So a sperm and an egg come together and form what\u2019s called a zygote. So that\u2019s the first cell okay and it\u2019s the first cell of the developing embryo that\u2019s going to go forward. So the DNA from the sperm gets together with the DNA from the \u2013 which is half the DNA comes from here and half the DNA came from the eggs \u2013 they come together and they form and fuse and they form this what\u2019s called a diploid but it has all their DNA for one cell present. And then this zygote then starts to have certain activities going on that will lead it to divide. It\u2019s called a cleavage event and it basically divides into two cells.<\/p>\n\n\n\n
At that point you now have an early developing embryo. And there will be more and more cell divisions going forward and eventually you have an embryo that doesn\u2019t have any defined structure per se and it\u2019s right before it starts to develop a structure and sort of starts developing a fetus eventually and so forth. So there\u2019s a cell type in the early embryo called an embryonic stem cell. Stem cells that are within that early embryo. And these are what are called \u2013 these cells have the capacity to turn into any cell in the body. And so as the embryo develops then essentially this cell will turn into a neuron and the brain will sort of develop from it, this one will turn into a liver and a hepatocyte develops from it. All these different cells come from this population of stem cells.<\/p>\n\n\n\n
So one of the questions that nobody really ever asked before was \u201cWell what forms the stem cells?\u201d It turns out that the sperm and the egg have a certain level of epigenetics. DNA methylation is one, there\u2019s other sort of things going on. There\u2019s epigenetics in the sperm and epigenetics in the egg, in terms of the methylation of DNA which has a chemical mark on the DNA that actually will help turn genes on and off and so forth. So these come together and there\u2019s full-blown DNA methylation of this zygote. The first cleavage event then, what happens is, immediately the DNA methylation, all these chemical modifications of DNA, they start to get erased. So it\u2019s that over, in the first four or five cell divisions all of a sudden the DNA methylation is erased and you have a much, much lower, it\u2019s not completely zero, but it\u2019s in the 10% – 15% range.<\/p>\n\n\n\n
So essentially then, this cell that is a stem cell is now pluripotent or totipotent. It can turn into anything because there\u2019s no DNA methylation. And when you actually start remethylating to make a neuron there\u2019s a cascade of methylation events to eventually get a neuron. Or for a heart cell it\u2019s a cascade of events to get a cardiac heart cell. All these cells will come from this population and it\u2019s the methylation that actually determines the lineage of that cell and what it\u2019s going turn into. So right at the level of conception you have this DNA methylation ratio and then it goes back up in a cell-specific manner. So epigenetics is critical from the very beginning.<\/p>\n\n\n\n
And then what happens during early development when it\u2019s just in that developing process, if you get an environmental stressor: a chemical, nutrition, stress, a whole series of environmental stressors that affect this early developmental sort of fetus or something or even postnatally – then essentially, you alter that programming. So you get a neuron that becomes a neuron but now it has a different epigenetics and may not function as it would\u2019ve normally. Or a cardiac cell that basically was going become a heart now it basically you\u2019re going get potentially a susceptibility to get heart disease because of those early insults when that programming is occurring. So epigenetics is required throughout all of development just like the gene expression in the genetics is as well.<\/p>\n","protected":false},"excerpt":{"rendered":"
So a sperm and an egg come together and form what\u2019s called a zygote. So that\u2019s the first cell okay and it\u2019s the first cell of the developing embryo that\u2019s going to go forward. So the DNA from the sperm gets together with the DNA from the \u2013 which is half the DNA comes from […]<\/p>\n","protected":false},"author":39,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"template-text-only.php","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-5272","page","type-page","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/content.scienceofecd.com\/transcript\/wp-json\/wp\/v2\/pages\/5272","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/content.scienceofecd.com\/transcript\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/content.scienceofecd.com\/transcript\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/content.scienceofecd.com\/transcript\/wp-json\/wp\/v2\/users\/39"}],"replies":[{"embeddable":true,"href":"https:\/\/content.scienceofecd.com\/transcript\/wp-json\/wp\/v2\/comments?post=5272"}],"version-history":[{"count":1,"href":"https:\/\/content.scienceofecd.com\/transcript\/wp-json\/wp\/v2\/pages\/5272\/revisions"}],"predecessor-version":[{"id":5273,"href":"https:\/\/content.scienceofecd.com\/transcript\/wp-json\/wp\/v2\/pages\/5272\/revisions\/5273"}],"wp:attachment":[{"href":"https:\/\/content.scienceofecd.com\/transcript\/wp-json\/wp\/v2\/media?parent=5272"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}