rRNA expression is correlated with the extent of rDNA promoter methylation. (A) As MDS samples had a higher average percentage of DNA methylation and lower rRNA expression, these variables were inversely correlated in all data (P < .01). (B) Pearson correlation estimates between pre-rRNA expression and rDNA promoter methylation at 23 CpGs in 8 control samples and 13 MDS samples are shown. Vertical lines represent 95% confidence intervals.