Somatic cell evolution: how to improve with age.

A recent article published in this journal illuminates a rare example of somatic evolution where cells improve rather than deteriorate with age. In mitotic intestinal crypts, stem cells with higher levels of a deleterious heteroplasmic germline mitochondrial mutation are purged through time, leading to crypts without the mutation. Similar somatic mitochondrial mutations are not purged from crypts, indicating that special conditions are needed to improve with age. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.