genome vs epigenome

Genetics is a very interesting branch of science as it provides a root-level explanation of biological phenomenon and opens very new frontiers for impactful intervention to help combat a lot of biological banalities that have plagued us throughout history. Genome (which I have covered in a previous article - dissecting genetic code) is essentially an organized molecular structure that holds biological instructions or code which get executed by special computer-analogous biological structures in cells to help ultimately render the various biological phenomenon that occur in nature. Different genomic codes hold different instructions and hence execute different biological functions. Alteration of biological code (through mutation) will alter the biological instructions and thereby the biological functions underlined by the code. Genomic code is ultimately what differentiates species (dog vs human) and even different individuals within the same species (human A vs human B). Genomic code can explain why human A ends up achieving centenarian status whereas human B unfairly dies early due to cancer or diabetes. The broad overview of genomics and its impact on our life may be more or less familiar with a good majority of people but there is a more interesting and arguably more consequential biological element which may be relatively less popular (at least it was in my case) than the genome which sort of acts a conduit of sorts that is responsible for deciding how the instructions stored in the genome effectively gets materialized into biological functions. The biological element in discussion here (as you might have guessed it from the title) is the epigenome. If the genome is a total set of biological instructions that can be executed, then the epigenome is a filter that can selectively hide or show only certain subsets of total set of instructions to get executed which is why the epigenome is very consequential when it comes to biological life. The genome represents the entire biological code we need for our overall functioning and is contained in all the cells, but the entire genomic code does not get executed in any cell and this is where the epigenome comes into the picture. Epigenome is effectively what distinguishes the different classes of cells within our body, for example : heart and liver cells in our body have the same genomic code but what differentiates them is the epigenetic code they possess where the parts of the overall genetic code that executed in the heart cells is very different from the parts of the overall genetic code that gets executed in the liver cells. While the genomic code is represented by a long strand which are organized sequences of special (A-T-C-G) molecules which represents the entire biological code we effectively need for our overall functioning, epigenomic code is represented by how the long genomic strand (~ 2 meters) is physically contained in a microscopic cell (< 10 micrometers) which in turn affects which parts of the genomic code gets executed and which parts of the genomic code gets omitted. The long genomic strand gets coiled around various protein molecules called histones within the cell and the parts of the strands which get tightly wrapped around the histone gets omitted as it is not available for code execution by the biological compiler which performs the requisite biological functions, and the loose parts of the genomic strand is what is ultimately available for the biological computation. While genomic code is not very easily alterable (unless through extreme measures such as mutation or genetic engineering), the epigenomic code is highly malleable and is influenced by a variety of factors (a lot of which is in our control). As mentioned earlier, all cells possess the same genomic code and what differentiates different cells is the different epigenomic code they possess but at inception i.e. the primary development stage, all cells possess the same epigenomic code as well (i.e. the same physical orientation of genome strand within the cell). Cells at the primary development stage are what are known as STEM cells which possess the same baseline epigenomic code and what makes STEM cells very useful in medical treatments is its ability to transform into any requisite cellular component of the body to help replace irreparably damaged cells in the body. STEM cells can be placed in different regions of the body as per the medical requirement after which it picks up region-specific biochemical signals which induces specific epigenomic changes in the cell thereby transforming the STEM cells into the requisite newly produced healthy cells to replace the irreparable damaged cells. As mentioned earlier, the epigenome is highly malleable and is influenced (both naturally and unnaturally) by different molecules which in turn affects the physical orientation of genome strands in the cell in different ways and effectively translates into different expressions of the same genomic code. A very important breakthrough in the field of epigenetics was unearthed by Japanese researcher Shinya Yamanaka who discovered 4 molecules called Yamanaka factors (for which he won the Nobel Prize in 2016) which could influence and effectively reverse the epigenomic code of developed cells back to the baseline epigenomic code thereby converting them to STEM cells. Professor David Sinclair who is a tenured professor in the field of genetics at Harvard Medical School uses the theory of epigenetics to explain biological aging and is exploring frontiers to slow down and even reverse biological aging. As we age, our epigenomic code changes due to which our biological functionalities change correspondingly and translate into what we observe as the age-related physiological changes in our body. Professor Sinclair reduces the concept of biological aging to the increasing disorder of epigenomic information in cells, where slowing down aging effectively means reducing the rate of change of epigenomic information with time and reversing aging is effectively trying to the transform our epigenomic code i.e. physical orientation of the genome strands into an orientation of an earlier time frame which is what happens in the case of exposing developed cells to Yamanaka factors where the epigenomic code transforms into the baseline (STEM cell-level) code of a cell. Professor Sinclair has successfully conducted experiments to reverse biological age in mice where he uses 3 of the 4 Yamanaka factors to transform the epigenomic code of mice cells to one of an earlier time frame but not the baseline code possessed by STEM cells which is age zero as the STEM cells with the baseline epigenetic code have been observed to be cancerous. Epigenetics opens the door to a more easily accessible frontier of indirectly controlling our hereditary genetic code to our advantage through the phenomenon of influenceable gene expression where we can selectively suppress the expression of harmful genes and express only the beneficial genetic information via simple interventions that involve specific diets and medicine.