In fact, elegant work from the Berman group has already developed transgenic fish that express human GM-CSF, stem cell factor, and stromal derived factor 1α and permit short-term engraftment of human hematopoietic stem cells and leukemia cells into larval fish, providing an important starting point for such studies (Rajan et al., 2020). The gene discussed is CSF2; the disease is leukemia.