Fig. 2. Klf5 is required to maintain ESCs in an undifferentiated state. (A) Klf5 KD causes a decrease in the number of APcs. CRL- or Klf5-shRNA transfected ESCs were plated at 80 cells/cm2 and grown for 6 days. The number of APcs was 2040±55 per 100-mm plate (n=5) for CRL shRNA (upper panel) and 158±14 per 100-mm plate (n=5) for Klf5 shRNA (lower panel). Scale bar: 1 mm. (B) ESCs shown in A were stained with anti-Oct3/4 or -Nanog antibodies. In Klf5-KD cells, the expression of these two proteins is drastically decreased. Scale bars: 100 µm. (C) Klf5 KD is accompanied by a significant (P<0.01) decrease of Oct3/4, Sox2 and Nanog mRNAs. β-actin mRNA was used as a control. Standard errors of three independent experiments are reported. (D) Silencing of Oct3/4 downregulates Klf5 expression. (E) RT-PCR analysis of mRNAs shows that Klf5 KD causes illegitimate expression of brachyury and Meox (mesoderm), and of Cdx2, PL-1 and Eomes (trophoblast).