Mice receiving transplants with TEL2-BM develop a chronic myelomonocytic-like disease. (A) Peripheral blood smear stained with May-Grünwald-Giemsa (MGG) of a diseased mouse that underwent TEL2-BM transplantation. Arrows indicate blastlike cells. (B) Cytospin preparation after MGG staining of bone marrow of a diseased mouse that underwent TEL2-BM transplantation, showing an excess of myeloid cells in early stages of differentiation. Arrows indicate blast cells. (C) Spleen—of a diseased mouse that underwent TEL2-BM transplantation—with an extensive red pulp infiltrate of myeloid cells with a high mitotic index (H&E, magnification × 40). Mitotic figures are indicated by white arrowheads. (D) The myeloid cells expressed GFP (brown stain), confirming their transplant derivation (anti-GFP, magnification × 40). (E) The myeloid population was primarily composed of immature cells that expressed MPO (brown stain), consistent with their granulocytic lineage (anti-MPO with cytoplasm localization, magnification × 40). (F) Top row shows a Western blot analysis of TEL2 expression in spleen samples of 1 MSCV-BM (MSCV, 10 months after transplantation) and 6 diseased TEL2-BM mice at the moment of death. The second row shows Bcl-xl and Bcl-xs expression in the same samples. Bcl-xl and Bcl-xs expression in leukemic spleen samples is not altered compared with that in the control spleen sample. The third row shows that 4 of 6 leukemic TEL2 spleens show increased Bcl2 expression (samples 1, 3, 4, and 5). The bottom row shows protein loading of the blot after staining with Coomassie blue.