Validation of Calreticulin and GRP75/Mortalin as potential protein biomarkers in a different muscle from a genetically distinct SMA mouse model. (A) Representative fluorescent western blots on gastrocnemius muscle from 'Taiwanese’ SMA mice (knockout (KO)) and littermate controls at P9 (mid/late-symptomatic) showing levels of TCPB, GRP75/Mortalin, Calreticulin and Ponceau (loading control). (B-D) Bar charts (mean ± standard error of the mean) showing expression levels of TCPB, GRP75/Mortalin and Calreticulin in control and 'Taiwanese’ SMA mice (KO) at P9 (N = 3 mice per genotype). TCPB levels showed no difference in expression levels in SMA mice compared with controls (ns, not significant; P > 0.05, unpaired, two-tailed t-test) (B). GRP75 levels were significantly increased in 'Taiwanese’ SMA mice compared with controls (**P < 0.01, unpaired, two-tailed t-test) (C). Calreticulin levels were also significantly increased in Taiwanese-SMA mice compared with controls (***P < 0.001, unpaired, two-tailed t-test) (D).