POU4F1 and melanoma: We found no correlation between SNV load and the expression of the BRN2-related factors BRN3a (POU4f1) (Supplemental Fig. S7A), BRN3b (POU4f2) which was poorly expressed in most melanomas (Supplemental Fig. S7B), MITF (Supplemental Fig. S7C), or a gene set comprising well-characterized MITF-target genes as a surrogate marker for MITF activity (Supplemental Fig. S7D).