As an example, deletion of a CTCF binding site insulating the promoter of TAL1 gene from regulatory elements adjacent to the CMPK1 promoter was shown by CRISPR/Cas9 experiments to cause activation of TAL1, an oncogenic driver of T cell acute lymphoblastic leukemia [11] (Fig. 3c). The gene discussed is CMPK1; the disease is T-cell acute lymphoblastic leukemia.