@article{9454, author = {Chan, Simon W.-L. and Zilberman, Daniel and Xie, Zhixin and Johansen, Lisa K. and Carrington, James C. and Jacobsen, Steven E.}, issn = {1095-9203}, journal = {Science}, keywords = {Multidisciplinary}, number = {5662}, pages = {1336}, publisher = {American Association for the Advancement of Science}, title = {{RNA silencing genes control de novo DNA methylation}}, doi = {10.1126/science.1095989}, volume = {303}, year = {2004}, } @article{9455, abstract = {Proteins of the ARGONAUTE family are important in diverse posttranscriptional RNA-mediated gene-silencing systems as well as in transcriptional gene silencing in Drosophila and fission yeast and in programmed DNA elimination in Tetrahymena. We cloned ARGONAUTE4 (AGO4) from a screen for mutants that suppress silencing of the Arabidopsis SUPERMAN(SUP) gene. The ago4-1 mutant reactivated silentSUP alleles and decreased CpNpG and asymmetric DNA methylation as well as histone H3 lysine-9 methylation. In addition,ago4-1 blocked histone and DNA methylation and the accumulation of 25-nucleotide small interfering RNAs (siRNAs) that correspond to the retroelement AtSN1. These results suggest that AGO4 and long siRNAs direct chromatin modifications, including histone methylation and non-CpG DNA methylation.}, author = {Zilberman, Daniel and Cao, Xiaofeng and Jacobsen, Steven E.}, issn = {1095-9203}, journal = {Science}, keywords = {Multidisciplinary}, number = {5607}, pages = {716--719}, publisher = {American Association for the Advancement of Science}, title = {{ARGONAUTE4 control of locus-specific siRNA accumulation and DNA and histone methylation}}, doi = {10.1126/science.1079695}, volume = {299}, year = {2003}, } @article{4255, abstract = {Humans and their closest evolutionary relatives, the chimpanzees, differ in ∼1.24% of their genomic DNA sequences. The fraction of these changes accumulated during the speciation processes that have separated the two lineages may be of special relevance in understanding the basis of their differences. We analyzed human and chimpanzee sequence data to search for the patterns of divergence and polymorphism predicted by a theoretical model of speciation. According to the model, positively selected changes should accumulate in chromosomes that present fixed structural differences, such as inversions, between the two species. Protein evolution was more than 2.2 times faster in chromosomes that had undergone structural rearrangements compared with colinear chromosomes. Also, nucleotide variability is slightly lower in rearranged chromosomes. These patterns of divergence and polymorphism may be, at least in part, the molecular footprint of speciation events in the human and chimpanzee lineages. }, author = {Navarro, Arcadio and Barton, Nicholas H}, issn = {0036-8075}, journal = {Science}, number = {5617}, pages = {321 -- 324}, publisher = {American Association for the Advancement of Science}, title = {{Chromosomal speciation and molecular divergence -- Accelerated evolution in rearranged chromosomes}}, doi = {10.1126/science.1080600 }, volume = {300}, year = {2003}, } @article{3757, abstract = {A central problem in biology is determining how genes interact as parts of functional networks. Creation and analysis of synthetic networks, composed of well-characterized genetic elements, provide a framework for theoretical modeling. Here, with the use of a combinatorial method, a library of networks with varying connectivity was generated in Escherichia coli. These networks were composed of genes encoding the transcriptional regulators Lacl, TetR, and lambda Cl, as well as the corresponding promoters. They displayed phenotypic behaviors resembling binary logical circuits, with two chemical “inputs” and a fluorescent protein “output.” Within this simple system, diverse computational functions arose through changes in network connectivity. Combinatorial synthesis provides an alternative approach for studying biological networks, as well as an efficient method for producing diverse phenotypes in vivo.}, author = {Guet, Calin C and Elowitz, Michael and Hsing, Weihong and Leibler, Stanislas}, issn = {0036-8075}, journal = {Science}, number = {5572}, pages = {1466 -- 1470}, publisher = {American Association for the Advancement of Science}, title = {{Combinatorial synthesis of genetic networks}}, doi = {10.1126/science.1067407}, volume = {296}, year = {2002}, } @article{9444, abstract = {Epigenetic silenced alleles of the Arabidopsis SUPERMANlocus (the clark kent alleles) are associated with dense hypermethylation at noncanonical cytosines (CpXpG and asymmetric sites, where X = A, T, C, or G). A genetic screen for suppressors of a hypermethylated clark kent mutant identified nine loss-of-function alleles of CHROMOMETHYLASE3(CMT3), a novel cytosine methyltransferase homolog. These cmt3 mutants display a wild-type morphology but exhibit decreased CpXpG methylation of the SUP gene and of other sequences throughout the genome. They also show reactivated expression of endogenous retrotransposon sequences. These results show that a non-CpG DNA methyltransferase is responsible for maintaining epigenetic gene silencing.}, author = {Lindroth, A. M. and Cao, Xiaofeng and Jackson, James P. and Zilberman, Daniel and McCallum, Claire M. and Henikoff, Steven and Jacobsen, Steven E.}, issn = {1095-9203}, journal = {Science}, keywords = {Multidisciplinary}, number = {5524}, pages = {2077--2080}, publisher = {American Association for the Advancement of Science}, title = {{Requirement of CHROMOMETHYLASE3 for maintenance of CpXpG methylation}}, doi = {10.1126/science.1059745}, volume = {292}, year = {2001}, } @article{3438, abstract = {As a discipline, phylogenetics is becoming transformed by a flood of molecular data. These data allow broad questions to be asked about the history of life, but also present difficult statistical and computational problems. Bayesian inference of phylogeny brings a new perspective to a number of outstanding issues in evolutionary biology, including the analysis of large phylogenetic trees and complex evolutionary models and the detection of the footprint of natural selection in DNA sequences.}, author = {Huelsenbeck, John and Ronquist, Fredrik and Nielsen, Rasmus and Bollback, Jonathan P}, issn = {0036-8075}, journal = {Science}, number = {5550}, pages = {2310 -- 2314}, publisher = {American Association for the Advancement of Science}, title = {{Bayesian inference of phylogeny and its impact on evolutionary biology}}, doi = {10.1126/science.1065889}, volume = {294}, year = {2001}, } @article{2601, abstract = {Targeted deletion of metabotropic glutamate receptor-subtype 1 (mGluR1) gene can cause defects in development and function in the cerebellum. We introduced the mGluR1α transgene into mGluR1-null mutant [mGluR1 (-/-)] mice with a Purkinje cell (PC)-specific promoter. mGluR1-rescue mice showed normal cerebellar long-term depression and regression of multiple climbing fiber innervation, events significantly impaired in mGluR1 (-/-) mice. The impaired motor coordination was rescued by this transgene, in a dose-dependent manner. We propose that mGluR1 in PCs is a key molecule for normal synapse formation, synaptic plasticity, and motor control in the cerebellum.}, author = {Ichise, Taeko and Kano, Masanobu and Hashimoto, Kouichi and Yanagihara, Dai and Nakao, Kazuki and Shigemoto, Ryuichi and Katsuki, Motoya and Aiba, Atsu}, issn = {0036-8075}, journal = {Science}, number = {5472}, pages = {1832 -- 1835}, publisher = {American Association for the Advancement of Science}, title = {{mGluR1 in cerebellar Purkinje cells essential for long-term depression, synapse elimination, and motor coordination}}, doi = {10.1126/science.288.5472.1832}, volume = {288}, year = {2000}, } @article{3491, abstract = {Fast and reliable activation of inhibitory interneurons is critical for the stability of cortical neuronal networks. Active conductances in dendrites may facilitate interneuron activation, but direct experimental evidence was unavailable. Patch-clamp recordings from dendrites of hippocampal oriens- alveus interneurons revealed high densities of voltage-gated sodium and potassium ion channels. Simultaneous recordings from dendrites and somata suggested that action potential initiation occurs preferentially in the axon with long threshold stimuli, but can be shifted to somatodendritic sites when brief stimuli are applied. After initiation, action potentials propagate over the somatodendritic domain with constant amplitude, high velocity, and reliability, even during high-frequency trains.}, author = {Martina, Marco and Vida, Imre and Jonas, Peter M}, issn = {0036-8075}, journal = {Science}, number = {5451}, pages = {295 -- 300}, publisher = {American Association for the Advancement of Science}, title = {{Distal initiation and active propagation of action potentials in interneuron dendrites}}, doi = {10.1126/science.287.5451.295}, volume = {287}, year = {2000}, } @article{3487, abstract = {It is widely accepted that individual neurons in the central nervous system release only a single fast transmitter. The possibility of corelease of fast neurotransmitters was examined by making paired recordings from synaptically connected neurons in spinal cord slices. Unitary inhibitory postsynaptic currents generated at interneuron-motoneuron synapses consisted of a strychnine-sensitive, glycine receptor-mediated component and a bicuculline-sensitive, γ-aminobutyric acid (GABA)(A) receptor-mediated component. These results indicate that spinal interneurons release both glycine and GABA to activate functionally distinct receptors in their postsynaptic target cells. A subset of miniature synaptic currents also showed both components, consistent with corelease from individual synaptic vesicles.}, author = {Jonas, Peter M and Bischofberger, Joseph and Sandkühler, Jürgen}, issn = {0036-8075}, journal = {Science}, number = {5375}, pages = {419 -- 424}, publisher = {American Association for the Advancement of Science}, title = {{Corelease of two fast neurotransmitters at a central synapse}}, doi = {10.1126/science.281.5375.419}, volume = {281}, year = {1998}, } @article{4281, abstract = {Most higher organisms reproduce sexually, despite the automatic reproductive advantage experienced by asexual variants. This implies the operation of selective forces that confer an advantage to sexuality and genetic recombination, at either the population or individual level. The effect of sex and recombination in breaking down negative correlations between favorable variants at different genetic loci, which increases the efficiency of natural selection, is likely to be a major factor favoring their evolution and maintenance. Various processes that can cause such an effect have been studied theoretically. It has, however, so far proved hard to discriminate among them empirically. }, author = {Barton, Nicholas H and Charlesworth, Brian}, issn = {0036-8075}, journal = {Science}, number = {5385}, pages = {1986 -- 1990}, publisher = {American Association for the Advancement of Science}, title = {{Why sex and recombination?}}, doi = {10.1126/science.281.5385.1986}, volume = {281}, year = {1998}, } @article{2571, abstract = {Subtype 2 of the metabotropic glutamate receptor (mGluR2) is expressed in the presynaptic elements of hippocampal mossy fiber-CA3 synapses. Knockout mice deficient in mGluR2 showed no histological changes and no alterations in basal synaptic transmission, paired-pulse facilitation, or tetanus-induced long-term potentiation (LTP) at the mossy fiber-CA3 synapses. Long-term depression (LTD) induced by low-frequency stimulation, however, was almost fully abolished. The mutant mice performed normally in water maze learning tasks. Thus, the presynaptic mGluR2 is essential for inducing LTD at the mossy fiber-CA3 synapses, but this hippocampal LTD does not seem to be required for spatial learning.}, author = {Yokoi, Mineto and Kobayashi, Kazuto and Manabe, Toshiya and Takahashi, Tomoyuki and Sakaguchi, Isako and Katsuura, Goro and Shigemoto, Ryuichi and Ohishi, Hitoshi and Nomura, Sakashi and Nakamura, Kenji and Nakao, Kazuki and Katsuki, Motoya and Nakanishi, Shigetada}, issn = {0036-8075}, journal = {Science}, pages = {645 -- 647}, publisher = {American Association for the Advancement of Science}, title = {{Impairment of hippocampal mossy fiber LTD in mice lacking mGluR2}}, doi = {10.1126/science.273.5275.645}, volume = {273}, year = {1996}, } @article{3469, abstract = {Glutamate-operated ion channels (GluR channels) of the L-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-kainate subtype are found in both neurons and glial cells of the central nervous system. These channels are assembled from the GluR-A, -B, -C, and -D subunits; channels containing a GluR-B subunit show an outwardly rectifying current-voltage relation and low calcium permeability, whereas channels lacking the GluR-B subunit are characterized by a doubly rectifying current-voltage relation and high calcium permeability. Most cell types in the central nervous system coexpress several subunits, including GluR-B. However, Bergmann glia in rat cerebellum do not express GluR-B subunit genes. In a subset of cultured cerebellar glial cells, likely derived from Bergmann glial cells. GluR channels exhibit doubly rectifying current-voltage relations and high calcium permeability, whereas GluR channels of cerebellar neurons have low calcium permeability. Thus, differential expression of the GluR-B subunit gene in neurons and glia is one mechanism by which functional properties of native GluR channels are regulated.}, author = {Burnashev, Nail and Khodorova, Alla and Jonas, Peter M and Helm, P. and Wisden, William and Monyer, Hannah and Seeburg, Peter and Sakmann, Bert}, issn = {0036-8075}, journal = {Science}, number = {5063}, pages = {1566 -- 1570}, publisher = {American Association for the Advancement of Science}, title = {{Calcium-permeable AMPA-kainate receptors in fusiform cerebellar glial cells.}}, doi = {10.1126/science.1317970}, volume = {256}, year = {1992}, }