Figure 4

Terminally differentiated primary duck and chicken muscle cultures immunolabeled for the muscle markers desmin and Pax7, counterstained with Harris’ Haematoxylin. Duck breast muscle cells fused en masse to form large multi-nucleated syncytia. Extensive desmin presence (brown staining) in duck myotubes (a, b) with reduced detection of desmin confined to a small proportion of duck myoblasts (b, arrows). Duck myoblasts were identified by the expression of Pax7 in the myonuclei (brown staining) (c, d). Note the absence of Pax7 protein in myotubes. Chicken breast muscle cells achieved comparable level of fusion; myotubes in panel a and e each contained over 300 nuclei. Morphologically, fused chicken cells displayed more typically the myotubular structural shape (e, f). Chicken muscle cultures showed similar expression patterns of myogenic markers to duck cultures with desmin detection in the sarcoplasm of myotubes (e, f) and Pax7 protein in myoblast nuclei (g, h)