Hereditary Hearing Loss Caused By Faulty Mitochondria

Hearing loss can be caused by multiple sources: injury, infection, or genetics.The American Journal of Pathology published research on hearing loss caused by malfunctioning mitochondria. To test the mitochondria's role in hearing loss, mice were modified to have a gene which codes for mitochondrial TFB1M. TFB1M has already been researched and found to be connected to hearing loss. When comparing the modified mice with the control mice (mice with TFB1M and mice without TFB1M), researchers noticed a difference in the spiral ganglion nerves and the stria vascularis of the mice. Damage to either of these parts of the ear could cause severe damage to hearing. The researchers theorized that the damage to these regions of the ear were caused by reactive oxygen species produced by the enzyme AMPK. To determine if AMPK was the true causes of the damage, more modified mice with TFB1M with observed, but half of these mice had their AMPK minimized. The mice with less AMPK, experienced less damage to their spiral ganglion nerves and their stria vascularis. The determination that AMPK causes hearing loss could possibly help prevent hearing loss in the future.

Determining the cause of hereditary hearing loss was an important first step to developing a cure for this disease. Not only were the researchers able to confirm the mitochondrial gene which causes hearing loss, but they also determined the protein which is responsible for the hearing loss. Another important discovery made in this experiment was that the AMPK levels in the non-affected mice did not contribute to hearing loss. Since these two factors were determined, there could be two possible ways which cures could be produced. The first way is that the gene for this trait could be altered. The second and more realistic way is to create a medicine to minimize AMPK levels in affected people.  

Activating a Single Gene Could Extend Life Span

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The UCLA conducted an experiment on 100,000 fruit flies. The scientists activated the gene AMPK and extended the life span of the flies by 1/3. The fruit flies with the activated gene lived for about eight weeks, while their normal life span is about six weeks. The gene activates a process called autophagy which allows cells to get rid of "junk DNA" that accumulates as we age and causes damage to the cells. In humans the AMPK gene is inactive and if activated the average life span for a human could come to be as high as 101 years as opposed to the current average of 78. The gene can be activated in different parts of the body and may serve as a treatment for diseases such as Alzheimer's, cancer, diabetes, and stroke. There are still many years to go before this process will be ready for human treatments but the prospects are promising.

I found this article to be particularly interesting because of our labs in the beginning of this semester with our own fruit flies. As we know fruit flies are an ideal test subject because their genome is completely sequenced, it's easy to go through many generations in a short period of time, and there are no ethics issues with using fruit flies in the lab. It's also interesting that we share certain genes with fruit flies and that tests done on them can make progress in the medical field. I'm looking forward to seeing the progress this and other studies like them make in the coming years.