Effect of expression of mutant Fpn on erythroid cell development. Blood samples from embryos treated as in Figure 1 were stained with Wright-Giemsa (A), diaminobenzidine (B), or Prussian blue (C). The arrow shows iron accumulation in erythrocytes from embryos expressing wild-type Fpn-GFP, but not in embryos expressing Fpn-GFP H32R.