PVALB and proximal spinal muscular atrophy: Furthermore, the expression of atrophy markers parvalbumin, MuRF-1 and atrogin-1 [57] was also restored towards normal levels, whereby parvalbumin expression was significantly increased (Fig. 7l), while MuRF-1 and atrogin-1 expression was significantly downregulated (Fig. 7m–n) in triceps of Fc-TWEAK-treated Smn−/−;SMN2 SMA mice compared to untreated SMA animals, further supporting an improvement in muscle health.