EKLF-null fetal liver cells yield a greater expansion of megakaryocytes. (A) E13.5 fetal liver cells from wild-type (wt) or EKLF-null (^−/−) embryos were monitored for levels of CD41, CD42b, and CD42d as indicated before (d0) or after (d1-4) incubation in TPO. A representative FACS is shown (top) along with a graph of 3 additional experiments. Values are shown for double-positive cells. All gates were drawn based on negative controls for each sample (not shown). Fetal liver cell numbers are within 10% between wild-type and null embryos. Numbers on plots are numbers of cells in that rectangle. (B) E13.5 fetal liver cells were monitored for megakaryocyte colony formation in MegaCult slides. Colony formation was visualized by Alexa 288–labeled 1B5 antibody. Typical colonies are shown on top, which is a composite of 9 different areas (separated by horizontal and vertical lines) that covers approximately 56% of the slide; circles demarcate the typical difference in wild-type (wt) versus EKLF-null (^−/−) colony size. Below is a graph of data from 5 experiments. (C) E13.5 fetal liver cells from wild-type (wt) or EKLF-null (null) were lineage-depleted (lin⁻) or CMP-sorted and monitored for megakaryocyte colony formation. The graph is an average of 3 experiments. Error bars represent SD. P-values are from t-tests.