Wednesday, March 17, 2010

mitochondrial dna varies within an individual

The Scientist | Mitochondrial genomes are not uniform across cells of the body as previously believed, but vary between different tissue types, according to a study published online today (March 3) in Nature.

The findings may affect forensics and the search for biomarkers, both of which utilize mitochondrial DNA.

"I was surprised," said molecular cell biologist Hans Spelbrink of the University of Tampere, Finland, who was not involved in the research. "Mostly the assumption is that from the start of life individuals are homoplasmic," meaning that within an individual, mitochondrial DNA (mtDNA) is the same. However, the results of this study demonstrate "that each individual is a mosaic of multiple [mt]DNA types in various frequencies in different tissues," he said.

Previous studies have documented some degree of heteroplasmy -- variation in mtDNA in an individual -- but these findings were limited and mostly restricted to people with mitochondrial disorders, "where one would expect" to find such variation, Spelbrink said. "This is the first time [mitochondrial variation] was properly documented" in normal individuals.