Through protein complexes formation with H3K4 methyltransferases, such as SET1A/B and MLL1–4, WDR5 plays an essential role in H3K4me3 and transcriptional activation of target genes involved in pluripotency, development, and cancer, such as MLL-rearranged leukaemia [39]. The gene discussed is KMT2A; the disease is cancer.