Dnmt1: Care taker of genomic imprints during pre-implantation development in mammals
Humans have approximately 30,000 genes but show far more complexity than these number of genes can answer to. So, how can the range of variation and depth of complexity observed in humans can be explained? There has to be something more than just the genes. Have you ever thought what causes these variations? And also how these variations inherited from parents are maintained during the development of the embryo? The answer to this is really intriguing.
We mammals are diploid organisms , and our off springs inherit two copies of same gene one from each parent and have the same level of potential to be active in a cell but certain genes show pattern of mono-allelic parental specific gene expression. These genes although have same DNA sequence but show differential expression within the same cell resulting in the variation. The molecular basis to this phenomenon can be best explained by an epigenetic mechanism known as genomic imprinting. Genomic imprinting has the ability to restrict the expression of a gene to one of the two paternal chromosomes. It affects the offspring irrespective of the sex and has significant importance during the developmental process in mammals. Thus the process of DNA methylation, has established the fact how genomic imprinting is achieved in mammals, making it possible to silence one of the parental genes
The process of DNA methylation is controlled by set of enzymes known as DNA methyltransferases- Dnmt1, Dnmt3a and Dnmt3b. Dnmt1 is known to maintain the DNA methylation in somatic cells as inherited from the parents and on the other hand Dnmt3a/Dnmnt3b are responsible for re-establishing the imprints in the germ cells specific to the sex of the gamete, in post-implantation embryos. At the same time it’s also known that during the cleavage stage prior to implantation there is occurrence of global de-methylation. So now the question arises- what maintains the parental specific methylation imprints during the cleavage stage prior to implantation of the embryo? And the reply is the "Dnmt1" enzyme.
The investigation by Hirasawa et al. [2008] showed that the presence isoforms of Dnmt1 in nucleus of oocytes and pre-implantation mice embryos is alone responsible and sufficient enough to maintain parent specific methylation imprints during pre implantation development in mammals.
To learn more about it refer to the main article at http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=18559477
Samikshya Biswal
41568400
We mammals are diploid organisms , and our off springs inherit two copies of same gene one from each parent and have the same level of potential to be active in a cell but certain genes show pattern of mono-allelic parental specific gene expression. These genes although have same DNA sequence but show differential expression within the same cell resulting in the variation. The molecular basis to this phenomenon can be best explained by an epigenetic mechanism known as genomic imprinting. Genomic imprinting has the ability to restrict the expression of a gene to one of the two paternal chromosomes. It affects the offspring irrespective of the sex and has significant importance during the developmental process in mammals. Thus the process of DNA methylation, has established the fact how genomic imprinting is achieved in mammals, making it possible to silence one of the parental genes
The process of DNA methylation is controlled by set of enzymes known as DNA methyltransferases- Dnmt1, Dnmt3a and Dnmt3b. Dnmt1 is known to maintain the DNA methylation in somatic cells as inherited from the parents and on the other hand Dnmt3a/Dnmnt3b are responsible for re-establishing the imprints in the germ cells specific to the sex of the gamete, in post-implantation embryos. At the same time it’s also known that during the cleavage stage prior to implantation there is occurrence of global de-methylation. So now the question arises- what maintains the parental specific methylation imprints during the cleavage stage prior to implantation of the embryo? And the reply is the "Dnmt1" enzyme.
The investigation by Hirasawa et al. [2008] showed that the presence isoforms of Dnmt1 in nucleus of oocytes and pre-implantation mice embryos is alone responsible and sufficient enough to maintain parent specific methylation imprints during pre implantation development in mammals.
To learn more about it refer to the main article at http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=18559477
Samikshya Biswal
41568400
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