Differentiation in Amount of Centromeric Heterochromatin between Subspecies of the Redlegged Frog, Rana aurora

Abstract To ensure error-free duplication of all (epi)genetic information once per cell cycle, DNA replication follows a cell type and developmental stage specific spatio-temporal program. Here, we analyze the spatio-temporal DNA replication progression in (un)differentiated mouse embryonic stem (mES) cells. Whereas telomeres replicate throughout S-phase, we observe mid S-phase replication of (peri)centromeric heterochromatin in mES cells, which switches to late S-phase replication upon differentiation. This replication timing reversal correlates with and depends on an increase in condensation and a decrease in acetylation of chromatin. We further find synchronous duplication of the Y chromosome, marking the end of S-phase, irrespectively of the pluripotency state. Using a combination of single-molecule and super-resolution microscopy, we measure molecular properties of the mES cell replicon, the number of replication foci active in parallel and their spatial clustering. We conclude that each replication nanofocus in mES cells corresponds to an individual replicon, with up to one quarter representing unidirectional forks. Furthermore, with molecular combing and genome-wide origin mapping analyses, we find that mES cells activate twice as many origins spaced at half the distance than somatic cells. Altogether, our results highlight fundamental developmental differences on progression of genome replication and origin activation in pluripotent cells.

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HP1α is not necessary for the structural maintenance of centromeric heterochromatin

Epigenetics ◽

10.4161/epi.6.3.13866 ◽

2011 ◽

Vol 6 (3) ◽

pp. 380-387 ◽

Cited By ~ 4

Author(s):

Artem K. Velichko ◽

Omar L. Kantidze ◽

Sergey V. Razin

Keyword(s):

Centromeric Heterochromatin

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Chromosomal analyses in Megalonema platanum (Siluriformes: Pimelodidae), an endangered species from South American rivers

Neotropical Ichthyology ◽

10.1590/s1679-62252011005000008 ◽

2011 ◽

Vol 9 (1) ◽

pp. 177-182 ◽

Cited By ~ 6

Author(s):

Rafael Augusto de Carvalho ◽

Sebástian Sanchez ◽

Ana Claudia Swarça ◽

Alberto Sergio Fenocchio ◽

Isabel C. Martins-Santos ◽

...

Keyword(s):

Diploid Number ◽

Secondary Constriction ◽

Centromeric Heterochromatin ◽

Large Chromosome ◽

South American ◽

Terminal Position ◽

Chromosomal Data ◽

First Time ◽

Secondary Constrictions ◽

Submetacentric Pair

This study presents chromosomal data of Megalonema platanum from rio Tibagi, Paraná, Brazil and from rio Paraná, Argentina. The diploid number was equal 54 with karyotype composition of 24m+16sm+2st+12a in both populations. The AgNOR sites were detected in the terminal position of a submetacentric pair of the two analyzed populations, coinciding with secondary constrictions on the short arm of pair 15. CMA3 and FISH with 18S rDNA probe displayed fluorescent signals that correspond to the AgNOR sites and secondary constriction. The presence of a small acrocentric supernumerary chromosome can be observed in M. platanum from rio Tibagi, with centromeric heterochromatin. Others heterochromatic blocks were evidenced in the terminal position of some chromosome and one metacentric large chromosome pair, probably the first pair, showed an interstitial heterochromatin. In the population of the rio Paraná were still observed heterochromatic blocks in both ends in some chromosomes. This work brings for the first time cytogenetic date of M. platanum, which is a very rare species in the rio Paraná basin and may be endangered.

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DNA methylation specifies chromosomal localization of MeCP2.

Molecular and Cellular Biology ◽

10.1128/mcb.16.1.414 ◽

1996 ◽

Vol 16 (1) ◽

pp. 414-421 ◽

Cited By ~ 223

Author(s):

X Nan ◽

P Tate ◽

E Li ◽

A Bird

Keyword(s):

Dna Methylation ◽

Cultured Cells ◽

Centromeric Heterochromatin ◽

Intact Protein ◽

Chromosomal Protein ◽

Mouse Cells ◽

Low Levels ◽

Mutant Cells

MeCP2 is a chromosomal protein that is concentrated in the centromeric heterochromatin of mouse cells. In vitro, the protein binds preferentially to DNA containing a single symmetrically methylated CpG. To find out whether the heterochromatic localization of MeCP2 depended on DNA methylation, we transiently expressed MeCP2-LacZ fusion proteins in cultured cells. Intact protein was targeted to heterochromatin in wild-type cells but was inefficiently localized in mutant cells with low levels of genomic DNA methylation. Deletions within MeCP2 showed that localization to heterochromatin required the 85-amino-acid methyl-CpG binding domain but not the remainder of the protein. Thus MeCP2 is a methyl-CpG-binding protein in vivo and is likely to be a major mediator of downstream consequences of DNA methylation.

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Immunodeficiency, centromeric heterochromatin instability of chromosomes 1, 9, and 16, and facial anomalies: the ICF syndrome

International Journal of Contemporary Pediatrics ◽

10.18203/2349-3291.ijcp20172706 ◽

2017 ◽

Vol 4 (4) ◽

pp. 1545

Author(s):

Shailesh Pande ◽

Mani Bhushan ◽

Anurita Pais ◽

Gauri Pradhan ◽

Chaitali Kadam ◽

...

Keyword(s):

Chromosomal Instability ◽

Immune Status ◽

Centromeric Region ◽

Fragile Sites ◽

Chromosome 1 ◽

Centromeric Heterochromatin ◽

Reference Laboratory ◽

Icf Syndrome ◽

Facial Anomalies ◽

Chromosomal Data

Instability of the heterochromatic centromeric regions of chromosomes 1 associated with immunodeficiency was found in a 3 and half months old girl. The case was referred to Department of Genetics, Global Reference Laboratory, Metropolis Healthcare Ltd, Mumbai with the suspicion of Downs Syndrome for chromosomal karyotyping. This patient had facial anomalies in addition to combined immunodeficiency and chromosomal instability. Stretching of the heterochromatic centromeric regions of chromosomes 1 and homologous and non-homologous associations of these regions were the most common cytogenetic findings in this patient. Multi-branched configurations and whole arm deletions of chromosomes 1 were also found. Comparing clinical and chromosomal data we conclude that the patient was suffering from immunodeficiency, centromeric heterochromatin instability and facial syndrome. The chromosomal karyotyping report was showing instability around vicinity of chromosome 1 and various abnormalities around vicinity of both chromosomes 1 were found in form of random breakages of chromosome 1, fragile sites, deletions/duplications of small and long arm, extra copies of chromosome 1 with rosette formations, exchange of arms and partial aneuploidies of chromosome 1. Further, the investigations regarding the immune status revealed that the level of IgM (5.98 mg/dl), IgA (<6.16mg/dl) and IgG (92.10 mg/dl) subgroup of immunoglobulin was very low. The results were consistent with The Immunodeficiency, Centromeric region instability, Facial anomalies (ICF) syndrome. Second sample from the patient for molecular studies could not be collected and performed since the patient failed to survive after 3 and half months.

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GENETIC ANALYSIS OF THE CENTROMERIC HETEROCHROMATIN OF CHROMOSOME 2 OF DROSOPHILA MELANOGASTER: DEFICIENCY MAPPING OF EMS-INDUCED LETHAL COMPLEMENTATION GROUPS

Genetics ◽

10.1093/genetics/83.4.765 ◽

1976 ◽

Vol 83 (4) ◽

pp. 765-782

Author(s):

Arthur J Hilliker

Keyword(s):

Drosophila Melanogaster ◽

Present Report ◽

Heterochromatic Region ◽

Centromeric Heterochromatin ◽

Genetic Constitution ◽

Genetic Dissection ◽

Chromosome 2 ◽

Multiple Alleles ◽

Products Analysis ◽

Dominance Tests

ABSTRACT Until recently, little was known of the genetic constitution of the heterochromatic segments of the major autosomes of Drosophila melanogaster. Our previous report described the genetic dissection of the proximal, heterochromatic region of chromosome 2 of Drosophila melanogasterby means of a series of overlapping deficiencies generated by the detachment of compound second autosomes (Hilliker and Holm 1975). Analysis of these deficiencies by inter se complementation, pseudo-dominance tests with proximal mutations and allelism tests with known deficiencies provided evidence for the existence of at least two loci between the centromere and the light locus in 2L and one locus in 2R between the rolled locus and the centromere. These data in conjunction with cytological observations demonstrated that light and rolled and three loci lying between them are located within the proximal heterochromatin of the second chromosome.——The present report describes the further analysis of this region through the induction with ethyl methanesulphonate (EMS) of recessive lethals allelic to the 2L and 2R proximal deficiencies associated with the detachment products. Analysis of the 118 EMS-induced recessive lethals and visible mutations recovered provided evidence for seven loci in the 2L heterochromatin and six loci in the 2R heterochromatin, with multiple alleles being obtained for most sites. Of these loci, one in 2L and two in 2R fall near the heterochromatic-euchromatic junctions of 2L and 2R respectively. None of the 113 EMS lethals behaved as a deficiency, implying that the heterochromatic loci uncovered in this study represent nonrepetitive cistrons. Thus functional genetic loci are found in heterochromatin, albeit at a very low density relative to euchromatin.

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The right place at the right time: Aurora B kinase localization to centromeres and kinetochores

Essays in Biochemistry ◽

10.1042/ebc20190081 ◽

2020 ◽

Vol 64 (2) ◽

pp. 299-311 ◽

Cited By ~ 2

Author(s):

Amanda J. Broad ◽

Jennifer G. DeLuca

Keyword(s):

Spindle Assembly Checkpoint ◽

Protein Complexes ◽

Centromeric Heterochromatin ◽

Aurora B ◽

Mitotic Chromosomes ◽

Large Protein ◽

Aurora B Kinase ◽

Centromeric Protein ◽

Spindle Microtubules ◽

The Right

Abstract The fidelity of chromosome segregation during mitosis is intimately linked to the function of kinetochores, which are large protein complexes assembled at sites of centromeric heterochromatin on mitotic chromosomes. These key “orchestrators” of mitosis physically connect chromosomes to spindle microtubules and transduce forces through these connections to congress chromosomes and silence the spindle assembly checkpoint. Kinetochore-microtubule attachments are highly regulated to ensure that incorrect attachments are not prematurely stabilized, but instead released and corrected. The kinase activity of the centromeric protein Aurora B is required for kinetochore-microtubule destabilization during mitosis, but how the kinase acts on outer kinetochore substrates to selectively destabilize immature and erroneous attachments remains debated. Here, we review recent literature that sheds light on how Aurora B kinase is recruited to both centromeres and kinetochores and discuss possible mechanisms for how kinase interactions with substrates at distinct regions of mitotic chromosomes are regulated.

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Topoisomerase II alpha is associated with the mammalian centromere in a cell cycle- and species-specific manner and is required for proper centromere/kinetochore structure.

The Journal of Cell Biology ◽

10.1083/jcb.134.5.1097 ◽

1996 ◽

Vol 134 (5) ◽

pp. 1097-1107 ◽

Cited By ~ 84

Author(s):

J B Rattner ◽

M J Hendzel ◽

C S Furbee ◽

M T Muller ◽

D P Bazett-Jones

Keyword(s):

Cell Cycle ◽

Topoisomerase Ii ◽

Chromatin Condensation ◽

Culture Cell ◽

Centromeric Heterochromatin ◽

Tissue Culture Cell ◽

Topoisomerase Ii Alpha ◽

A Cell ◽

Topo Ii ◽

Species Specific

A study of the distribution of Topoisomerase II alpha (Topo II) in cells of six tissue culture cell lines, human (HeLa), mouse (L929), rat, Indian muntjac, rat kangaroo (PTK-2), and wallaby revealed the following features: (1) There is a cell cycle association of a specific population of Topo II with the centromere. (2) The centromere is distinguished from the remainder of the chromosome by the intensity of its Topo II reactivity. (3) The first appearance of a detectable population of Topo II at the centromere varies between species but is correlated with the onset of centromeric heterochromatin condensation. (4) Detectable centromeric Topo II declines at the completion of cell division. (5) The distribution pattern of Topo II within the centromere is species- and stage-specific and is conserved only within the kinetochore domain. In addition, we report that the Topo II inhibitor ICRF-193 can prevent the normal accumulation of Topo II at the centromere. This results in the disruption of chromatin condensation sub-adjacent to the kinetochore as well as the perturbation of kinetochore structure. Taken together, our studies indicate that the distribution of Topo II at the centromere is unlike that reported for the remainder of the chromosome and is essential for proper formation of centromere/kinetochore structure.

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The effects of chromosome rearrangements on the expression of heterochromatic genes in chromosome 2L of Drosophila melanogaster.

Genetics ◽

10.1093/genetics/125.1.141 ◽

1990 ◽

Vol 125 (1) ◽

pp. 141-154 ◽

Cited By ~ 13

Author(s):

B T Wakimoto ◽

M G Hearn

Keyword(s):

Drosophila Melanogaster ◽

Chromosome Rearrangements ◽

Centromeric Heterochromatin ◽

Chromosome 2 ◽

Regulatory Requirement ◽

Position Effects ◽

Heterochromatic Genes

Abstract The light (lt) gene of Drosophila melanogaster is located at the base of the left arm of chromosome 2, within or very near centromeric heterochromatin (2Lh). Chromosome rearrangements that move the lt+ gene from its normal proximal position and place the gene in distal euchromatin result in mosaic or variegated expression of the gene. The cytogenetic and genetic properties of 17 lt-variegated rearrangements are described in this report. We show that five of the heterochromatic genes adjacent to lt are subject to inactivation by these rearrangements and that the euchromatic loci in proximal 2L are not detectably affected. The properties of the rearrangements suggest that proximity to heterochromatin is an important regulatory requirement for at least six 2Lh genes. We discuss how the properties of the position effects on heterochromatic genes relate to other proximity-dependent phenomena such as transvection.

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