Regulation of megakaryopoiesis by Ikaros. We propose that Ikaros controls megakaryocytic development through 3 different mechanisms: Ikaros inhibits the NOTCH-induced megakaryocytic specification from hematopoietic progenitors, interferes with GATA-1 expression and function to inhibit differentiation and terminal maturation, and directly represses expression of several megakaryocytic genes.