Catálogo de publicaciones - revistas

<jats:title>From Nucleoside Recycling to Histiocytosis</jats:title> <jats:p> Macrophages remove billions of apoptotic cells daily, releasing their nucleic acid material through lysosomal degradation, which allows the resulting nucleosides to be recycled. <jats:bold> Hsu <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="89" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1213682">89</jats:related-article> , published online 15 December) found that the nucleoside transporter, equilibrative nucleoside transporter 3 (ENT3), was highly expressed in macrophages and showed that mice deficient in this transporter develop histiocytosis and features of lysosomal storage disease. When exposed to apoptotic cells, macrophages carrying human ENT3 mutations accumulated adenosine and increased their lysosomal pH. These changes contributed to an enhanced signaling through macrophage colony-stimulating factor (M-CSF) receptor and, ultimately, to M-CSF–driven myeloproliferative disease. </jats:p>

<jats:title>Going LARGE</jats:title> <jats:p> Dystroglycan (DG) is a highly glycosylated extracellular matrix (ECM) receptor involved in a variety of physiological processes, including maintenance of skeletal muscle membrane integrity and the structure and function of the central nervous system. The like-acetylglucosaminyltransferase (LARGE) is responsible for posttranslational modifications of alpha-dystroglycan (α-DG) required for its function. Now, <jats:bold> Inamori <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="93" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1214115">93</jats:related-article> ) demonstrate that LARGE is a bifunctional glycosyltransferase able to transfer xylose and glucuronic acid. These modifications allow α-DG to bind the laminin-G domain–containing ECM ligands: laminin, agrin, and neurexin. </jats:p>

<jats:title>Making Heterochromatin</jats:title> <jats:p> Heterochromatin is a particularly compact DNA-protein assembly that can repress gene expression. Constitutive heterochromatin is found, for example, at centromeres and the subtelomeric regions. Working with <jats:italic>Schizosaccharomyces pombe</jats:italic> , <jats:bold> Zofall <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="96" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1211651">96</jats:related-article> , published online 1 December) examined the heterochromatin islands often found near meiotic genes, which are maintained in a silenced state during vegetative growth. Heterochromatin formation at these loci did not generally involve the RNA interference machinery, as is observed at centromeres, but did require transcription. The exosome, an RNA-degrading machine, was involved in the formation of the heterochromatin islands, which could be remodeled in response to sexual differentiation. </jats:p>

<jats:title>Live Fast, Die Faster</jats:title> <jats:p> Treatment of <jats:italic>Mycobacterium tuberculosis</jats:italic> infections is complicated by the need for a prolonged course of antibiotics to fully eliminate all the bacteria present in an infected individual. Most antibiotics target growth and division machinery; thus, <jats:bold> Aldridge <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="100" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1216166">100</jats:related-article> , published online 15 November) postulated that heterogeneity in the growth properties of mycobacterial cells underlies variable antibiotic susceptibility. Cell division in mycobacteria was found to be asymmetrical, with one cell inheriting the growing pole and elongating rapidly, while the other cell elongated more slowly. Over multiple cell divisions, the rapidly growing cells became more susceptible to antibiotic treatment, helping to explain the observed heterogeneity in response to antibiotic therapy. </jats:p>

<jats:title>The Dark Side of Langerhans Cells</jats:title> <jats:p> Several immune cell populations reside in the skin and are thought to provide a protective barrier against infections and to act as sentinels against malignant transformation. However, studies in mice that lack Langerhans cells, a subset of dendritic cells, have suggested that these cells may actually promote tumorigenesis. Using a mouse model of squamous cell carcinoma, <jats:bold> Modi <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="104" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1211600">104</jats:related-article> ) now reveal how Langerhans cells may promote the transformation of skin epithelial cells. In response to the carcinogen 7,12-dimethylbenz[α]anthracene (DMBA), Langerhans cells increased their expression of the cytochrome P-450 enzyme CYP1B1, which can metabolize DMBA to the mutagenic DMBA- <jats:italic>trans</jats:italic> -3,4-diol. Thus, besides their functions in regulating the adaptive immune response, Langerhans cells may participate in the metabolism of environmental carcinogens. </jats:p>

<jats:title>Stop, Don't Go There</jats:title> <jats:p> Decision-making in complex brains requires the reaching of a consensus based on information relayed by multiple neurons. A similar situation occurs in the decision-making process of swarming bees, where multiple individuals relay information about suitable hive sites, but a single site is chosen by the swarm. <jats:bold> Seeley <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="108" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1210361">108</jats:related-article> , published online 8 December; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="43" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1216563"> <jats:bold>Niven</jats:bold> </jats:related-article> ) show that consensus in this system is reached as information from scouting bees accumulates within the hive. Stop signals were given by scout bees from a particular site to those scout bees signaling from other sites. As the signals accumulate, scouting ceases and the bees prepare to swarm to the site that was best represented among the scouts. When this process was simulated, the results indicated that cross-inhibition among the bees functions similarly to that which occurs among neurons within complex brains. In both cases, such cross-inhibition prevents the overall system from coming to an impasse. </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>

<jats:p>The show includes the parallel evolution of "supersoldier" ants, Ohm's law at the atomic scale, connecting obesity to cancer, and more.</jats:p>

<jats:p> This issue of <jats:italic>Science</jats:italic> includes the program of the 2012 AAAS Annual Meeting. The theme of the AAAS Annual Meeting in Vancouver, Canada, 16 to 20 February 2012, is "Flattening the World: Building a Global Knowledge Society." </jats:p> <jats:p> A <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.sciencemag.org/cgi/reprint/335/6064/113.pdf">PDF</jats:ext-link> of the program as it appears in this issue is available here; for more information on the meeting (including registration forms and information on accommodations), please visit <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="www.aaas.org/meetings/">www.aaas.org/meetings/</jats:ext-link> . </jats:p>