Fig. 5

Age-dependent progressive disorganization of muscle fibers of col6a1^ama605003 mutants.

Light photomicrographs of Richardson’s stained semi-thin 1-µm sections from wild type (WT, A1-4), heterozygous (HT, B1-4) and homozygous (HM, C1-4) col6a1^ama605003 mutants at 2 days, 3 weeks and 4 months post-fertilization (2 dpf, 3wpf, 4 mpf, respectively). Right from 2 dpf in HT (B1) as in HM (C1) mutants, we observed abnormal vacuoles (red arrowheads) in the centre of some of the muscle fibers. Muscle fibers adjacent to abnormal ones remained similar to the ones WT (A1). At 3 wpf and at 4 mpf, in HT (B2-4) as in HM (C2-4), the number and the size of abnormal vacuoles in myofibers varied from one area to another. Abnormal myofibers with vacuoles were scattered among unaffected myofibers identical to those observed in WT (A2-4). In sagittal sections of muscle from 3 wpf HT we observed breaks in fiber tethering (B2, red arrowhead) or cell in advanced degradation (C2, red arrowheads). Sections were cut according to transversal plane, except A2, B2, and C2 which were sagittal sections. Scale bars, 10 µm.