Epigenetics: Nursing pathophysiology

Epigenetics is the study of how an individual's environment and behavior can modify DNA without altering the DNA sequence.

These modifications regulate genes by turning genes on increasing gene expression or off decreasing gene expression. Epigenetic modifications can occur through three mechanisms.

Histone modifications, DNA, methylation and RNA based mechanisms. As a quick review, the nucleus of each of the body's cells contains DNA, the genetic material that holds the instructions or code for synthesizing specific proteins.

These proteins direct the function of cells which give rise to an individual's phenotype or their observable characteristics and traits.

The complete set of DNA instructions found in each cell is called the genome. Ok.

So to make a protein, certain genes within the genome need to be activated or expressed, whether a gene is expressed or not is regulated through epigenetic modifications that shape the function of the genome.

Consequently, epigenetics can help explain a lot of things like how cells in the body, such as skin cells and brain cells can differ from one another.

Even though they all contain the same DNA, it can also help explain why identical twins with the same DNA often have subtle differences in their appearance, personality and even diseases that might develop.

Now, epigenetic modifications arise from fetal development and continue throughout an individual's lifetime. These modifications can be the result of early experiences in life such as growing up in a nurturing environment, experiencing abuse or deprivation and even through dietary choices, use of certain medications or exposure to industrial pollutants, whatever the cause, these modifications can impact physical and mental health outcomes through their influence on DNA activity.

For example, since epigenetic mechanisms can switch on or off genes involved in cell growth, like tumor suppressor genes, they can promote uncontrolled cell growth.

Like with cancer, certain cancers can also occur when genes that code for a protein that repairs DNA aren't expressed. In contrast, the epigenetic effects of dietary folate during pregnancy can promote proper fetal development and prevent neural tube defects.

Finally, keep in mind that epigenetic mechanisms are flexible and potentially reversible. Since they can react to changes in the environment.

Also, certain epigenetic modifications can be heritable or passed down from a parent to an offspring because some modifications can be copied during the process of cell division.

Ok. Now, let's take a closer look at the type of epigenetic mechanisms starting with histone modification to begin.

Recall that DNA is a very long molecule that's tightly coiled around special proteins called histones. As the DNA wraps around the histones, they form nucleosomes that are then packed together to form structures called chromatin.

Now, during histone modification, an acetyl group is either added to the histones. A process called acetylation or deleted from the histones.

A process called deacetylation. This process can change the interaction between histones and DNA during protein synthesis, which is when part of the DNA unwraps from the histone exposing a specific DNA sequence during a process called transcription.

Histone modification affects whether chromin is in an open or closed state during transcription, which determines if a DNA sequence is available or unavailable for protein synthesis.

For example, with acetylation, chromatins are open. So there's less attraction between the DNA and the histone and the DNA becomes less tightly bound around the histone.

As a result, certain genes are more exposed and therefore more easily transcribed and expressed. On the other hand, deacetylation has the opposite effect as this causes the DNA to wrap tighter around the histone.

So the genes are less easily transcribed and expressed. Next DNA methylation occurs when a methyl group attaches to a cytosine, which is one of the four bases found in DNA.

And this typically occurs in regions where cytosine is followed by another base called guanine referred to as a CPG site.

Methylation can silence gene expression by insulating the DNA from access. So it can't be transcribed and expressed.

Lastly, RNA based mechanisms are modifications involving noncoding RNA A or NC RNA. For short, normally RNA is involved in a process that ultimately results in protein synthesis.

However, non coding RNAs are not translated into a protein. For example, one type of noncoding RNA is Microrna or M IRN.

For short micro RNA binds to and marks messenger RN or MRNA type of RNA that carries genetic information from DNA. As a result, the M RN is destroyed or recycled.

This process effectively silences gene expression. All right.

As a quick recap, epigenetics is the study of how an individual's environment and behavior can modify DNA without altering the DNA sequence.

These modifications change the way a gene is expressed by turning a gene on, increasing its expression or off, decreasing its expression.

Epigenetic modifications can occur through three mechanisms. Histone modifications, DNA, methylation or RNA based mechanisms.