Teratoma formation and in vivo developmental potential of FVB background protein-iPS cell. (A) FVB-sFB-protein-iPS cells were injected into NOD/SID mice. Four weeks later, well-demarcated tumors were observed. (B) H&E staining showed well-differentiated teratomas. (C) Chimera mice produced by protein-iPS cells. FVB-sFB-protein-iPS cells contributed to the viable chimera after being injected into the C57 host blastocysts. Mice with mixed coat colors are chimeras. As a control, C57-ES cells (extract-protein donors) were injected into ICR blastocysts. (D) A fetus derived from GFP-transduced FVB background protein-iPS by tetraploid blastocyst complementation. The arrow indicates a beating heart. (E) Genomic DNA PCR showed the origin of fetus is FVB background protein-iPS cells. (F) The accurate sizes of amplified products were confirmed using fluorescent primers.