Figure 3.

TVA-expressing megakaryocyte-lineage cells can be serially infected with avian retroviruses. Bone marrow cells from TVA-expressing mice were cultured in the presence of IL-3, SCF, and TPO, infected with RCAS-PURO, and then subjected to puromycin selection. HPAP staining 48 hr after the puromycin-resistant cells were infected with RCAS-AP demonstrates that essentially all cells express HPAP (A), whereas no HPAP expression is seen in the mock-infected puromycin-resistant cells (B). FACS analysis of the puromycin-resistant cells using anti-CD41 (green) or an isotype control (red), and gating on live cells by use of propidium iodide staining, demonstrates that essentially the entire cell population expresses CD41. Wright-Giemsa (D) and immunohistochemical stains for vWF (E), P-selectin (F), and TVA (G) show the CD41-expressing, puromycin-resistant cells to be quite homogeneous.