Fig. 2: Glucose deprivation of the optic nerve induces autophagy and loss of myelin integrity.
From: Oligodendroglial fatty acid metabolism as a central nervous system energy reserve
a, Electron microscopic images of optic nerve cross-sections (wild-type mice aged 2 months), taken after 24 h of incubation in medium with 10 mM glucose (top: N = n = 3) or 0.5 mM glucose (bottom: N = n = 3). b, Scatter plot of calculated g-ratios (outer fiber diameter/axon diameter) as a function of axon caliber, revealing myelin loss when optic nerves are exposed to low glucose (red dots, bottom) compared with 10 mM glucose-containing medium (black dots, top). c, Bar graph with calculated mean g-ratios (same data as in b) (N = n = 3 for both 0 mM and 10 mM; error bars: mean ± s.e.m.; unpaired, two-tailed Student’s t-test). d, Schematic depiction of the pCNP-mTagRFP-mWasabi-LC3 transgene used for oligodendrocyte-specific expression of the LC3 fusion protein. The two fluorophores (red and green) give LC3 a yellow color and reveal diffuse cellular distribution. Note that mTagRFP-mWasabi-LC3 becomes an autophagosome-specific marker, when LC3 is translocated to the membrane of newly formed autophagophore/autophagosomes (green puncta). e, Live imaging of optic nerves (ex vivo) from a mTagRFP-mWasabi-LC3 transgenic mouse, incubated in aCSF with 10 mM (left) or 0 mM (middle) glucose. Note the ubiquitous expression of the LC3 fusion protein. Specific labeling of autophagosomes (green puncta, arrows on image inset) occurs only in the absence of glucose with an all-or-none difference. Right, the accumulation of autophagosomes also in oligodendrocytes in the presence of 10 mM glucose (Glc) after applying the specific inhibitor, Lys05 (10 µM). f, Quantification of the data in e, normalized to the number of cell bodies (adult mice, aged 2–5 months; N = n = 4 for 10 mM Glc, N = n = 5 for 10 mM Glc + Lys05 and N = n = 3 for 0 mM Glc; error bars: mean ± s.e.m.; one-way ANOVA, Tukey’s test).
