Specification of Drosophila hematopoietic lineage by conserved transcription factors

Two major classes of cells observed within the Drosophila hematopoietic rep ertoire are plasmatocytes/macrophages and crystal cells. The transcription factor Lz (Lozenge), which resembles human AML1 (acute myeloid leukemia-1) protein, is necessary for the development of crystal cells during embryonic and larval hematopoiesis. Another transcription factor, Gcm (glial cells m issing), has previously been shown to be required for plasmatocyte developm ent. Misexpression of Gcm causes crystal cells to be transformed into plasm atocytes. The Drosophila GATA protein Srp (Serpent) is required for both Lz and Gcm expression and is necessary for the development of both classes of hemocytes, whereas Lz and Gcm are required in a lineage-specific manner. G iven the similarities of Srp and Lz to; mammalian GATA and AML1 proteins, o bservations in Drosophila are Likely to have broad implications for underst anding mammalian hematopoiesis and leukemias.