Heterochromatin regions become accessible in MM and are associated with increased activity of regulatory elements. (A) Bar chart displaying the overlap between open chromatin identified (by ATAC-seq) in MM, memB, PB, and PC samples and the 15 ChromHMM states defined in GM12878. Chromatin states are indicated by colors. The right panel indicates the absolute number of open chromatin regions that overlap with the GM12878 heterochromatin state. The dotted lines indicate the mean number of open chromatin regions within the GM12878 heterochromatin state in MM and normal controls. (B) Scatter plot of normalized H3K27Ac and ATAC-seq (open chromatin) signals in the indicated chromatin states (data from 1 representative MM). cor, correlation.