Fig. 4: TRAK2 mRNA trafficking directs cell-size-scaling of mitochondria distribution.

a, b Images of MitoTracker-labelled mitochondria in whole protrusions (a) or the distal-most 10 µm of protrusions (b) of Wt or ΔTRAK2 ECs cultured on CDM (brackets indicate distal-most 10 µm, 20 µm and 30 µm of protrusions; dashed line indicates cell outline). c Mitochondria levels at the indicated positions of Wt or ΔTRAK2 EC protrusions following culture on CDM (data is normalised to Wt, n = 29 cells Wt, n = 32 cells ΔTRAK2, unpaired Kruskal–Wallis test and Dunn multiple comparison test, **P = 0.0042, ns P ≥ 0.9999). d Quantification of protrusion morphometrics (area, aspect ratio, circularity, and protrusion length) of Wt or ΔTRAK2 ECs cultured on CDM (n = 29 cells Wt, n = 32 cells ΔTRAK2, two-tailed Mann–Whitney test, ns P ≥ 0.1109). e Plots comparing the number of TRAK2 mRNA spots (grey data points and dashed line) and mitochondria levels (magenta data points and dashed line) at the indicated distal-most positions of Wt or ΔTRAK2 EC protrusions (n = 31 cells Wt TRAK2, 28 cells ΔTRAK2 TRAK2, 29 cells Wt mitochondria, 32 cells ΔTRAK2 mitochondria, two-tailed Mann–Whitney test, **P = 0.0030 for % of total mitochondria in Wt, ns P = 0.4115 for % of total mitochondria in ΔTRAK2). f Mitochondria levels at the indicated positions of Wt or ΔTRAK2 EC protrusions following culture on glass (data is normalised to Wt, n = 17 cells Wt, n = 19 cells ΔTRAK2, two-tailed Mann–Whitney test, ns P ≥ 0.2711). g Plots comparing mitochondria levels in the distal-most 10 µm of protrusions in Wt or ΔTRAK2 ECs with protrusions of the indicated length (data is normalised to Wt, n = 48 cells Wt, n = 46 cells ΔTRAK2, two-tailed Mann–Whitney test, *P = 0.0494 for 50–70 µm, 0.0293 for >70 µm, **P = 0.0067, ns P = 0.3426 for 20–40 µm, 0.0919 for 30–50 µm, 0.0786 for 40–60 µm; two-sided analysis of covariance, magenta asterisk, **P = 0.0083 Wt versus ΔTRAK2). For analyses in (g) data for cells cultured on glass and CDM were pooled. h, i Mitochondria levels in protrusions of Wt or ΔTRAK2 ECs with protrusions either <60 µm in length (h) or >60 µm in length (i) and following culture on CDM (data is normalised to Wt, n = 15 cells Wt <60 µm, n = 13 cells ΔTRAK2 < 60 µm, n = 14 cells Wt >60 µm, n = 19 cells ΔTRAK2 > 60 µm, unpaired Kruskal–Wallis test and Dunn multiple comparison test, ***P = 0.0009, ns P = > 0.4018). Data are mean ± s.e.m. (c–i). a scale bars, 10 µm. b scale bar, 7.5 µm. Source data are provided as a Source Data file.