Fig. 4
Schwann cell Nrg1 promotes survival and migration of Schwann cells. a Survival assay with primary rat Schwann cells after 2 days in vitro (2div) with or without an ErbB2 inhibitor (CAS 928207-02-7, 30 µM). Representative before/after pictures (left panels) with quantification (right panel; a–c: n = 3 independent Schwann cell preparations per group, paired Student’s T test). b Survival assay with primary mouse Schwann cells from wild-type and NRG1cKO mice after 3div. c In the same experiment as in b, the apoptosis rate was assessed by terminal deoxinucleotidyl transferase-mediated dUTP-fluorescein nick end labeling (TUNEL) assay. d Quantification of Schwann cell apoptosis as measured by percentage of TUNEL-positive nuclei on sciatic nerve longitudinal sections from 11-day-old mice (wild type n = 6, NRG1cKO n = 5, CMT1A n = 6, CMT1A-NRG1cKO n = 9, NRG1-I OE n = 3, one-way analysis of variance (ANOVA), Tukey’s post test). e Quantification of Schwann cell nuclei per area (15,740 µm2) on electron micrographs of 4-month-old wild type (n = 4), NRG1cKO (n = 6), CMT1A (n = 6), and CMT1A-NRG1cKO (n = 6) mice (one-way ANOVA and Tukey’s post test). f Fluorescent immunohistochemistry on tibial nerve cross-sections from 4-month-old control (n = 4) and Neuregulin-1 type 1 (NRG1-I) overexpression (OE) (n = 3) mice against SOX10 (left panels) and respective quantification (right panel, Student’s T test). g Schematic set-up of Boyden chamber migration experiments (left panel) and respective quantification (right panel) of the percentage of cells that migrated from the top compartment through the mesh (green in left panel). The top compartment was always seeded with wild-type (wt) Schwann cells, whereas in the bottom compartment either with wild type (wt, black, set to 100%) or NRG1cKO Schwann cells were seeded and the latter without (ko, red) or with (ko+ NRG1, blue) recombinant NRG1 (quantification of three independent experiments, one-way ANOVA, Tukey’s post test). h BaseScopeTM in situ hybridization with a Nrg1-I probe (magenta) on sciatic nerve cross-sections of 18-day-old wild-type and CMT1A mice. Myelin was counterstained with MBP (green) and together with the phase contrast demonstrates Nrg1-I expression in myelinating Schwann cells in the CMT1A mouse (arrows, scale bar 5 µm). i BaseScope in situ hybridization with a Nrg1-I probe (magenta) on sciatic nerve cross-sections of a 4-month-old NRG1-OE mouse showing expression of Nrg1-I (magenta) in Schwann cells (S100, green). Note that supernumerary Schwann cells (closed arrows) are located nearby a Nrg1-I-expressing myelinating Schwann cell (open arrow, scale bar 5 µm, DAPI: nuclei). Source data are provided as a source data file. All respective p values are depicted as a range of significance with *p < 0.05; **p < 0.01; and ***p < 0.001
