title: Direct interplay between two candidate genes in FSHD muscular dystrophy.
abstract: Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common neuromuscular disorders. The major form of the disease (FSHD1) is linked to decrease in copy number of a 3.3-kb tandem repeated macrosatellite (D4Z4), located on chromosome 4q35. D4Z4 deletion alters chromatin structure of the locus leading to aberrant expression of nearby 4q35 genes. Given the high variability in disease onset and progression, multiple factors could contribute to the pathogenesis of FSHD. Among the FSHD candidate genes are double homeobox 4 (DUX4), encoded by the most telomeric D4Z4 unit, and FSHD region gene 1 (FRG1). DUX4 is a sequence-specific transcription factor. Here, we located putative DUX4 binding sites in the human FRG1 genomic area and we show specific DUX4 association to these regions. We found also that ectopically expressed DUX4 up-regulates the endogenous human FRG1 gene in healthy muscle cells, while DUX4 knockdown leads to a decrease in FRG1 expression in FSHD muscle cells. Moreover, DUX4 binds directly and specifically to its binding site located in the human FRG1 gene and transactivates constructs containing FRG1 genomic regions. Intriguingly, the mouse Frg1 genomic area lacks DUX4 binding sites and DUX4 is unable to activate the endogenous mouse Frg1 gene providing a possible explanation for the lack of muscle phenotype in DUX4 transgenic mice. Altogether, our results demonstrate that FRG1 is a direct DUX4 transcriptional target uncovering a novel regulatory circuit contributing to FSHD.
authors.affiliation: Division of Regenerative Medicine, Stem Cells, and Gene Therapy, Dulbecco Telethon Institute at San Raffaele Scientific Institute, DIBIT2, 5A3, Via Olgettina 58, 20132 Milan, Italy Università Vita-Salute San Raffaele, Milan, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Ferri
authors.affiliation: Division of Regenerative Medicine, Stem Cells, and Gene Therapy, Dulbecco Telethon Institute at San Raffaele Scientific Institute, DIBIT2, 5A3, Via Olgettina 58, 20132 Milan, Italy Università Vita-Salute San Raffaele, Milan, Italy.
authors.forename: Claudia H
authors.initials: CH
authors.lastname: Huichalaf
authors.affiliation: Division of Regenerative Medicine, Stem Cells, and Gene Therapy, Dulbecco Telethon Institute at San Raffaele Scientific Institute, DIBIT2, 5A3, Via Olgettina 58, 20132 Milan, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Caccia
authors.affiliation: Division of Regenerative Medicine, Stem Cells, and Gene Therapy, Dulbecco Telethon Institute at San Raffaele Scientific Institute, DIBIT2, 5A3, Via Olgettina 58, 20132 Milan, Italy gabellini.davide@hsr.it.
authors.forename: Davide
authors.initials: D
authors.lastname: Gabellini
mesh_terms: D000368:Aged; D000818:Animals; D002460:Cell Line; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D056915:DNA Copy Number Variations; D017353:Gene Deletion; D056426:Genetic Loci; D057809:HEK293 Cells; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008840:Microfilament Proteins; D008875:Middle Aged; D032342:Muscle Cells / Q000166:cytology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism; D020391:Muscular Dystrophy, Facioscapulohumeral / Q000235:genetics* / Q000473:pathology; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins; D015854:Up-Regulation
chemical_list: D002843:Chromatin; C121257:DUX4L1 protein, human; C532958:Dux4 protein, mouse; C101270:FRG1 protein, human; C484440:Frg1 protein, mouse; D018398:Homeodomain Proteins; D008840:Microfilament Proteins; D009687:Nuclear Proteins; D011506:Proteins; D016601:RNA-Binding Proteins