How important is DNA. The genetic code is the centerpiece of life, Which in the case of humans stores the information that allows the body to develop among the nearly 20,000 genes that make up the genome. All cells in the same body have the same DNA.
So how is it possible for them to act differently? On the contrary, how is a neuron a neuron and not a hepatocyte, if it has the same DNA? The answer lies in epigenetics.
What is epigenetics
Although it contains information, the chain of deoxyribonucleic acid is not all, because there is an important component which is the environment. Here is the epigenetic term, “about genetics” or “in addition to genetics”.
There are factors external to the genetic code that regulate expression of different genes, but still keeping the DNA sequence intact. It is a mechanism which has its relevance: if all the genes were active at the same time, it would not be good at all, it is therefore necessary to control the expression.
The term epigenetics was coined by Scottish geneticist Conrad Hal Waddington in 1942 to refer to the study of the relationship between genes and the environment.
A simple way to understand epigenesis was given to me by a good friend with this example: if we think DNA is a library, genes are books, and gene expression is the librarian. But the libraries themselves, the dust, the shelves, the fires … anything that prevents or helps the librarian to access the books would be epigenetics.
The reality is that the human genome is made up of more than 20,000 genesBut these are not always active at the same time. Depending on the type of cell, the stage of development of the organism or even the environment in which the individual lives, some genes will be active and others not. The presence of a group of proteins responsible for controlling gene expression without modifying the DNA sequence, i.e. without causing mutations or translocations, for example, allows this.
Know the epigenome
The concept of epigenome was born as a result of the emergence of epigenetics, and is nothing more than all the components that are part of this regulation of gene expression.
Unlike the genome, which remains stable and unchanging from birth to old age (or at least it should be), the epigenome is dynamic and variable. Throughout development it changes, it can be affected by the environment, And it is not the same depending on the type of cell. To put an environmental effect, we have seen that tobacco consumption has a negative impact on the epigenome, which promotes the appearance of cancer.
Before continuing, it is advisable to do a little overview of genetics to understand the purpose of DNA. The genetic code does not contain anything, but it is precisely for this reason that it would have no consequences. Usually a protein complex called RNA polymerase “reads” this gene and transcribes it to another type of nucleic acid strand called “messenger RNA” (mRNA), which consists only of the fragment of the read gene.
This obtained RNA must be translated into the final product, which is nothing but a protein, formed by another molecular complex called a ribosome, which synthesizes the protein from mRNA. Having clear how it works, I proceed.
DNA is a very large structure that, in the case of humans, is almost two meters long, much larger than the diameter of any cell.
Nature is wise and has found a method to drastically reduce the size and pack it inside the cell nucleus: through structural proteins called “histones”, Which are grouped together in groups of eight to form the nucleosome, support the DNA strand to wrap around it and facilitate folding.
The DNA strand does not compact itself completely, leaving more free parts for the cell to perform its functions. The truth is, folding makes it difficult for RNA polymerase to read genes, so it is not always folded the same in different cells. By not allowing access to RNA polymerase, that’s all exercise control over gene expression without changing the sequence.
It would be very simple if it were just that, but the epigenome it also uses chemical markers. The best known is DNA methylation, which involves the binding of a methyl group (-CH3) to deoxyribonucleic acid. This mark, depending on its location, can both stimulate reading of a gene and prevent its realization by RNA polymerase.
Is the epigenome hereditary?
The genome, which is invariable, is inherited of each of the parents of an individual. But does the same thing happen with the epigenome? This question has given rise to much controversy and doubt.
Remember that unlike the genetic code, the epigenome is dynamic. There are scientific groups who are convinced that it is also inherited, and the most common example they give is the case of a village in Sweden where the grandchildren of hungry grandparents live longer. for a long time, as a result of an “ epigenetics ”.
The main problem with these studies is that they do not describe the process, but are just conjectures without proof that resolves the doubt.
As for those who believe that the epigenome is not hereditary, they rely on a study which reveals a family of genes whose main function is restart the epigenome in the zygote. However, the same study clearly shows that the epigenome does not restart completely, but that 5% of genes escape this process, leaving a small door open.
The importance of epigenetics
The importance given to the study of epigenetics is that it may be the way forward investigate and understand life processes like aging, mental processes or stem cells.
The area in which more results are obtained is the understanding of the biology of cancer, the search for targets to generate new pharmacological therapies to fight this disease.
As mentioned above in the text, the epigenome of each cell changes depending on the stage of development the person is in.
There are studies that have proven it. For example, it has been observed that the genome varies in the human brain from birth to maturity, while in adulthood to old age, it remains stable. As we age there are changes again, but this time downwards rather than upwards.
For this study, they focused on DNA methylations, seeing that they were generated more during adolescence and descended into old age. In that case, lack of methylation hinders the work of RNA polymerase, Which leads to a decrease in the efficiency of neurons.
As an app for understanding aging, there is a study that uses DNA methylation patterns in bloodline cells as indicators of biological age. Sometimes chronological age does not coincide with biological age, and with the use of this model one could know the patient’s health status and mortality in a more concrete way.
Cancer and pathologies
Cancer is a cell that for some reason ceases to be specialized in its original tissue and begins to behave as if it were an undifferentiated cell, without limiting its proliferation or movement to other fabrics.
Logically, it is normal to think that changes in the epigenome they can make a cell cancerous by affecting gene expression.
In the DNA there genes called “cancer suppressors”; its own name indicates what its function is. Eh well, in some cases of cancer these genes have been seen to be methylated so that they inactivate the gene.
We are currently studying whether epigenetics affect other types of pathologies. There is some evidence to suggest that it is also involved in arteriosclerosis and certain types of mental illnesses.
The pharmaceutical industry is focusing on the epigenome which, thanks to its dynamism, is a feasible target for future therapies. They are already put into practice treatments for certain types of cancer, Primarily in leukemia and lymphoma, where the drug targets DNA methylation.
It should be noted that this is effective as long as the origin of the cancer is epigenetic and not another, such as by a mutation.
However, the biggest challenge is to get all the information about the human epigenome, much like sequencing the human genome. With wider knowledge, in the future more personalized treatments could be designed and individualized, to be able to know the needs of the cells of the damaged area in a specific patient.
Science needs more time
Epigenetics is a fairly recent field of research and further studies are needed to better understand the subject.
What should be clear is that epigenetics it consists of regulation of gene expression which do not alter the DNA sequence. It is not uncommon to find erroneous epigenetic mentions in case of mutations, for example.