P.149 Differential expression of intermediate filament proteins: lamins A/C and desmin within and between adult skeletal muscles

The cell cytoskeleton is composed of three main components: microfilaments, microtubules, and intermediate filaments. Intermediate filaments consist of intermediate filament proteins that are widely distributed in cells and tissues, either in the cytoplasm or the nucleus. Desmin is a tissue-specific cytoplasmic intermediate filament protein, while A-type lamins including lamin A/C are ubiquitously expressed nuclear intermediate filament proteins. Both play major roles in skeletal muscle functions. Mutations in the DES gene, encoding Desmin, and LMNA gene, encoding A-type lamins, lead to a group of rare disorders called desminopathies and laminopathies, respectively. The most frequent pathologies are those involving skeletal muscles. Despite the universal expression of lamins A/C in almost all cells and tissues, different phenotypes associated with laminopathies reflect a high degree of tissue-specificity, the reasons for which are not completely understood. It has also been shown that specific muscles/muscle groups are affected earlier than others in these myopathies. We hypothesized that desmin and lamins A/C are not uniformly expressed in different skeletal muscles and or muscle parts. Accordingly, we have investigated the relative expression of desmin, lamin A & lamin C in 9 skeletal muscles, of which 7 were divided into belly and myotendinous junction (MTJ). Our preliminary results revealed that there is no significant difference in the relative expression of desmin and lamins A/C between bellies and MTJs within a single muscle. We also observed that the relative expression of lamins A & C is correlated with myogenic markers; MyoD and myogenin, while desmin is not. Strikingly, FDB muscle showed the highest expression of lamins A/C compared to other muscles. We are currently investigating desmin, lamin A and lamin C protein levels by western blot and immunohistochemistry and the effect of age and exercise on the expression of these intermediate filament proteins.