[Cascade of gene activation in Landouzy Dejerine muscular dystrophy].

Abstract

Our laboratory studies the Landouzy Dejerine muscular dystrophy or FSHD, a genetic disease which affects 7 in 100,000 individuals. The genetic defect is a deletion on chromosome 4 that decreases the copy number of a repeated DNA element, disturbs chromatin structure and activates the expression of neighbouring genes. The originality of our team has been to identify a gene within the repeated element itself and to show its activation in FSHD muscle cells. This gene expresses DUX4, a transcription factor that targets tens of genes, some of which express other transcription factors which target other genes, leading to a general deregulation. This DUX4-mediated cascade recapitulates by itself the major pathological features of FSHD: muscle atrophy, differentiation defect, oxidative stress... The homologous DUX4c gene located 42 kb from the repeat array expresses a protein that triggers myoblast proliferation. Its high expression level in severe cases of FSHD most probably contributes to the pathology by interfering with myoblast fusion with the muscle fibers at the last steps of muscle regeneration. We are performing global analyses of proteins and metabolites in healthy and FSHD myotubes (collaboration R Wattiez and JM Colet, UMONS) to identify abnormalities and their links with DUX4 or DUX4C.