Fig 2: Changes in Y172 immunoreactivity in MNs from mutant mice (P60) overexpressing NRG1 type III. (A–F) The density (per 100 µm2 MN soma, A,B) and size (in µm2, C,D) of total (A,C) and peripheral (periph., B,D) Y172-positive profiles and the percentage of these profiles showing a spatial association with VAChT-positive C-boutons (E) and NRG1 type III-positive spots (F) in MNs from WT and NRG1 type III-overexpressing mice. Note that NRG1 type III overexpression was associated with a prominent decrease in the density of total Y172-positive profiles (A) and a significant increase in the number of those located peripherally (B) in MNs; the area of both total and peripheral Y172-positive profiles was dramatically increased in MNs from NRG1 type III-overexpressing animals (C,D). Additionally, the percentage of Y172-positive profiles showing a close association with VAChT- (E) or NRG1 type III-positive (F) spots significantly increased or decreased, respectively, in MNs from NRG1 type III-overexpressing animals; 10–15 randomly selected MNs from 3 to 4 mice per condition were analyzed; *p < 0.05 and ***p < 0.001 vs. WT; student’s t-test). (G1–G4) Representative confocal micrographs of an NRG1 type III-overexpressing MN immunostained with Y172 (green) and anti-NRG1 type III (red) antibodies and counterstained with fluorescent Nissl stain (blue) for neuron visualization. Note that, compared to MNs of adult CD1 mice (see, for instance, Figure 1 or Figure 3), MNs overexpressing NRG1 type III exhibit an enlargement of Y172-positive profiles located in the periphery of the cell body, which correlated with the redundant and expanded SSCs previously described in Salvany et al. (2019); note also the expansion of NRG1 type III immunolabeling peripherally located in MN soma. (H1–H3) A higher magnification image of the area delimited in (G4) by the dotted-line rectangle corresponding to Y172, NRG1 type III and merged channels, as indicated, is shown. Scale bars: G4 = 10 µm (valid for G1-G3); H3 = 2.5 µm (valid for H1, H2).