HDAC9 and acute lymphoblastic leukemia: Importantly, Hdac9, Hdac4, Hdac1 and Bcl2 exhibited significantly higher expression levels in MH mice when compared to wild-type (WT) counterparts,12 in agreement with the earlier finding that patients with MEF2D fusions exhibited much higher HDAC9 expression over other subtypes of BCP-ALL, whereas the transcriptional activity of MEF2D fusions towards HDAC9 was stronger than that of WT MEF2D. 1