Figure 5.

scAAV9-STMN1 treatment improves NMJ pathology in vulnerable muscles of SMA mice. Immunohistochemistry analysis of NMJ innervation in vulnerable (TVA, RA and EO) and resistant (levator auris longus (rostral), AS and AAL) muscles from unaffected, untreated SMA and STMN1-treated SMA mice. Muscles were immunostained to label the axon (NF-H), axon terminal (SV) and endplate (AChRs). (A) Representative images of PND18 TVA and RA (vulnerable) muscles showing reduced frequency of denervated endplates in scAAV9-STMN1-treated SMA mice (right panel) compared to untreated SMA mice (middle panel). Unaffected controls show no denervated endplates (left panel). Maximum projection confocal microscope images taken at ×20 magnification. White arrows point to the location of denervated endplates. (B, C and D) Quantification of NMJ denervation showing percentages of fully innervated, partially innervated and fully denervated endplates in vulnerable muscles. (E, F and G) Quantification of NMJ denervation in resistant muscles showing percent fully innervated, partially innervated and fully denervated NMJs. Denervation analysis shows that STMN1 treatment increases frequency of fully innervated endplates in SMA vulnerable muscles without affecting innervation of resistant muscles. For ease of presentation, only statistical comparisons of fully innervated NMJ percentages are presented. Data analyzed by a two-way ANOVA followed by a Tukey post hoc test for multiple comparisons. Data expressed as mean ± SEM. ^****P < 0.0001, ^***P < 0.001, n.s. = not significant. n = 3 animals per treatment.