Grab is required for heme synthesis during erythropoiesis. (A) qRT-PCR validating knockdown of Grab in mouse primary fetal liver erythroblasts by 2 shRNAs. **P < .01. (B) Quantification of the hemoglobin content in control and Grab-silencing mouse primary fetal liver erythroblasts. *P < .05; **P < .01. (C-D) Immunoblotting analyses validating the knockout of Grab in MEL cells (C) and K562 cells (D). (E-F) o-Dianisidine staining of hemoglobin in wild-type and Grab knockout MEL cells (E) and K562 cells (F) post–erythroid-like induction. Scale bars, 10 μm. (G-H) Quantification of heme levels in MEL cells (G) and K562 cells (H) by fluorescence porphyrin assays. **P < .01. (I-J) Analysis of heme content in control zebrafish embryos, rab3il1 morphants, and rab3il1 morphants coinjected with rab3il1 mRNA. The zebrafish embryos were analyzed at 48 hours postfertilization. (I) and (J) are the representative images of o-dianisidine staining and quantification of total heme, respectively. The number of embryos with reduced o-dianisidine staining over the total number analyzed is shown in each image. *P < .05; **P < .01.