Potential roles for RUNX1 and its orthologs in determining hematopoietic cell fate

Runx1 (also known as AML1, Cbfa2 and Pebpa2b) and Cbfb encode a DNA-binding alpha subunit and the non-DNA-binding beta subunit of a mammalian core-bin ding factor (CBF). The discovery of RUNX1 and CBFB as genes real-ranged in human leukemias prompted predictions that both genes would play important r oles in normal hematopoiesis. These predictions were borne out, as indeed R unx1 and its Xenopus and Drosophila homologs, Xaml and lozenge (lz), appear to determine hematopoietic cell fate during development. We will review wh at is known about Runx1 function in hematopoiesis in three model organisms, mouse, frog and fly, focusing on the earliest events of hematopoietic cell emergence in the embryo.