Thus, identification and investigation of potential agrin-cleaving proteases other than neurotrypsin may be important for the understanding of the data from this study, how agrin cleavage may be increased in the absence of neurotrypsin, and how agrin cleavage may be increased in associated skeletal muscle conditions such as sarcopenia (Reif et al., 2007; Stephan et al., 2008; Matsumoto-Miyai et al., 2009). Here, PRSS12 is linked to sarcopenia.