Myonuclear morphology is abnormal in <i>lmna</i>-null mice.

<p>DAPI staining of representative EDL and soleus myofibres from wild-type (WT) <i>lmna^+/+</i>mice show that myonuclei are evenly distributed and have similar shape, size and heterochromatin content (<b>a and d</b>). By contrast, myonuclei in <i>lmna</i>^−/− myofibres are unevenly distributed, with variable size and shape, and heterogeneous chromatin content and distribution (<b>b and e</b>). Myofibres isolated from the <i>mdx</i> mouse model of DMD contain myonuclei of a more regular size, shape and heterochromatin organization (<b>c and f</b>). Unlike in <i>lmna</i>^−/− myofibres, myonuclei in <i>mdx</i> mice are often located in a chain in the centre of the myofibre, indicative of a recent regenerative event (<b>c and f</b>). Representative TEM images of longitudinal sections of soleus muscle from wild-type <i>lmna^+/+</i> (<b>g</b>) and <i>lmna</i>^−/− (<b>h</b>) mice. WT myonuclei (thin red arrows) are regularly shaped, and have an even layer of highly condensed chromatin around the nuclear rim, in addition to centrally located condensations (<b>g</b>). Myonuclei (thin red arrows) from <i>lmna</i> null mice are irregularly shaped and have disorganized chromatin throughout with occasional vacuoles (<b>h</b> - red *). A thick red arrow indicates an abnormally elongated myonucleus. Note connective tissue between myofibres and the disruption of the sarcomeric arrangements near the abnormal myonuclei (red open square). Scale bar for (<b>a–f</b>) is 50 µm and 10 µm for (<b>g and h</b>).