Fig. 6. Provision of iron-dextran to cia erythroid precursors bypasses the requirement for tfr1a function. (A) (top) Injection of iron-dextran at the 1-cell stage causes (middle) direct delivery of a cytoplasmic iron to all cells in the embryo, resulting (bottom) in the rescue of hypochromia in 40 hpf cia^iu089 embryos. (B) (top) Intravenous injection of iron-dextran into 48 hpf cia^iu089 places (middle) excess iron into embryonic circulation, but this iron cannot be obtained by cia red cells due to a block at the level of iron acquisition across the cell membrane, resulting (bottom) in the failure of this iron provision to remedy cia hypochromia.