reticulum aminopeptidase involved in peptide trimming before HLA class I presentation, only affect ankylosing spondylitis risk in HLA-B27-positive individuals. These findings provide strong evidence that HLA-B27 operates in ankylosing spondylitis through a mechanism involving aberrant processing of antigenic peptides.     

NAD(P)H:quinone oxidoreductase 1 NQO1*2 genotype (P187S) is a strong prognostic and predictive factor in breast cancer

NQO1 guards against oxidative stress and carcinogenesis and stabilizes p53. We find that a homozygous common missense variant (NQO1(*)2, rs1800566(T), NM_000903.2:c.558C>T) that disables NQO1 strongly predicts poor survival among two independent series of women with breast cancer (P = 0.002, N = 1,005; P = 0.005, N = 1,162), an effect particularly evident after anthracycline-based adjuvant chemotherapy with epirubicin (P = 7.52 x 10(-6)) and in p53-aberrant tumors (P = 6.15 x 10(-5)). Survival after metastasis was reduced among NQO1(*)2 homozygotes, further implicating NQO1 deficiency in cancer progression and treatment resistance. Consistently, response to epirubicin was impaired in NQO1(*)2-homozygous breast carcinoma cells in vitro, reflecting both p53-linked and p53-independent roles of NQO1. We propose a model of defective anthracycline response in NQO1-deficient breast tumors, along with increased genomic instability promoted by elevated reactive oxygen species (ROS), and suggest that the NQO1 genotype is a prognostic and predictive marker for breast cancer.     

Genome-wide variation and identification of vaccine targets in the Plasmodium falciparum genome

One goal in sequencing the Plasmodium falciparum genome, the agent of the most lethal form of malaria, is to discover vaccine and drug targets. However, identifying those targets in a genome in which approximately 60% of genes have unknown functions is an enormous challenge. Because the majority of known malaria antigens and drug-resistant genes are highly polymorphic and under various selective pressures, genome-wide analysis for signatures of selection may lead to discovery of new vaccine and drug candidates. Here we surveyed 3,539 P. falciparum genes ( approximately 65% of the predicted genes) for polymorphisms and identified various highly polymorphic loci and genes, some of which encode new antigens that we confirmed using human immune sera. Our collections of genome-wide SNPs ( approximately 65% nonsynonymous) and polymorphic microsatellites and indels provide a high-resolution map (one marker per approximately 4 kb) for mapping parasite traits and studying parasite populations. In addition, we report new antigens, providing urgently needed vaccine candidates for disease control.     

Crystal structure of the channelrhodopsin light-gated cation channel

Channelrhodopsins (ChRs) are light-gated cation channels derived from algae that have shown experimental utility in optogenetics; for example, neurons expressing ChRs can be optically controlled with high temporal precision within systems as complex as freely moving mammals. Although ChRs have been broadly applied to neuroscience research, little is known about the molecular mechanisms by which these unusual and powerful proteins operate. Here we present the crystal structure of a ChR (a C1C2 chimaera between ChR1 and ChR2 from Chlamydomonas reinhardtii) at 2.3?? resolution. The structure reveals the essential molecular architecture of ChRs, including the retinal-binding pocket and cation conduction pathway. This integration of structural and electrophysiological analyses provides insight into the molecular basis for the remarkable function of ChRs, and paves the way for the precise and principled design of ChR variants with novel properties.