Supporting the common transcription factory/contact first hypothesis are also observations of MLL-AF4 mRNA fusion transcripts in the absence of the corresponding gene fusion in both tumor and normal hematopoietic cells from infant ALL patients (Uckun et al., 1998) and in peripheral blood mononuclear cells from healthy individuals (Kowarz et al., 2011). This evidence concerns the gene KMT2A and acute lymphoblastic leukemia.