Increased density of erythroid cells in erythropoietic organs of Th3 and T-E(M) mice contributes to enhanced ERFE production. Mice generated from Th3 × E(M) breeding were analyzed at 16 weeks. Males are depicted as closed circles and females as open circles. Erythroid precursor cell density was estimated in (A-C) BM and (D-F) spleen (extramedullary) by measuring (A,D) Gypa mRNA and (B,E) Tfrc mRNA. (C,F) Correlation between Gypa mRNA and Erfe mRNA in (C) BM and (D) spleen of E(M) and T-E(M) mice. (C,F) P values and R² were determined using Pearson correlation analysis.