Here we set out to understand the h

Here we set out to understand the heterogeneity of fetal hemoglobin (HbF) activation by developing techniques to purify and profile differentiation stage-matched late erythroblast F-cells and non-F cells (A-cells) from the human HUDEP2 erythroid cell line and primary CD34 cell erythroid cultures. Transcriptional and proteomic profiling of these cells demonstrated very few differences between F- and A-cells at the RNA level either under baseline conditions of following treatment with HbF inducers hydroxyurea or pomalidomide. Surprisingly, we did not find RNA or protein level differences in any known HbF regulator such as BCL11A or LRF that would account for HbF activation. Our analysis shows that F-erythroblasts are not significantly different from non HbF-expressing cells and that the primary differences likely occur at the transcriptional level at the b-globin locus.