Fig. 3

Morphological analysis and quantifications of morpholino-injected embryos.

(A) Morphological features of STD-MO (ctrl) and morphants, observed under DMR microscope and subdivided into classes according to somite appearance: C1 completely formed, C2 partially disrupted, C3 unformed or totally disrupted somites (morphological features of ATGdnm2a-MO and I5E6dnm2a-MO-injected embryos are overlapping and representative images are shown). (B left) Toluidine blue-stained transverse and longitudinal sections at 4 dpf show evident muscle fibre disorganization in ATGdnm2a-MO and I5E6dnm2a-MO-injected embryos compared to STD-MO. Scale bar = 20 µm. (B right) Electron micrographs of longitudinal sections show myofibrils less regularly arranged, abundant membranous structures, vesicles and tubules (asterisks) in ATGdnm2a-MO and I5E6dnm2a-MO-injected embryos, compared to STD-MO. Scale bar = 1 µm. (C) Quantitation of central nuclei per fibre shows significantly more central nuclei in ATGdnm2a-MO and even more in I5E6dnm2a-MO-injected embryos than STD-MO. (D) Quantitation of fibre diameter indicates that the distribution of fibre diameters is shifted towards larger diameters in ATGdnm2a-MO and I5E6dnm2a-MO-injected embryos compared to STD-MO. Morphological analysis were performed on 6 embryos for each group (ATGdnm2a-MO, I5E6dnm2a-MO and STD-MO), chosen randomly from 6 independent injections.