Abstract
Basically epigenetic mechanisms control development and regulate gene expression in various types of cells of the organism, each carrying similar DNA sequence. In simple language, the nucleotides of DNA are letters of the complicated text and these epigenetic labels or marks are the spaces, punctuations, sentences, paragraphs and styles which give meaning to this complicated text. Here we have tried to discuss the epigenetic markers like DNA methylation at CpG dinucleotide, covalent modifications of histone proteins and details of noncoding RNA’s including long ncRNA’s, miRNA. Besides importance of lncRNA’S has been discussed in dosage compensation in X linked genes with role of Xi where heavy dosage of X linked genes get compensated with role of Xist and long noncoding RNAs and further the value of genome imprinting in ART and various disorders like Beckman Wiedeman Syndrome (BWS), Russell silver syndrome (RSS) is discussed with just opposing marks on similar loci on same chromosomes. Further role of environmental stressors in stresses is discussed. Role of famines in both Chinese as well as Dutch famines highlights immediate changes can affect on future generations. Environmental pollutants and medications may affect fetal epigenetic marks e.g., is in choline intake in pregnancy increased placental promoter methylation of cortisol regulation genes CRH and NR3IC=>improved stress response in children by lowering cortisol levels in H-P-A axis. Thus future of epigenetics research lies in understanding the effects of interaction of epigenetics and environment emphasis on fetal programming understanding and uncovering role of medicine and nutrition and assesses risk for adult onset disease.
Highlights
Epigenetic mechanisms play a fundamental role in controlled development and gene expression in different types of cells of an organism, carrying the same genomic DNA sequence
Such imprinting centres (ICs) are characterized by differential methylated regions (DMRs). These DMRs carry parent of origin specific DNA methylation and histone modification marks. These cis acting DMRs along with Trans acting factors form the basis of the parent of origin specific gene expression of imprinted genes, e.g., are insulin like growth factor 2 [(IGF2/H19)-IC core regulates the paternal expression of IGF2, with the maternal expression of H19,2 genes located practically in the same imprinted domain 90 kilobase apart [41]
We have tried to discuss the epigenetic markers like DNA methylation at CpG dinucletotide, covalent modifications of histone proteins and details of noncoding RNAs including long ncRNAs, micro RNA (miRNA)
Summary
Epigenetic mechanisms play a fundamental role in controlled development and gene expression in different types of cells of an organism, carrying the same genomic DNA sequence. Different type of epigenetic marks work in concert to drive appropriate gene expression These are DNA methylation at CpG dinucleotides, covalent modifications of histone proteins, noncoding RNA’s (ncRNA) along with other complementary mechanisms contributing to higher order chromatin organization, within the cell nucleus. Genetic as well as environmental factors impact genetic marks, which develop phenotypic differences varying from normal variation to human disease [4] Both environmental factors e.g., starvation as well as artificial reproductive technologies (ART) have been shown to affect the epigenome of the embryo e.g., of the epigenetic changes which are associated with maternal starvation in fetal life can remain throughout adulthood, contributing to late onset disorders e.g., CVS disorders and type 2 diabetes mellitus [5,6,7,8,9]
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