In circumvallate taste buds, intragemmal cells express BMP4-ß-gal within 24 hours of cell birth. Co-expression of BMP4-ß-gal (Xgal; blue) and BrdU (dark brown) was detected beginning at 24 hours after BrdU injection (A), and was still observed at 48 hours (B), and 72 hours (C). White asterisks indicate double-labeled intragemmal cells. An arrow in B points to a BrdU immunopositive perigemmal cell that does not express BMP4-ß-gal. D. The mean number of intragemmal cells labeled for both BrdU and BMP4-ß-gal is plotted with respect to time post-BrdU injection. The incidence of double labeled cells per bud profile peaks at 48 hrs. Taste buds were tallied throughout the circumvallate papilla, and only taste buds with a clear taste pore were included. (Mean +/- standard error, n = 3 mice for each time point, At least 200 taste buds were counted for each time point). Scale bars: 10 μm.