Hematopoietic stem cells (HSCs) must be capable of both self-renewal and production of progenitor cells that give rise to all of the blood cell types, the two basic principles of stem cell biology. Investigations into gene networks controlling HSC response to stress have been conducted using model organisms such as Drosophila melanogaster. One of the factors controlling vertebrate HSC multipotency and differentiation is the GATA:FOG complex. GATA:FOG complexes regulate the development of a number of blood lineages. In Drosophila, the GATA:FOG complex blocks the differentiation of hematopoietic progenitors into the stress-responsive lamellocyte lineage. Drosophila hematopoietic progenitors are strikingly similar to HSCs and are used as a model for these vertebrate stem cells. We used fly genetics to identify GATA:FOG network members that block the stress-response of hematopoietic progenitors.