FIG. 2.
Maintenance of ES cell identity in the absence of Dppa4. (A) TNAP staining of fixed ES cell colonies carrying the indicated Dppa4 alleles. (B) Immunoblot showing expression of marker proteins (Sox2, Oct4, and Nanog) characteristic for pluripotent cells. (C) Result of sensitive fluorescence-based competition assay (23) directly comparing self-renewal ability of Dppa4-deficient ES cells with Dppa4-proficient controls. Red fluorescent, Dppa4-deficient ES cells of clone 243.12 and 248.28 were mixed at indicated ratios with appropriate Dppa4Flox/+ ancestor ES cells (nonfluorescent) and cultured under nondifferentiating conditions. At each passage the percentage of tdRFP-positive (red bars) and tdRFP-negative (gray bars) cells was measured by flow cytometry. WT, wild type; KO, knockout; α, anti.