Extended Data Figure 9: Long-term drift towards monoclonality of labelled crypts.

Predicted frequency of monoclonal crypts over time expressed as a percentage of surviving clones after pulse labelling of stem cells at clonal density. Points show the predictions of the biophysical model defined in the main text and Supplementary Notes using the same parameters as those inferred from the short-term live-imaging assay (see Fig. 3 and Supplementary Notes) after the representative marking of stem cells at the crypt base, and the line shows the predictions of the strictly one-dimensional neutral drift dynamics model introduced previously⁸, with a stem-cell loss replacement rate of 0.24 per day and a total of 8 stem cells. The convergence of these two model predictions at longer times shows that, first, the behaviour of the quasi-one-dimensional model approaches that of the strictly one-dimensional model at longer times and, second, that the effective loss/replacement rate and stem-cell number in the new model is essentially fixed by the rate P_ccλ = 0.24 per day and the eight stem cells that occupy the central region. Significantly, these parameters translate to the ratio P_ccλ/N_stem² = 0.026 per week, very close to the figure of 0.025 per week obtained from a fit of the measured monoclonal crypt fraction to the one-dimensional neutral drift dynamics model in ref. 8. (For the labelling protocol and the experimental data points, we refer to the original reference.)