A decrease in the number of megakaryocytes undergoing apoptosis is detected in BclxL transgenic mice.

BM cultures of transgenic line 19 (Tg19) or control (WT) mice were enriched for megakaryocytes by indirect immunomagnetic negative separation. Following this procedure, there are still numerous, contaminating BM cells. (A) Apoptotic cells were detected by dark staining with the ApopTag Plus Peroxidase in situ Apoptosis Detection kit. Arrows point to some of the nonapoptotic megakaryocytes (original magnification, × 200). The experiment shown is representative of 3 performed. Terminal dioxyl transferase (TdT) enzyme control was always included in the study, because contaminant magnetic beads often give a positive signal. (B) Isolated megakaryocytes were cytospun and stained with Cy3-labeled rabbit antibodies to human BclxL (which also reacts with mouse BclxL; original magnification, × 400). In the center of the WT panel are proplatelet-forming cells with poor BclxL expression. The arrows point to cellular extensions (as also demonstrated in detail in Figure 7), which do not appear in megakaryocytes with high abundance of BclxL (eg, Tg19; indicated by arrowheads).