Fig. 1: Tubular ER is enriched in developing myelin and contacts the myelin membrane.
From: Nonvesicular lipid transfer drives myelin growth in the central nervous system
a Volume EM (ATUM-SEM) analysis of developing myelin from postnatal day 14 (P14) mouse optic nerve. Different compartments are marked on the bottom left image: axon (A), myelin (M) and inner tongue (I). ER membrane and axon membrane are segmented, and labeled in magenta and yellow, respectively. 3D reconstruction of ER network is shown together with (upper) or without (bottom) axon membrane, from an 11.25 µm-thick stack (226 slices with 50 nm interval, scale cube 1x1x1 µm). b Representative image of the TEM dataset for quantification of membrane-bound organelles in the inner tongue. Arrow heads: ER. c Examples of other membrane-bound organelles (arrows). d Ratio of inner tongues containing specified organelles, showing mean \(\pm \,\)SD, ER: 82.36 \(\pm\) 1.51, others: 20.13 \(\pm\) 3.80 (n = 3 wildtype P14 mice, two-tailed unpaired t-test, t = 26.37, df = 4, ****p < 0.0001). e Immunohistochemistry of developing myelin from P14 mouse spinal cord shows tubular ER markers (REEP5 and RTN4) appear as puncta and overlap with MBP marked myelin. f Ratio of myelin (MBP+ ring) overlapping with specified tubular ER marker. Quantification of (e) showing mean \(\pm \,\)SD, REEP5: 81.80 \(\pm\)3.97, RTN4: 72.79 \(\pm\) 3.91 (n = 3 wild-type P14 mice). g An example with zoom-in views showing short distance between the ER and myelin membrane. h Distribution of inner tongue and axonal ER’s distance from the plasma membrane. For inner tongue ER, 62% ≤ 10 nm, 83% ≤ 20 nm, 90% ≤ 30 nm (n = 175 ER from three wild-type P14 mice). For axonal ER, 5% ≤ 10 nm, 16% ≤ 20 nm, 29% ≤ 30 nm (n = 337 ER from three wild-type P14 mice). Scale bars: 0.5 µm (a), 0.5 µm (b), 0.1 µm (c), 1 µm (e), 100 nm (g left), 50 nm (g zoom-in). Source data are provided as a Source Data file.
