The myocardin-related transcription factors Mrtfa and Mrtfb, also known as megakaryoblastic leukemia 1 and 2 (Mkl1 and Mkl2), respectively, are conserved regulators of cellular actin dynamics linking actin polymerization and transcriptional control. The gene discussed is MRTFB; the disease is adult acute megakaryoblastic leukemia.