Slot blots of amplified cDNA from various positions in the hematopoietic precursor hierarchy.

On the left are shown 2 alternative layouts (A and B) for the blots shown in subsequent figures. Layouts indicate the lineage potential of each stage, and the number (in parentheses) of independent amplified cDNA samples pooled before application to the blot. E, erythroid; Mg or Meg, megakaryocyte; Mc or Mac, monocyte/macrophage; Mst, mast cell; N, neutrophil; BFU-E, precursors of large erythroid-only 6- to 8-day colonies; CFU-E, precursors of small erythroid 2 day colonies; p, unipotent precursors of 7-day colonies. The left column of each blot contains pentapotent (E/Mg/Mc/N/Mst), tetrapotent, tripotent, bipotent, and unipotent precursor cell cDNAs. Middle and right columns contain unipotent precursor cell cDNAs (pMac) and samples from terminally maturing cells (E, N, Mast, etc). The sample indicated by “?” was of uncertain origin but probably mature macrophage. On the top right is an autoradiogram of a type A layout blot hybridized with a radiolabeled probe for L32. Below is a hierarchy tree representative of the various stages arrayed on the blots. The topmost level represents pentapotent precursors, the next levels tetrapotent, tripotent, bipotent, and unipotent precursors, while the bottom row represents terminally maturing cells in the indicated lineages. The ghosted circle represents a committed mast cell precursor stage, assumed to exist but not actually sampled. Radiographic densities from the autoradiogram were excised, squared, and superimposed on the corresponding positions in the hierarchy.