Extended Data Figure 4. Culture and passaging method employed for samples bearing P53 mutations.

a, P53 mutations were observed in hPSCs grown in a broad array of culture media including home-made medium supplemented with knockout serum replacement (KOSR), and defined, commercial media such as E8. b, Similar numbers of P53 mutations were observed from cells grown with feeder cells or under feeder-free conditions. c, Since passaging hPSCs can introduce stresses or clonal bottlenecks, we examined whether P53 mutations were consistently seen when a particular passaging method was used, but we observed a wide variety of passaging methods associated with these mutations. Note that the interpretation of these data are complicated by the fact that the culture methods employed in the final published study may not reflect the previous culture history of that cell line, which may have previously passed through multiple laboratories, as well as by the lack of detail about culture methods present in some published studies. d, The addition of supplements such as rock inhibitor at passages does not appear to be sufficient to prevent P53 mutations in hPSCs.