CTCF and posterior cortical atrophy: To determine if PCa risk-associated CTCF anchor regions that we identified to be involved in looping do in fact control the expression of specific genes, we used the CRISPR/Cas9 system to delete PCa risk-associated CTCF anchor regions and then assessed the effects of these deletions on the transcriptome (Fig. 5; see also Additional file 5: Table S4 for sequences of guide RNAs used for all deletion studies).