Hypermethylation of the rDNA promoter and decreased rRNA expression in MDS CD34⁺ cells. (A-B) The average percentage of DNA methylation across the 23 CpGs of the rDNA promoter was higher (P < .0001; A) and the pre-rRNA expression level was lower (P < .01; B) in the 13 MDS samples compared with the 8 control samples. The ends of the whiskers represent minimum and maximum values and the bar indicates the median value (50th percentile). Significance was determined using the Mann-Whitney test.