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At least 19 recordsLinked to original sources
PubMed1975

Characterization of the DNA from the dinoflagellate Crypthecodinium cohnii and implications for nuclear organization.

Although dinoflagellates are eucaryotes, they possess many bacterial nuclear traits. For this reason they are thought by some to be evolutionary intermediates. Dinoflagellates also possess some unusual nuclear traits not seen in either bacteria or higher eucaryotes, such as a very large number of identical appearing, permanently condensed chromosomes suggesting polyteny or polyploidy. We have studied the DNA of the dinoflagellate Crypthecodinium cohnii with respect to DNA per cell, chromosome counts, and renaturation kinetics. The renaturation kinetic results tend to refute extreme polyteny and polyploidy as the mode of nuclear organization. This organism contains 55-60% repeated, interspersed DNA typical of higher eucaryotes. These results, along with the fact that dinoflagellate chromatin contains practically no basic protein, indicate that dinoflagellates may be organisms with a combination of both bacterial and eucaryotic traits.

Animals↗
PubMed1975

Basic principles of nuclear organization.

The preceding discussion is summarized in Table 1. It is clear that the organization of the genetic material and the ability to transmit information to the cytoplasm involve a number of different components that must maintain specific chemical and physical relationships to one another. An alteration of any of these relationships could affect a variety of cellular processes, including development.

Animals↗
PubMed1992

[The analysis of nuclear organizer regions of astrocytomas with various histologic malignancies].

Nucleolar organizer regions (NORs) correspond to the loops of DNA which encode the ribosomal RNA. Acid proteins related to NORs can be stained by the silver colloidal technique (AgNORs). Since the configurations of AgNORs may be related to the protein metabolism or the proliferative activity of the cell, we tried to evaluate the corelationship between the morphology of AgNOR and the histologic malignancy in astrocytic tumors. For the quantitative evaluation the histographic pattern of AgNORs was analysed. Twenty-seven surgical specimens of astrocytomas (astrocytoma; 7 Cases, anaplastic astrocytoma; 9 cases, glioblastoma; 11 cases) were examined. The average of the means of AgNOR count in astrocytoma, anaplastic astrocytoma, glioblastoma were 1.68, 1.85 and 2.76 respectively. The averages of standard deviations (S. D.) of AgNOR count were 0.87, 1.03 and 1.26, respectively. In those tumors, the AgNOR histograms were flattered and the means and S. D. increased significantly as the malignancy increased. We speculate that the increased number and variations of AgNOR count could be a reflection of phenotypic alterations of astrocytoma cells such as cellular anaplasia and pleomorphism.

Astrocytoma↗
PubMed1992

[Premature ovarian insufficiency and nuclear organizer regions in triplicate].

Silver-staining of the nucleolus organizer region, which represents transcription of ribosomal ribonucleic acid genes, was herein studied in the acrocentric chromosomes of a patient with premature ovarian failure. The demonstration of an additional nucleolar organizer region in the peripheral lymphocytes, suggests a causal relationship between transcriptive activity and this type of ovarian failure.

Adult↗
PubMed2025

Dynamic changes in chromosome and nuclear architecture during maturation of normal and ALS C9orf72 motor neurons.

We have investigated changes in chromosome conformation, nuclear organization, and transcription during differentiation and maturation of control and mutant motor neurons harboring hexanucleotide expansions in the C9orf72 gene that cause amyotrophic lateral sclerosis (ALS). Using an in vitro reprogramming, differentiation and neural maturation protocol, we obtained highly purified populations of post-mitotic motor neurons for both normal and diseased cells. As expected, as fibroblasts are reprogrammed into iPSCs, and as iPSCs differentiate into motor neurons, chromatin accessibility, chromosome conformation, and nuclear organization change along with large-scale alterations in transcriptional profiles. We find that the transcriptome changes extensively during the first three weeks of post-mitotic neuronal maturation, with thousands of genes changing expression, but then is relatively stable for the next three weeks. In contrast, chromosome conformation and nuclear organization continue to change over the entire 6-week maturation period: chromosome territoriality increases, long-range interactions along chromosomes decrease, compartmentalization strength increases, and centromeres and telomeres increasingly cluster. In motor neurons derived from ALS patients such changes in chromosome conformation were much reduced. Chromatin accessibility changes also showed delayed maturation. The transcriptome in these cells matured relatively normally but with notable changes in expression of genes involved in lipid, sterol and mitochondrial function. We conclude that neural maturation is associated with large scale post-mitotic changes in gene expression, chromosome conformation and nuclear organization, and that these processes are defective in motor neurons derived from ALS patients carrying C9orf72 hexanucleotide repeat expansions.

Journal Article↗
PubMed1992

Transforming growth factor-beta 1 induces expression of statin during differentiation of human promonocytic leukemia cells.

Transforming growth factor-Beta (TGF-beta) is a potent growth inhibitor for several cell types including epithelial cells and hematopoietic progenitor cells. Using a human promonocytic leukemia cell line, THP-1, we have shown that TGF-beta inhibits their proliferation and promotes differentiation into cells exhibiting macrophage-like properties. Therefore, a key question is whether TGF-beta influences the expression of genes associated with proliferation and/or growth inhibition. TGF-beta treatment of THP-1 cells results in downregulation of expression of c-myc. We also observe that TGF-beta 1-treated cells express reduced levels of the cell cycle regulated histone, H2B, but express elevated levels of an RNA splicing variant of this histone that has been observed to be upregulated in growth inhibited and terminally differentiated cells. In addition, a nuclear protein associated with senescence and withdrawal of cells from the cell cycle, statin, is also expressed by THP-1 cells in response to TGF-beta 1 treatment. These results suggest that TGF-beta 1 is capable of inducing expression of specific nuclear proteins associated with differentiation and/or cessation of proliferation that may result in changes in nuclear organization and altered gene expression. Such changes in nuclear organization may be incompatible with continued proliferation of the cells.

Cell Adhesion↗
PubMed2025

Differential Crosslinking and Contractile Motors Drive Nuclear Chromatin Compaction.

During interphase, a typical cell nucleus features spatial compartmentalization of transcriptionally active euchromatin and repressed heterochromatin domains. In conventional nuclear organization, euchromatin predominantly occupies the nuclear interior, while heterochromatin, which is approximately 50% more dense than euchromatin, is positioned near the nuclear periphery. Peripheral chromatin organization can be further modulated by the nuclear lamina, which is itself a deformable structure. While a number of biophysical mechanisms for compartmentalization within rigid nuclei have been explored, we study a chromatin model consisting of an active, crosslinked polymer tethered to a deformable, polymeric lamina shell. Contractile motors, the deformability of the shell, and the spatial distribution of crosslinks all play pivotal roles in this compartmentalization. We find that a radial crosslink density distribution, even with a small linear differential of higher crosslinking density at the edge of the nucleus, combined with contractile motor activity, drives genomic segregation, in agreement with experimental observations. This arises from contractile motors preferentially drawing crosslinks into their vicinity at the nuclear periphery, forming high-density domains that promote heterochromatin formation. We also find an increased stiffness of nuclear wrinkles given the preferential heterochromatin compaction below the lamina shell, which is consistent with instantaneous nuclear stiffening under applied nanoindentation. We conclude with the potential for experimental validation of our model predictions.

Journal Article↗
PubMed2025

Differential Crosslinking and Contractile Motors Drive Nuclear Chromatin Compaction.

During interphase, a typical cell nucleus features spatial compartmentalization of transcriptionally active euchromatin and repressed heterochromatin domains. In conventional nuclear organization, euchromatin predominantly occupies the nuclear interior, while heterochromatin, which is approximately 50% more dense than euchromatin, is positioned near the nuclear periphery. Peripheral chromatin organization can be further modulated by the nuclear lamina, which is itself a deformable structure. While a number of biophysical mechanisms for compartmentalization within rigid nuclei have been explored, we study a chromatin model consisting of an active, crosslinked polymer tethered to a deformable, polymeric lamina shell. Contractile motors, the deformability of the shell, and the spatial distribution of crosslinks all play pivotal roles in this compartmentalization. We find that a radial crosslink density distribution, even with a small linear differential of higher crosslinking density at the edge of the nucleus, combined with contractile motor activity, drives genomic segregation, in agreement with experimental observations. This arises from contractile motors preferentially drawing crosslinks into their vicinity at the nuclear periphery, forming high-density domains that promote heterochromatin formation. We also find an increased stiffness of nuclear wrinkles given the preferential heterochromatin compaction below the lamina shell, which is consistent with instantaneous nuclear stiffening under applied nanoindentation. We conclude with the potential for experimental validation of our model predictions.

Journal Article↗
PubMed1976

The structural organization of nuclear messenger RNA precursor. I. Reassociation and hybridization properties of double-stranded hairpin-like loops in messenger RNA precursor.

The hybridization and renaturation properties of double-stranded hairpin-like loops isolated from giant nuclear messenger RNA precursor of mouse liver or ascites carcinoma cells were studied. About half of the hairpins in messenger RNA precursor appear to contain similar sequences, as indicated by the very fast kinetics of renaturation of the denatured double-stranded RNA sequences. These sequences have no tissue specificity. About one third of the hairpin sequences can hybridize to messenger RNA. It is suggested that the long hairpins in messenger RNA precursor play the role of sequences separating messenger RNA sequences from non-informative sequences and that these hairpins are recognized by processing enzymes.

Animals↗
PubMed1977

The structural organization of nuclear pre-mRNA. II. Very long double-stranded structures in nuclear pre-mRNA.

High molecular weight nuclear pre-messenger RNA (pre-mRNA or hnRNA) isolated from Ehrlich ascites carcinoma cells contains besides moderately long (100--200 base pairs) snap-back double-stranded structures, also longer double-stranded structure containing at least 300--800 base pairs. Their double-stranded nature was proved by Cs2SO4 gradient centrifugation. Very long double-stranded sequences are not able to snap-back after RNA melting. While the moderately long double-stranded RNA (dsRNA) is renatured at C0t1/2 approximately equal to 5-10(-4), the very long dsRNA shows a higher complexity (C0t1/2 approximately equal to 2-10(-2). They also hybridize to less reiterated class of DNA than moderately long dsRNA. Two classes of dsRNA are represented by different sequences as followed from cross-renaturation experiments. Very long dsRNA forms stable hybrids with 20% of total poly(A)+mRNA of cytoplasm. The properties of different classes of ds structures present in nuclear pre-mRNA are compared and their possible nature is discussed. The presence of very long dsRNA may reflect either the symmetric transcription of structural genes, or the transcription from those DNA sequences which are complementary to each other but located in different parts of the genome.

Animals↗
PubMed2026

The TUBG meshwork is associated with centromere dynamics and micronuclear organization.

This study investigates how γ-tubulin and the centrosome contribute to interphase centromere dynamics and nuclear organization. Although classically associated with mitotic microtubule nucleation, here we show that γ-tubulin associates with chromatin and is enriched within centromere-defined volumes. Using live-cell imaging, immunofluorescence, and chromatin immunoprecipitation sequencing, we detect γ-tubulin-associated signal at satellite-rich, centromere-proximal chromatin. Reduced γ-tubulin levels are associated with increased centromere fluorescence intensity and reduced mobility, linking the γ-tubulin network to centromere organization. Under acute cisplatin-induced stress, centromere mobility increases, whereas centromere clustering is observed in separate fixed-cell analyses. Ser131 phosphorylation is associated with γ-tubulin self-assembly and centromere-related dynamics. Additionally, γ-tubulin accumulates in micronuclei, coinciding with increased replication-associated signal and DNA fluorescence. In primary clear cell renal cell carcinoma cells, stress is associated with higher γ-tubulin fluorescence intensity within centromere-defined volumes. Together, these findings support an association between the γ-tubulin meshwork and centromere organization, chromatin compartmentalization, and responses to genomic stress.

Centromere↗
PubMed1977

[Nuclear alterations on organ cultures of human malignant melanomas (author's transl)].

Report on ultrastructurally striking nuclear anomalies in organ cultures obtained from amelanotic and pigmented human melanomas. These nuclear anomalies are more impressive than the nuclear invaginations present in tumours cells of several other malignant growths. Numerous nuclear fragments varying in size and held together by nuclear membrane bands may occur. The karyoplasm of these nuclei reveals nothing unusual no degenerative changes can be found.

Cell Nucleus↗
PubMed2025

An Optimized Adaptation of DamID for NGS Applications.

Recent studies have implicated higher-order genome organization in the regulation of genes and cellular state. Lamina-Associated Domains (LADs) are regions of heterochromatin associated with the nuclear envelope and the nuclear lamina, a protein network involved in both nuclear organization and genome structure. LADs are developmentally regulated, and their dysregulation is associated with several diseases and pathological states, including cancer and premature aging. In addition to LADs, other nuclear protein compartments appear to scaffold or support unique chromatin environments to affect gene expression. These revelations carry profound implications for our comprehension of developmental processes and the pathogenesis of various diseases, especially given the numerous disorders already directly associated with, for example, mutations in lamin and INM proteins. This spatial compartmentalization of chromatin subtypes to unique protein compartments has led to the adoption of proximity-labeling methods, such as DamID (DNA Adenine Methyltransferase Identification), to identify these unique chromatin compartments.

Humans↗
PubMed2025

Extrinsic heterogeneity: Collectivity in isotropic conformational fluctuations of chromosomes.

Eukaryotic interphase chromosomes maintain a three-dimensional conformation within the nucleus and undergo fluctuations. However, the analysis of chromosome conformational fluctuations has been mainly limited to chromosome conformation capture data that record the contact frequencies between chromosomal regions. Herein, we investigated chromosome fluctuations as polymers based on experimental data from sequential fluorescence in situ hybridization using a multiomics methodology. To describe the principal modes of chromosome fluctuations, we applied principal-component analysis to the three-dimensional conformation information of single chromosomes in 446 mouse embryonic stem cells obtained from sequential fluorescence in situ hybridization data analysis for spatial genomics and signals of nuclear factors (histone marks, repeat DNAs, and proteins in interchromosomal nuclear compartments). We found that chromosome fluctuations exhibit both isotropic and anisotropic modes. The isotropic conformational fluctuations of all chromosome types tended to synchronize each other, reflecting extrinsic heterogeneity in chromosome conformation that is independent of the cell cycle. In contrast, anisotropic conformational fluctuations, occurring in a spindle-like shape, were associated with the interactions between repeat DNAs and nuclear factors. These results highlight the importance of dissecting cell-cycle-independent nuclear organization based on the conformational folding of chromosomes and the interactions between genomic regions and nuclear factors.

Animals↗
PubMed1975

Editorial: Guidelines for radioactive tracer studies of the heart and circulation. Report of the Inter-society Commission for Heart Disease Resources.

The Inter-Society Commission for Heart Disease Resources report concerning optimal resource guidelines for radioactive tracer studies of the heart and circulation is described. This report is an overview of the status of cardiovascular radionuclide diagnostic studies as well as a guideline to the hospital resources (physical and human) required for a high-quality nuclear medicine laboratory dealing with this area of study. These guidelines are directed to physicians and hospital administrators who are currently responsible for planning and organizing nuclear medicine programs or who anticipate a future need for such services in their community.

Cardiovascular Diseases↗
PubMed1978

The organization, composition and matrix of hepatocyte nuclei exposed to alpha-amanitin.

Alterations in the structure and molecular composition of avian hepatocyte nuclei were compared following administration in vivo of lethal and sub-lethal doses of alpha-amanitin. This toxin interferes with extranucleolar transcription by direct inhibition of RNA polymerase II activity. the resultant effects include: extensive condensation of chromatin, displacement of nucleoplasmic contents and fragmentation of nucleoli. Changes in nuclear morphology were quantitated by stereometry and related to variations in RNA and residual, non-histone proteins (NHP). Gross alterations in nuclear structure and depletion of RNA and NHP levels were of similar magnitude with both doses of amanitin. The effects were fully reversible, however, with a minimal dose but terminal with a lethal dose. DNA and histone protein levels remained unchanged at all stages. These results imply that the process of transciption may itself keep and/or maintain chromatin in a dispersed state, and that in the absence of transcription chromatin naturally condenses. Modification of nuclear proteins may be necessary only to maintain chromatin compacted permanently or for extended periods of time. A model of nuclear organization is proposed to incorporate these considerations and to identify the probable location of the nuclear matrix in situ.

Amanitins↗
PubMedDate not supplied

[Influence of dibutyryl cyclic AMP and theophylline on the frequency of nuclear microtubules and microfilaments of sympathetic neurons].

In vivo dibutyryl cyclic AMP and theophylline, as does electrical stimulation, increase the frequency of nuclear microtubules and microfilaments in neurons of cat stellate ganglia. These and previous results lead us to conclude that cyclic AMP mediates the process of assembly of these two structural components from preformed protein subunits and thus triggers the formation of highly organized nuclear inclusions corresponding to the so-called intranuclear rodlets of light microscopy.

Animals↗