Supplementary Figure 1: Staining of OCT4-positive cells in human fetal testis and comparison between mixed ChIP-Seq and Standard ChIP-Seq.

(a) Cross-section of human fetal testis (22 weeks) with immunostaining of OCT4. Scale bar represents 50 µm. (b) Immunostaining of OCT4 and cKIT in human fetal testis. Arrows indicate co-staining cells. Scale bar represents 50 µm. (c) Immunostaining of OCT4 and DDX4 proteins in human fetal testis. Arrows indicate cells that only express OCT4. Scale bar represents 50 µm. Immunostaining experiments in (a-c) were independently repeated a minimum of three times with similar results. (d) Schematic strategy for comparing mixed ChIP with conventional ChIP. (e) ChIP-qPCR for detection of peaks at OCT4 locus. ChIP-qPCR were independently repeated a minimum of three times with similar results. (f) Scatterplot comparing OCT4 ChIP-seq data generated in pure ESCs and 1% ESCs mixed with fibroblast cells. Correlation was computed using whole genome data within 10kb of transcription start site (TSS) of RefSeq genes. Sample size n=2 and Pearson’s correlation coefficient was used for the correlation analysis. (g) Venn diagram showing overlapping genes bound by OCT4 generated by ChIP-seq data in pure ESCs and 1% ESCs mixed with fibroblast cells. (h) Venn diagram showing overlapping genes bound by OCT4 generated by ChIP-seq data derived from two biological replicates.