Fig. 8

Misaligned sarcomeres in col6a1^ama605003 mutant fish muscle.

TEM pictures of sagittal section of muscle from wild type (WT, A1-3) and col6a1^ama605003 heterozygous (HT, B1-3) and homozygous (HM, C1-3) mutants at 2 dpf (A1, B1, C1), 3 wpf (A2, B2, C2) and 4 mpf (A3, B3, C3). As shown in Fig 7 (transversal sections), we observed a swelling of the sarcoplasmic reticulum (B, C, arrowheads), the presence of abnormal mitochondria (B, C, arrows) and vacuoles with membrane blebbing of possibly autophagic nature (B and C, asterisks) in HT and HM mutants at all three ages. In the same myofibre, we also observed disorganized (d) regions amongst still well-organized (o) myofibrils. In sagittal section of HT (B) and HM (C) mutants muscles, the position of the Z-discs and M-bands revealed a conspicuous misalignment of adjacent sarcomeres (white lines). Finally, in HM at 3wpf and 4 mpf (C2-3), the actin filaments in some sarcomeres appeared detached from the Z-line where the vacuole/autophagic vesicles were present (asterisks). No ultrastructural abnormalities as the ones described above were seen in WT (A1-3).