Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “reprogramming”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed2003

Epigenetic characteristics and development of embryos cloned from donor cells treated by trichostatin A or 5-aza-2'-deoxycytidine.

Development to blastocyst following nuclear transfer is dependent on the donor cell's ability to reprogram its genome to that of a zygote. This reprogramming step is inefficient and may be dependent on a number of factors, including chromatin organization. Trichostatin A (TSA; 0-5 microM), a histone deacetylase inhibitor, was used to increase histone acetylation and 5-aza-2'-deoxycytidine (5-aza-dC; 0-5 microM), a DNA methyl-transferase inhibitor, was used to decrease methylation of chromatin in donor cells in an attempt to improve their reprogrammability. Adult fibroblast cells treated with 1.25 or 5 microM TSA had elevated histone H3 acetylation compared to untreated controls. Cells treated with 0.3 microM 5-aza-dC had decreased methylation compared to untreated controls. Both drugs at 0.08 microM caused morphological changes of the donor cells. Development to blastocysts by embryos cloned from donor cells after 0.08 or 0.3 microM 5-aza-dC treatments was lower than in embryos cloned from untreated control cells (9.7% and 4.2%, respectively, vs. 25.1%), whereas 0.08 microM TSA treatment of donor cells increased blastocyst development compared to controls (35.1% vs. 25.1%). These results indicate that partial erasure of preexisting epigenetic marks of donor cells improves subsequent in vitro development of cloned embryos.

Acetylation↗
PubMed2003

Oct-4 expression in pluripotent cells of the rhesus monkey.

The POU (Pit-Oct-Unc)-domain transcription factor, Oct-4, has become a useful marker of pluripotency in the mouse. It is found exclusively in mouse preimplantation-stage embryos after embryonic genome activation and is a characteristic of mouse embryonic stem (ES) cells, and its absence in knockout mice precludes inner cell mass (ICM) formation in blastocysts. Expression of Oct-4 has also been associated with pluripotency in primate cells. Here, we undertook a systematic study of Oct-4 expression in rhesus macaque preimplantation embryos produced by intracytoplasmic sperm injection and in ES cells before and after exposure to differentiating conditions in vitro. We also evaluated Oct-4 expression as a means of monitoring the extent of reprogramming following somatic cell nuclear transfer. Oct-4 was detected by reverse transcription-polymerase chain reaction and immunocytochemistry with a monoclonal antibody. Monkey pronuclear-stage zygotes and cleaving embryos up to the 8-cell stage showed no detectable Oct-4. Nuclear staining for Oct-4 first became obvious at the 16-cell stage, and a strong signal was observed in morula and compact morula stages. Both ICM and trophectodermal cell nuclei of monkey early blastocysts were positive for Oct-4. However, the signal was diminished in trophectodermal cells of expanded blastocysts, whereas expression remained high in ICM nuclei. Similar to the mouse, hatched monkey blastocysts showed strong Oct-4 expression in the ICM, with no detectable signal in the trophectoderm. Undifferentiated monkey ES cells derived from the ICM of in vitro-produced blastocysts expressed Oct-4, consistent with their pluripotent nature, whereas ES cell differentiation was associated with signal loss. Therefore, Oct-4 expression in the monkey, as in the mouse, provides a useful marker for pluripotency after activation of the embryonic genome. Finally, the observed lack or abnormal expression of Oct-4 in monkey nuclear transfer embryos suggests inadequate nuclear reprogramming.

Animals↗
PubMed2000

Analysis of gene transcription in bovine nuclear transfer embryos reconstructed with granulosa cell nuclei.

The low efficiency of animal production using somatic cell nuclear transfer procedures is considered to be the result of an incomplete reprogramming of the donor somatic cell nucleus, which leads to a lack of, or abnormal expression of developmentally important genes. However, our current understanding of the process of somatic cell nuclear reprogramming and its effect on gene expression is limited. In this study, we compare the transcription patterns of six developmentally important genes, Oct4, IL6, FGF2, FGF4, FGFr2, and gp130 in single in vitro fertilized (IVF) and nuclear transfer embryos reconstructed using granulosa cells for the donor nuclei. Similar patterns of transcription were detected for Oct4, FGF2, and gp130 in IVF and nuclear transfer embryos during the preimplantation stages of development. However, a number of morula- and blastocyst-stage embryos derived from nuclear transfer procedures showed abnormal transcription of IL6, FGF4, and FGFr2. Previous studies have demonstrated that these three genes play an important role in implantation, early postimplantation development, or both in the mouse. Therefore, the aberrant transcription patterns detected in nuclear transfer embryos may lead to a reduction in embryo viability.

Animals↗
PubMed2002

Nucleolar changes in bovine nucleotransferred embryos.

This study focused on nucleolar changes in bovine embryos reconstructed from enucleated mature oocytes fused with blastomeres of morulae or with cultured, serum unstarved bovine fetal skin fibroblasts (embryonic vs. somatic cloning). The nucleotransferred (NT) embryos were collected and fixed at time intervals of 1-2 h (early 1-cell stage), 10-15 h (late 1-cell stage), 22-24 h (2-cell stage), 37-38 h (4-cell stage), 40-41 h (early 8-cell stage), 47-48 h (late 8-cell stage), and 55 h (16-cell stage) after fusion. Immunocytochemistry by light and electron microscopy was used for structure-function characterization of nucleolar components. Antibodies against RNA, protein B23, protein C23, and fibrillarin were applied. In addition, DNA was localized by the terminal deoxynucleotidyl transferase (TdT) technique, and the functional organization of chromatin was determined with the nick-translation immunogold approach. The results show that fully reticulated (active) nucleoli observed in donor cells immediately before fusion as well as in the early 1-cell stage after fusion were progressively transformed into nucleolar bodies displaying decreasing numbers of vacuoles from the 2- to 4-cell stage in both types of reconstructed embryos. At the late 8-cell stage, morphological signs of resuming nucleolar activity were detected. Numerous new small vacuoles appeared, and chromatin blocks reassociated with the nucleolar body. During this period, nick-translation technique revealed numerous active DNA sites in the periphery of chromatin blocks associated with the nucleolar body. Fully reticulated nucleoli were again observed as early as the 16-cell stage of embryonic cloned embryos. In comparison, the embryos obtained by fetal cloning displayed a lower tendency to develop, mainly during the first cell cycle and during the period of presumed reactivation. Correlatively, the changes in nucleolar morphology (desegregation and rebuilding) were at least delayed in many somatic NT embryos in comparison with the embryonic NT group. It is concluded that complete reprogramming of rRNA gene expression is part of the general nuclear reprogramming necessary for development after NT.

Animals↗
PubMed2002

In vitro development of horse oocytes reconstructed with the nuclei of fetal and adult cells.

This study investigated the basic conditions required for the production of horse embryos by the transfer of the nuclei of fetal and adult fibroblast cells to enucleated oocytes. Cumulus-oocyte complexes were recovered from abattoir ovaries and matured in vitro in groups of 20-30 for 28-30 h in tissue culture medium 199 containing 20% v:v fetal bovine serum in coculture with equine oviduct epithelial cells. Fetal fibroblast cells (FFC) were derived from a 32-day-old Thoroughbred x Pony fetus, and adult skin fibroblast cells (SFC) were obtained from subdermal biopsies recovered from a 4-yr-old female Pony. The rates of fusion between the recipient cytoplasm with either FFC or SFC were significantly greater when the cells were treated with a combination of direct current (DC) pulses and Sendai virus rather than with DC pulses alone (81%-82% vs. 49%-57%, P < 0.05). There were no differences in the rates of nuclear reprogramming between FFC and SFC (88% vs. 84%), but the rate of cleavage of the resulting embryos to the 2-cell stage was higher when FFC were used (53%) than when SFC were used (35%). Blastocysts were obtained from oocytes reconstructed with both types of donor cells and after culture in vitro for 6-7 days, but the overall proportion of blastocysts produced was very low in both cases (FFC, 4%; SFC, 7%). These results demonstrate a very limited potential for in vitro development of horse embryos after nuclear reprogramming following the transfer of nuclei from either fetal or adult fibroblasts into recipient enucleated oocytes.

Animals↗
PubMed2002

Nuclei of nonviable ovine somatic cells develop into lambs after nuclear transplantation.

Here we report on the successful reprogramming of nuclei from somatic cells rendered nonviable by heat treatment. Granulosa cells from adult sheep were heated to nonphysiological temperatures (55 degrees C or 75 degrees C) before their nuclei were injected into enucleated metaphase II oocytes. Reprogramming was demonstrated by the capacity of the reconstructed embryos to develop to the blastocyst stage in vitro and into fetuses and viable offspring in suitable foster mothers. To our knowledge, this is the first report of cloned mammalian offspring originating from nonviable cells. In addition, our experiments show that heat-treating donor nuclei destabilizes higher-order features of chromatin (but leaves intact its nucleosomal organization) and results in a high proportion of reconstructed embryos developing to the blastocyst stage and beyond.

Animals↗
PubMed2002

Gene array identification of Epstein Barr virus-regulated cellular genes in EBV-converted Burkitt lymphoma cell lines.

Epstein Barr virus (EBV) is associated with various B-cell neoplasms such as post-transplant lymphoproliferative disease or Burkitt lymphoma. B-lymphocyte reprogramming by EBV involves the control of numerous cellular genes. To identify such EBV-deregulated genes, we have compared the gene expression profile of EBV-negative Burkitt lymphoma cell lines (BL) (BL2, BL30, BL70) with their EBV-converted counterpart (BL2-B95, BL30-B95, BL70-B95) by cDNA array. Statistical analysis of the results was made using Ward's cluster analysis method. Results showed that the expression of up to 26% of the 1176 cellular genes analyzed may be modified in EBV-converted BL cells. Within this set of genes, a subset of genes markedly regulated in EBV-converted BL cells was defined as those for which expression in EBV+ cells was increased or decreased more than 2-fold. Expression of various genes was modulated in agreement with their previously reported regulation by EBV or by transcription factors activated by EBV. Numerous genes were newly identified as modulated in EBV-converted BL cells. Some of these results were verified by both semiquantitative RT-PCR and Western blotting, and were consistent with functional studies. Functional classification of EBV-regulated genes gave a comprehensive picture of cellular reprogramming by EBV in BL, by pointing out cellular modules such as cell cycle, apoptosis, and signal transduction pathways, including BCR and TNF receptor family and interferon pathways. Furthermore, and perhaps most importantly, cDNA array results point to three families of transcription factors, Rel/NF-kappaB, STAT1, and Ets-related proteins Spi-B, Elf-1, and Ets-1 as putative cellular targets of EBV.

Apoptosis↗
PubMed2025

Hormetic nutrient stress promotes longevity by orchestrating histone acetylation on key lipid catabolism and antioxidant defense genes.

Exposure to low levels of environmental challenges, known as hormetic stress, such as nutrient deprivation and heat shock, fosters subsequent stress resistance and promotes healthy aging in later life. However, specific mechanisms governing transcriptional reprogramming upon hormetic nutrient stress remain elusive. In this study, we identified histone H3 lysine 27 acetylation (H3K27ac) as a crucial driver of transcriptomic adaptation to hormetic fasting. Beyond its immediate function of enhancing lipid catabolism for alternative energy sources, stress-induced H3K27ac activates lifelong antioxidant defenses, thereby reducing reactive oxygen species (ROS) produced by stress-induced fatty acid oxidation and their accumulation during aging. The increase in H3K27ac, mediated by pioneer factor PHA-4/FOXA and cooperating transcription factor NHR-49/HNF4, is crucial for lifespan extension under hermetic nutrient stress in Caenorhabditis elegans. Our findings establish H3K27ac as a key transcriptional switch that bridges nutrient status with transcriptomic reprogramming, underpinning the pro-longevity effects of hormetic fasting through orchestrating lipid catabolism and antioxidative defenses.

Journal Article↗
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↗
PubMed2002

Oct4 distribution and level in mouse clones: consequences for pluripotency.

Somatic cell clones often fail at a developmental stage coincident with commencement of differentiation. The transcription factor Oct4 is expressed during cleavage stages and is essential for the differentiation of the blastocyst. Oct4 expression becomes restricted to the inner cell mass and epiblast. After gastrulation Oct4 is active only in germ cells and is silent in somatic cells. Here, Oct4 and an Oct4-GFP transgene were used as markers for which gene reprogramming could be directly related to the developmental potential of somatic cell clones. Cumulus cell clones initiated Oct4 expression at the correct stage but showed an incorrect spatial expression in the majority of blastocysts. The ability of clones to form outgrowths was reduced, and the outgrowths had low or even undetectable levels of Oct4 RNA or GFP. The quality of GFP signals in blastocysts correlated with the ability to generate outgrowths that maintain GFP expression and the frequency of embryonic stem (ES) cell derivation. Abnormal Oct4 expression in clones is either directly or indirectly caused by reprogramming errors and is indicative of a general failure to reset the genetic program. The abnormal Oct4 expression may be associated with aberrant expression of other crucial developmental genes, leading to abnormalities at various embryonic stages. Regardless of other genes, the variations observed in Oct4 levels alone account for the majority of failures currently observed for somatic cell cloning.

Animals↗
PubMed1985

Incidence and management of pacemaker-related complications during dual-chamber pacing.

To evaluate the complication rate during AV universal pacing (DDD), 41 consecutive patients with complete heart block were studied and followed up for 2-30 (mean 10.8) months. The Cordis Sequicor Theta was used in 6 patients and the Siemens-Elema 674 in 35. Clinical problems related to the pacemaker treatment occurred in 12 patients (pacemaker tachycardia triggered by retrograde atrial activation in 2, atrial oversensing in 3 and undersensing in 2, ventricular oversensing in 2 and undersensing in 1). Ventricular fibrillation occurred during threshold measurement in one patient. Seven of the problems could be ascribed to the DDD mode. Four of these 7 problems could be solved by reprogramming the pacemaker. A nonprogrammable atrial refractory period in the Cordis Sequicor was found to be a limitation in patients with endless loop tachycardia. In 3 cases reoperation had to be performed. In another 3 cases there were problems with ventricular sensing which in one could be solved by reprogramming. Apart from ventricular fibrillation, which could not be ascribed to the DDD mode, there were no serious problems in the clinical management of the patients.

Adult↗
PubMed2002

Microarray-based analysis of anti-angiogenic activity of demethoxycurcumin on human umbilical vein endothelial cells: crucial involvement of the down-regulation of matrix metalloproteinase.

cDNA microarray-based gene expression analysis has been successfully employed to explore the action mechanism and to validate the targets of several drugs. In the present study, we evaluated anti-angiogenic activity of demethoxycurcumin (DC), a structural analog of curcumin, isolated from Curcuma aromatica, and investigated the effect of DC on genetic reprogramming in cultured human umbilical vein endothelial cells (HUVECs) using cDNA microarray analysis. Of 1024 human cancer-focused genes arrayed, 187 genes were up-regulated and 72 genes were down-regulated at least 2-fold by DC. Interestingly, 9 angiogenesis-related genes were down-regulated over 5-fold in response to DC, suggesting that the genetic reprogramming was crucially involved in anti-angiogenesis by the compound. To verify the results obtained from cDNA microarray analysis, matrix metalloproteinase-9 (MMP-9), the product of one of the angiogenesis-related genes down-regulated over 5-fold by DC, was investigated using gelatin zymography. DC potently inhibited the expression of MMP-9, yet showed no direct effect on its activity. These data show that gene expressional change of MMP-9 is a major mediator for angiogenesis inhibition by DC. All genes identified and microarray data are available on the web at http://dasan.sejong.ac.kr/~bioprobe/.

Angiogenesis Inhibitors↗
PubMed1988

Transdifferentiation of ocular tissues in larval Xenopus laevis.

Transdifferentiation phenomena offer a useful opportunity to study experimentally the mechanisms on which cell phenotypic stability depends. The capacities of vertebrate eye tissues to reprogram cell differentiation are well known in avian and mammalian embryos, and in larval and adult newt. From research into the capacity of anuran eye tissues to reprogram differentiation into a new pathway, considerable data have accumulated concerning the transdifferentiative capacities of eye tissues in larval Xenopus laevis. This work reviews the data concerning the transdifferentiative phenomena of eye tissues in that species and, based on these, aims to establish the extent of our knowledge about the mechanism controlling these processes. In larval Xenopus laevis the outer cornea can regenerate a lens by a lens-transdifferentiation process triggered and substained by a factor(s), probably of a protein nature, produced by the neural retina. In a normal eye phenotypic stability of the outer cornea is guaranteed by the presence of the inner cornea and lens, which prevent the spread of retinal factor(s). The stimulus for lens transdifferentiation of the outer cornea can be supplied by other tissues as well, but this capacity is not widely distributed. The iris and retinal pigmented epithelium can transdifferentiate into neural retina if isolated from the surrounding tissues and implanted in the vitreous chamber. As for lens transdifferentiation of the outer cornea, retinal transdifferentiation of the iris can be stimulated by certain nonocular tissues as well.

Animals↗
PubMed1981

Short-term threshold behavior of human ventricular pacing electrode: noninvasive monitoring with a multiprogrammable pacing system.

Twenty-two patients were studied for 8 to 12 weeks following pacemaker implantation. A unipolar multiprogrammable pacing system was used to assess and compensate for early post-implant changes in pulse width threshold (PWT). Changes in PWT were estimated by noninvasive measurements of the lowest pulse width required for 100% capture at constant voltage. All patients showed an early increase in PWT. The magnitude of this change was unpredictable and ranged from 2- to 10-fold. For pacing, we selected an appropriate margin of safety to be a pulse width three times the PWT. During the study period, 4 patients showed critical increases in PWT, requiring reprogramming to an increased pulse width as above, whereas only one patient required lead repositioning. The majority of patients achieved a stable low PWT and were reprogrammed to a reduced pulse width. The programmable pacing system provides a safe accurate technique for monitoring early changes in PWT, defines the need for appropriate alterations in programmable functions, decreases the risk of early pacemaker failure, and offers promise for improved pacemaker longevity in many patients.

Aged↗
PubMed1982

Induction of ventricular tachycardia by pacemaker programming.

The induction of ventricular tachycardia or ventricular fibrillation by competitive pacing, especially in the setting of acute myocardial ischemia, is well known. A case of ventricular tachycardia induced by a multiprogrammable unipolar cathodal ventricular pacemaker is reported. The arrhythmia was caused by reprogramming, which necessitates a short switch to fixed rate pacing in this model (Spectrax 5985 SX). This potential hazard is not well established in patients with unipolar pacemakers. The use of the magnet as one of the preconditions for reprogramming should be avoided in future pacemakers.

Bradycardia↗
PubMed1984

Apparent pacemaker failure due to reversion circuitry within the programming device.

While being evaluated for a recurrent tachyarrhythmia, a patient with a permanent pacemaker underwent reprogramming of the unit from the DVI to the VVI mode for assessment of the underlying rhythm. Subsequent reprogramming of the pacemaker to the DVI or DDD mode was impossible despite multiple attempts and the use of multiple programmers. The problem was considered to be a malfunction of the pacemaker circuitry, and plans were made for the pacemaker to be explanted and a replacement unit implanted. Before the procedure, the pacemaker company was notified of the explantation. We subsequently learned that a special programming sequence had to be carried out because of reversion circuitry present in the pacemaker but not described in the available literature. This report emphasizes the need for familiarity with each of the individual pacemakers being implanted and the need for the manufacturer to be as specific as possible given the complexity of current units.

Equipment Design↗
PubMed1985

Reversion mode activation by myopotential sensing in a ventricular inhibited demand pacemaker.

Pacemaker follow-up in a 72-year-old woman revealed occasional failure to sense and pace, which was confirmed by Holter monitor. Neither reprogramming the pacemaker sensitivity nor repositioning the lead resolved the problem. A recheck of the Holter recordings revealed pacing and sensing failures were concurrent with "baseline artifact," suggestive of myopotentials. Furthermore, the inappropriate pacing spikes occurred at a rate of 90 pulses per minute (ppm). It was theorized that myopotential sensing was alternately inhibiting the pacer and activating the reversion mode, an asynchronous rate of 90 ppm. Reprogramming the unit to a lower sensitivity restored normal pacer function.

Aged↗
PubMed1986

Pacemaker follow-up: its role in the detection and correction of pacemaker system malfunction.

The goal of pacemaker follow-up is not only to detect battery depletion but also to detect all malfunctions of the pacing system and, when possible, to correct such problems using programming. During one year, we discovered 61 such malfunctions in a clinic of 1065 patients (5.7%). These were more frequent in the first year (7.7%) than in the third to fifth years of follow-up (range 3.1-4.8%). The incidence rose again in the sixth and subsequent years (7-7.7%). Despite a significant occurrence of malfunctions (5.2%) among multiprogrammable pacemakers, the necessity for operative intervention for their correction was low (1.2%). Sensing problems were the most common (57%) and the most likely to be corrected by reprogramming (85%); problems involving loss of capture were less likely to be corrected by programming (38.5%). Battery depletion accounted for only 18% of malfunctions, occurring earliest in the forty-third month of follow-up. Pulse generator longevity of those devices reaching end of battery life during the study period was 68.6 +/- 16.7 months (mean + SD). We conclude that specialized pacemaker follow-up continues to be necessary despite improved pulse generator reliability and longevity. Indeed, with reprogramming, it presently plays an even more important role than in the past. Follow-up should be oriented not only to the detection of battery depletion but also toward a comprehensive surveillance of pacemaker system function.

Equipment Failure↗