Expression of mutant Fpn in zebrafish affects hemoglobinization of erythrocytes. Zebrafish embryos were injected with wild-type or mutant Fpn-GFP. At 48 hpf, the embryos were homogenized (A), and Fpn-GFP levels were assayed by Western blot analysis or (B) stained with o-dianisidine to detect hemoglobinized cells (brown color denoted by the arrow). The figures are representative of 6 different experiments in which 100 embryos were injected with each construct. The survival rate (n = 600) was 69.6% for embryos injected with wild-type constructs, 50.8% for embryos injected with H32R constructs, 64.7% for embryos injected with N144H constructs, and 48.2% for embryos injected with N174I constructs. (C) Embryos were injected with wild-type or H32R constructs with or without coinjection of iron-dextran. The survival rate was 70% for wild-type embryos injected with or without iron-dextran, 50% for wild-type embryos injected with H32R without iron-dextran, and 62% for wild-type embryos injected with iron-dextran.