DNase I HS analysis in erythroid cells. (A) Schematic of the mouse and human β-globin loci, to scale. Positions of PCR amplimers used in the DNaseI assay are indicated as gray bars beneath each locus. The region of homology between mouse and human to which HS-E1 maps is marked by the line between the 2 loci (see also supplemental Figure 1). HS analysis was performed for the murine β-globin locus using primary erythroid cells harvested from (B) E12.5 peripheral blood and (C) E15.5 fetal liver. HS analysis was also performed for the human β-globin locus using the K562 cell line (D). Analysis was performed using qPCR and the loss in fluorescent signal indicated a decrease in amplification product. This value was interpreted as an increase in hypersensitivity, and the inverse of this value was represented heregraphically.