Catálogo de publicaciones - revistas

<jats:title>Destination Specificity</jats:title> <jats:p> During brain development, some types of neurons migrate from where they are born to their final functional locations. Some neurons migrate radially, from the inside to the outside, while others migrate tangentially. <jats:bold> Di Meglio <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="204" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229326">204</jats:related-article> ) analyzed the migration of a group of tangentially migrating neurons in the hindbrain. Although these neurons all entered the same migratory stream, they each retained positional information such that their relative organization in the destination site reflected their original organization. Interactions between epigenetic signals and the genes encoding Hox transcription factors encoded the positional information and fine-tuned migration. </jats:p>

<jats:title>Pupfish Speciation</jats:title> <jats:p> Evolution moves along phenotypic trajectories that can be visualized as a topographic landscape of multiple peaks of relatively high-fitness and low-fitness valleys. <jats:bold>Martin and Wainwright</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="208" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1227710">208</jats:related-article> ) examined the adaptive landscape of three species of <jats:italic>Cyprinodon</jats:italic> pupfishes. These species represent a recent adaptive radiation, each having moved into a difference niche within their specialized environment. Examining replicate hybrid transplants relative to parental types in high- and low-density enclosures, the authors recovered the specialist parental phenotypes and observed higher survival and growth. Thus, high density can drive multiple fitness peaks during the early stages of adaptive radiation. </jats:p>

<jats:title>Stress Protector</jats:title> <jats:p> During prolonged fasting, the oxidation of fatty acids leads to increased accumulation of <jats:sc>d</jats:sc> -β-hydroxybutyrate (βOHB) in the bloodstream. Such increased concentrations of βOHB inhibit class I histone deacetylases. Histone acetylation in turn influences transcriptional activity at various genes. <jats:bold> Shimazu <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="211" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1227166">211</jats:related-article> , published online 6 December; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6116" page="148" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1233423"> <jats:bold>Sassone-Corsi</jats:bold> </jats:related-article> ) found that among the genes showing increased transcription in animals treated with high concentrations of βOHB were two genes implicated in cellular responses to oxidative stress. When treated ahead of time with βOHB, mice were protected from the toxic effects of the oxidative stress causing poison paraquat. </jats:p>

<jats:title>Repair and Recombination</jats:title> <jats:p> In most sexually reproducing organisms, the haploid gametes are produced by meiosis, a specialized cell-division during which recombination between the parental chromosomes ensures proper chromosome segregation. Double-strand breaks (DSB) generated in the DNA drive this recombination and are linked to recombination hotspots in the chromatin where histone H3 is methylated on lysine residue 4 (H3K4me) by the Set1C/COMPASS enzyme complex. <jats:bold> Acquaviva <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="215" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1225739">215</jats:related-article> , published online 15 November) show that the Mer2/Mei4/Rec114 complex of the DSB generating machinery is linked to the Set1C/COMPASS enzyme complex through the Spp1 subunit, which contains a PHD-finger capable of binding to H3K4me. The Spp1 subunit recruits the Mer2 protein to sites where recombination will occur, probably by binding to both the H3K4me-marked chromatin and other factors. </jats:p>

<jats:title>Macrophage JNK in Metabolic Disease</jats:title> <jats:p> Inflammation is thought to be an important driver of diet-induced obesity and insulin resistance. Proinflammatory, M1 phenotype macrophages and the c-jun NH <jats:sub>2</jats:sub> terminal kinases (JNK) are central players in this process. But whether JNK expression is specifically required inside macrophages is unclear. In mice containing a macrophage-specific deletion in both <jats:italic>Jnk1</jats:italic> and <jats:italic>Jnk2</jats:italic> , <jats:bold> Han <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="218" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1227568">218</jats:related-article> , published online 6 December; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6116" page="147" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1233223"> <jats:bold>Ferrante Jr.</jats:bold> </jats:related-article> ) found that the mice were protected against many of the diet-induced metabolic changes, including insulin resistance, despite similar weight gain as control mice on a high-fat diet. This protection was associated with a decrease in the presence of M1 macrophages in adipose tissue. </jats:p>

<jats:title>SAM, Histones, and Stem Cells</jats:title> <jats:p> Mouse embryonic stem cells require threonine for growth and express large amounts of the enzyme that catalyzes the first step in threonine metabolism. To find out what is so important about threonine in these cells, <jats:bold> Shyh-Change <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="222" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1226603">222</jats:related-article> , published online 1 November; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6116" page="148" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1233423"> <jats:bold>Sassone-Corsi</jats:bold> </jats:related-article> ) monitored changes in metabolism by mass spectrometry in induced pluripotent stem cells. Threonine was required to maintain cellular concentrations of S-adenosylmethionine (SAM), a substrate used for protein methylation. Restriction of threonine inhibited methylation of histones, which is characteristic of chromatin in embryonic stem cells. Thus, altered metabolism of threonine and methionine in stem cells may be linked to epigenetic changes that influence genetic reprogramming and decisions of stem cells to proliferate or differentiate. </jats:p>

<jats:title>Diffraction Before Destruction</jats:title> <jats:p> A bottleneck in x-ray crystallography is the growth of well-ordered crystals large enough to obtain high-resolution diffraction data within an exposure that limits radiation damage. Serial femtosecond crystallography promises to overcome these constraints by using short intense pulses that out-run radiation damage. A stream of crystals is flowed across the free-electron beam and for each pulse, diffraction data is recorded from a single crystal before it is destroyed. <jats:bold> Redecke <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="227" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1229663">227</jats:related-article> , published online 29 November; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6116" page="146" related-article-type="in-this-issue" vol="339" xlink:href="10.1126/science.1233209">Helliwell</jats:related-article> </jats:bold> ) used this technique to determine the structure of an enzyme from <jats:italic>Trypanosoma brucei</jats:italic> , the parasite that causes sleeping sickness, from micron-sized crystals grown within insect cells. The structure shows how this enzyme, which is involved in degradation of host proteins, is natively inhibited prior to activation, which could help in the development of parasite-specific inhibitors. </jats:p>

<jats:p>Listen to stories on China's one-child policy, anti-inflammatory therapy for chronic disease, selling expertise to investors and more.</jats:p>

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