Cholesterol and isoprenoids regulate erythropoiesis. (A-D) Embryos were treated at sphere stage with ATOR, Ro 48 8071 (Ro-48) to inhibit cholesterol, lonafarnib to inhibit isoprenoids, or vehicle control (DMSO). At 4 dpf, embryos (n = 33 DMSO, n = 45 ATOR, n = 41 Ro-48, and n = 44 lonafarnib) were stained with o-dianisidine to observe mature RBCs. (A′-D′) Full body images of stained larvae at 4 dpf. Images were taken with a 10× optical lens at 8× (A-D) and 6.3× (A′-D′) objective zoom. ^#P = .0001. P value indicates the number of affected embryos affected is statistically significant according to Fisher’s exact test. (E) The concentration of hemoglobin was measured in embryos treated with ATOR, Ro-48 to inhibit cholesterol, lonafarnib to inhibit isoprenoids, or vehicle control (DMSO) at 4 dpf. The number indicates total larvae analyzed across 3 biological replicates. *P = .000381218, **P = 2.20098e-05, ***P = 1.42e-05.