MEF2D and acute lymphoblastic leukemia: The prenatal origins for other ALL subtypes either remain inconclusive, as is the case for TCF3-PBX1 [41,42], or have yet to be backtracked, such as BCR-ABL1-like (Ph-like) ALL [43,44] and other relatively recently described molecular subtypes including rearrangements of DUX4 [45,46], ZNF384 [47], and MEF2D [48].