Figure 5.

Chimeric embryos derived from Rex1 KO ES cells. When HP4-EGFP ES cells, which were homozygotes for the mutant Rex1 allele and marked by the constitutively-active Egfp transgene, were injected into blastocysts, the embryos developed to chimeras at 12.5 dpc in which widespread contributions of GFP-positive cells were observed in fluorescent microscopic observation.