FSHD myoblasts fail to downregulate intermediate filament protein vimentin during myogenic differentiation

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant hereditary neuromuscular di- sorder. The clinical features of FSHD include weakness of the facial and shoulder girdle muscles followed by wasting of skeletal muscles of the pelvic girdle and lower extremities. Although FSHD myoblasts grown in vitro can be induced to differentiate into myotubes by serum starvation, the resulting FSHD myotubes have been sho- wn previously to be morphologically abnormal. Aim. In order to find the cause of morphological anomalies of FSHD myotubes we compared in vitro myogenic differentiation of normal and FSHD myoblasts at the protein level. Methods. We induced myogenic differentiation of normal and FSHD myoblasts by serum starvation. We then compared protein extracts from proliferating myoblasts and differentiated myotubes using SDS-PAGE followed by mass spectrometry identification of differentially expressed proteins. Results. We demonstrated that the expression of vimentin was elevated at the protein and mRNA levels in FSHD myotubes as compared to nor- mal myotubes. Conclusions. We demonstrate for the first time that in contrast to normal myoblasts, FSHD myo- blasts fail to downregulate vimentin after induction of in vitro myogenic differentiation. We suggest that vi- mentin could be an easily detectable marker of FSHD myotubes.