Figure 2. Pou4f2^Cre recombination patterns. A: Diagram of the Ai9 Cre reporter construct. This fluorescent reporter is driven by the CAG promoter and is designed to transcribe red fluorescent protein (RFP) after Cre-mediated recombination removes the transcription termination cassette. B: The cartoon diagram showing varying Cre-mediated recombination patterns, which were dependent upon the parent carrying Pou4f2^Cre and the reporter. Bi: Ubiquitous production of RFP in offspring when Pou4f2^Cre and Ai9 are carried by the sire. Bii–iv: Pou4f2^Cre specific recombination was observed in offspring when the sire carries Pou4f2^Cre and the dam carries Ai9 (ii), Pou4f2^Cre and Ai9 are carried by the dam (iii), or Ai9 is carried by the sire and the dam carries Pou4f2^Cre (iv). C–E: Images of cryosections and tissue biopsies (ear) that are counterstained with 4,6-diamidino-2-phenylindole (DAPI). C: No RFP was detected in mice that carried Ai9 only. D: Offspring with germline recombination. RFP was detected throughout all tissues. E: Offspring with Pou4f2^Cre-specific recombination. RFP was detected in the retina, brain, intestine, heart, and gonads. Scale bars = 100 μm (retina-kidney, scale bar in the retina image; ear punch, scale bar in the image).