Thursday, July 10, 2014

Mutations in Mitochondrial DNA

A new study suggests that DNA mutations in some of the mitochondria of healthy people may be a lot more common than scientists thought.

The term heteroplasmy describes a situation in which some mitochondria of a cell have mutant mitochondrial DNA (mtDNA) and other mitochondria have normal mtDNA.  Cell function can become disordered, perhaps producing disease, when the balance of mutant vs. normal mtDNA crosses a certain threshold.

The recent study shows that about 90% of healthy people studied in the 1000 Genomes Project had at least one heteroplasmy.  Some of these (about 20%) have been shown to correlate to disease.  That's a lot more than we were thinking prior to the study (25%-65% heteroplasmy rate).

We don't  know the significance of this finding yet, but it could influence how likely it is for mitochondrial diseases to develop over time—or to be inherited.  Could the mutant/normal mtDNA balance get skewed as oocytes form, thus giving different offspring different probabilities of inheriting mitochondrial disorders?  Or change the probabilities from one generation to the next?  Mitochondrial dysfunction is thought to be a mechanism of agingcould the rate of heteroplasmy be part of the aging mechanism?

What can we use from this in teaching undergraduate A&P?  The fact that we now know that mtDNA mutations are common in healthy people will be interesting and useful to students.

Want to know more?

Mutations Pervade Mitochondrial DNA

  • Jyoti Madhusoodanan. The Scientist ( July 7, 2014
  • This is a plain-English article summarizing the new findings; includes quotes from the researchers.

Extensive pathogenicity of mitochondrial heteroplasmy in healthy human individuals

  • K. Ye et al., Proceedings of the National Academy of Science (PNAS), doi:10.1073/pnas.1403521111, 2014. 
  • This is the original research report.

Want a FREE labeled image of mtDNA that you can use in your presentation, handout, or other course material?

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