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Fig. 8 Posterior Hox proteins function as transcriptional activators leading to the Cdx-mediated inhibition of hindbrain formation. Expression of krox20 in wild-type control embryos (A) and embryos that received an injection of 25 pg of hoxa9a RNA (B), 25 pg of hoxb9a RNA (C), cdx1a/4MOs and hoxa9a RNA (D), cdx1a/4MOs and hoxb9a RNA (E), cdx1a/4MOs and 25 pg of En-hoxa9a RNA (F), cdx1a/4MOs and 25 pg of En-hoxb9a RNA (G), cdx1a/4MOs and 25 pg of VP-hoxa9a RNA (H) or cdx1a/4MOs and 25 pg of VP-hoxb9a RNA (I). Overexpression of hoxa9a, hoxb9a, VP-hoxa9a or VP-hoxb9a suppresses the expression of krox20 in its normal and ectopic positions. Overexpression of En-hoxa9a or En-hoxb9a did not suppress the ectopic krox20 expression (marked by arrowheads). Scale bar: 100 μm.