View Full Version : Geneticists:Mitochondrial disease/ POLG deletion question

05-23-2012, 09:15 AM
Here's a research question 6 hours of Googling hasn't answered:

Is there such a thing as a benign POLG deletion in a human person? I don't even know if I asked that right. What I know about genetics is... like, there's a spiral involved or something, and people have genes and so do bananas or something. This is waaaaaaay outside any of my near-competence zones.

Thank you! (Feel free to answer here or PM me or whatever. ;))

05-23-2012, 11:23 AM
"Benign POLG deletion" as this exact term obviously does not exist, but...

Benign means mild or harmless.

POLG means polymerase gamma, which is an enzyme (a molecule that can cause a break down of other molecules to two or more pieces), in this case it can delete pieces of "mitochondrial DNA." Mitochondrial DNA is a spiral molecule within mitochondria, which are parts of the body cells that can convert nutrients to energy. The mitochondrial DNA determines how mitochondria work.

There are certain genetic diseases in which polymerase gamma (POLG) is changed and causes abnormal deletions of the mitochondrial DNA, what results in "mitochondrial diseases," such as Alpers syndrome and others.

So, if I rewrite ""Benign POLG deletion:"
There are several genetic errors of POLG in humans that cause abnormal deletions of the mitochondrial DNA. Such errors may cause severe diseases, but mild, that is benign, variations of these diseases exist.

05-23-2012, 04:46 PM
Thank you!

So (again, this is *not* an area of strength for me) *basically* POLG deletions (specifically, as compared to other mutations) *always* cause disease, though the severity may vary?

Thanks so much.

05-23-2012, 05:14 PM
The term "benign," when used in general, may be sometimes confusing, because it may mean no obvious disease or a mild form of a disease. When used to describe POLG deletions, "benign" often, but not always, means "something," for example:

Progressive external ophthalmoplegia [an example of a mitochondrial disease with POLG deletions] clinically follows a benign route [..with weakness of limbs...].

Individuals with POLG deletions and no symptoms (and therefore no disease) are "asymptomatic." When they have only one of two (one from mother, one from father) genes impaired, they are called "asymptomatic carriers." A piece of text from the article Mitochondrial Encephalopaties (http://www.ninds.nih.gov/news_and_events/proceedings/20090629_mitochondrial.htm) (with POLG deletions):

...prevalence of the mutation in asymptomatic carriers may exceed 2 per 1000..

It is also important to distinguish between changes in mitochondrial DNA that cause disease and benign genetic variations.

So, POLG deletions in humans do not always cause a disease.

05-24-2012, 08:12 PM

That probably answers my question, but I'm too dopey to know if it does or not. ;)

05-24-2012, 11:11 PM
HoneyBadger, your question was: Do benign POLG deletions in humans exist and may they result either in no disease or mild disease?

One example of a benign mitochondrial disease with POLG deletions is "benign infantile myopathy." The symptoms of these disease include weakness and respiratory problems. So, it's benign, but this includes some symptoms. The other form of this disease is "fatal infantile myopathy."

But as you see, the word "benign" in my answer is used to describe a disease (disease means that something actually goes wrong for the affected person, which usually means some symptoms).

"POLG deletions" by themselves are only mechanisms of mitochondrial diseases, so something on the molecular level that may or may not result in a disease. It is not usual to use the word "benign" to describe mechanisms, so the term "benign POLG deletions" sounds awkward. It is a disease (which results from POLG deletions) that can be either benign or more serious.

In conclusion, POLG deletions in humans may result in: 1. no consequences for a person at all 2. benign, that is mild form of a disease 3. severe or even fatal form of a disease.

If I still haven't answered you, it would help me to know the context of your question.

05-25-2012, 03:51 AM
*NOW* I get it!

Thanks so much. See, I know so little about genetics that I can't even ask the question properly. ;)