TEL-ABL–induced myeloproliferative disease is polyclonal and originates from multipotential progenitor cells.

(A) Multiple clones contribute to TEL-ABL–induced SBS and CML-like disease. Genomic DNA isolated from spleens of animals withTEL-ABL–induced SBS (lanes c-l), mixed SBS and CML-like disease (mix; lanes m and n), and CML-like disease (lanes o-v) was digested with BglII and analyzed by Southern blotting with a probe from the neomycin-resistance gene that yields a distinct band for each individual proviral integrant. For comparison, DNA results in spleens of 2 mice with p210 BCR-ABL–induced CML-like disease given transplants contemporaneously with the TEL-ABLmice are included (B/A; lanes a and b). Genomic DNA from a cell line containing a single provirus (con) is shown at the extreme left, and the positions of DNA size markers are indicated. The blot was stripped and reprobed with an ABL probe that detects a common 2.2-kb fragment from all proviruses (PV) as well as the endogenous murine c-abl gene, thereby permitting quantitation of the proviral copy number per diploid genome2 (bottom panels). (B) The cell initiatingTEL-ABL–induced CML-like disease is a multipotential progenitor. Hematopoietic cells from different lineages were isolated, and genomic DNA was isolated and analyzed by Southern blotting with a neomycin gene probe as described in the legend for panel A. The same spectrum of proviral clones was observed in spleen cells, PB leukocytes (principally maturing neutrophils), peritoneal macrophages, splenic erythroid cells (spl. T119⁺), splenic B-lymphoid cells (spl. B220⁺), thymocytes, and peripheral node lymphocytes (LN) from one mouse with TEL-ABL–induced CML-like disease (left panel), whereas spleen cells, PB leukocytes, erythroid progenitors, and B-lymphoid progenitors shared the same proviral clones in a second mouse (right panel), thus demonstrating that these clones repopulate multiple hematopoietic lineages in the recipients. The blots were stripped and reprobed with an ABL probe to determine the proviral copy number, as described in the legend for panel A, and this demonstrated the presence of provirus at similar levels in all populations. (C) Cells initiating TEL-ABL–induced myeloproliferative disease include progenitors that can generate day-12 spleen colonies in secondary recipients. Day-12 spleen colonies were isolated from secondary recipients of bone marrow from 2 different donor mice (top and bottom panels) with TEL-ABL–induced CML-like disease, genomic DNA isolated, and Southern blotting was done as described in the legend for panel A. Both primary mice contained multiple TEL-ABL–transduced clones that were capable of generating day-12 spleen colonies (lanes 1-18 of each blot). However, not every clone in the primary mice (represented by spleen DNA [left]) contained CFU-S₁₂. Lane 18 (top panel) is likely a mixture of 2 different colonies, whereas lane 17 (top) and lane 10 (bottom) likely represent CFU-S₁₂ containing 2 distinct proviruses.