Repression of exosome-complex component expression during erythroid maturation. (A) Schematic diagram and crystal structure of the human exosome complex.²⁶  Solid line, direct interactions; dashed line, indirect interactions; red, associated components with catalytic activity. (B) Expression profile of mRNA levels for exosome complex components in primary mouse bone marrow erythroblasts during distinct maturation stages mined from the Erythron DB.²⁹  P, proerythroblast; B, basophilic erythroblast; O, orthochromatic erythroblast; R, reticulocyte. (C) Expression profile of mRNAs encoding exosome-complex components during primary human erythroid differentiation mined from the Human Erythroblast Maturation (HEM) Database.³⁰  C, colony-forming unit-erythroid (CFU-E); P, proerythroblast; I, intermediate-stage erythroblast; L, late-stage erythroblast. (D) Expression profile of mRNAs encoding exosome-complex components during ex vivo differentiation of primary mouse fetal liver–derived erythroid precursor cells. 1, R1 population: progenitor cells; 2, R2 population: proerythroblasts and early basophilic erythroblasts; 3, R3 population: early and late basophilic erythroblasts. 4, R4/5 population: polychromatophilic, orthochromatic erythroblasts, and reticulocytes.