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991.
Dunham A Matthews LH Burton J Ashurst JL Howe KL Ashcroft KJ Beare DM Burford DC Hunt SE Griffiths-Jones S Jones MC Keenan SJ Oliver K Scott CE Ainscough R Almeida JP Ambrose KD Andrews DT Ashwell RI Babbage AK Bagguley CL Bailey J Bannerjee R Barlow KF Bates K Beasley H Bird CP Bray-Allen S Brown AJ Brown JY Burrill W Carder C Carter NP Chapman JC Clamp ME Clark SY Clarke G Clee CM Clegg SC Cobley V Collins JE Corby N Coville GJ Deloukas P Dhami P Dunham I Dunn M Earthrowl ME Ellington AG 《Nature》2004,428(6982):522-528
Chromosome 13 is the largest acrocentric human chromosome. It carries genes involved in cancer including the breast cancer type 2 (BRCA2) and retinoblastoma (RB1) genes, is frequently rearranged in B-cell chronic lymphocytic leukaemia, and contains the DAOA locus associated with bipolar disorder and schizophrenia. We describe completion and analysis of 95.5 megabases (Mb) of sequence from chromosome 13, which contains 633 genes and 296 pseudogenes. We estimate that more than 95.4% of the protein-coding genes of this chromosome have been identified, on the basis of comparison with other vertebrate genome sequences. Additionally, 105 putative non-coding RNA genes were found. Chromosome 13 has one of the lowest gene densities (6.5 genes per Mb) among human chromosomes, and contains a central region of 38 Mb where the gene density drops to only 3.1 genes per Mb. 相似文献
992.
Mechelli A Crinion JT Noppeney U O'Doherty J Ashburner J Frackowiak RS Price CJ 《Nature》2004,431(7010):757
Humans have a unique ability to learn more than one language--a skill that is thought to be mediated by functional (rather than structural) plastic changes in the brain. Here we show that learning a second language increases the density of grey matter in the left inferior parietal cortex and that the degree of structural reorganization in this region is modulated by the proficiency attained and the age at acquisition. This relation between grey-matter density and performance may represent a general principle of brain organization. 相似文献
993.
Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate changes 总被引:6,自引:0,他引:6
The Atlantic meridional overturning circulation is widely believed to affect climate. Changes in ocean circulation have been inferred from records of the deep water chemical composition derived from sedimentary nutrient proxies, but their impact on climate is difficult to assess because such reconstructions provide insufficient constraints on the rate of overturning. Here we report measurements of 231Pa/230Th, a kinematic proxy for the meridional overturning circulation, in a sediment core from the subtropical North Atlantic Ocean. We find that the meridional overturning was nearly, or completely, eliminated during the coldest deglacial interval in the North Atlantic region, beginning with the catastrophic iceberg discharge Heinrich event H1, 17,500 yr ago, and declined sharply but briefly into the Younger Dryas cold event, about 12,700 yr ago. Following these cold events, the 231Pa/230Th record indicates that rapid accelerations of the meridional overturning circulation were concurrent with the two strongest regional warming events during deglaciation. These results confirm the significance of variations in the rate of the Atlantic meridional overturning circulation for abrupt climate changes. 相似文献
994.
Suh GS Wong AM Hergarden AC Wang JW Simon AF Benzer S Axel R Anderson DJ 《Nature》2004,431(7010):854-859
All animals exhibit innate behaviours in response to specific sensory stimuli that are likely to result from the activation of developmentally programmed neural circuits. Here we observe that Drosophila exhibit robust avoidance to odours released by stressed flies. Gas chromatography and mass spectrometry identifies one component of this 'Drosophila stress odorant (dSO)' as CO2. CO2 elicits avoidance behaviour, at levels as low as 0.1%. We used two-photon imaging with the Ca2+-sensitive fluorescent protein G-CaMP to map the primary sensory neurons governing avoidance to CO2. CO2 activates only a single glomerulus in the antennal lobe, the V glomerulus; moreover, this glomerulus is not activated by any of 26 other odorants tested. Inhibition of synaptic transmission in sensory neurons that innervate the V glomerulus, using a temperature-sensitive Shibire gene (Shi(ts)), blocks the avoidance response to CO2. Inhibition of synaptic release in the vast majority of other olfactory receptor neurons has no effect on this behaviour. These data demonstrate that the activation of a single population of sensory neurons innervating one glomerulus is responsible for an innate avoidance behaviour in Drosophila. 相似文献
995.
996.
Genetic and developmental basis of evolutionary pelvic reduction in threespine sticklebacks 总被引:1,自引:0,他引:1
Shapiro MD Marks ME Peichel CL Blackman BK Nereng KS Jónsson B Schluter D Kingsley DM 《Nature》2004,428(6984):717-723
Hindlimb loss has evolved repeatedly in many different animals by means of molecular mechanisms that are still unknown. To determine the number and type of genetic changes underlying pelvic reduction in natural populations, we carried out genetic crosses between threespine stickleback fish with complete or missing pelvic structures. Genome-wide linkage mapping shows that pelvic reduction is controlled by one major and four minor chromosome regions. Pitx1 maps to the major chromosome region controlling most of the variation in pelvic size. Pelvic-reduced fish show the same left-right asymmetry seen in Pitx1 knockout mice, but do not show changes in Pitx1 protein sequence. Instead, pelvic-reduced sticklebacks show site-specific regulatory changes in Pitx1 expression, with reduced or absent expression in pelvic and caudal fin precursors. Regulatory mutations in major developmental control genes may provide a mechanism for generating rapid skeletal changes in natural populations, while preserving the essential roles of these genes in other processes. 相似文献
997.
van Boekel R Min M Leinert Ch Waters LB Richichi A Chesneau O Dominik C Jaffe W Dutrey A Graser U Henning T de Jong J Köhler R de Koter A Lopez B Malbet F Morel S Paresce F Perrin G Preibisch T Przygodda F Schöller M Wittkowski M 《Nature》2004,432(7016):479-482
Our Solar System was formed from a cloud of gas and dust. Most of the dust mass is contained in amorphous silicates, yet crystalline silicates are abundant throughout the Solar System, reflecting the thermal and chemical alteration of solids during planet formation. (Even primitive bodies such as comets contain crystalline silicates.) Little is known about the evolution of the dust that forms Earth-like planets. Here we report spatially resolved detections and compositional analyses of these building blocks in the innermost two astronomical units of three proto-planetary disks. We find the dust in these regions to be highly crystallized, more so than any other dust observed in young stars until now. In addition, the outer region of one star has equal amounts of pyroxene and olivine, whereas the inner regions are dominated by olivine. The spectral shape of the inner-disk spectra shows surprising similarity with Solar System comets. Radial-mixing models naturally explain this resemblance as well as the gradient in chemical composition. Our observations imply that silicates crystallize before any terrestrial planets are formed, consistent with the composition of meteorites in the Solar System. 相似文献
998.
Tschöp M Castañeda TR Joost HG Thöne-Reineke C Ortmann S Klaus S Hagan MM Chandler PC Oswald KD Benoit SC Seeley RJ Kinzig KP Moran TH Beck-sickinger AG Koglin N Rodgers RJ Blundell JE Ishii Y Beattie AH Holch P Allison DB Raun K Madsen K Wulff BS Stidsen CE Birringer M Kreuzer OJ Schindler M Arndt K Rudolf K Mark M Deng XY Whitcomb DC Halem H Taylor J Dong J Datta R Culler M Craney S Flora D Smiley D Heiman ML Withcomb DC 《Nature》2004,430(6996):1 p following 165; discussion 2 p following 165
Batterham et al. report that the gut peptide hormone PYY3-36 decreases food intake and body-weight gain in rodents, a discovery that has been heralded as potentially offering a new therapy for obesity. However, we have been unable to replicate their results. Although the reasons for this discrepancy remain undetermined, an effective anti-obesity drug ultimately must produce its effects across a range of situations. The fact that the findings of Batterham et al. cannot easily be replicated calls into question the potential value of an anti-obesity approach that is based on administration of PYY3-36. 相似文献
999.
During Drosophila embryogenesis, segments, each with an anterior and posterior compartment, are generated by the segmentation genes while the Hox genes provide each segment with a unique identity. These two processes have been thought to occur independently. Here we show that abdominal Hox proteins work directly with two different segmentation proteins, Sloppy paired and Engrailed, to repress the Hox target gene Distalless in anterior and posterior compartments, respectively. These results suggest that segmentation proteins can function as Hox cofactors and reveal a previously unanticipated use of compartments for gene regulation by Hox proteins. Our results suggest that these two classes of proteins may collaborate to directly control gene expression at many downstream target genes. 相似文献
1000.
Seymour B O'Doherty JP Dayan P Koltzenburg M Jones AK Dolan RJ Friston KJ Frackowiak RS 《Nature》2004,429(6992):664-667
The ability to use environmental stimuli to predict impending harm is critical for survival. Such predictions should be available as early as they are reliable. In pavlovian conditioning, chains of successively earlier predictors are studied in terms of higher-order relationships, and have inspired computational theories such as temporal difference learning. However, there is at present no adequate neurobiological account of how this learning occurs. Here, in a functional magnetic resonance imaging (fMRI) study of higher-order aversive conditioning, we describe a key computational strategy that humans use to learn predictions about pain. We show that neural activity in the ventral striatum and the anterior insula displays a marked correspondence to the signals for sequential learning predicted by temporal difference models. This result reveals a flexible aversive learning process ideally suited to the changing and uncertain nature of real-world environments. Taken with existing data on reward learning, our results suggest a critical role for the ventral striatum in integrating complex appetitive and aversive predictions to coordinate behaviour. 相似文献