Increased levels of Calreticulin and GRP75/Mortalin in skin biopsies correlate with disease progression in SMA mice. (A) Representative fluorescent western blots on skin tissue from 'Taiwanese’ SMA mice and littermate controls at P9 (mid/late-symptomatic) showing levels of GRP75/Mortalin, Calreticulin and Ponceau (loading control). (B,D) Bar charts (mean ± standard error of the mean) showing expression levels of GRP75/mortalin and Calreticulin in 'Taiwanese’ SMA mice (knockout (KO)) and controls at P9 (N = 3 mice per genotype). (B) GRP75/Mortalin levels were significantly increased in 'Taiwanese’ SMA mice compared with controls (***P < 0.01, unpaired, two-tailed t-test). (D) Calreticulin levels were significantly increased in Taiwanese SMA mice compared with controls (**P < 0.01, unpaired, two-tailed t-test). (C,E) Time course of GRP75/Mortalin and Calreticulin expression in skin biopsies from 'Taiwanese’ SMA mice (KO) compared to controls (Het) (N = 3 mice per genotype/time-point). Tissue was analysed in mice at P1, P5 (both pre/early-symptomatic), P7 (early-symptomatic) and P9 (mid/late-symptomatic). (C) There was no increase in GRP75/Mortalin levels in Taiwanese SMA mice until after overt disease onset. (E) Similarly, there was no increase in Calreticulin levels in Taiwanese SMA mice until after overt disease onset.