Untersuchungen von menschlichen Zellen mit ungewöhnlicher Chromatin-Anordnung und Zellkernform

Extensive changes of higher order chromatin arrangements can be observed during prometaphase, terminal cell differentiation and cellular senescence. Experimental systems where major reorganization of nuclear architecture can be induced under defined conditions, may help to better understand the functional implications of such changes. Here, we report on profound chromatin reorganization in fibroblast nuclei by chaetocin, a thiodioxopiperazine metabolite. Chaetocin induces strong condensation of chromosome territories separated by a wide interchromatin space largely void of DNA. Cell viability is maintained irrespective of this peculiar chromatin phenotype. Cell cycle markers, histone signatures, and tests for cellular senescence and for oxidative stress indicate that chaetocin induced chromatin condensation/clustering (CICC) represents a distinct entity among nuclear phenotypes associated with condensed chromatin. The territorial organization of entire chromosomes is maintained in CICC nuclei; however, the conventional nuclear architecture harboring gene-dense chromatin in the nuclear interior and gene-poor chromatin at the nuclear periphery is lost. Instead gene-dense and transcriptionally active chromatin is shifted to the periphery of individual condensed chromosome territories where nascent RNA becomes highly enriched around their outer surface. This chromatin reorganization makes CICC nuclei an attractive model system to study this border zone as a distinct compartment for transcription. Induction of CICC is fully inhibited by thiol-dependent antioxidants, but is not related to the production of reactive oxygen species. Our results suggest that chaetocin functionally impairs the thioredoxin (Trx) system, which is essential for deoxynucleotide synthesis, but in addition involved in a wide range of cellular functions. The mechanisms involved in CICC formation remain to be fully explore

Meiotic chromosome mobility in fission yeast is resistant to environmental stress

This work was supported in part by a grant from the Deutsche Forschungsgemeinschaft (DFG; SCHE350/10-1, SPP1384) to HS, and a start-up grant from the College of Life Sciences and Medicine, University of Aberdeen, UK, to AL. We thank M. Port (Institut für Radiobiologie der Bundeswehr in V.m.d. Univ. Ulm, Munich, Germany) for support, and F. Klein (University of Vienna, Austria), J. Kohli (University of Berne, Switzerland), P. Nurse (The Francis Crick Institute, London, UK), S. Oliferenko (King’s College London, UK), and the National BioResource Project (NBRP), Japan, for strains. We are grateful to M. Lassmann (University of Würzburg, Germany) and Y. Saka (University of Aberdeen, UK) for stimulating discussions on radiation dose effects.Peer reviewedPublisher PD

Remodeling of nuclear landscapes during human myelopoietic cell differentiation maintains co-aligned active and inactive nuclear compartments

Background Previous studies of higher order chromatin organization in nuclei of mammalian species revealed both structural consistency and species-specific differences between cell lines and during early embryonic development. Here, we extended our studies to nuclear landscapes in the human myelopoietic lineage representing a somatic cell differentiation system. Our longterm goal is a search for structural features of nuclei, which are restricted to certain cell types/species, as compared to features, which are evolutionary highly conserved, arguing for their basic functional roles in nuclear organization. Results Common human hematopoietic progenitors, myeloid precursor cells, differentiated monocytes and granulocytes analyzed by super-resolution fluorescence microscopy and electron microscopy revealed profound differences with respect to global chromatin arrangements, the nuclear space occupied by the interchromatin compartment and the distribution of nuclear pores. In contrast, we noted a consistent organization in all cell types with regard to two co-aligned networks, an active (ANC) and an inactive (INC) nuclear compartment delineated by functionally relevant hallmarks. The ANC is enriched in active RNA polymerase II, splicing speckles and histone signatures for transcriptionally competent chromatin (H3K4me3), whereas the INC carries marks for repressed chromatin (H3K9me3). Conclusions Our findings substantiate the conservation of the recently published ANC-INC network model of mammalian nuclear organization during human myelopoiesis irrespective of profound changes of the global nuclear architecture observed during this differentiation process. According to this model, two spatially co-aligned and functionally interacting active and inactive nuclear compartments (ANC and INC) pervade the nuclear space

Remodeling of nuclear landscapes during human myelopoietic cell differentiation maintains co-aligned active and inactive nuclear compartments

Background Previous studies of higher order chromatin organization in nuclei of mammalian species revealed both structural consistency and species-specific differences between cell lines and during early embryonic development. Here, we extended our studies to nuclear landscapes in the human myelopoietic lineage representing a somatic cell differentiation system. Our longterm goal is a search for structural features of nuclei, which are restricted to certain cell types/species, as compared to features, which are evolutionary highly conserved, arguing for their basic functional roles in nuclear organization. Results Common human hematopoietic progenitors, myeloid precursor cells, differentiated monocytes and granulocytes analyzed by super-resolution fluorescence microscopy and electron microscopy revealed profound differences with respect to global chromatin arrangements, the nuclear space occupied by the interchromatin compartment and the distribution of nuclear pores. In contrast, we noted a consistent organization in all cell types with regard to two co-aligned networks, an active (ANC) and an inactive (INC) nuclear compartment delineated by functionally relevant hallmarks. The ANC is enriched in active RNA polymerase II, splicing speckles and histone signatures for transcriptionally competent chromatin (H3K4me3), whereas the INC carries marks for repressed chromatin (H3K9me3). Conclusions Our findings substantiate the conservation of the recently published ANC-INC network model of mammalian nuclear organization during human myelopoiesis irrespective of profound changes of the global nuclear architecture observed during this differentiation process. According to this model, two spatially co-aligned and functionally interacting active and inactive nuclear compartments (ANC and INC) pervade the nuclear space

EXOSC10/Rrp6 is post-translationally regulated in male germ cells and controls the onset of spermatogenesis

Abstract EXOSC10 is a catalytic subunit of the exosome that processes biologically active transcripts, degrades aberrant mRNAs and targets certain long non-coding RNAs (lncRNAs). The yeast orthologue Rrp6 is required for efficient growth and gametogenesis, and becomes unstable during meiosis. However, nothing is known about the localization, stability and function of EXOSC10 in the rodent male germline. We detect the protein in nucleoli and the cytoplasm of mitotic and meiotic germ cells, and find that it transiently associates with the XY body, a structure targeted by meiotic sex chromosome inactivation (MSCI). Finally, EXOSC10 becomes unstable at later stages of gamete development. To determine Exosc10’s meiotic function, we inactivated the gene specifically in male germ cells using cre recombinase controlled by Stra8 or Ddx4/Vasa promoters. Mutant mice have small testes, show impaired germ cell differentiation and are subfertile. Our results demonstrate that EXOSC10 is post-translationally regulated in germ cells, associate the protein with epigenetic chromosome silencing, and reveal its essential role in germ cell growth and development

MOESM5 of Remodeling of nuclear landscapes during human myelopoietic cell differentiation maintains co-aligned active and inactive nuclear compartments

Additional file 5. Comparative topology of SC35 and RNA Pol II Ser5P, markers for transcriptional activity in relation to chromatin density maps. (A) 3D-SIM light optical mid-sections from whole 3D acquisitions of nuclei and representative inset magnifications delineating DAPI stained DNA (gray), immuno-stained SC35 (green) and RNA Pol II Ser5P (red). SC35, an integral part of splicing speckles is seen almost exclusively in the IC compartment while RNA Pol II Ser5P shows a preferential localization at decondensed chromatin sites or at the surface of compacted chromatin domain clusters (compare additional file 4). Scale bars: 2 µm; insets 0.5 µm (B) graphs highlighted with yellow background: relative signal distribution of SC35 (green) and RNA Pol II Ser5P (red) within respective DAPI defined DNA intensity classes. p < 0.001 for DAPI vs. SC35 and RNA Pol II Ser5P, and for SC35 vs. RNA Pol II Ser 5P, except for SC35 vs. RNA Pol II Ser5P in granulocytes (p = 0.004). Graphs highlighted with light-blue background: quantified levels of relative enrichment (positive values) or depletion (negative values) of SC35 (green) and RNA Pol II Ser5P (red) signals relative to the DAPI signals confirm massive enrichment of SC35 signals in class 1 reflecting the IC compartment. n = number of analysed nuclei; error bars = standard deviation