An Abcb7^E433K mutation results in siderocytosis with increased zinc protoporphyrin. (A) Siderocytes (arrows) in the peripheral blood of an Abcb7^E433K chimera (Fe stain). Transmission electron micrographs of Abcb7^E433K chimera reticulocytes unstained (B) or with Fe stain (C). Original magnification ×44 000. (D) RBC zinc protoporphyrin-to-heme ratio as a function of Abcb7^E433K chimerism measured by Gpi1 isozyme. Normal is typically less than 100 ng/μg for mice.