Genome-wide prediction of TAL1 OSs as enhancers. (A) Epigenetic marks overlapping a TAL1 peak within Gypc. Tracks displayed on the UCSC Genome Browser  show, in descending order, the DNA segment tested for enhancer activity, occupancy by TAL1 and GATA1, the gene model, DNase hypersensitive sites in G1E cells, G1E-ER4 cells treated with estradiol, and mouse primary fetal liver-derived early erythroid progenitors (EPC CD117+, CD71+, TER119-) and differentiating erythroblasts (EPC CD117-, CD71+, TER119+). (B) Overview of ChIP-seq data for epigenetic features at TAL1 peaks. (C, D) Erythroid enhancer activity of TAL1 OSs in a transient transfection assay. (C) Biological replicates (two different days of transfection, Rep1 and Rep2) and technical replicates (eight for each biological replicate) of the enhancer assays of a negative control vector and an expression vector containing TAL1 OS from the Gypc intron. (D) Enhancer assay results for 70 TAL1 OSs, ordered by activity. The distribution of results for each TAL1 OS is shown as a box plot, with the internal line indicating the median value. Boxes for inactive TAL1 OSs are shaded blue, those in the threshold zone are pink, and those with activity are shaded red. (E, F, G) Tissue-specific enhancer activities of TAL1 OSs in transgenic mouse assays. (E) Partitions of 66 TAL1 OSs by enhancer activity. (F) Four examples of whole mouse embryos with in vivo enhancer activity at E11.5. (G) Distribution of tissues showing enhancement by the TAL1 OSs. For TAL1 OSs active in multiple tissues, each tissue was counted for the distribution. (H) Comparison of the results of the two enhancer assays on nine TAL1 OSs. Stained mouse images are from the VISTA Enhancer Browser.