Maternal effect mutations affecting macronuclear determination and development in <i>Paramecium tetraurelia</i>

Berger, James D.; Havelka, Monika

doi:10.1002/dvg.1020120308

Cited by 6 publications

(2 citation statements)

References 26 publications

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“…It is also possible that RelB cooperates with other co-repressors such as histone deacetylases to mediate gene repression. Histone deacetylases reverse acetylation of histone (77), and overexpression of histone deacetylase isoforms has been shown to inhibit TNF␣ transcription in monocytes (32). In any event, RelB is both necessary and sufficient in regulating some acute proinflammatory genes in connection with chromatin remodeling (44).…”

Section: Discussionmentioning

confidence: 99%

Epigenetic Silencing of Tumor Necrosis Factor α during Endotoxin Tolerance

Gazzar

Yoza

et al. 2007

Journal of Biological Chemistry

135

139

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Sustained silencing of potentially autotoxic acute proinflammatory genes like tumor necrosis factor ␣ (TNF␣) occurs in circulating leukocytes following the early phase of severe systemic inflammation. Aspects of this gene reprogramming suggest the involvement of epigenetic processes. We used THP-1 human promonocytes, which mimic gene silencing when rendered endotoxin-tolerant in vitro, to test whether TNF␣ proximal promoter nucleosomes and transcription factors adapt to an activation-specific profile by developing characteristic chromatinbased silencing marks. We found increased TNF␣ mRNA levels in endotoxin-responsive cells that was preceded by dissociation of heterochromatin-binding protein 1␣, demethylation of nucleosomal histone H3 lysine 9 (H3(Lys 9 )), increased phosphorylation of the adjacent serine 10 (H3(Ser 10 )), and recruitment of NF-B RelA/p65 to the TNF␣ promoter. In contrast, endotoxintolerant cells repressed production of TNF␣ mRNA, retained binding of heterochromatin-binding protein 1␣, sustained methylation of H3(Lys 9 ), reduced phosphorylation of H3(Ser 10 ), and showed diminished binding of NF-B RelA/p65 to the TNF␣ promoter. Similar levels of NF-B p50 occurred at the TNF␣ promoter in the basal state, during active transcription, and in the silenced phenotype. RelB, which acts as a repressor of TNF␣ transcription, remained bound to the promoter during silencing. These results support an immunodeficiency paradigm where epigenetic changes at the promoter of acute proinflammatory genes mediate their repression during the late phase of severe systemic inflammation.Gene reprogramming during severe systemic inflammation generates, among other patterns, silencing of acute proinflammatory genes, such as TNF␣ 2 and IL-1␤, that initiate acute systemic inflammation and damage to multiple organs (1, 2). The silencing of acute proinflammatory genes, which normally follows an initial activation phase (3), is clinically relevant in humans because it participates in generating an acquired state of immunodeficiency that correlates with poor prognosis and increased mortality (4). Gene silencing as a result of disrupted transcription occurs in circulating and tissue leukocytes during severe systemic inflammation in animals and humans (2, 5, 6). The silenced component of gene reprogramming is characterized by a tolerance to endotoxin and can persist for days or even weeks (5). Endotoxin tolerance is defined by the repressed expression of a set of proinflammatory genes in response to the stimulation of the Toll-like receptor 4 by endotoxin. Endotoxin tolerance is constitutively present in blood leukocytes obtained from humans and animals with severe systemic inflammation and can be generated in vitro by using endotoxin as a primary stimulus of macrophages (7).The complex mechanisms responsible for gene silencing are regulated at many levels and continue to emerge. At the level of chromatin, covalent modifications of the NH 2 -terminal tails of the four core histones (H2A, H2B, H3, and H4) play an essential role ...

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Section: Discussionmentioning

confidence: 99%

Epigenetic Silencing of Tumor Necrosis Factor α during Endotoxin Tolerance

Gazzar

Yoza

et al. 2007

Journal of Biological Chemistry

135

139

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“…The development of the macronuclear anlagen is apparently under the control of the macronucleus (1,9). However, its initial step for determining the macronuclear anlagen must be dependent on a positional information of the cytoplasm (4, 9).…”

Section: Discussionmentioning

confidence: 99%

Effects of K⁺ and the K⁺ Ionophore Valinomycin on the Post‐Conjugational Nuclear Differentiation of Paramecium caudatum

Mikami

Ohtsu

1994

Dev Growth Differ

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For determination of the effect of K+ on macro-and micronuclear differentiation Paramecium caudaturn exconjugants were transferred to medium with various concentrations of Valinomycin andlor K+ at the critical stage of nuclear differentiation. The differentiation was not disturbed by transfer to medium containing 1.5 rnM to 50 mM KCI. Injection of KCI solution at the critical stage also did not affect differentiation of the macronucleus appreciably. But change of the KCI concentration in the medium at the critical stage interrupted of normal development of the macronucleus.Macro-and micronuclear differentiations after conjugation are known to be determined by the antero-posterior localization of postzygotic micronuclei. This nuclear localization is achieved by elongation of mitotic spindles and marked shortening of the cell length at the time of micronuclear division. Successive measurements of cell length at 25°C showed that cells began to shorten 1.5 hr after mating-pair separation, reaching to half the initial length about 2.5 hr after the separation, and then returning to recover their initial length within about 50 min. In a solution of K+ (50 mM) plus Valinomycin (l,ug/ml or more), cell shortening was inhibited. It is not known whether elongation of mitotic spindles at the time of critical nuclear division was disordered by this treatment , but the macronuclear anlagen developed in the treated cells. Thus shortening in the cell length is not indispensable for nuclear differentiation.

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Directed positioning of nuclei in living Paramecium tetraurelia: Use of the laser optical force trap for developmental biology

Aufderheide

Fry

1992

Dev. Genet.

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We have constructed a laser optical force trap ("laser tweezers") by coupling an Nd:YAG laser to an optical microscope with a high numerical aperture objective. The laser beam (approximately 0.1 W power) is focused to a diffraction-limited spot at the specimen plane of the objective: the wavelength chosen (1,064 nrn) is not strongly absorbed by most biological materials and is thus not ablative. Because the intensity of the laser beam increases towards the center of the focal spot, small particles brought near the spot will be attracted to the center and held there. Movement of the laser beam will tend to move any trapped particles with it. The laser tweezers can permit precise, nondestructive repositioning of small structures inside a living cell, without recourse to rnicromanipulators. Initial work has involved the use of laser tweezers on cells of Paramecium tetraurelia held by a rotocornpressor. We have been able to trap and reposition small organelles, especially the highly refractile structures known as crystals. Using a trapped crystal as a "tool," we have been able to push micronuclei and other structures for many micrometers to virtually any desired location in a cell. In spite of extended exposure of specific structures and of individual cells to the laser beam, no damage has been detectible. Exposed cells, which were removed from the rotocornpressor and cultured, showed complete viabilty. The laser tweezers technique shows tremendous potential for applications to the study of many fundamental cellular and developmental phenomena in paramecia and other ciliates. For example, we intend to use this technique to investigate temporal and spatial characteristics of nuclear determining regions during sexual reorganization in Paramecium. 0 1992 Wiley-Llss, Inc ulation of neutral atoms and molecules in vacuum [for review, see Chu, 19911. However, the technique was found to apply also to small particles in aqueous solutions, including bacteria and structures in eukaryotic cells [Ashkin and Dziedzic, 19871. Several intriguing projects have made use of the unexcelled ability of laser tweezers to capture and reposition biological structures without damage. Although the mechanical forces generated by the tweezers are extremely small, further exploration of potential applications of this technique to biological questions is amply justified.The principle of the laser tweezers depends on the radiation pressure generated by focused laser illumination [Chu, 19911. In practice, a laser beam is directed into a light microscope objective of high numerical aperture [Ashkin et al., 1986 Ashkin and Dziedzic, 19871. The beam is focused into a diffraction-limited spot in the field of the objective. Small particles near this spot will tend to be attracted into its center and held there. Physically, the process is analogous to the attraction between a speck of dust and a comb carrying a high electrostatic charge. The large electric field gradient near the comb produces a force on a n adjacent neutral object (the dust part...

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Maternal effect mutations affecting macronuclear determination and development in Paramecium tetraurelia

Cited by 6 publications

References 26 publications

Epigenetic Silencing of Tumor Necrosis Factor α during Endotoxin Tolerance

Epigenetic Silencing of Tumor Necrosis Factor α during Endotoxin Tolerance

Effects of K⁺ and the K⁺ Ionophore Valinomycin on the Post‐Conjugational Nuclear Differentiation of Paramecium caudatum

Directed positioning of nuclei in living Paramecium tetraurelia: Use of the laser optical force trap for developmental biology

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Maternal effect mutations affecting macronuclear determination and development in Paramecium tetraurelia

Cited by 6 publications

References 26 publications

Epigenetic Silencing of Tumor Necrosis Factor α during Endotoxin Tolerance

Epigenetic Silencing of Tumor Necrosis Factor α during Endotoxin Tolerance

Effects of K+ and the K+ Ionophore Valinomycin on the Post‐Conjugational Nuclear Differentiation of Paramecium caudatum

Directed positioning of nuclei in living Paramecium tetraurelia: Use of the laser optical force trap for developmental biology

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Effects of K⁺ and the K⁺ Ionophore Valinomycin on the Post‐Conjugational Nuclear Differentiation of Paramecium caudatum