Fig2b. Copyright: This image is from [doi:10.1002/ar.a.10089] Ehlermann J; Pfisterer P; Schorle H, "Dynamic expression of Kruppel-like factor 4 (Klf4), a target of transcription factor AP-2alpha during murine mid-embryogenesis." Anat Rec A Discov Mol Cell Evol Biol 2003 273(2):677-80. Reprinted with permission of Wiley-Liss Inc. [PMID:12845703]