Something to Think About When You're Thinking About Biomarkers
Mitochondrial DNA, or mtDNA, is increasingly assayed for early evidence of a disease which will eventually become manifest. Take a sample, amplify the DNA, examine it and look for change - makes sense, right? Your genes are the ones you're born with, right? And if they've changed that can't be good, right?
Well, it turns out that you, or your mitochondria at least, evolve or mutate within the course of your lifetime - and it's perfectly normal. We may have started out with Mom's mitochondria but it looks like by the time we're adults mitochondria in different parts of the body don't just express different genes, they have different genes. That's the conclusion of "Heteroplasmic Mitochondrial DNA Mutations in Normal and Tumour Cells" just published in Nature.
There's a great write-up of the findings at TheScientist.com and it makes two very important points for those of us dealing with litigation involving mtDNA biomarkers.
1) "we have to keep in mind [that] some of the changes we see may not really be [disease-related] mutations." - quote from author Nickolas Papadopoulos
2) "there's a big question mark about how early this increase in mtDNA variation appears in the blood. If it's only apparent once the cancer is well established then it isn't much use as a biomarker." - email from molecular biologist Ian Holt to The Scientist
