DNA methylation plays an essential role in mammalian development[1].However,how DNA methylation is inherited between generations and if there is family-specific DNA methylation pattern remains to be elucidated[2].In this study,we collect male blood samples including a big pedigree of the descendants of an ancient Chinese empire and samples from different haplogroups to study their whole genome DNA methylation pattern.We find 115 male family-specific methylation sites from three families.The difference of whole genome DNA methylation pattern correlates
Detecting cell-free DNA(cfDNA) or circulating tumor DNA(ctDNA) in plasma or serum could serve as a "liquid biopsy", which would be useful for numerous diagnostic applications. cfDNA methylation detection is one of the most promising approaches for cancer risk assessment. Here, we reviewed the literature related to the use of serum or plasma circulating cell-free DNA for cancer diagnosis in the early stage and their power as future biomarkers.
Background:Induced pluripotent stem cells(iPSCs)and embryonic stem cells(ESCs)share many common features,including similar morphology,gene expression and in vitro differentiation profiles.However,genomic stability is much lower in iPSCs than in ESCs.In the current study,we examined whether changes in DNA damage repair in iPSCs are responsible for their greater tendency towards mutagenesis.Methods:Mouse iPSCs,ESCs and embryonic fibroblasts were exposed to ionizing radiation(4 Gy)to introduce dou-ble-strand DNA breaks.At 4 h later,fidelity of DNA damage repair was assessed using whole-genome re-sequencing.We also analyzed genomic stability in mice derived from iPSCs versus ESCs.Results:In comparison to ESCs and embryonic fibroblasts,iPSCs had lower DNA damage repair capacity,more somatic mutations and short indels after irradiation.iPSCs showed greater non-homologous end joining DNA repair and less homologous recombination DNA repair.Mice derived from iPSCs had lower DNA damage repair capacity than ESC-derived mice as well as C57 control mice.Conclusions:The relatively low genomic stability of iPSCs and their high rate of tumorigenesis in vivo appear to be due,at least in part,to low fidelity of DNA damage repair.
Histone methylation is a kind of important epigenetic modification which occurs on the lysine residue or arginine residue of histone tails（Zhang and Reinberg,2001）.It takes part in multiple biological processes,including gene expression,genomic stability,stem cell maturity,genetic imprinting,mitosis and development（Fischle et al.,2005）.
N6-methyl-adenosine （m6A） is one of the most common and abundant modifications on RNA molecules present in eukaryotes. However, the biological significance of m6A methylation remains largely unknown. Several independent lines of evidence suggest that the dynamic regulation ofm6A may have a profound impact on gene expression regulation. The m6A modification is catalyzed by an unidentified methyltransferase complex containing at least one subunit methyltransferase like 3 （METTL3）. m6A modification on messenger RNAs （mRNAs） mainly occurs in the exonic regions and 3＇-untranslated region （3＇-UTR） as revealed by high-throughput m6A-seq. One significant advance in m6A research is the recent discovery of the first two m6A RNA demethylases fat mass and obesity- associated （FTO） gene and ALKBH5, which catalyze m6A demethylation in an cx-ketoglutarate （a-KG）- and FeZ ＋ -dependent manner. Recent studies in model organisms demonstrate that METTL3, FTO and ALKBH5 play important roles in many biological processes, ranging from devel- opment and metabolism to fertility. Moreover, perturbation of activities of these enzymes leads to the disturbed expression of thousands of genes at the cellular level, implicating a regulatory role ofm6A in RNA metabolism. Given the vital roles of DNA and histone methylations in epigenetic regulation of basic life processes in mammals, the dynamic and reversible chemical m6A modification on RNA may also serve as a novel epigenetic marker of profound biological significances.
Yamei NiuXu ZhaoYong-Sheng WuMing-Ming LiXiu-Jie WangYun-Gui Yang
