Marrow cells from Mll-AF4 mice expressed additional lymphoid (CD19, PAX5, TdT, D_H-J_H but not sIgM) and myeloid markers (c-fms and lysozyme) when cultured under pro-B culture conditions. (A) FACS analysis of B220/CD19 and B220/sIgM. (B) PAX5, TdT, c-fms, and lysozyme expression detected by RT-PCR. Lane 1, H₂O control; lane 2, mouse spleen cells as control; lanes 3-4, bone marrow cells from 2 Mll-AF4 mice cultured for 21 days. (C) Immunoglobulin D_H-J_H heavy-chain rearrangement detected by PCR. Lane 1, molecular weight marker; lane 2, mouse spleen DNA as control; lane 3, mouse kidney DNA as control; and lanes 4-5, DNA of bone marrow cells from 2 Mll-AF4 mice cultured for 21 days.