The fusion gene of MLL-PTD and MLL plays a critical role in the pathogenesis of these AML.     ///    "25 patients with de novo AML-M4 or M5 with normal karyotypes excluding M4eo and MLL fusion gene or MLL-PTD were selected, the amplification and direct sequencing analysis of full length MLL gene exons were carried out, then the mutations found were verified at genomic DNA level. "