mRNA Expression Of DNA Methyltransferases Research Articles

Breed-specific patterns of hepatic gluconeogenesis and glucocorticoid action in pigs

Abstract. In the present study, Erhualian and Pietrain pigs were employed to investigate the breed-specific patterns of hepatic gluconeogenesis by detecting the related enzyme mRNA expression, and to analyse the relationship with the hepatic glucocorticoid receptors and 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) expression. Furthermore, hepatic DNA methyltransferase 1 (DNMT1) expression was determined to detect DNA methyltransferase state difference between the two breeds. The results demonstrated that the Erhualian pigs exhibited significantly lower plasma lactate acid concentration, but higher liver lactate acid content than the Pietrain pigs. A significantly higher expression of pyruvate carboxylase (PC), fructose-1, 6-bisphosphatase (FBP) and the mitochondria phosphoenolpyruvate carboxykinase (PCK2) mRNA were observed in Erhualian pigs. The Erhualian pigs demonstrated a significantly higher expression of glucocorticoid receptor and 11β-HSD1 mRNA than the Pietrain pigs, though there was no difference in the hepatic cortisol content between the two breeds. The hepatic DNMT1 mRNA expression in the Erhualian pigs was significantly lower, and the DNMT1 protein content in Erhualian pigs tended to be decreased compared with Pietrain pigs (P=0.066). The results suggest that the Erhualian pigs demonstrated higher hepatic gluconeogenesis capacity in comparison to the Pietrain pigs. The up-regulation of hepatic glucocorticoid receptor and 11β-HSD1 expression may be involved in the enhanced hepatic gluconeogenesis in Erhualian pigs. Moreover, the down-regulation of DNMT1 in Erhualian pigs implies possible involvement of DNA methylation in a breed-specific pattern of hepatic gluconeogenesis.

The comprehensive effects of hyperlipidemia and hyperhomocysteinemia on pathogenesis of atherosclerosis and DNA hypomethylation in ApoE<sup>−/−</sup> mice

Atherosclerosis (AS) is a disease induced by multiple factors, including genetic and environmental elements. The aim of the present study is to investigate the comprehensive effects of high cholesterol, high methionine diet, and apolipoprotein E deficiency (ApoE(-/-)) on the pathogenesis of AS. ApoE(-/-) mice were fed with high cholesterol and methionine diet for 15 weeks to induce hyperlipidemia and hyperhomocysteinemia. The methylation levels of genomic DNA (gDNA) and B1 repetitive elements in aortic tissues were measured by both methylation-dependent restriction analysis and nested methylation-specific polymerase chain reaction (PCR). Methylation sequence-bias pattern was assayed by DNA methyl-accepting capacity with restriction endonuclease digestion. The mRNA expression of DNA methyltransferase-1, 3 (DNMT1, 3) was detected by real-time PCR. The concentrations of S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) were determined by high-performance liquid chromatography. The results showed hypomethylation of gDNA and B1 repetitive elements. The mRNA expression of DNMT1 was reduced. The levels of SAM, SAH, and SAM/SAH ratio were increased. The atherosclerotic lesion areas strongly correlated with the risk factors. The distribution of DNA demethylation was preferred to non-CpG islands, which may suggest the major impact of hypomethylation on DNA integrity and genomic instability. Overall, our data unequivocally showed that the comprehensive role of high cholesterol, high methionine diet, and ApoE(-/-) is not uniformly consistent with the role of a single risk factor. The DNA methylation pattern in AS is quite complex and depends on genetic background and many involved risk factors.

Association of increased DNA methyltransferase expression with carcinogenesis and poor prognosis in pancreatic ductal adenocarcinoma

Epigenetic modifications play an important role in multistage carcinogenesis. The role of the three functional DNA methyltransferases (DNMTs) in pancreatic carcinogenesis has not been fully understood. The main goal of this study was to examine DNMT expression in different stages of pancreatic ductal adenocarcinoma (PDAC), and evaluate their prognostic significance in PDAC. A large number of premalignant and malignant pancreatic lesions were obtained by manual microdissection. Quantitative real-time RT-PCR was used to detect DNMTs mRNA expression. Nonparametric test, logrank test and Cox regression analysis were used to evaluate the clinical significance of DNMT expression. The mRNA expression of the three DNMTs increased with the development of pancreatic cancer from normal duct to pancreatic intraductal neoplasia and further to PDAC, and were statistically correlated with each other. Expression of the three DNMTs was statistically correlated with TNM staging and history of chronic pancreatitis. DNMT3A and DNMT3B, but not DNMT1 expression, was statistically correlated with tumour size. Patients with higher levels of DNMT1, DNMT3A and/or DNMT3B expression had an overall lower survival than those with lower levels of expression. Univariate analysis showed that high expression levels of DNMTs, alcohol consumption, tumour differentiation and TNM staging were statistically significant risk factors. Multivariate analysis showed that high level of DNMT3B expression and tumour differentiation were statistically significant independent poor prognostic factors. These results suggested that pancreatic carcinogenesis involves an increased mRNA expression of three DNMTs, and they may become valuable diagnostic and prognostic markers as well as potential therapeutic targets for pancreatic cancer.

Hypomethylation mediated by decreased DNMTs involves in the activation of proto-oncogene MPL in TK6 cells treated with hydroquinone

Hydroquinone (HQ), one of the most important metabolites derived from benzene, is known to be associated with acute myelogenous leukemia (AML) risk, however, its carcinogenic mechanism remains unclear. In this study, the epigenetic mechanism of HQ exposure was investigated. We characterized the epigenomic response of TK6 cells to HQ exposure, and examined the mRNA expression of DNA methyltransferases (DNMTs) including DNMT1, DNMT3a and DNMT3b, methyl-CpG-binding domain protein 2 (MBD2) and six proto-oncogenes (MPL, RAF1, MYB, MYC, ERBB2 and BRAF). Compared to the control cells, HQ exposure (2.5, 5.0, 10.0 and 20.0μM for 48h) resulted in the decrease of DNMTs and MBD2 expression, the global hypomethylation and increase of MPL at mRNA level. Meanwhile, most of these changes were in dose-dependent manner. Moreover, inhibition of DNMTs induced by 5-aza-2′-deoxycytidine (5-AZA), an identified DNMT inhibitor, caused more induction of MPL expression at mRNA level compared to the HQ (10.0μM) pre-treated group. Furthermore, treatment of HQ potentially led to MPL itself hypomethylation (10.0 and 20.0μM reduced by 47% and 44%, respectively), further revealing that the activation of proto-oncogene MPL was related to hypomethylation in its DNA sequences. In conclusion, hypomethylation, including global and specific hypomethylation, might be involved in the activation of MPL, and the hypomethylation could be induced by decreased DNMTs in TK6 cells exposed to HQ.

Effects of Cumulus Cells on In Vitro Maturation of Oocytes and Development of Cloned Embryos in the Pig

The purpose of this study was to investigate the role of porcine cumulus cells (CC) in oocyte maturation and somatic cell nuclear transfer (SCNT) embryo development in vitro. Denuded pig oocytes were co-cultured with CC or routinely cultured in maturation medium without a feeder layer. Porcine CC inactivated with mitomycin C or non-inactivated were used for the feeder layer in co-culture with porcine SCNT embryos to investigate comparatively the developmental competence of cloned embryos. The DNA damage aspects of apoptosis and expression pattern of genes implicated in apoptosis (Fas/FasL) as well as the mRNA expression of DNA methyltransferase (Dnmt1, Dnmt3a) of porcine SCNT embryos were also evaluated by comet assay or real-time RT-PCR, respectively. The results showed that co-culture with CC improved the extrusion rate of pbI (49.3% vs 31.5%, p<0.05) and survival rate (75.7% vs 53.3%, p<0.05) of denuded oocytes, but had no effects on blastocyst developmental rate or 2-cell-stage survival rate of in vitro fertilization embryos. Co-culture with CC inactivated by mitomycin C improved the blastocyst developmental rate (26.6% vs 13.0%, p<0.05) and decreased the apoptotic incidence (27.6% vs 46.2%, p<0.05) of porcine cloned embryos. Co-culture with inactivated CC reduced Fas and FasL mRNA expression of cloned embryos at the blastocyst stage compared with NT controls (p<0.05), but there were no differences in Dnmt1 and Dnmt3a mRNA expression among groups. Co-culture with inactivated cumulus cell monolayer significantly increased blastocyst formation and decreased the apoptotic incidence in porcine cloned embryos during in vitro development.

Expression of DNA methyltransferases in liver cancer and its clinical significance

Objective To investigate the expression of DNA methyltransferases (DNMTs) in liver cancer and its clinical significance. Methods The specimens of liver cancer tissues, adjacent tissues, cirrhotic tissues and chronic hepatitis tissues were collected from 50 patients who received radical resection at the First Affiliated Hospital of Sun Yat-Sen University from July 2007 to April 2008. The mRNA and protein expressions of DNMT1,DNMT3a and DNMT3b in liver cancer tissues, adjacent tissues, cirrhotic tissues and chronic hepatitis tissues were detected by real-time quantitative PCR and immunohistochemical staining. The mRNA expression of DNMTs in the liver cancer tissues was compared with those in the adjacent tissues, cirrhotic tissues and chronic hepatitis tissues by using t test and Mann-Whitney U test. The correlation between the protein expression of DNMTs in the liver cancer tissue and the clinicopathological features was analyzed by chi-square test or Fisher exact test, and the tumor-free survival time was analyzed by using Kaplan-Meier method and the difference in tumor-free survival rate between different patients was analyzed by Log-rank test. Results The mRNA expressions of DNMT1, DNMT3a and DNMT3b in the liver cancer tissue were 2.57, 2.29 and 4.86 times higher than those in the adjacent tissues (t = 3.94, 2. 72, 4. 06, P ＜ 0.05 ). The mRNA expressions of DNMT1, DNMT3a and DNMT3b were 2.38,2.14 and 4.66 times higher than those in the cirrhotic tissues, and 6.12, 4.58 and 12.99 times higher than those in the chronic hepatitis tissues. The mRNA expressions of DNMT1, DNMT3a and DNMT3b in the liver cancer tissue were significantly higher than those in the cirrhotic tissues and chronic hepatitis tissues ( U = 587.5,730. 0,562.5; 65.5, 64.5, 71.0, P ＜ 0.05). The protein expression of DNMT1 was correlated with the size, number,TNM stages and vascular invasion of tumors ( x2 = 4.08, 5.95, 4.08, P ＜ 0.05 ). The protein expression of DNMT3a was correlated with the size, number and TNM stages of tumors (x2 = 4.08, 5.95, 4.08, P ＜ 0.05 ).The mean tumor recurrence time of patients with low expressions of DNMT1 and DNMT3a were 9.4 and 8.7 months, which were significantly longer than 5.0 and 3.2 months of those with high expressions of DNMT1 and DNMT3a (x2 =3.89, 9.91, P＜0.05). Conclusions DNMTs play an important role in hepatocarcinogenesis.High expressions of DNMT1 and DNMT3a are correlated with the postoperative recurrence of liver cancer, which are valuable prognostic factors for liver cancer. Key words: Liver neoplasms; DNA methyltransferases; Tumor recurrence

Histone deacetylation directs DNA methylation in survivin gene silencing

DNA methylation and histone acetylation are major epigenetic modifications in gene silencing. In our previous research, we found that the methylated oligonucleotide (SurKex) complementary to a region of promoter of survivin could induce DNA methylation in a site-specific manner leading to survivin silencing. Here, we further studied the role of histone acetylation in survivin silencing and the relationship between histone acetylation and DNA methylation.First we observed the levels of histone H4 and H4K16 acetylation that were decreased after SurKex treatment by using the chromatin immunoprecipitation (ChIP) assay. Next, we investigated the roles of histone acetylation and DNA methylation in survivin silencing after blockade of histone deacetylation with Trichostatin A (TSA). We assessed survivin mRNA expression by RT-PCR, measured survivin promoter methylation by bisulfite sequencing and examined the level of histone acetylation by the ChIP assay. The results showed that histone deacetylation blocked by TSA reversed the effects of SurKex on inhibiting the expression of survivin mRNA, inducing a site-specific methylation on survivin promoter and decreasing the level of histone acetylation. Finally, we examined the role of histone acetylation in the expression of DNA methyltransferase 1 (DNMT1) mRNA. The results showed that histone deacetylation blocked by TSA reversed the increasing effect of histone deacetylation on the expression of survivin mRNA. This study suggests that histone deacetylation guides SurKex-induced DNA methylation in survivin silencing possibly through increasing the expression of DNMT1 mRNA.

Abstract 1429: TGF-β mediates epigenetic regulation of DNA damage in the prostate cancer associated stroma

Abstract DNA damage of stromal fibroblastic cells is known to promote tumorigenesis in number of tissues including the breast and pancreas. 69% of prostate cancer patients lose expression of the Tgfbr2 in the stromal compartment. We previously described, transforming growth factor-beta (TGF-ß) responsiveness of the prostate stromal fibroblastic cells can promote tumorigenesis in transgenic mice. It is known TGF-ß promotes DNA stability, however the mechanism is not known. We found that human prostate cancer stroma has significant number of cells with DNA double stranded breaks, as determined by phosphorylated Ser139-histone H2 (γH2AX) immunolocalization. Similarly, prostate stromal cells from mice with a conditional Tgfbr2-knockout were positive for γH2AX staining. Further promoter methylation array analysis of prostate stromal cells from Tgfbr2-knockout and Tgfbr2-flox (control) indicated 17 DNA damage repair genes to be methylated in Tgfbr2-knockout cells versus the control. Thus, we hypothesized that the loss of stromal TGF-ß responsiveness facilitates stromal DNA damage accumulation through epigenetic regulation. We sought to test the role of stromal TGF-ß signaling in epigenetic regulation. Fourteen of 17 genes were RT-PCR verified to be silenced in Tgfbr2-KO cells and re-expressed following 5-azaDC (de-methylating agent) treatment. Homologous genes were found to be epigenetically silenced in human prostate CAF (carcinoma associated fibroblasts) cultured from primary tumors compared to NAF (normal prostate fibroblasts) from 10 prostate cancer patients. A downstream mediator of TGF-ß signaling includes Smad3 activation. Thus, a similar methylation array analysis of Smad3-knockout prostate stromal cells was performed. We found none of the DNA damage repair genes to be silenced in Smad3-KO cells. Next, we measured DNA methyltransferase-1 (DNMT1) mRNA, protein and activity in Tgfbr2-KO and Tgfbr2-flox cultured prostate stromal cells. Interestingly, protein expression and activity of DNMT1 was 3-fold greater in Tgfbr2-KO stroma over Tgfbr2-flox cells, in the absence of DNMT1 mRNA expression differences. DNMT3b differed little between the two cell types. The use of proteasome inhibitor, MG-132, suggested DNMT1 to be down regulated by TGF-ß in a post-translational manner. Finally, tissue recombinant experiments of Tgfbr2-KO prostate stromal cells with LNCaP, human prostate cancer epithelia, developed large tumors in orthotopic grafts. Similar grafts with wild type and Smad3-KO stromal cells with LNCaP epithelia developed small tumors. Strikingly Tgfbr2-KO stromal cells treated with 5-azaDC and subsequently grafted with LNCaP cells developed smaller tumors. These results for the first time support the role of TGF-ß signaling on stromal DNA stability in tumorigenesis and support a mechanism for TGF-ß responsiveness results in epigenetic silencing of DNA damage repair genes. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1429.

Co‐treatment with quercetin to enhance the chemopreventive effect of green tea in prostate cancer

The low bioavailability and extensive biotransformation in vivo limit the anti‐cancer potential of green tea polyphenols such as (−)‐epigallocatechin‐3‐gallate (EGCG). We found that fifty percent or more of EGCG was present in methylated form (4″‐O‐methyl EGCG) in human prostate tissue after drinking 6 cups of green tea daily and in mouse xenograft prostate tumors after consuming green tea in drinking water. In LNCaP prostate cancer cells, incubated with EGCG, 50% was found in form of 4″‐O‐methyl EGCG. Since EGCG methylation significantly decreased the activity of EGCG to inhibit proliferation and NFkB stimulation, and to induce apoptosis in LNCaP cells, we investigated whether co‐treatment of EGCG with quercetin will decrease EGCG methylation. Co‐treatment of LNCaP cells with quercetin, a natural inhibitor of both multidrug resistance proteins and catechol‐O‐methyltransferase (COMT), increased the absorption of EGCG 10‐fold in a dose‐dependent manner as well as significantly reduced the methylation of intracellular EGCG by 50%. The co‐treatment exhibited a stronger inhibitory effect on mRNA expression of DNA methyltransferase 1 and COMT compared to EGCG treatment alone. These results support our hypothesis that co‐treatment of EGCG with quercetin decreased EGCG methylation which may increase the chemopreventive effect of green tea. This research was supported by RO1 CA116242.

Relationship of impairment induced by intracellular S-adenosylhomocysteine accumulation with DNA methylation in human umbilical vein endothelial cells treated with 3-deazaadenosine.

The aim of this study was to estimate the relationship of endothelial dysfunction induced by intracellular S-adenosylhomocysteine (SAH) accumulation and DNA methylation in human umbilical vein endothelial cells (HUVEC). The isolated HUVEC were incubated with 3-deazaadenosine (DZA) to induce experimental intracellular SAH accumulation. The impairment of HUVEC function was assessed by changes in morphology and proliferative ability. The expression of DNA methyltransferase-1 (DNMT1) and the atherosclerosis related genes [oestrogen receptor-alpha (ER-alpha), extracellular superoxide dismutase (EC-SOD) and monocyte chemoattractant protein-1 (MCP-1)] were analysed using quantitative real-time PCR. Global DNA methylated status was measured using the cytosine extension assay. The methylated patterns of ER-alpha, EC-SOD and MCP-1 genes were determined with methylation-specific PCR. We found that DZA administration increased intracellular SAH levels progressively and simultaneously decreased Hcy content in medium. Moreover, the supplementation induced HUVEC apoptosis, inhibited proliferation ability and DNMT1 mRNA expression (P < 0.05) and furthermore reduced global DNA methylation status (P < 0.05). Correlation analysis showed the presence of a negative correlation between intracellular SAH concentration, proliferative ability, and expression of ER-alpha, EC-SOD, and DNMT1 (r = -0.89, -0.86, -0.92 and -0.88 respectively, P < 0.001); and a positive correlation with MCP-1 expression and DNA [(3)H]-dCTP incorporation (r = 0.89 and 0.93 respectively, P < 0.001). Our results showed that endothelial dysfunction induced by intracellular SAH accumulation is mediated by regulating the expression of atherosclerosis related genes in HUVEC, which is not related with gene promoter methylated patterns, but may be associated with altered global DNA hypomethylated status. These findings suggest that SAH can act as the potential molecular biological marker in the promotion of atherogenesis.

Ultraviolet B exposure of peripheral blood mononuclear cells of patients with systemic lupus erythematosus inhibits DNA methylation

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease, in which sunlight (especially ultraviolet B (UVB) 290-320 nm) is known to induce exacerbation of disease. DNA methylation regulates gene expression, and hypomethylation is associated with abnormal cell function in SLE. The purpose of this study was to investigate the effect of UVB on DNA methylation in SLE and its significance in the pathogenesis of SLE. Forty-five patients with SLE and 20 healthy controls were enrolled in the study, which involved the investigation of DNA methylation and DNA methyltransferase 1 (DNMT1) of peripheral blood mononuclear cells with UVB irradiation. Our results demonstrate the following: The level of DNA methylation in patients with SLE was lower than that in the control group. DNA methylation was decreased after UVB irradiation at different dosages especially in patients with marlar rashes and leucopenia, but no significant difference was observed in the DNMT1 mRNA expression. DNA methylation levels in patients with active SLE were more sensitive to UVB. In conclusion, UVB exposure is able to inhibit DNA methylation, which subsequently takes part in the pathogenesis of SLE.

Effect of DNA methyltransferase 1 gene silencing on proliferation and apoptosis of HeLa cells

To observe the effect of DNA methyltransferase 1 (DNMT1) gene silencing by RNA interfering technology on the proliferation and apoptosis of HeLa cells. Recombinant plasmid pshRNA-DNMT1-A, B and C were respectively transfected into HeLa cells by lipofectamine 2000, while cells transfected plasmid vector pSilencer3. 1-H1 and cells untreated as control groups. RT-PCR was adopted to select the recombinant plasmid which showed the most optimal inhibition effect. RT-PCR and western blotting was used to detected the mRNA and protein expression of DNMT1 in HeLa cells transfected for 24, 48 and 72 hours. Cell counting kit-8 (CCK-8) assay was used to investigate the proliferation of the HeLa cells after transfection, while apoptosis was detected by flowcytometry (FCM) method. Three DNMT1-targeted short hairpin RNA (shRNA) A,B and C were successfully inserted into the plasmid vector pshRNA, and the coding sequences of the obtained shRNA were consistent with the designed fragments. The results indicated that both recombinant plasmid pshRNA-DNMT1-A and B could effectively knock down the expression of DNMT1 gene in human cervical cancer cells, of which pshRNA-DNMT1-B was the better choice. While no effect of pshRNA-DNMT1-C was seen. RT-PCR results showed that the relative mRNA expression of DNMT1 gene in HeLa cells transfected with pshRNA-DNMT1 for 24, 48 and 72 hours were 0.406 +/- 0.057, 0.191 +/- 0.036 and 0. 104 +/- 0.015, which were significantly lower than that in HeLa cells transfected by empty vector and non-transfected cells (0.520 +/- 0.020, 0.537 +/- 0.041, respectively, P < 0. 05). The western blotting analysis manifested that the relative expression of DNMT1 protein of HeLa cells transfected by pshRNA-DNMT1 for 24, 48 and 72 hours were 0.197 +/- 0.024, 0.075 +/- 0.015, 0.040 +/- 0. 013, which were significantly lower than that in transfected cells by empty vector and non-transfected cells (0.273 +/- 0.010, 0.283 +/- 0.016, respectively, P < 0.05). The CCK-8 results showed that the cell survival rates of HeLa cells transfected by pshRNA-DNMT1 for 24, 48, 72, 96 and 120 hours were 70.8%, 64.8%, 51.6%, 45.3% and 38.0%, there were statistically different compared with cells transfected by empty vector and non-transfected cells at different time-points (P < 0.01). The results of FCM indicated that the apoptosis rate of HeLa cells transfected with pshRNA-DNMT1 for 24, 48 and 72 hours were (17.7 +/- 1.3)%, (35.3 +/- 1.3)%, (47.6 +/- 1.6)%, which were significantly higher than empty vector transfected cells and non-transfected cells [(4.9 +/- 0.5)%, (5.1 +/- 0.7)%, respectively, P < 0.05]. DNMT1 can be successfully silenced by RNA interfering in cervical HeLa cells. Downregulation of DNMT1 can inhibit cervical cancer cells proliferation and induce cell apoptosis.

Inhibition of DNA methyltransferase 1 expression in bovine fibroblast cells used for nuclear transfer

The aberrant expression of DNA methyltransferase 1 (DNMT1) in cloned embryos has been implicated as a possible factor in the improper donor genome reprogramming during nuclear transfer. DNMT1 is responsible for maintaining DNA methylation and the subsequent differentiation status of somatic cells. The presence of DNMT1 transcript in the donor cell may contribute to perpetuation of the highly methylated status of the somatic nuclei in cloned embryos. The objective of the present study was to determine the methylation pattern of cloned embryos reconstructed with cells treated with DNMT1-specific small interfering RNA (siRNA). Bovine fibroblasts were transfected with a DNMT1-specific siRNA under optimised conditions. The expression patterns of DNMT1 were characterised by Q-PCR using the DeltaDeltaC(T) method. The level of DNMT1 was successfully decreased in bovine fibroblast cells using a DNMT1-specific siRNA. Additionally, reduction in the expression of DNMT1 mRNA and DNMT1 protein led to a moderate hypomethylation pattern in the siRNA-treated cells. The use of siRNA-treated cells as donor nuclei during nuclear transplantation induced a reduction in methylation levels compared with controls but did not reduce methylation levels to that of IVF embryos. Further studies are required to determine if this level of reduced methylation is sufficient to improve subsequent development.

Effect on proliferation and apoptosis of T24 cell lines via silencing DNMT1 with RNA interference

Expression of DNA methyltransferase 1 (DNMT1), which plays an important role on aberrantly methylated CpG in the promoter regions of tumor suppressor genes (TSGs), is higher in bladder cancer cells than in normal bladder cells. Therefore, its overexpression is closely related to tumor formation. In this study, the eukaryotic vector pshRNA-DNMT1 was constructed and transfected into T24 cells. Levels of DNMT1 mRNA and protein were detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blot. Relative to the blank control at the 24th, 48th and 72nd hour after transfection of pshRNA-DNMT1, the inhibitory rates of DNMT1 mRNA levels in T24 cells were 28.44%, 52.48%, 70.91%, respectively. Those of DNMT1 proteins were 24.27%, 57.79%, and 77.74%, respectively. Proliferation and apoptosis were assayed by MTT and flow cytometry with Annexin-V-FITC/PI staining. The growth inhibition rates of pshRNA-DNMT1 at the 24th, 48th and 72nd hour after transfection of pshRNA-DNMT1 were (4.34 ± 0.76)%, (9.87 ± 1.54)% and (13.78 ± 1.93)%, respectively. There were statistically significant differences between pshRNA-DNMT1 and the control blank at each time points (P < 0.01); 24, 48 and 72 hours after T24 cells were transfected by pshRNA-DNMT1, the apoptosis rates of pshRNA-DNMT1 were (3.87 ± 0.81)%, (8.69 ± 1.23)% and (11.46 ± 1.24)%, respectively (P < 0.01 vs blank control). Based on this case, our conclusion is that the recombinant plasmid pshRNA-DNMT1 can silence the expression of gene DNMT1 mRNA and protein effectively, and to some extent, it also can inhibit the proliferation of bladder cancer cell and promote the cellular apoptosis.

GABAA Receptor Promoter Hypermethylation in Suicide Brain: Implications for the Involvement of Epigenetic Processes

Epigenetic mechanisms may be involved in the reprogramming of gene expression in response to stressful stimuli. This investigation determined whether epigenetic phenomena might similarly be associated with suicide/depression. The expression of DNA methyltransferase (DNMT) mRNA was assessed in several brain regions of individuals who had committed suicide and had been diagnosed with major depression relative to that of individuals who had died suddenly as a result of factors other than suicide. The DNMT gene transcripts' expression was altered in several brains regions of suicides, including frontopolar cortex, amygdala, and the paraventricular nucleus of the hypothalamus. Importantly, an increase of both mRNA and protein expression was found in the frontopolar cortex. In addition, although transcript abundance of various forms of DNMT was highly correlated in normal control subjects, this coordination of DNMT isoform expression was diminished in suicide brain. Further, within the frontopolar cortex, gene-specific aberrations in DNA methylation were apparent in the gamma-aminobutyric acid (GABA)(A) receptor alpha1 subunit promoter region, the transcript of which is underexpressed in suicide/major depressive disorder (MDD) brains. Indeed, three cytosine/guanosine sites were hypermethylated relative to control subjects. Finally, we found that DNMT-3B mRNA abundance was inversely correlated to alpha1 mRNA abundance. These data show that DNMT mRNA expression was altered in suicide brain, and this change in expression in the frontopolar cortex was associated with increased methylation of a gene whose mRNA expression has previously been shown to be reduced. These observations suggest that epigenetic mechanisms may be associated with altered gene expression in suicide/MDD.

Synthesized small interfering RNA inhibits the expression of DNA methyltransferase 1 in salivary adenoid cystic carcinoma

To select the effective siRNA which could inhibit the expression of DNA methyltransferase 1 (DNMT-1) in adenoid cystic carcinoma (ACC) and discuss the time-, and dose-dependent effect of RNA interference (RNAi). Four pairs of siRNA were designed, synthesized and transfected through oligofectamine reagent into ACC cell lines ACC-2, ACC-3 and ACC-M. 24, 48 and 72 h after transfection, total RNA and protein were harvested respectively. mRNA and protein expression level of DNMT-1 were detected by real time PCR, RT-PCR and Western blot, and then the effective siRNA was subsequently selected. ACC-3 as also transfected by different concentration of siRNA and the dose-dependent effect of RNAi was discussed. Cy(3) labelled GAPDH siRNA was used as a positive control. Two of 4 pairs of siRNA inhibited the mRNA expression of DNMT-1 in three ACC cell lines and the expression of DNMT-1 was downregulated by 67%, 86%, 92% and 76%, 76%, 86% respectively. The gene inhibition was detected at 24 h or 48 h after transfection, maintained only 1 - 2 days and showed direct relationship to the concentration of siRNA. The change of protein expression level of DNMT-1 was consistent to the changes of mRNA. The effective siRNA which could inhibited the expression of DNMT-1 of ACC were achieved. The inhibition effect of RNAi was time-dependent and dose-dependent.

Selective epigenetic alteration of layer I GABAergic neurons isolated from prefrontal cortex of schizophrenia patients using laser-assisted microdissection

Among the most consistent results of studies of post-mortem brain tissue from schizophrenia patients (SZP) is the finding that in this disease, several genes expressed by GABAergic neurons are downregulated. This downregulation may be caused by hypermethylation of the relevant promoters in affected neurons. Indeed, increased numbers of GABAergic interneurons expressing DNA methyltransferase 1 (DNMT1) mRNA have been demonstrated in the prefrontal cortex (PFC) of SZP using in situ hybridization. The present study expands upon these findings using nested competitive reverse transcription-polymerase chain reaction combined with laser-assisted microdissection to quantitate the extent of DNMT1 mRNA overexpression in distinct populations of GABAergic neurons obtained from either layer I or layer V of the PFC of SZP. In a cohort of eight SZP and eight non-psychiatric subject (NPS) post-mortem BA9 tissue samples, DNMT1 mRNA was found to be selectively expressed in GABAergic interneurons and virtually absent in pyramidal neurons. DNMT1 mRNA expression was approximately threefold higher in GABAergic interneurons microdissected from layer I of SZP relative to the same neurons microdissected from NPS. GABAergic interneurons obtained from layer V of the same samples displayed no difference in DNMT1 mRNA expression between groups. In the same samples, the GABAergic neuron-specific glutamic acid-decarboxylase(67) (GAD(67)) and reelin mRNAs were underexpressed twofold in GABAergic interneurons isolated from layer I of SZP relative to GABAergic interneurons microdissected from layer I of NPS, and unaltered in GABAergic interneurons of layer V. These findings implicate an epigenetically mediated layer I GABAergic dysfunction in the pathogenesis of schizophrenia, and suggest novel strategies for treatment of the disease.

Sex‐specific windows for high mRNA expression of DNA methyltransferases 1 and 3A and methyl‐CpG‐binding domain proteins 2 and 4 in human fetal gonads

DNA methyltransferases (DNMTs) and 5-methyl-CpG-binding domain proteins (MBDs) are involved in the acquisition of parent-specific epigenetic modifications in human male and female germ cells. Reverse Northern blot analyses demonstrated sex-specific differences in mRNA expression for the maintenance DNMT1 and the de novo DNMT3A in developing testis and ovary. In fetal testis DNMT1 and DNMT3A expression peaked in mitotically arrested spermatogonia around 21 weeks gestation. In fetal ovary transcriptional upregulation of DNMT1 and DNMT3A occurred during a very brief period at 16 weeks gestation, when the oocytes proceeded through meiotic prophase. Fetal gonads showed several fold higher DNMT3A expression levels than fetal brain and adult tissues. The most abundant DNMT3A isoform in fetal testis and ovary was DNMT3A2, whereas in all other analyzed tissues DNMT3A1 predominated. The catalytically inactive DNMT3A3 isoform was also present at relatively high levels in developing gonads and may perform a regulatory function(s). In both male and female fetal gonads expression of genes for MBD2 and MBD4, which may be implicated in chromatin remodeling of methylated genomic DNA sequences, was tightly linked to DNMT expression. We propose that the sex-specific time windows for concomitant upregulation of DNMT1, DNMT3A, MBD2, and MBD4 are associated with prenatal remethylation of the human male and female germ line.

Arsenic trioxide inhibits DNA methyltransferase and restores methylation-silenced genes in human liver cancer cells

In the present study, we investigated methylation status of the CpG islands of some major tumor suppressor genes both in human hepatocellular carcinoma and liver cancer cell lines and examined whether demethylation by arsenic trioxide (As2O3) could restore their expression in the cell lines. HepG2 and Huh-7 cells were treated with 2 to 10 micromol/L of AS2O3 and/or 1 micromol/L of 5-aza-2'-deoxycytidine for 24, 48, and 72 hours. The methylation status of the CpG island around the promoter regions of p161NK4a, RASSF1A, E cadherin, and GSTP1 was detected by a methylation-specific polymerase chain reaction (MSP). The messenger RNA (mRNA) and protein levels of these genes were determined by quantitative real-time reverse transcriptase-polymerase chain reaction, Western blot, and immunohistochemical analyses. The DNA methyltransferase (DNMT) mRNA levels and enzyme activity were also examined. The hypermethylated status of the promoter regions of p16INK4a, RASSF1A, E cadherin, and GSTP1 was observed in 10 (40%), 14 (56%), 6 (24%), and 12 (48%) of 25 patients with hepatocellular carcinoma, respectively. CpG methylation of the p16INK4a, RASSF1A, E cadherin, and GSTP1 genes was correlated to the reduction of mRNA levels in the cell lines, and mRNA expression of these 4 genes were indeed restored by low concentrations (2-6 micromol/L) of As2O3 through demethylation, as well as 1 micromol/L of 5-aza-2'-deoxycytidine. Western blot and immunohistochemical analyses confirmed that each protein was markedly enhanced after treatment with a low concentration of As2O3. In contrast, As2O3 at a high concentration (10 micromol/L) damaged cell membranes and remarkably suppressed these 4 protein levels. As2O3 decreased the mRNA expression of DNMT 1 and also dose-dependently inhibited DNMT activity. In conclusion, a low concentration of As2O3 induces CpG island demethylation of tumor suppressor genes by inhibition of DNMT and reactivates the partially/fully silenced genes in liver cancer cells.

Down-regulation of interferon regulatory factor 4 gene expression in leukemic cells due to hypermethylation of CpG motifs in the promoter region

Although the bcr-abl translocation has been shown to be the causative genetic aberration in chronic myeloid leukemia (CML), there is mounting evidence that the deregulation of other genes, such as the transcription factor interferon regulatory factor 4 (IRF-4), is also implicated in the pathogenesis of CML. Promoter methylation of CpG target sites or direct deletions/insertions of genes are mechanisms of a reversible or permanent silencing of gene expression, respectively. Therefore, we investigated whether IRF-4 promoter methylation or mutation may be involved in the regulation of IRF-4 expression in leukemia cells. Whereas promoter mutations or structural rearrangements could be excluded as a cause of altered IRF-4 expression in hematopoietic cells, the IRF-4 promoter methylation status was found to significantly influence IRF-4 transcription. First, treatment of IRF-4-negative lymphoid, myeloid and monocytic cell lines with the methylation-inhibitor 5-aza-2-deoxycytidine resulted in a time- and concentration-dependent increase of IRF-4 mRNA and protein levels. Second, using a restriction-PCR-assay and bisulfite-sequencing we identified specifically methylated CpG sites in IRF-4-negative but not in IRF-4-positive cells. Third, we clearly determined promoter methylation as a mechanism for IRF-4 down-regulation via reporter gene assays, but did not detect an association of methylational status and mRNA expression of DNA methyltransferases or methyl-CpG-binding proteins. Together, these data suggest CpG site-specific IRF-4 promoter methylation as a putative mechanism of down-regulated IRF-4 expression in leukemia.