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. 2019 May 7;8:e44702. doi: 10.7554/eLife.44702

Figure 4. De novo fatty acid synthesis by oligodendrocytes is required to maintain structural stability of myelinated axons.

(a) Exemplary EM images of aberrant myelin-axon profiles showing vacuolation (examples indicated by arrowheads) in the ventral white matter of spinal cords of P14 cMUs. Where identifiable, axons associated with aberrant structures are indicated by asterisks. Scale bars: I = 5 µm, II = 2 µm, III = 2 µm, IV = 2 µm, V = 5 µm, VI = 2 µm, VII = 2 µm. (b) Corresponding graph with quantification of the percentage of aberrant myelin-axon profiles. Data points represent n = 3 mice for each, CT and cMU (unpaired two-tailed two sample Student’s t-test; at P14: cMU vs. CT p<0.0001, t = 21.16), ***p<0.001. At least 8300 axons per mouse analyzed in random fields selected in the same anatomical area. (c) Total FA composition of myelin purified from spinal cords of P60 CT and cMU mice, divided in non-essential FAs (NEss), conditional-essential FAs (Cond Ess) and essential FAs (Ess). Data points represent n = 3 mice for CT and n = 4 mice for cMU (unpaired two-tailed two sample Student’s t-test; NEss: cMU vs. CT, p=0.2609, t = 1.267; Cond Ess: cMU vs. CT, p=0.6625, t = 0.4635; Ess: cMU vs. CT, p=0.4435, t = 0.8317). (d) Quantification of the most abundant FAs found in myelin purified from spinal cords of CT and cMU mice. Data points represent n = 3 mice for CT and n = 4 mice for cMU (unpaired two-tailed two sample Student’s t-test; Oleic: cMU vs. CT, p=0.2525, t = 1.293; Palmitic: cMU vs. CT, p=0.7377, t = 0.3542; Stearic: cMU vs. CT, p=0.4966, t = 0.7328). (e, f, g) Content of ceramides (e), cerebrosides (f) and sphingomyelin (g) in myelin isolated from spinal cords of cMU compared to CT mice. Data points represent n = 4 mice for each, CT and cMU (unpaired two-tailed two sample Student’s t-test; ceramides: cMU vs. CT, p=0.2822, t = 1.181; cerebrosides: cMU vs. CT, p=0.2722, t = 1.209; sphingomyelin: cMU vs. CT, p=0.2310, t = 1.333). (h, i, j, k) Total content of phosphatidylinositols (PI), phosphatidylserines (PS), phosphatidylcholines (PC) and phosphatidylethanolamines (PE) in myelin isolated from spinal cords of CT and cMU mice. Data points represent n = 4 mice for each, CT and cMU (unpaired two-tailed two sample Student’s t-test; PI: cMU vs. CT, p=0.1765, t = 1.532; PS: cMU vs. CT, p=0.0031, t = 4.784; PC: cMU vs. CT, p=0.2698, t = 1.216; PE: cMU vs. CT, p=0.7236, t = 0.3706), **p<0.01. Bars represent mean ±SEM. CT = control, cMU = conditional mutant.

Figure 4.

Figure 4—figure supplement 1. De novo fatty acid synthesis by oligodendrocytes supports structural stability of myelinated axons in the optic nerve.

Figure 4—figure supplement 1.

(a) EM images of aberrant myelinated axon profiles (examples indicated by arrowheads) in the optic nerve of P14 cMU mice. Scale bars: I = 2 µm, II = 1 µm, III = 2 µm, IV = 1 µm, V = 1 µm, VI = 1 µm. (b) Corresponding graph with quantification of percentage of aberrant myelin-axon profiles. Data points represent n = 3 mice for each, CT and cMU (unpaired two-tailed two sample Student’s t-test; at P14: cMU vs. CT, p=0.0101, t = 4.595), *p<0.05. At least 3600 axons per mouse analyzed, in random fields selected in the same anatomical area. Bars represent mean ±SEM. CT = control, cMU = conditional mutant.
Figure 4—figure supplement 2. Lipid profiles of spinal cord myelin of adult control and FASN mutant mice.

Figure 4—figure supplement 2.

Lipids extracted from myelin isolated from spinal cords of control (CT) and mutant (cMU) mice were identified and quantified by liquid chromatography-mass spectrometry. Individual species of 10 highest total FAs (a), all identified ceramides (b), cerebrosides (c), and sphingomyelin (d), 10 highest phosphatidylcholines (PC) (e), phosphatidylinositols (PI) (f), phosphatidylserines (PS) (g), and phosphatidylethanolamines (PE) (h) are shown. Lipid amounts were normalized to total protein content of samples. Significance was calculated compared to controls. Data points represent n = 3 mice for CT and n = 4 mice for cMU for analysis of total FAs, and n = 4 mice for each, CT and cMU for all other lipid analysis (unpaired two-tailed two sample Student’s t-test; Total Fatty Acids: 18:1n9, p=0.2525, t = 1.293; 16:0, p=0.7377, t = 0.3542; 18:0, p=0.4966, t = 0.7328; 18:1n11, p=0.9865, t = 0.01774; 20:4n6, p=0.7340, t = 0.3593; 22:6n3, p=0.6994, t = 0.4091; 22:4n6, p=0.6471, t = 0.4866; 20:0, p=0.9834, t = 0.02188; 22:1n7, p=0.4538, t = 0.8119; 14:0, p=0.5017, t = 0.7237; Ceramides: 18:0, p=0.4388, t = 0.8291; 24:1, p=0.3224, t = 1.078; 22:1, p=0.2792, t = 1.189; 24:0, p=0.2705, t = 1.214; 24:2, p=0.4223, t = 0.8609; 20:0, p=0.1532, t = 1.635; 22:0, p=0.4065, t = 0.8925; 18:1, p=0.2146, t = 1.387; 20:1, p=0.1721, t = 1.55; Cerebrosides: 24:1, p=0.8276, t = 0.2274; 24:0, p=0.1838, t = 1.502; 18:0, p=0.2138, t = 1.39; 22:0, p=0.2293, t = 1.338; 22:1, p=0.1417, t = 1.691; 24:2, p=0.9312, t = 0.0899; 20:0, p=0.1270, t = 1.771; 26:1, p=0.3540, t = 1.004; Sphingomyelin: 24:1, p=0.2507, t = 1.271; 18:0, p=0.4947, t = 0.7268; 24:0, p=0.3124, t = 1.103; 22:0, p=0.2253, t = 1.352; 20:0, p=0.2421, t = 1.298; 22:1, p=0.2618, t = 1.239; 24:2, p=0.4736, t = 0.7643; 16:0, p=0.9749, t = 0.03276; 18:1, p=0.8476, t = 0.2007; PC: 34:1, p=0.1620, t = 1.594; 36:1, p=0.0993, t = 1.948; 32:0, p=0.4570, t = 0.7948; 34:0, p=0.8025, t = 0.2614; 38:1, p=0.5828, t = 0.5803; 36:2, p=0.1624, t = 1.593; 38:2, p=0.4233, t = 0.8591; 38:6, p=0.3106, t = 1.107; 38:4, p=0.7018, t = 0.4018; 32:1, p=0.7399, t = 0.3478; PI: 38:4, p=0.1932, t = 1.465; 38:5, p=0.2254, t = 1.351; 40:6, p=0.6283, t = 0.5099; 36:4, p=0.0097, t = 3.73; 38:6, p=0.1153, t = 1.84; 36:1, p=0.0445, t = 2.534; 34:1, p=0.0715, t = 2.186; 40:4, p=0.8491, t = 0.1986; 40:5, p=0.9242, t = 0.09923; 36:2, p=0.0351, t = 2.711; PS: 36:1, p=0.0113, t = 3.602; 40:6, p=0.1262, t = 1.775; 38:1: p=0.0075, t = 3.949; 36:2, p=0.0193, t = 3.173; 38:4, p=0.0631, t = 2.277; 40:4, p=0.6789, t = 0.4349; 38:2, p=0.0065, t = 4.075; 40:2, p=0.0544, t = 2.385; 38:3, p=0.7193, t = 0.3768; 34:1, p=0.0276, t = 2.893; PE: 40:6, p=0.8894, t = 0.1451; 38:4, p=0.5126, t = 0.6958; 38:1, p=0.2972, t = 1.141; 36:1, p=0.5587, t = 0.619; 36:2, p=0.1676, t = 1.57; 38:5, p=0.9192, t = 0.1058; 34:1, p=0.1794, t = 1.52; 38:2, p=0.4110, t = 0.8834; 40:4, p=0.3597, t = 0.9915; 38:6, p=0.4677, t = 0.7751), *p<0.05, **p<0.01. Bars represent mean ±SEM. CT = control, cMU = conditional mutant.