RNA unplugged

I love this molecule. It is so clever. Where DNA writes the code for our genes, it is RNA which does all the hard work. RNA molecules perform many functions and exist in pre-cursor form as well as spliced, alternatively spliced or even shortened or degraded molecules. All of these are important controls in gene expression and each gene will have it's own RNA processing. But in it's basic form, RNA is transcribed from DNA, a process in which introns of the gene sequence are removed from the final molecule leaving only the functional or coding sequences.

Of course, it's often more complex than that, and there are some very elegant experiments to demonstrate this. So let's concentrate on a more simple experiment that I have worked on extensively. Using a method devised by Chomzynski in 1987, molecular biologists can extract RNA from living cells. As these cells are living and performing all their normal functions, it is possible therefore to get a 'snapshot' of gene activity at the moment the nuclear material is extracted. In this method, total RNA is extracted. This includes tRNA, rRNA and mRNA. I'll continue with mRNA ,or messenger RNA, and come back to the others in another blog.


mRNA is a short-lived molecule. This means that when genes are activated and transcribed, mRNA is then available to be translated into a functional protein. Proteins are made up of blocks of amino acids which confer activity and functionality to the molecule, such as enzymes, hormones and cytokines. But first, it is possible to measure gene expression (activity) in cells and tissues by a method known as real time PCR. For a description of how PCR works see this iconic work by Kary Mullis. *A lot of good work was done in the late 80's, Peter!*


In a clever twist, we can reverse transcribe the mRNA extracted from cells into cDNA, which is simply DNA without introns. Then we use real time PCR to quantitate the amount of gene expression in the sample, relative to a known amount of gene expression. This is a very sensitive method of gene expression, using very small amounts of material, so we can measure large numbers of genes in multiple cells and tissues.
We are interested in gene expression because we know that variations in the genetic code can lead to changes in gene expression, which in turn affects protein production, and this may manifest itself in the body, as shown in diverse conditions from cancer to heart disease and cystic fibrosis in between. All clear?


Well, not entirely. This is true for many genes, but we have been working on a gene for which no protein has been identified, but which is strongly associated with increased risk of cardiovascular disease. This gene is known as a non-coding RNA gene, but how does it influence cardiovascular disease risk? The fact is, we still don't quite know, although we do know a lot about the gene. It seems that the RNA from this gene influences the expression of other genes, particularly cell cycle genes, thereby affecting cell proliferation. If this happens within the arteries around your heart, it could lead to abnormal thickening or inflammation of the artery wall, resulting in a heart attack.


So when you are thinking about complex multifactorial conditions, remember that RNA plays it's part, too.

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Nature or nurture?

This is a well-travelled argument, but what does it mean in genetic terms? Who cares, I hear you ask? I do, and so should you.

We now know that many modern illnesses are multi-factorial complex diseases. That means that there is more than one cause of the condition, and often more than one treatment. Cancer and cardiovascular disease are good examples of this. For example, you might hear someone say 'they never smoked, always exercised, the heart attack came out of the blue'. We are told to eat five fresh fruit and veg a day, we are encouraged to know our numbers - blood pressure and cholesterol, we are implored to exercise for at least thirty minutes three times a week. But all of this will mean nothing if your genetics are against you. 


Cardiologists talk of risk stratification. This is a complicated formula which takes into account weight (body mass index), waist to hip ratio, blood pressure, cholesterol levels and family history, amongst other measurements. A family history of heart disease is a strong indicator of a genetic link, but often the science of genetics has not yet identified the culprit gene variant, or variants, or discovered the mechanism of the fault in causing disease.


So, in terms of genetics, the nature versus nurture argument is all about a person's individual DNA pattern interacting with one's environment, the individual lifestyle choices we all make. And both genetics and lifestyle contribute to the overall risk of disease; we just don't know yet what to do about this. But, this is a rapidly growing area of research which it is hoped will yield valuable insights into the risk of cardiovascular disease and cancer.


Fingers crossed.

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