{"id":13841,"date":"2018-07-12T20:01:17","date_gmt":"2018-07-12T18:01:17","guid":{"rendered":"https:\/\/news.embl.de\/?p=13841"},"modified":"2024-03-22T10:54:36","modified_gmt":"2024-03-22T09:54:36","slug":"parental-chromosomes-kept-apart-during-embryos-first-division","status":"publish","type":"post","link":"https:\/\/www.embl.org\/news\/science\/parental-chromosomes-kept-apart-during-embryos-first-division\/","title":{"rendered":"Parental chromosomes kept apart during first division"},"content":{"rendered":"\n<p>It was long thought that during an embryo\u2019s first cell division, one spindle is responsible for segregating the embryo\u2019s chromosomes into two cells. EMBL scientists now show that in mice, there are actually two spindles, one for each set of parental chromosomes, meaning that the genetic information from each parent is kept apart throughout the first division. <em>Science<\/em> publishes the results \u2013 bound to change biology textbooks \u2013 on 12 July 2018.<\/p>\n\n\n\n<p>This dual spindle formation might explain part of the high error rate in the early developmental stages of mammals, spanning the first few cell divisions. \u201cThe aim of this project was to find out why so many mistakes happen in those first divisions,\u201d says <a href=\"https:\/\/www.embl.de\/research\/units\/cbb\/ellenberg\/index.html\" target=\"_blank\" rel=\"noopener noreferrer\">Jan Ellenberg, the group leader at EMBL<\/a> who led the project. \u201cWe already knew about dual spindle formation in simpler organisms like insects, but we never thought this would be the case in mammals like mice. This finding was a big surprise, showing that you should always be prepared for the unexpected.\u201d<\/p>\n\n\n<div\n  class=\"vf-embed vf-embed--custom-ratio\"\n\n  style=\"--vf-embed-max-width: 100%;\n    --vf-embed-custom-ratio-x: 640;\n    --vf-embed-custom-ratio-y: 360;\"><iframe loading=\"lazy\" width=\"640\" height=\"360\" src=\"https:\/\/www.youtube.com\/embed\/TkJPbmXIIL0\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen><\/iframe><\/div>\n\n\n\n<p class=\"vf-figure__caption\"><br \/>Video revealing how the two parental genomes (labelled in pink and blue) remain spatially separate throughout the first cell division (text continues below).<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Solving a 20-year-old mystery<\/h2>\n\n\n\n<p>Scientists have always seen parental chromosomes occupying two half-moon-shaped parts in the nucleus of two-cell embryos, but it wasn\u2019t clear how this could be explained. \u201cFirst, we were looking at the motion of parental chromosomes only, and we couldn\u2019t make sense of the cause of the separation,\u201d says Judith Reichmann, scientist in EMBL\u2019s Ellenberg group and first author of the paper. \u201cOnly when focusing on the microtubules \u2013 the dynamic structures that spindles are made of \u2013 could we see the dual spindles for the first time. This allowed us to provide an explanation for this 20-year-old mystery.\u201d<\/p>\n\n\n<div class=\"vf-box vf-box--normal vf-box-theme--primary\">\n<h2 class=\"vf-box__heading\">What is mitosis?<\/h2>\n<p class=\"vf-box__text\">Mitosis is the process of cell division, when one cell splits into two daughter cells. It occurs throughout the lifespan of multi-cellular organisms but is particularly important when the organism grows and develops. The key step of mitosis is to pass an identical copy of the genome to the next cell generation. For this to happen, DNA is duplicated and organised into dense thread-like structures known as chromosomes. The chromosomes are then attached to long protein fibres \u2013 organised into a spindle \u2013 which pulls the chromosomes apart and triggers the formation of two new cells.<\/p>\n<h2 class=\"vf-box__heading\">What is the spindle?<\/h2>\n<p class=\"vf-box__text\">The spindle is made of thin, tube-like protein assemblies known as microtubules. During mitosis of animal cells, groups of such tubes grow dynamically and self-organise into a bi-polar spindle that surrounds the chromosomes. The microtubule fibres grow towards the chromosomes and connect with them, in preparation for chromosome separation to the daughter cells. Normally there is only one bi-polar spindle per cell, however, this research suggests that during the first cell division there are two: one each for the maternal and paternal chromosomes.<\/p>\n<p class=\"vf-box__text\"><\/p><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">New molecular targets<\/h2>\n\n\n\n<p>\u201cThe dual spindles provide a previously unknown mechanism \u2013 and thus a possible explanation \u2013 for one of the common mistakes we see in the first divisions of mammalian embryos,\u201d Ellenberg explains. Such mistakes can result in cells with multiple nuclei, terminating development. \u201cNow, we have a new mechanism to go after and identify new molecular targets. It will be important to find out if it works the same in humans, because that could provide valuable information for research on how to improve human infertility treatment, for example.\u201d<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">The beginning of life<\/h2>\n\n\n\n<p>Furthermore, the knowledge from this paper might impact legislation. In some countries, the law states that human life begins \u2013 and is thus protected \u2013 when the maternal and paternal nuclei fuse after fertilisation. If it turns out that the dual spindle process works the same in humans, this definition is not fully accurate, as the union in one nucleus happens slightly later, after the first cell division.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Impossible until now<\/h2>\n\n\n\n<p>This discovery would have been impossible without the light-sheet microscopy technology developed in Ellenberg\u2019s and Lars Hufnagel\u2019s group at EMBL, which is now available through the EMBL spin-off company Luxendo. This allows for real-time and 3D imaging of the early stages of development, when embryos are very sensitive to light and would be damaged by conventional light microscopy methods. The high speed and spatial precision of light-sheet microscopy drastically reduce the amount of light that the embryo is exposed to, making a detailed analysis of these formerly hidden processes possible.<\/p>\n\n\n\n<p><em>This work was supported by the ERC Advanced Grant \u201cCorema\u201d (grant agreement 694236) and by the European Molecular Biology Laboratory. The authors were further supported by the EMBL Interdisciplinary Postdoc Programme (EIPOD) under Marie Curie Actions COFUND; by the EMBO long-term postdoctoral fellowship and EC Marie Sklodowska-Curie postdoctoral fellowship; by a Boehringer Ingelheim Fonds Phd fellowship, and by a Humboldt Foundation postdoctoral fellowship.<\/em><\/p>\n\n\n<hr class=\"vf-divider\"\/>\n\n\n\n<h2 class=\"wp-block-heading\" id=\"de\">Die Chromosomen der Eltern bleiben w\u00e4hrend der ersten Teilung des Embryos getrennt<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Wissenschaftler des EMBL zeigen, dass das Leben von S\u00e4ugetieren anders beginnt als gedacht<\/h3>\n\n\n\n<p>Lange dachte man, dass bei der ersten embryonalen Zellteilung nur eine Spindel f\u00fcr die Auftrennung aller Chromosomen des Embryos in zwei Zellen verantwortlich ist. EMBL-Wissenschaftler zeigen nun, dass es tats\u00e4chlich aber zwei Spindeln gibt, eine f\u00fcr jeden elterlichen Chromosomensatz; das bedeutet, dass die genetischen Informationen von Mutter und Vater w\u00e4hrend der ersten Teilung getrennt gehalten werden. Science ver\u00f6ffentlicht die Ergebnisse \u2013 die ein Umschreiben der Biologielehrb\u00fccher zur Folge haben d\u00fcrften \u2013 am 12. Juli 2018.<\/p>\n\n\n\n<figure class=\"vf-figure wp-block-image size-large\"><img decoding=\"async\" class=\"vf-figure__image\" src=\"https:\/\/www.embl.org\/news\/wp-content\/uploads\/2018\/07\/Science-Ellenberg-ib.jpg\" alt=\"\"\/><figcaption class=\"vf-figure__caption\">K\u00fcnstlerische 3D Darstellung der Doppelspindel in der S\u00e4ugetierzygote.&nbsp;Bildrechte: Cartasiova\/Hoissan\/Reichmann\/Ellenberg, EMBL<br \/>In Gr\u00fcn sind die Mikroturboli dargestellt aus denen die Spindel besteht und Pink stellt das Zentrosom dar: Das Hauptzentrum, das die Mikroturboli organisiert. Die DNA ist in Blau dargestellt, und Orange zeigt die Kinetochoren: Proteinstrukturen, an denen sich die Mikroturboli w\u00e4hrend der Zellteilung befestigen, um die Chromosomen auseinander zu ziehen.<\/figcaption><\/figure>\n\n\n\n<p>Die Bildung dieser Doppelspindel k\u00f6nnte einen Teil der hohen Fehlerrate in den fr\u00fchen Entwicklungsstadien w\u00e4hrend der ersten Zellteilungen von S\u00e4ugetieren erkl\u00e4ren. \u201eZiel dieses Projekts war es, herauszufinden, warum bei den ersten Teilungen so viele Fehler passieren\u201c, sagt Jan Ellenberg, der Gruppenleiter am EMBL, der das Projekt leitete. \u201eWir wussten bereits, dass bei einfacheren Tieren wie Insekten zwei Spindeln gebildet werden, h\u00e4tten aber niemals vermutet, dass dies auch bei S\u00e4ugetieren wie M\u00e4usen der Fall ist. Dieses Ergebnis war eine gro\u00dfe \u00dcberraschung f\u00fcr uns und zeigt, dass man immer auf das Unerwartete vorbereitet sein sollte.\u201c<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Aufl\u00f6sung eines 20 Jahre alten R\u00e4tsels<\/h2>\n\n\n\n<p>Wissenschaftler hatten schon lange beobachtet, dass die elterlichen Chromosomen sich in den runden Zellkernen zweizelliger Embryonen wie zwei Halbmonde anordnen, doch niemand wusste eine Erkl\u00e4rung daf\u00fcr. \u201eAnfangs haben wir die Bewegungen der elterlichen Chromosomen verfolgt, wir konnten aber keine Ursache f\u00fcr diese Verteilung finden\u201c, erkl\u00e4rt Judith Reichmann, Wissenschaftlerin in der Ellenberg-Gruppe am EMBL und Erstautorin des Artikels. \u201eErst, als wir unsere Aufmerksamkeit auf die Mikrotubuli \u2013 die dynamischen Strukturen, aus denen die Spindeln bestehen \u2013 richteten, konnten wir zum ersten Mal die Doppelspindeln sehen. Damit konnten wir eine Erkl\u00e4rung f\u00fcr dieses 20 Jahre alte R\u00e4tsel liefern.\u201c<\/p>\n\n\n<div\n  class=\"vf-embed vf-embed--custom-ratio\"\n\n  style=\"--vf-embed-max-width: 100%;\n    --vf-embed-custom-ratio-x: 640;\n    --vf-embed-custom-ratio-y: 360;\"><iframe loading=\"lazy\" width=\"640\" height=\"360\" src=\"https:\/\/www.youtube.com\/embed\/TkJPbmXIIL0\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen><\/iframe><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">Neue molekulare Zielstrukturen<\/h2>\n\n\n\n<p>\u201eDie Doppelspindeln liefern einen bisher unbekannten Mechanismus \u2013 und damit eine m\u00f6gliche Erkl\u00e4rung \u2013 f\u00fcr einen der Fehler, die wir bei den ersten Teilungen von S\u00e4ugetierembryonen beobachten\u201c, erkl\u00e4rt Ellenberg. Solche Fehler k\u00f6nnen zu mehrkernigen Zellen und dadurch zum Abbruch der Entwicklung des Embryos f\u00fchren. \u201eJetzt haben wir einen bisher unbekannten Mechanismus, den wir untersuchen k\u00f6nnen, um neue molekulare Zielstrukturen zu identifizieren. Es wird in Zukunft auch wichtig sein herauszufinden, ob dieser Prozess beim Menschen genauso abl\u00e4uft. Dadurch k\u00f6nnte man zum Beispiel wertvolle Informationen f\u00fcr die zuk\u00fcnftige Forschung zur Verbesserung der Behandlung der Unfruchtbarkeit beim Menschen erhalten.\u201c<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Der Beginn des Lebens<\/h2>\n\n\n\n<p>Dar\u00fcber hinaus k\u00f6nnten die Erkenntnisse dieser Arbeit Auswirkungen auf Gesetzestexte haben. Nach der Rechtsauffassung in einigen L\u00e4ndern beginnt das menschliche Leben \u2013 und damit sein Schutz \u2013 mit der Verschmelzung des m\u00fctterlichen und des v\u00e4terlichen Zellkerns nach der Befruchtung. Sollte die Doppelspindelbildung beim Menschen \u00e4hnlich ablaufen wie in M\u00e4usen, w\u00e4re diese Definition nicht mehr ganz richtig. Die Bildung eines gemeinsamen Zellkerns f\u00e4nde dann erst nach der ersten Zellteilung statt.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Erst jetzt m\u00f6glich<\/h2>\n\n\n\n<p>Diese Entdeckung w\u00e4re ohne die Lichtblattmikroskopie nicht m\u00f6glich gewesen. Diese Technologie wurde in der Gruppe um Jan Ellenberg und Lars Hufnagel am EMBL weiterentwickelt und ist inzwischen \u00fcber das EMBL-Spin-off-Unternehmen Luxendo erh\u00e4ltlich. Mithilfe dieses Verfahrens lassen sich die fr\u00fchen Entwicklungsstadien, in denen Embryonen sehr lichtempfindlich sind und durch herk\u00f6mmliche lichtmikroskopische Methoden gesch\u00e4digt w\u00fcrden, in Echtzeit und 3D beobachten. Die sehr kurze und r\u00e4umliche pr\u00e4zise Beleuchtung in der Lichtblattmikroskopie verringert drastisch die Lichtenergie, mit der der Embryo untersucht wird, und erm\u00f6glichte damit eine detaillierte Untersuchung dieser bislang verborgenen Vorg\u00e4nge.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Mammalian life begins differently than we thought<\/p>\n","protected":false},"author":58,"featured_media":13842,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[2,17591],"tags":[66,302,665,663,664,667,620,1748,666],"embl_taxonomy":[],"class_list":["post-13841","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science","category-science-technology","tag-cell-division","tag-ellenberg","tag-embryo","tag-fertilisation","tag-genome","tag-light-sheet-microscopy","tag-mitosis","tag-press-release","tag-spindle"],"acf":{"article_intro":"<p>EMBL scientists show that mammalian life begins differently than we thought<\/p>\n","related_links":[{"link_description":"Research of the Ellenberg group","link_url":"https:\/\/www.embl.de\/research\/units\/cbb\/ellenberg\/"}],"article_sources":[{"source_description":"<p>Reichmann, J. <em>et al<\/em>. Dual-spindle formation in zygotes keeps parental genomes apart in early mammalian embryos. <em>Science<\/em>, published online 12 July 2018.<\/p>\n","source_link_url":"http:\/\/science.sciencemag.org\/content\/361\/6398\/189.full"}],"vf_locked":false,"featured":false,"color":"#007B53","show_featured_image":false,"in_this_article":false,"youtube_url":"","mp4_url":"","video_caption":"","translations":[{"translation_language":"German","translation_anchor":"#de"}],"press_contact":"EMBL Generic"},"embl_taxonomy_terms":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v26.2 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Parental chromosomes kept apart during first division | EMBL<\/title>\n<meta name=\"description\" content=\"EMBL scientists show that there are two spindles, one for each set of parental chromosomes, keeping them apart throughout the first division.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.embl.org\/news\/science\/parental-chromosomes-kept-apart-during-embryos-first-division\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Parental chromosomes kept apart during first division | EMBL\" \/>\n<meta property=\"og:description\" content=\"EMBL scientists show that there are two spindles, one for each set of parental chromosomes, keeping them apart throughout the first division.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.embl.org\/news\/science\/parental-chromosomes-kept-apart-during-embryos-first-division\/\" \/>\n<meta property=\"og:site_name\" content=\"EMBL\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/embl.org\/\" \/>\n<meta property=\"article:published_time\" content=\"2018-07-12T18:01:17+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2024-03-22T09:54:36+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.embl.org\/news\/wp-content\/uploads\/2018\/07\/Science-Ellenberg-ib.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"620\" \/>\n\t<meta property=\"og:image:height\" content=\"425\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"Iris Kruijen\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@IrisKruijen\" \/>\n<meta name=\"twitter:site\" content=\"@embl\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Iris Kruijen\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"7 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"NewsArticle\",\"@id\":\"https:\/\/www.embl.org\/news\/science\/parental-chromosomes-kept-apart-during-embryos-first-division\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.embl.org\/news\/science\/parental-chromosomes-kept-apart-during-embryos-first-division\/\"},\"author\":{\"name\":\"Iris Kruijen\",\"@id\":\"https:\/\/www.embl.org\/news\/#\/schema\/person\/bdd9b4c648f9ed37311c369a20ac77e1\"},\"headline\":\"Parental chromosomes kept apart during first division\",\"datePublished\":\"2018-07-12T18:01:17+00:00\",\"dateModified\":\"2024-03-22T09:54:36+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.embl.org\/news\/science\/parental-chromosomes-kept-apart-during-embryos-first-division\/\"},\"wordCount\":1475,\"publisher\":{\"@id\":\"https:\/\/www.embl.org\/news\/#organization\"},\"image\":{\"@id\":\"https:\/\/www.embl.org\/news\/science\/parental-chromosomes-kept-apart-during-embryos-first-division\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.embl.org\/news\/wp-content\/uploads\/2018\/07\/Science-Ellenberg-ib.jpg\",\"keywords\":[\"cell division\",\"ellenberg\",\"embryo\",\"fertilisation\",\"genome\",\"light-sheet microscopy\",\"mitosis\",\"press release\",\"spindle\"],\"articleSection\":[\"Science\",\"Science &amp; 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