Abstract
Kaur K
Abstract
Introduction: 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. These mechanisms control differences in the gene expression that are mitotically heritable although not altering the primary DNA sequence [1]. A large number of proteins write, read or erase particular epigenetic modifications and thus define where and when the transcriptional machinery can access the primary DNA sequence to drive normal growth and differentiation in the developing embryo along with the fetus. 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. There are two special examples e.g., chromosome inactivation and genome imprinting, which explains how 2016 Vol. 2 No. 4: 20 Journal of Clinical Epigenetics ISSN 2472-1158 2 This article is available in: http://www.clinical-epigenetics.imedpub.com/ important are the epigenetic mechanisms in regulating correct patterns of gene expression during early development chromosome inactivation basically is an example of dosage compensation in females leading to monoallelic expression of a huge number of X linked genes in female. Genome imprinting is a process in which special genes carrying epigenetic marks from parents of origin have the capacity for getting monoallelic parent of origin specific cell types at specific times of development. In germ cells in development as well as in embryo, there is genome wide reprogramming which is responsible for erasure as well as reestablishing of the correct epigenetic patterns. In contrast to these naturally occurring processes, the processes used in induced pluripotent stem cells from somatic cells are quite different [2], reviewed by Huang et al[3]. Changes in epigenetics can occur by different mechanisms and lead to infertility and imprinting disorders. 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 [5-9].