NOTCH1 and acute lymphoblastic leukemia: Given the dynamic expression of miR-181 miRNAs during normal lymphocyte development and during T-ALL progression [14]–[18] and that Notch1 oncogenes utilize genetic programs in early thymic progenitor cells for T-ALL development [13], we used loss-of-function analyses to identify the mir-181 allele with critical roles in the development of normal thymic progenitor cells and in development of NOTCH-induced T-ALL.