Fig. 3

Selective growth advantage of cells carrying methylated FMR1 alleles with large CGG repeats. a–c The repeat size, methylation status, and FMR1 mRNA levels of the indicated cultures were monitored as described in the “Methods” section. The “+” and “−” signs indicate the presence or absence of predigestion by the methylation-sensitive restriction enzyme, HpaII. M, 100-bp DNA size ladder and rpts, CGG repeats. a, b Data for 37D and 37A lineages that were maintained in culture for extended periods of time. The DNA methylation status is indicated by the grey line and symbols in the right hand panel, and the mRNA level is indicated by the black line and symbols. c Growth of methylated 37A and unmethylated 37D cells. Late passage 37A cells that were completely methylated and late passage 37D cells that were unmethylated were either grown separately (i) or in a ~1:1 mixture (ii) for ~20 passages. S refers to the cells at the start of the experiment and E to the cells at the end of the experiment. Data for the mixed cultures are shown from two independent experiments (Rep 1 and Rep 2). Panel (iii) shows the DNA methylation for each set of cultures at the start and end of the experiment as an average from two experiments and the error bars indicate standard deviation