Figure 4.

Expression of various differentiation marker genes was examined by reverse transcription–PCR of EB cultures (A) and ES-OP9 cocultures (B). Number of days in culture is given at the top. Amplified hypoxanthine phosphoribosyltransferase (HPRT) is shown as a positive control. (A) No differences in gene expression between genotypes were observed in EB cultures. (B) Embryonic (βH1) and adult (β^major) globin, and Epo receptor (EpoR) transcripts were diminished in flk-1 (−/−)-derived cells compared with flk-1 +/−-derived cells in the OP9 system. c-kit was down-regulated by day 5, whereas scl was not expressed in flk-1 (−/−) cultures. vegf was constitutively expressed in these cultures, whereas flk-1 and flk-1/lacZ expression was induced upon ES differentiation.