The Cytoskeleton in the Extraocular Muscles of Desmin Knockout Mice.

Abstract

To investigate the effect of absence of desmin on the extraocular muscles (EOMs) with focus on the structure and composition of the cytoskeleton. The distribution of synemin, syncoilin, plectin, nestin, and dystrophin was evaluated on cross and longitudinal sections of EOMs and limb muscles from 1-year-old desmin knockout mice (desmin-/-) by immunofluorescence. General morphology was evaluated with hematoxylin and eosin while mitochondrial content and distribution were evaluated by succinate dehydrogenase (SDH) and modified Gomori trichrome stainings. The muscle fibers of the EOMs in desmin-/- mice were remarkably well preserved in contrast to those in the severely affected soleus and the slightly affected gastrocnemius muscles. There were no signs of muscular pathology in the EOMs and all cytoskeletal proteins studied showed a correct location at sarcolemma and Z-discs. However, an increase of SDH staining and mitochondrial aggregates under the sarcolemma was detected. The structure of the EOMs was well preserved in the absence of desmin. We suggest that desmin is not necessary for correct synemin, syncoilin, plectin, and dystrophin location on the cytoskeleton of EOMs. However, it is needed to maintain an appropriate mitochondrial distribution in both EOMs and limb muscles.