Fig. 2

Specialization of synaptic nuclei during development. A Whole-mount staining of tibialis anterior (TA) muscles from mice at different developmental stages (P0, P7, P14, P30, or adult). BTX (red), DAPI (blue). The boxes are enlarged. Note that synaptic nuclei were enriched around NMJs in myofibers around P14. P, postnatal. B Quantification in A. Images were from three mice. n = 19 NMJs in P0; n = 19 NMJs in P7, n = 19 NMJs in P14, n = 19 NMJs in P30, n = 18 NMJs in adult. One-way ANOVA with Tukey’s post hoc test for multiple comparisons F (4,89) = 57.25. C DAPI staining in SR/NSR in P3 and adult TA muscles. DAPI (blue), R-BTX (red). D Quantification in A. n = 77 nuclei in NSR from P0, n = 61 nuclei in SR from P0; n = 66 nuclei in NSR from P7, n = 54 nuclei in SR from P7; n = 55 nuclei in NSR from P14, n = 51 nuclei in SR from P14; n = 67 nuclei in NSR from P30, n = 59 nuclei in SR from P30; n = 70 nuclei in NSR from adult, n = 63 nuclei in SR from adult. Images were from three mice. Two-way ANOVA with Sidak’s post hoc test for multiple comparisons: localization F (1,613) = 285.2; developmental time F (4,613) = 2.775. E Quantification in A. n = 43 nuclei in NSR from P0, n = 40 nuclei in SR from P0; n = 41 nuclei in NSR from P7, n = 40 nuclei in SR from P7; n = 37 nuclei in NSR from P14, n = 40 nuclei in SR from P14; n = 30 nuclei in NSR from P30, n = 30 nuclei in SR from P30; n = 40 nuclei in NSR from adult, n = 33 nuclei in SR from adult. Images were from three mice. Two-way ANOVA with Sidak’s post hoc test for multiple comparisons: localization F (1,364) = 0.8689; developmental time F (4,364) = 8.918. Unless otherwise specified, three independent experiments were performed; the mean ± SEM is shown; *p < 0.05, and ***p < 0.001. ns, non-significant