The gene fusion product involving RBM15 and megakaryocytic leukemia 1 (MKL1), termed the RBM15-MKL1 fusion protein (also referred to as OTT-MAL), was initially identified in a pediatric patient with acute megakaryoblastic leukemia harboring the t(1;22)(p13;q13) translocation (82). This evidence concerns the gene RBM15 and acute megakaryoblastic leukemia.