Forced expression of MLL-FKHRL1 immortalizes murine myeloid progenitors.

(A) Schematic diagram of MLL-FKHRL1 and the retroviral constructs used in transduction/transplantation assays (left). Conserved motifs in MLL-FKHRL1 include the DNA methyltransferase homology region (MTase), AT hook DBD (AT hook), forkhead DBD (FK), conserved region 2 (CR2), which contains 3 α helices shown as thin vertical bars, and conserved region 3 (CR3). Bar graph (right) shows numbers of colonies obtained after each round of plating in methylcellulose (average of 3 independent assays). (B) Typical morphology of colonies generated at third plating of bone marrow cells transduced with retroviruses expressing the indicated constructs (original magnification, × 100). (C) Phenotypic analysis of cells immortalized by MLL-FKHRL1. Gray histograms represent FACS staining obtained with antibodies specific for the indicated cell surface antigens. Black lines represent staining obtained with isotype control antibodies.