Northern blot analysis of mRNA of growth factor receptors. Total liver RNA (10 μg) from wild-type (lane 1), c/ebpα+/− (lane 2), or c/ebpα−/− (lane 3) newborn mice, 10 μg of total brain RNA from wild-type mice (lane 4), or 2 μg of total peritoneal cell RNA from thioglycollate-stimulated wild-type mice (lane 5) were electrophoresed in 1% agarose/formaldehyde gels, transferred to nylon membranes, and probed with murine cDNAs of G-CSF receptor (G-CSFr; ref. 43), erythropoietin receptor (EPOr; ref. 44), GM-CSF receptor α (GM-CSFr; ref. 45), or M-CSF receptor (M-CSFr; ref. 46). The position of each signal is indicated on the left side. GM-CSF receptor α mRNA is expressed at relatively low levels in newborn livers, but densitometry demonstrated that the level of GM-CSF receptor α mRNA is not significantly reduced in −/− liver compared with the +/+ or +/− animals.