Catálogo de publicaciones - revistas

<jats:title>A Different Cycle for Differentiation</jats:title> <jats:p> The regulated expression of transcription factors determines cell fate decisions during cell differentiation. The transcription factor PU.1 is an important determinant in the differentiation of hematopoietic progenitors to lymphocytes or myeloid cells, where high expression induces macrophage differentiation, whereas low expression leads to the development of B lymphocytes. How PU.1 expression levels are regulated during this cell fate choice, however, is not well understood. <jats:bold> Kueh <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6146" page="670" related-article-type="in-this-issue" vol="341" xlink:href="10.1126/science.1240831">670</jats:related-article> , published online 18 July) found that in mice, reduced transcription of PU.1 led to its reduced expression in developing B lymphocytes, whereas in macrophages, PU.1 was able to accumulate stably because of a lengthening of the cell cycle. Exogenous expression of PU.1 in progenitors supported cell cycle lengthening and macrophage differentiation, and mathematical modeling suggested that such a feedback loop could maintain a slow-dividing macrophage developmental state. </jats:p>

<jats:title>Help Shared</jats:title> <jats:p> Germinal centers are specialized structures within lymph nodes, where B cells undergo the changes required to produce high-affinity antibodies. This process relies on T follicular helper (Tfh) cells. The dynamic properties of Tfh cells and how they affect the selection of B cells, however, are not well understood. Using two-photon laser scanning microscopy of mouse lymph nodes, <jats:bold> Shulman <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6146" page="673" related-article-type="in-this-issue" vol="341" xlink:href="10.1126/science.1241680">673</jats:related-article> , published online 25 July) find that Tfh cells are not restricted to a single germinal center, but instead emigrate into neighboring germinal centers within the same lymph nodes. Furthermore, newly activated T cells can enter already established germinal centers and presumably influence ongoing B cell selection and differentiation. Such active movement may ensure maximal diversification of the B cell response and promote the production of high-affinity antibodies. </jats:p>

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<jats:title>Understanding Xist-ance</jats:title> <jats:p> Large noncoding RNAs (lncRNAs) are increasingly appreciated to play important roles in the cell. A number of lncRNAs act to target chromatin regulatory complexes to their sites of action. <jats:bold> Engreitz <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.sciencemag.org/content/341/6147/1237973..full">10.1126/science.1237973</jats:ext-link> , published online 4 July; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6147" page="720" related-article-type="in-this-issue" vol="341" xlink:href="10.1126/science.1243257"> <jats:bold>Dimond and Fraser</jats:bold> </jats:related-article> ) found that the mouse Xist lncRNA, which initiates X-chromosome inactivation, was transferred from its site of transcription to distant sites on the X chromosome purely through their close three-dimensional proximity to the <jats:italic>Xist</jats:italic> gene. Xist initially localized to the periphery of active genes on the X chromosome but gradually spread across them using its A-repeat domain, until the Xist RNA bound broadly across the inactive X chromosome in differentiated female cells. </jats:p>