ALBERT

Description: Ultra-compact dwarf galaxies are among the densest stellar systems in the Universe. These systems have masses of up to 2 x 10(8) solar masses, but half-light radii of just 3-50 parsecs. Dynamical mass estimates show that many such dwarfs are more massive than expected from their luminosity. It remains unclear whether these high dynamical mass estimates arise because of the presence of supermassive black holes or result from a non-standard stellar initial mass function that causes the average stellar mass to be higher than expected. Here we report adaptive optics kinematic data of the ultra-compact dwarf galaxy M60-UCD1 that show a central velocity dispersion peak exceeding 100 kilometres per second and modest rotation. Dynamical modelling of these data reveals the presence of a supermassive black hole with a mass of 2.1 x 10(7) solar masses. This is 15 per cent of the object's total mass. The high black hole mass and mass fraction suggest that M60-UCD1 is the stripped nucleus of a galaxy. Our analysis also shows that M60-UCD1's stellar mass is consistent with its luminosity, implying a large population of previously unrecognized supermassive black holes in other ultra-compact dwarf galaxies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Seth, Anil C -- van den Bosch, Remco -- Mieske, Steffen -- Baumgardt, Holger -- den Brok, Mark -- Strader, Jay -- Neumayer, Nadine -- Chilingarian, Igor -- Hilker, Michael -- McDermid, Richard -- Spitler, Lee -- Brodie, Jean -- Frank, Matthias J -- Walsh, Jonelle L -- England -- Nature. 2014 Sep 18;513(7518):398-400. doi: 10.1038/nature13762.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, University of Utah, 115 South 1400 East, Salt Lake City, Utah 84112, USA. ; Max-Planck Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany. ; European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, 7630355, Chile. ; School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia. ; Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA. ; 1] Max-Planck Institut fur Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany [2] European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany. ; 1] Smithsonian Astrophysical Observatory, 60 Garden Street MS09, Cambridge, Massachusetts 02138, USA [2] Sternberg Astronomical Institute, Moscow State University, 13 Universitetski prospect, Moscow 119992, Russia. ; European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany. ; 1] Australian Astronomical Observatory, 105 Delhi Road, Sydney, New South Wales 2113, Australia [2] Department of Physics and Astronomy, Macquarie University, Sydney, New South Wales 2109, Australia. ; University of California Observatories and Department of Astronomy and Astrophysics, University of California, Santa Cruz, California 95064, USA. ; Landessternwarte, Zentrum fur Astronomie der Universitat Heidelberg, Konigsstuhl 12, D-69117 Heidelberg, Germany. ; Department of Astronomy, The University of Texas at Austin, 1 University Station C1400, Austin, Texas 78712, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25230660" target="_blank"〉PubMed〈/a〉

Description: The large family of KRAB zinc finger (KZNF) genes are transcription factors implicated in recognizing and repressing repetitive sequences such as transposable elements (TEs) in our genome. Through successive waves of retrotransposition-mediated insertions, various classes of TEs have invaded mammalian genomes at multiple timepoints throughout evolution. Even though most of the TE classes in our genome lost the capability to retrotranspose millions of years ago, it remains elusive why the KZNFs that evolved to repress them are still retained in our genome. One hypothesis is that KZNFs become repurposed for other regulatory roles. Here, we find evidence that evolutionary changes in KZNFs provide them not only with the ability to repress TEs, but also to bind to gene promoters independent of TEs. Using KZNF binding site data in conjunction with gene expression values from the Allen Brain Atlas, we show that KZNFs have the ability to regulate gene expression in the human brain in a region-specific manner. Our analysis shows that the expression of KZNFs shows correlation with the expression of their target genes, suggesting that KZNFs have a direct influence on gene expression in the developing human brain. The extent of this regulation and the impact it has on primate brain evolution are still to be determined, but our results imply that KZNFs have become widely integrated into neuronal gene regulatory networks. Our analysis predicts that gene expression networks have been repeatedly innovated throughout primate evolution, continuously gaining new layers of gene regulation mediated by both TEs and KZNFs in our genome. This article is part of a discussion meeting issue ‘Crossroads between transposons and gene regulation’.