We are all mosaics: genetic diversity found between cells in a single person

Summary

Human chromosomes (artificially coloured) vary widely from cell to cell, according to an investigation of the DNA in more than 100 cells from a single person. Credit: Cavallini James/BSIP/Science Photo LibraryIn a technological tour de force, researchers have sequenced the whole genomes of more than 100 individual cells from one 74-year-old man. The results exposed chaos within: an extra chromosome arm here, a missing chunk of chromosome there, and smaller snippets of DNA altered, deleted or duplicated. In several of the cells, the Y chromosome had been lost entirely.“There were some cells in there that were very messed up,” says Joe Luquette, who studies bioinformatics at Harvard Medical School in Boston, Massachusetts, and is an author of the study.Cancer drugs are closing in on some of the deadliest mutationsThe findings, which were posted earlier this month on the preprint server bioRxiv1 and have not yet been peer reviewed, paint a comprehensive portrait of the genetic variation present within a person. That portrait is just the beginning: the study is a pilot project for a US$140-million consortium that aims to catalogue mutations in cells from 19 sites in the body, using cells from 150 donors2.The resulting catalogue will provide a valuable tool for researchers studying the influence of genetic variation between the cells of a single individual — a phenomenon known as mosaicism — on health and on diseases such as cancer, says Soichi Sano, who studies mosaicism in the cardiovascular system at Japan’s National Cerebral and Cardiovascular Center in Suita. “I’m sure that this field will be accelerated very rapidly,” he says.A lifetime of mutationsPeople accumulate changes to their DNA over the course of their life, whether from errors that occur during DNA replication and repair, or from exposure to DNA-damaging environmental factors, such as ultraviolet light or tobacco smoke.As DNA-sequencing technologies have improved, researchers have gained a clearer picture...