L-744,832 inhibits CFU-GM colony growth from fetal liver cells. Fetal hematopoietic cells from Nf1+/+ (),Nf1+/− (), or Nf1−/− (▩) embryos were cultured in methylcellulose medium supplemented with 1 unit/mL of recombinant murine GM-CSF with either 0, 1, 10, or 25 μmol/L of L-744,832. CFU-GM colonies were counted after 7 days in culture.