POU4F3 and Merkel cell skin cancer: Indeed, DNase hypersensitivity in 4 VP-MCC and 3 VN-MCC cell lines showed that VP-MCC cells had shared sites of open chromatin, which were absent in VN-MCC cells (Figure 4, A and B), that were enriched in CR TF motifs including ATOH1, ISL1, LHX3, POU4F3, and SOX2 (Figure 4C).