CTCF boundary regulates HOXA locus chromatin structure and gene expression. (A) Enrichment of downregulated genes involved in the HOXA9 regulatory pathway in CBS7/9^+/− MOLM13 cells compared with WT control, as shown by GSEA. (B) Overlap between downregulated genes, as determined by comparing RNA-seq data obtained from CBS7/9^+/− cells and the HOXA9-KD gene expression data set (accession number GSE13714). (C) A model depicts that the CBS7/9 chromatin boundary defines an aberrant posterior HOXA chromatin domain and coordinates oncogenic transcription programs for leukemic transformation and invasion.