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Fig. 5 BiP accumulation is also responsible for the impaired mitochondrial dynamics. Live images of 6 dpf DMSO- (A and B), tunicamycin- (Tm-) (C and D), or thapsigargin-treated (Tg-treated) (E and F) larvae showing mosaic expression of actc1b:mitoGFP labeling the mitochondria in green. While DMSO-treated larvae display small mitochondria, some of which form an intricate network, mitochondria in Tm- and Tg-treated larvae were large and rounded, as determined using a χ2 test. B, D, and F (scale bar: 15 μm) are zoomed in views of A, C, and E (scale bar: 100 μm), respectively. (G) The proportion of muscle fibers displaying altered mitochondrial morphology following DMSO, Tm, or Tg treatment, determined using a χ2 test. (H–O) Live images of 6 dpf larvae coexpressing Mito-GFP with mCherry (H–K) or BiP-mCherry (L–O). K and O are zoomed in views of J and N, respectively. Scale bar: 150 μm (first, second, and third columns); 15 μm (last column). (P) The proportion of muscle fibers displaying altered mitochondrial morphology comparing mCherry overexpression with BiP overexpression, as per Fisher’s exact test. (Q and R) Live images of 6 dpf atrogin-1–/– mutant larvae on the Tg(actc1b:KalTA4;cryaa:GFPpc54Tg) only (labeled as Control (KaltA4)) or Tg(actc1b:KalTA4;cryaa:GFPpc54Tg) and Tg(4XUAS:NLSCas9;cmlc2:RFP gl37Tg) (labeled as BiP KO) background, showing mosaic expression of actc1b:mitoGFP labeling the mitochondria in green. While control atrogin-1–/– mutants display large and rounded mitochondria, atrogin-1–/– mutants with BiP deficiency specifically in the muscle have small mitochondria that form an intricate network, as determined using a χ2 test. Scale bar: 100 μm. (S) The proportion of muscle fibers displaying altered mitochondrial morphology in control and BiP-KO atrogin-1–/– mutants, as per Fisher’s exact test. *P < 0.05, ***P < 0.001. All experiments performed in triplicate with the total number of fish examined in each replicate being documented in Supplemental Table 2.