Figure 2.
Figure 2. Bak and Bax are dispensable for platelet production. (a) Proplatelet formation by large, mature fetal liver–derived MGKs in culture. Data represent mean ± SEM. MGKs were pooled from two animals per genotype. n = 2 technical replicates. Representative of three independent experiments. (b) Representative images of wild-type and Bak−/− Bax−/− MGKs on day 6 and 8 of culture. On day 8, wild-type cultures contained mostly cell debris; in contrast, Bak−/− Bax−/− wells contained elaborate proplatelet formations. Bars, 50 µm. (c) Platelet counts in response to anti-platelet serum (APS)–induced thrombocytopenia in mice lacking Bak and Bax. Data represent mean ± SEM. n = 8–11 mice at 120 h (except Bak+/+Bax−/−, n = 3); n = 5–6 at 144 h; and n = 3–6 at 192 h per genotype, per time point. (d, left) Morphologically recognizable MGKs before and after APS in H&E-stained sections of BM from mice lacking Bak and Bax. Mean number per field of view (200×) from 10 fields per individual mouse. Data represent overall mean ± SD. n = 4–14 untreated mice per group; n = 5–6 at 96 h; n = 12–15 at 120 h; and n = 3 at 144 h. (middle and right) Naked MGK nuclei in H&E-stained sections of BM from mice lacking Bak and Bax, at steady state, and in response to APS-induced thrombocytopenia (taken 96, 120, and 144 h after injection). (d, middle) Data represent mean number per field of view (200×) from 6 fields per individual mouse ± SEM. n = 4–15 untreated mice per group; n = 5–6 at 96 h; n = 12–17 mice per group at 120 h; and n = 3 at 144 h. (d, right) Fold change in naked nuclei. Number of nuclei post-APS divided by mean number in corresponding untreated group (0 h). (e) Representative images of H&E-stained sections of BM from wild-type and Bak−/− BaxPf4Δ/Pf4Δ mice, 120 h after injection of APS. Arrows indicate naked nuclei. Bars, 20 µm. (f) Platelet counts in response to APS-induced thrombocytopenia. Lethally irradiated mice were reconstituted with FLCs lacking Bak and Bax and injected with APS 8 wk after transplantation. A group of recipients was splenectomized 3–4 wk before reconstitution. Data represent mean ± SEM. n = 7–10 mice per group at 120 h; n = 3–5 mice per group at 96 and 144 h. *, P < 0.05; **, P < 0.005; ***, P < 0.0001.

Bak and Bax are dispensable for platelet production. (a) Proplatelet formation by large, mature fetal liver–derived MGKs in culture. Data represent mean ± SEM. MGKs were pooled from two animals per genotype. n = 2 technical replicates. Representative of three independent experiments. (b) Representative images of wild-type and Bak−/− Bax−/− MGKs on day 6 and 8 of culture. On day 8, wild-type cultures contained mostly cell debris; in contrast, Bak−/− Bax−/− wells contained elaborate proplatelet formations. Bars, 50 µm. (c) Platelet counts in response to anti-platelet serum (APS)–induced thrombocytopenia in mice lacking Bak and Bax. Data represent mean ± SEM. n = 8–11 mice at 120 h (except Bak+/+Bax−/−, n = 3); n = 5–6 at 144 h; and n = 3–6 at 192 h per genotype, per time point. (d, left) Morphologically recognizable MGKs before and after APS in H&E-stained sections of BM from mice lacking Bak and Bax. Mean number per field of view (200×) from 10 fields per individual mouse. Data represent overall mean ± SD. n = 4–14 untreated mice per group; n = 5–6 at 96 h; n = 12–15 at 120 h; and n = 3 at 144 h. (middle and right) Naked MGK nuclei in H&E-stained sections of BM from mice lacking Bak and Bax, at steady state, and in response to APS-induced thrombocytopenia (taken 96, 120, and 144 h after injection). (d, middle) Data represent mean number per field of view (200×) from 6 fields per individual mouse ± SEM. n = 4–15 untreated mice per group; n = 5–6 at 96 h; n = 12–17 mice per group at 120 h; and n = 3 at 144 h. (d, right) Fold change in naked nuclei. Number of nuclei post-APS divided by mean number in corresponding untreated group (0 h). (e) Representative images of H&E-stained sections of BM from wild-type and Bak−/− BaxPf4Δ/Pf4Δ mice, 120 h after injection of APS. Arrows indicate naked nuclei. Bars, 20 µm. (f) Platelet counts in response to APS-induced thrombocytopenia. Lethally irradiated mice were reconstituted with FLCs lacking Bak and Bax and injected with APS 8 wk after transplantation. A group of recipients was splenectomized 3–4 wk before reconstitution. Data represent mean ± SEM. n = 7–10 mice per group at 120 h; n = 3–5 mice per group at 96 and 144 h. *, P < 0.05; **, P < 0.005; ***, P < 0.0001.

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