The significant reduction in the number of CFU-S progenitors in the fetal livers of jmj^trap/trapembryos. Representative photographs of CFU-S colonies from 5 × 10⁶ cells from 13.5 dpc fetal livers ofjmj^+/+ (A) and jmj^trap/trapembryos (B). Scale bar, 2 mm. (C) Number of CFU-S colonies per fetal liver. The open and closed columns indicate the average numbers of colonies from jmj^+/+ andjmj^+/trap embryos and fromjmj^trap/trap embryos, respectively. The number of experiments is shown above each column and the error bars indicate SEM.