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Fig. 1 | Acta Neuropathologica Communications

Fig. 1

From: The p75NTR neurotrophin receptor is required to organize the mature neuromuscular synapse by regulating synaptic vesicle availability

Fig. 1

Abnormal NMJ postsynaptic complexity and structure in p75NTR−/− mice. a-c Whole-mounts of LAL muscles of 2–4 months old WT and p75NTR−/− mice were stained to reveal presynaptic motor terminals (2H3 plus SV2 antibodies, red), postsynaptic AChRs (BTX, green) and terminal Schwann cells (S-100 antibody, white). Laser confocal images of the R3 innervation region of WT and p75NTR−/− mice LAL muscle (a) show full coverage of AChR pretzels by presynaptic motor axons and terminal Schwann cells (b). Scale bar: 50 μm. c Quantification of the apposition of postsynaptic AChR pretzels by presynaptic motor axons. The plots correspond to > 35 NMJs per mice. d-h Diaphragm muscles from 2 months old WT and p75NTR−/− mice were stained with fluorescent-conjugated BTX to reveal AChR aggregates. d Postsynaptic apparatuses were classified into those having one or multiple peripheral openings and the relative abundance of these shapes was quantified (e). The plot corresponds to 130–220 NMJs per mouse. From 3D images, the area (f), surface (g) and volume (h) of individual pretzels were quantified. The plots correspond to 50–100 NMJs per animal. in Diaphragm NMJs from 2 to 4 months old p75NTR−/− and WT mice were analyzed by transmission electron microscopy. i Representative images of WT and p75NTR−/− NMJs. Scale bar: 500 nm. j The number of secondary folds is also expressed regarding the pre- and postsynaptic apposition length. k The postsynaptic perimeter was quantified as the length of the muscle membrane within the secondary folds (red line in i) expressed regarding the apposition length between the pre- and postsynaptic contact zone. l The depth of secondary folds was measured in a straight line traced between the beginnings of the invagination to the deepest point of the fold (green dotted line in i). m Quantification of the width of the secondary fold (blue line in i). n Quantification of the primary fold width, corresponding to the synaptic cleft width (black line in i). The plots correspond to 3–4 NMJs per animal. The bars represent the mean ± SEM of n = 3 (WT and p75NTR−/−) mice in (ac) and (in), n = 8 (WT and p75NTR−/−) mice in (dh). n.s, non-significant, *p < 0.5, **p < 0.01, ***p < 0.001, two-way ANOVA (e), or unpaired t-test (c, fh, jn)

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