ABSTRACT
In mammals, DNA methyltransferases transfer a methyl group from S-adenosylmethionine to the 5 position ofcytosine in DNA. The product of this reaction, 5-methylcytosine (5mC), has many roles, particularly insuppressing transposable and repeat elements in DNA. Moreover, in many cellular systems, cell lineagespecification is accompanied by DNA demethylation at the promoters of genes expressed at high levels in thedifferentiated cells. However, since direct cleavage of the C-C bond connecting the methyl group to the 5position of cytosine is thermodynamically disfavoured, the question of whether DNA methylation wasreversible remained unclear for many decades. This puzzle was solved by our discovery of the TET (TenEleven Translocation) family of 5-methylcytosine oxidases, which use reduced iron, molecular oxygen and thetricarboxylic acid cycle metabolite 2-oxoglutarate (also known as a-ketoglutarate) to oxidise the methyl groupof 5mC to 5-hydroxymethylcytosine (5hmC) and beyond. TET-generated oxidised methylcytosines areintermediates in at least two pathways of DNA demethylation, which differ in their dependence on DNAreplication. In the decade since their discovery, TET enzymes have been shown to have important roles inembryonic development, cell lineage specification, neuronal function and cancer. We review these findings anddiscuss their implications here.
ABSTRACT
Objective To study the effect of long non-coding RNAs (lncRNAs) maternally imprinted genes 3 (MEG3) on human abortion vilii development and to explore the related molecular mechanisms. Methods We collected the vilii samples from 15 spontaneous abortion (SA) and 15 induced abortion (IA) patients. Immunohistochemistry was applied to detect the expressions of apoptosis factor Bax and apoptosis inhibitory factor Bcl-2 in vilii samples. Real-time quantitative polymerase chain reaction (qPCR) was used to analyze the levels of MEG3 of vilii samples. Overexpression of MEG3 in human trophoblast cell line HTR-8/SVneo was identified by qPCR; the invasion ability of HTR-8/SVneo cells was examined by matrigel invasion assay in MEG3 overexpression and control groups. Results Immunohistochemistry showed that the expression of Bax in IA group was lower than that in SA group, while the expression of Bcl-2 was higher (P<0.01). The level of MEG3 in IA group was significantly higher than that in SA group (P<0.01). The expression of MEG3 was obviously increased and invasion ability was inhibited in MEG3 overexpressed HTR-8/SVneo cells (P<0.01). Conclusion LncRNAs MEG3 may regulate the apoptosis and invasive ability of bizarre trophoblastic cells and influence on the development of human villi.
ABSTRACT
DNA methylation is essential in X chromosome inactivation and genomic imprinting, maintaining repression of XIST in the active X chromosome and monoallelic repression of imprinted genes. Disruption of the DNA methyltransferase genes DNMT1 and DNMT3B in the HCT116 cell line (DKO cells) leads to global DNA hypomethylation and biallelic expression of the imprinted gene IGF2 but does not lead to reactivation of XIST expression, suggesting that XIST repression is due to a more stable epigenetic mark than imprinting. To test this hypothesis, we induced acute hypomethylation in HCT116 cells by 5-aza-2′-deoxycytidine (5-aza-CdR) treatment (HCT116-5-aza-CdR) and compared that to DKO cells, evaluating DNA methylation by microarray and monitoring the expression of XIST and imprinted genes IGF2, H19, and PEG10. Whereas imprinted genes showed biallelic expression in HCT116-5-aza-CdR and DKO cells, the XIST locus was hypomethylated and weakly expressed only under acute hypomethylation conditions, indicating the importance of XIST repression in the active X to cell survival. Given that DNMT3A is the only active DNMT in DKO cells, it may be responsible for ensuring the repression of XIST in those cells. Taken together, our data suggest that XIST repression is more tightly controlled than genomic imprinting and, at least in part, is due to DNMT3A.
Subject(s)
Humans , DNA Methylation/genetics , Epigenetic Repression/genetics , Genome, Human , Genome/genetics , Genomic Imprinting/genetics , Insulin-Like Growth Factor II/genetics , RNA, Long Noncoding/genetics , Azacitidine/administration & dosage , Azacitidine/analogs & derivatives , /genetics , DNA Methylation/drug effects , Gene Knockout Techniques , Genome, Human/drug effects , In Situ Hybridization, Fluorescence/methods , Microarray Analysis , Polymorphism, Single Nucleotide , Proteins/metabolism , RNA, Long Noncoding/metabolism , Real-Time Polymerase Chain Reaction/methods , Reverse Transcriptase Polymerase Chain Reaction/methodsABSTRACT
Little evidence supports the existence of imprinted genes in chicken. Imprinted genes are thought to be intimately connected with the acquisition of parental resources in mammals; thus, the predicted lack of this type of gene in chicken is not surprising, given that they leave their offspring to their own heritance after conception. In this study, we identified several imprinted genes and their orthologs in human, mouse, and zebrafish, including 30 previously identified human and mouse imprinted genes. Next, using the HomoloGene database, we identified six orthologous genes in human, mouse, and chicken; however, no orthologs were identified for SLC22A18, and mouse Ppp1r9a was not included in the HomoloGene database. Thus, from our analysis, four candidate chicken imprinted genes (IGF2, UBE3A, PHLDA2, and GRB10) were identified. To expand our analysis, zebrafish was included, but no probe ID for UBE3A exists in this species. Thus, ultimately, three candidate imprinted genes (IGF2, PHLDA2, and GRB10) in chicken were identified. GRB10 was not significant in chicken and zebrafish based on the Wilcoxon-Mann-Whitney test, whereas a weak correlation between PHLDA2 in chicken and human was identified from the Spearman's rank correlation coefficient. Significant associations between human, mouse, chicken, and zebrafish were found for IGF2 and GRB10 using the Friedman's test. Based on our results, IGF2, PHLDA2, and GRB10 are candidate imprinted genes in chicken. Importantly, the strongest candidate was PHLDA2.
Subject(s)
Animals , Humans , Mice , Chickens , Fertilization , Parents , ZebrafishABSTRACT
Little evidence supports the existence of imprinted genes in chicken. Imprinted genes are thought to be intimately connected with the acquisition of parental resources in mammals; thus, the predicted lack of this type of gene in chicken is not surprising, given that they leave their offspring to their own heritance after conception. In this study, we identified several imprinted genes and their orthologs in human, mouse, and zebrafish, including 30 previously identified human and mouse imprinted genes. Next, using the HomoloGene database, we identified six orthologous genes in human, mouse, and chicken; however, no orthologs were identified for SLC22A18, and mouse Ppp1r9a was not included in the HomoloGene database. Thus, from our analysis, four candidate chicken imprinted genes (IGF2, UBE3A, PHLDA2, and GRB10) were identified. To expand our analysis, zebrafish was included, but no probe ID for UBE3A exists in this species. Thus, ultimately, three candidate imprinted genes (IGF2, PHLDA2, and GRB10) in chicken were identified. GRB10 was not significant in chicken and zebrafish based on the Wilcoxon-Mann-Whitney test, whereas a weak correlation between PHLDA2 in chicken and human was identified from the Spearman's rank correlation coefficient. Significant associations between human, mouse, chicken, and zebrafish were found for IGF2 and GRB10 using the Friedman's test. Based on our results, IGF2, PHLDA2, and GRB10 are candidate imprinted genes in chicken. Importantly, the strongest candidate was PHLDA2.
Subject(s)
Animals , Humans , Mice , Chickens , Fertilization , Parents , ZebrafishABSTRACT
Objective To investigate the expression of H19 imprinted genes in the villus tissues of women with spontaneous abortion.Methods Reverse transcription-polymerse chain reaction method(RT-PCR) was employed to detect H19 imprinted genes allele-specific expression levels of the villus tissues extracted from 45 cases of spontaneous abortion and 30 cases of normal pregnancy.Results Nineteen cases of 21 heterozygous cases in spontaneous abortion samples showed billelic expression of H19(19/21),whereas no billelic expression was found in the normal pregnancy samples(0/13)(P