Résumé :
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Background FSHD is an autosomal dominant myopathy characterized by selective muscle involvement. We previously demonstrated that, in contrast with myoblastes issued from non affected territories, FSHD myoblastes from affected territories display defect in myogenic differentiation. This study is aimed to correlate the extent of muscle involvement to the alteration in differentiation observed in FSHD myoblastes issued from differentially affected territories and gain more inside in FSHD physiopathological process. Methods We analyzed 4 myoblasts cultures issued from non dystrophic FSHD vastus lateralis (VL) muscle,4 from subscapularis (SS) FSHD affected muscle with different level of dystrophy and 4 matched controls. Dynamic gene expression profile was performed on a specific chip containing 6682 genes. 5 timepoints were analyzed: the cell cycle withdrawal (D0), and 24, 48, 72 and 144 hours after inducing myogenic differentiation. The results were analyzed using SAM multiclass analysis and expressed in term of variant or invariant gene during differentiation correlated or not correlated with variation in control myoblasts gene expression. Pathway connectivity analysis and visualisation of different pathways was done using a specific metasearch tool. The expression of 4q35 gene FRG1, ANT1 was analyzed both by microarray and Taqman real time PCR. Results Controls myoblasts issued from VL and SS muscles display clear differences in gene expression at D0 and during differentiation. The dynamic gene expression profile in FSHD myoblasts during differentiation confirm the defect in both cell cycle withdrawal and differentiation mostly in FSHD cell culture from highly dystrophic muscles. 4q35 genes overexpression were seen only in dystrophic SS derived muscle cultures after differentiation suggesting a role of these gene in differentiation defect. Conclusions Our results suggest that selective muscle involvement in FSHD patients can be due to different alteration in the ability of derived myoblasts to regenerate muscle. The role of 4q35 gene overexpression will be discussed as well as the implications for autologous cell therapy.
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