Mosaic Mutations May Not Be Rare

Most novel mutations in an individual are thought to originate in the germline. Other mutations, somatic mosaic mutations—which are only present in a subset of a person’s cells—can either be passed down from a parent or originate during early development. Such mosaic mutations were thought to be fairly rare, but according to a study published today (June 5) in The American Journal of Human Genetics, they may contribute to as much as 6.5 percent of an individual’s genomic variation. If confirmed, the results could affect how researchers estimate a person’s risk of passing disease-linked alleles on to their children.

The findings “highlight that mosaicism may be more common than we had appreciated so far,” geneticist Anne Goriely of the University of Oxford wrote in an e-mail to The Scientist. “The main value of the present study is an attempt to quantify this process,” added Goriely, who was not involved in the work.

Mosaicism can result when a de novo mutation arises after an embryo is formed. Using newer, more sensitive sequencing technologies, researchers have recently...