Verification of microarray results. (A) A subset of the genes, including 5 early differentiation markers overexpressed in all the huES cell lines by microarray, were confirmed by RT-PCR. (B) RT-PCR analysis of PSIP1 and GDF3 genes. β-actin served as internal control and reverse transcriptase (RT) as a no-enzyme negative control. (C-D) Protein expression of 2 undifferentiated markers of huES cells was confirmed by immunocytochemistry. Undifferentiated human ES cells (GE01) were cultured, fixed, and processed for immunocytochemistry using specific antibodies to CD24 and GTCM-1 (original magnification, × 20).