Conditionally immortalized GMPs generated from WT and TAFAZZIN-KO fetal liver hematopoietic progenitors. (A) Schematic outlining the generation of conditionally immortalized WT and TAFAZZIN-KO GMPs via the retroviral expression of the ER-Hoxb8 fusion protein, resulting in unlimited ex vivo expansion of progenitors in the presence of estrogen. (B) Immunoblotting confirms the absence of TAFAZZIN expression in the TAFAZZIN-KO GMPs using 2 different antibodies; β-actin and COX-IV are included as housekeeping controls. (C) Wright-Giemsa staining of WT and TAFAZZIN-KO mature neutrophils. (D) Cell-surface staining of CD11b (Mac1) and GR1 (Ly6G/C) was assayed by flow cytometry in the GMPs (day 0) and as the cells differentiated out of estrogen to mature neutrophils (days 3 and 5). There was no apparent difference between WT and TAFAZZIN-KO clones. (E) Transmission electron microscopy of WT and TAFAZZIN-KO GMPs demonstrated more distinct mitochondrial cristae in the WT cells (black arrows, top), with spiral cristae structures more prevalent in the KO (white arrow, bottom). In many cases, the mitochondria within the TAFAZZIN-KO cells were encircled by RER (black arrows, bottom). Scale bar: 500 nm.