Fixation and Spread of Somatic Mutations in Adult Human Colonic Epithelium

Publication date: Available online 17 May 2018
Source:Cell Stem Cell
Author(s): Anna M. Nicholson, Cora Olpe, Alice Hoyle, Ann-Sofie Thorsen, Teja Rus, Mathilde Colombé, Roxanne Brunton-Sim, Richard Kemp, Kate Marks, Phil Quirke, Shalini Malhotra, Rogier ten Hoopen, Ashraf Ibrahim, Cecilia Lindskog, Meagan B. Myers, Barbara Parsons, Simon Tavaré, Mark Wilkinson, Edward Morrissey, Douglas J. Winton
We investigated the means and timing by which mutations become fixed in the human colonic epithelium by visualizing somatic clones and mathematical inference. Fixation requires two sequential steps. First, one of approximately seven active stem cells residing within each colonic crypt has to be mutated. Second, the mutated stem cell has to replace neighbors to populate the entire crypt in a process that takes several years. Subsequent clonal expansion due to crypt fission is infrequent for neutral mutations (around 0.7% of all crypts undergo fission in a single year). Pro-oncogenic mutations subvert both stem cell replacement to accelerate fixation and clonal expansion by crypt fission to achieve high mutant allele frequencies with age. The benchmarking of these behaviors allows the advantage associated with different gene-specific mutations to be compared irrespective of the cellular mechanisms by which they are conferred.

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Teaser

Winton and colleagues describe stem cell dynamics in normal human colon to identify the efficiency of clone fixation within the epithelium and the rate of subsequent lateral expansion. Against these benchmarks biased stem cell behaviors advantaged in both fixation and expansion can be quantified to predict the age-related burden of pro-oncogenic mutation.


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