Fig. 3: Slc44a2 regulates mitochondrial number and function.

a Representative transmission electron microscopy images of platelets from Slc44a2(WT) and Slc44a2(KO) mice. Arrow indicates an individual mitochondrion. b Platelet mitochondria DNA copy number measured by qPCR. n = 4. *P < 0.05 in a two-tailed Student’s t test (c) Slc44a2 is present in lysate of mitochondria purified from platelets (left immunoblot) and Slc44a2 is enriched in the mitochondrial fraction of platelets but not in the cytosolic fraction of platelets (right immunoblot). d Slc44a2 does not regulate choline transport into whole cells, as measured by cellular uptake of radiolabeled choline competed with nonlabeled choline. (n = 3 biologically independent samples ±S.D. and *P < 0.05 for WT vs. KO). e Slc44a2 regulates transport of choline into isolated mitochondria, as measured by mitochondrial uptake of radiolabeled choline competed with nonlabeled choline. (n = 3 biologically independent samples ±S.D. and *P < 0.05 for WT vs. KO). f Metabolite profiles in platelets from Slc44a2(KO) mice relative to Slc44a2(WT) mice as measured by mass spectroscopy. (n = 2–3). g Mitochondrial oxygen consumption rate (OCR) of platelets from Slc44a2(KO) and Slc44a2(WT) mice: basal and uncoupled OCR are decreased in Slc44a2(KO) platelets (n = 4 biologically independent samples ±S.D.; *P < 0.05 WT vs. KO in a two-tailed Student’s t test). h Mitochondrial OCR during treatment with choline (n = 4 biologically independent samples ±S.D.; *P < 0.05 WT vs. KO in a two-tailed Student’s t test). For stress testing, Antimycin A = 1.0 µM, FCCP = 1.0 µM and Rotenone = 0.5 µM. Choline was added at 20 µM for all experiments. (For all panels, *P < 0.05 WT vs. KO in a two-tailed Student’s t test). Source data are provided as a Source Data file.