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DNA sequencing is slowly making the long anticipated move from the research lab into clinical use. After a few isolated reports last year where it was used to diagnose individual patients, now we see one of the first reports of it being used successfully on a larger scale, in 42 infants suspected of mitochondrial disease.
Mitochondria carry their own DNA but also rely on nuclear DNA for part of their functioning, and mutations in either of the two can cause malfunctioning of the mitochondria. Mitochondrial diseases may lead to a wide variety of symptoms and can be hard to diagnose, despite recent advances in genetic and biochemical tests.
All the infants in the study had clinical and biochemical evidence of mitochondrial oxidative phosphorylation disease. The researchers performed "MitoExome" sequencing of the mitochondrial DNA (mtDNA) and exons of approximately 1,000 nuclear genes encoding mitochondrial proteins. Firm diagnoses were enabled in 10 patients (24 percent) who had mutations in genes previously linked to disease. Thirteen more patients (31 percent) had mutations in nuclear genes not previously linked to disease. These patients can expect a full diagnosis once studies confirm the function of these genes.
A few years ago, or maybe even one year ago, the cost of sequencing one individual's DNA was too prohibitive to even think of using clinically. Now that the cost of sequencing one genome has come down to around $1,000 and will probably come down even lower, genome sequencing will soon be cheaper than ordering more than two or three individual genetic tests. Although the current study only completely sequenced the mitochondrial DNA, it is a great example of how the technology can aid in diagnosis and even point to the existence of previously unknown mutations as origins of disease. We eagerly await the day that full-genome sequencing is just another test that is performed within the time of your doctor visit who directly receives and interprets the results.
This post also appears on medGadget, an Atlantic partner site.