1,721,023 research outputs found
Investigating the role of nuclear myosin I in the low serum induced repositioning of chromosome 10 in interphase nuclei
No full textThis thesis was submitted for the degree of Master of Philosophy and awarded by Brunel University.The nucleus of mammalian cells has been proven to be highly organised. A recent study on interphase chromosome positioning has identified low serum induced rapid chromosome repositioning. Chromosome 10 initially localised at an intermediate position in normal proliferating human dermal fibroblasts (HDF) was found to relocate to the nuclear periphery 15 minutes after the cells have been incubated in low serum. Whereas chromosome X has remained in
a peripheral position. The relocation of chromosome 10 has been shown to be dependant on both actin and myosin functions. In this project we have further investigated the possible role of nuclear myosin I in chromosome 10 repositioning. Using siRNA to block the expression of the nuclear myosin I
(NMI) we were able to identify this nuclear myosin as necessary for the rapid repositioning of chromosome 10. Furthermore, using image analysis software we investigated the effect of the NMI knock down on the overall nuclear size and shape. The analysis has revealed that while the nuclear size of normal proliferating cells remained unchanged after the low serum incubation both in cells expressing the NMI and NMI depleted cells, the knock down of the
NMI seems to have affected the nuclear shape when the cells were subjected to the serum incubation. On the other hand, the analysis of the chromosome territories area has revealed significant differences in the chromosome territories sizes before and after the low serum incubation, in normal proliferating HDF cells .Part funded by the School of Health Sciences and Social Car
Farnesyltransferase inhibitor treatment restores chromosome territory positions and active chromosome dynamics in Hutchinson-Gilford progeria syndrome cells
Full text linkCopyright @ 2011 Mehta et al.; licensee BioMed Central Ltd. This article has been made available through the Brunel Open Access Publishing Fund.
This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.BACKGROUND: Hutchinson-Gilford progeria syndrome (HGPS) is a premature ageing syndrome that affects children leading to premature death, usually from heart infarction or strokes, making this syndrome similar to normative ageing. HGPS is commonly caused by a mutation in the A-type lamin gene, LMNA (G608G). This leads to the expression of an aberrant truncated lamin A protein, progerin. Progerin cannot be processed as wild-type pre-lamin A and remains farnesylated, leading to its aberrant behavior during interphase and mitosis. Farnesyltransferase inhibitors prevent the accumulation of farnesylated progerin, producing a less toxic protein. RESULTS: We have found that in proliferating fibroblasts derived from HGPS patients the nuclear location of interphase chromosomes differs from control proliferating cells and mimics that of control quiescent fibroblasts, with smaller chromosomes toward the nuclear interior and larger chromosomes toward the nuclear periphery. For this study we have treated HGPS fibroblasts with farnesyltransferase inhibitors and analyzed the nuclear location of individual chromosome territories. We have found that after exposure to farnesyltransferase inhibitors mis-localized chromosome territories were restored to a nuclear position akin to chromosomes in proliferating control cells. Furthermore, not only has this treatment afforded chromosomes to be repositioned but has also restored the machinery that controls their rapid movement upon serum removal. This machinery contains nuclear myosin 1β, whose distribution is also restored after farnesyltransferase inhibitor treatment of HGPS cells. CONCLUSIONS: This study not only progresses the understanding of genome behavior in HGPS cells but demonstrates that interphase chromosome movement requires processed lamin A.This work was funded by an ORSAS award and the Brunel Progeria Research Fund
Genomic analysis of the fresh water mollusc Biomphalaria glabrata to understand host: Parasite interactions
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The fresh water mollusc Biomphalaria glabrata is the intermediate host for the trematode parasite Schistosoma mansoni, this parasite is responsible for the human disease Schistosomiasis. The significance of B. glabrata in the transmission of schistosomiasis is such that it has been selected for complete genome sequencing.
The Biomphalaria glabrata embryonic cell line is an important resource for researchers investigating the interaction between the snail and parasite. The genome of the Bge cells was analysed at the chromosomal level, using DAPI karyotyping. The karyotype revealed extensive aneuploidy, whereby a modal chromosome complement of 63 and 67 was observed in two isolates of the Bge cells, which exceeds B. glabrata’s 2n=36 chromosome number. Indeed, in addition to characterising the Bge cell chromosomes, a method was established for mapping single copy B. glabrata genes onto the chromosomes from the Bge cells using fluorescence in situ hybridisation. Despite the Bge cell’s inherent aneuploidy, the four genes mapped onto diploid homologous chromosomes. This methodology will be an important resource for the genome sequencing consortium.
The interphase nucleus is an organised organelle, whereby chromosomes and gene loci have been shown to be located non-randomly and hence it is hypothesised that the organisation of the interphase nucleus is pertinent to the function of the genome. Since there is no data on how the genes of the snail genome behaves in interphase, it was assessed in the Bge cells line. Again, this is important for the sequencing initiative, but also for evolutionary biology. Radially distributed chromosome territories were observed in the nuclei of the Bge cells. The territory position was organised according to territory size, with small chromosome territories positioned towards the interior and large territories intermediately located. In addition, four B. glabrata genes were positioned non-randomly in the interphase nuclei of the Bge cells, again emphasising organised positioning of the genome.
With co-culture of S. mansoni miracidia with the Bge cells there is up regulation of specific genes known to be involved in the host response to parasite. These genes are dramatically relocated within the interphase nuclei, implying that these are specific parasite induced nuclear events.
An analysis of the genomic distribution of specific histone modified chromatin in the interphase nuclei of B. glabrata, revealed different nuclear distribution of modified chromatin. Indeed, a statistically significant difference in these patterns was observed between juvenile and adult snails, indicating developmental differences in the organisation of the snails’ genome. These differences maybe relevant to the snails’ resistance/susceptibility to the parasite
Rapid chromosome territory relocation by nuclear motor activity in response to serum removal in primary human fibroblasts
Full text linkThis article has been made available through the Brunel Open Access Publishing Fund.Background: Radial chromosome positioning in interphase nuclei is nonrandom and
can alter according to developmental, differentiation, proliferation, or disease status.
However, it is not yet clear when and how chromosome repositioning is elicited.
Results: By investigating the positioning of all human chromosomes in primary
fibroblasts that have left the proliferative cell cycle, we have demonstrated that in
cells made quiescent by reversible growth arrest, chromosome positioning is altered
considerably. We found that with the removal of serum from the culture medium,
chromosome repositioning took less than 15 minutes, required energy and was
inhibited by drugs affecting the polymerization of myosin and actin. We also
observed that when cells became quiescent, the nuclear distribution of nuclear myosin
1ß was dramatically different from that in proliferating cells. If we suppressed the
expression of nuclear myosin 1ß by using RNA-interference procedures, the
movement of chromosomes after 15 minutes in low serum was inhibited. When high
serum was restored to the serum-starved cultures, chromosome repositioning was
evident only after 24 to 36 hours, and this coincided with a return to a proliferating
distribution of nuclear myosin 1ß.
Conclusions: These findings demonstrate that genome organization in interphase
nuclei is altered considerably when cells leave the proliferative cell cycle and that
repositioning of chromosomes relies on efficient functioning of an active nuclear
motor complex that contains nuclear myosin 1ß.Brunel Open Access Publishing Fun
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Understanding ovarian cancer and chemoresistance through chromosome spatial organisation and nuclear motors
Full text linkThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.20% of patients diagnosed with ovarian cancer (OC) cannot receive treatment at all due to the
severity of the disease when discovered. The 80% of patients that receive treatment, as much as,
90% relapse in less than six months and, by the end of two years fail to respond to treatment as a
result of multi-drug resistance. As genetic studies fail to provide a complete picture in the biology
of disease, epigenetics including spatial and radial organisation of the genome has become a well established that provides a greater understanding beyond the sequence. Chromosomes are non randomly organised within interphase nuclei, which can vary slightly from cell type to cell type, their
proliferation and disease status. The functional organisation within interphase nuclei is kept in place
and regulated by a plethora of structural and mechanical proteins such as lamins and nuclear
myosins (NMs), and along with many other proteins are known together as the nucleoskeleton.
Irregularities in these proteins have been implicated in many diseases, including metastatic cancers
and their chemoresistant counterparts. NM1 role in spatial chromosome organisation has been
established, and with the emergence of NM6 role in nuclear organisation, both their overexpression
in OC and involvement transcription presents them as an attractive co-study.
This research investigates the disease-related chromosome territory (CT) positionings of OC through
four key chromosomes in a panel of OC cells; SKOV-3 PEO-1 PEO-4 MDAH-2774, in addition to a
control control cell line HOSEpi. Internally located CT were observed for chromosomes 1, 13 and 17 and a peripheral localisation was observed chromosome X. Chromosomes were subsequently
assessed for location post-NM1/6 knockdown revealing that chromosome territories relocalised
closer to the localisations of the control cell line, and following the acquisition of platinum-resistance
of MDAH-2774, all four chromosomes predominated centrally in nuclei. The analysis also revealed
that chromosome X might play a more fundamental role in ovarian tissue and cancer that than
previously thought and the initial aim of its use as a control was challenged. Distribution
discrepancies in the OC cells were found in the nuclear lamins and myosins with further
investigations revealing significant elevations of NM1 and NM6. The elevations also displayed a
different stoichiometry ratio in the platinum-resistant cell line PEO-4 which led to the creation of a
novel lab-grade platinum-resistant cell line MDAH-2774CR from the naïve line MDAH-2774 to
investigate further resistant-specific NM1/NM6 stoichiometry and spatial CT organisation in OC.
Moreover, combination assays with MDAH-2774CR and NM1 knockdown resulted in cell death that
surpassed its sensitive counterpart, that has future clinical potential to treat chemoresistant OC.
In this research, we aim to broaden the comprehension of the many mechanisms involved in the
development and progression of an aggressive cancer. The analysis of the CT positioning of 4 out
of 23 chromosomes was able to reveal characteristics within OC nuclei at key milestones of the
disease, making this level of investigation, and information, important in understanding OC and its
successful treatment
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Epigenetic factors affect the host:pathogen interaction between schistsoma mansoni and biomphalaria glabrata
Full text linkThis thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonSchistosomiasis, also known as Bilharzia, is a neglected tropical disease (NTD) caused by the Schistosoma genus of trematode parasite and is estimated to affect 250 million people globally. The nucleus is a highly organised organelle with chromosomes and genes occupying distinct and reproducible locations. However, this spatial organisation is not fixed and different events such as differentiation, environmental stimuli, stress and replicative senescence can trigger genome reorganisation within nuclei. Previous work has already shown that when Schistosoma mansoni infects its obligate intermediate host Biomphalaria glabrata, a freshwater snail, it induces chromatin reorganisation resulting in subsequent upregulation of genes. B. glabrata genome organisation is more similar to mammalian than other invertebrates, meaning that there is potential for what can be discovered in the snail model to be applicable to the mechanism of infection in the human population.
The mechanisms that are responsible for inducing gene movement or chromatin reorganisation are poorly understood, but hypothesised to be partly as a result of epigenetic signalling. Histone methyl modification patterning within the nuclei of B. glabrata were investigated following several events known to induce or result in chromatin reorganisation, heat-shock, infection and ageing. Following comparisons between controls and experimental groups several changes in pattern distribution were identified. Infection of B. glabrata by S. mansoni H3K79me3 showed significant alteration not replicated by heat-shock or ageing indicating that modification of H3K79me3 is an important target for the parasite infection. As such a protocol was developed to further investigate the visual co-localisation of gene and histone modification signals.
To investigate the effects that potentially disrupting this induced chromatin reorganisation can cause, several drugs have been screened in the snail to assess their effect on subsequent changes in susceptibility. Susceptibility to infection was either assessed by one of two means. An absolute method scoring for complete resistance to infection. The second was counting the number of cercariae, the human infective stage of the Schistosoma lifecycle, that were shed from the snail. Drugs chosen were shown to either inhibit gene movement or target epigenetic factors that could be signalling for genome reorganisation to occur. Preliminary data have shown that affecting the acetylation within B. glabrata nuclei affects the snail’s susceptibility to S.mansoni infection.
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B. glabrata interphase genome organisation exhibits similarity to human nuclei, making it an excellent model organism for investigating the effects of genome reorganisation in vivo and as an invertebrate could be used to replace higher order models to reduce the use of animal models in research in line with the NC3R initatives. With a comparatively short lifespan of 12 months it is ideal for exploring, in vivo, ageing related changes to genome organisation. We have previously shown that gene movement and relocation to a new non-random location is possible within a short time period following a heat shock or an infection within juvenile snails. In 12 month aged snails it is demonstrated that significant genome reorganisation has occurred, with the heat shock protein 70kDa (hsp70) loci occupying a new non-random location within the nuclei and that neither heat-shock nor S. mansoni infection can induce gene relocation. Thus indicating not just significant changes to genome organisation but a potential loss of the mechanisms that are responsible for reorganisation of the chromatin.
Using fluorescent imaging techniques, alterations to histone markers, protein distribution and gene loci positioning within nuclei were investigated at varying ages within B. glabrata. This verifies work done in human senescent cells in vitro replicating changes to genome organisation and chromobility. As such this work presents B. glabrata as a new model for investigating the effects of ageing on nuclear organisation in vivo
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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