A Functional Role for 4qA/B in the Structural Rearrangement of the 4q35 Region and in the Regulation of FRG1 and ANT1 in Facioscapulohumeral Dystrophy

Université Paris-Sud 11, CNRS UMR 8126, Interactions moléculaires et cancer, Institut de Cancérologie Gustave-Roussy, Villejuif, France.
PLoS ONE (Impact Factor: 3.23). 02/2008; 3(10):e3389. DOI: 10.1371/journal.pone.0003389
Source: PubMed


The number of D4Z4 repeats in the subtelomeric region of chromosome 4q is strongly reduced in patients with Facio-Scapulo-Humeral Dystrophy (FSHD). We performed chromosome conformation capture (3C) analysis to document the interactions taking place among different 4q35 markers. We found that the reduced number of D4Z4 repeats in FSHD myoblasts was associated with a global alteration of the three-dimensional structure of the 4q35 region. Indeed, differently from normal myoblasts, the 4qA/B marker interacted directly with the promoters of the FRG1 and ANT1 genes in FSHD cells. Along with the presence of a newly identified transcriptional enhancer within the 4qA allele, our demonstration of an interaction occurring between chromosomal segments located megabases away on the same chromosome 4q allows to revisit the possible mechanisms leading to FSHD.

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Available from: Yegor Vassetzky
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    • "Several FSHD features, such as variability in severity and rate of progression, gender bias in penetrance, asymmetric muscle wasting, and monozygotic twin discordance, strongly suggest the involvement of epigenetic factors (Neguembor and Gabellini, 2010). Accordingly, DNA methylation (van Overveld et al., 2003), histone marks (Bodega et al., 2009; Zeng et al., 2009), and higher order chromatin structure (Bodega et al., 2009; Petrov et al., 2006; Pirozhkova et al., 2008) are altered in FSHD patients. These changes have been associated with the inappropriate de-repression of several 4q35 genes, among which DUX4 is currently the leading FSHD candidate (Gabellini et al., 2002; Lemmers et al., 2010). "
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    ABSTRACT: Repetitive sequences account for more than 50% of the human genome. Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal-dominant disease associated with reduction in the copy number of the D4Z4 repeat mapping to 4q35. By an unknown mechanism, D4Z4 deletion causes an epigenetic switch leading to de-repression of 4q35 genes. Here we show that the Polycomb group of epigenetic repressors targets D4Z4 in healthy subjects and that D4Z4 deletion is associated with reduced Polycomb silencing in FSHD patients. We identify DBE-T, a chromatin-associated noncoding RNA produced selectively in FSHD patients that coordinates de-repression of 4q35 genes. DBE-T recruits the Trithorax group protein Ash1L to the FSHD locus, driving histone H3 lysine 36 dimethylation, chromatin remodeling, and 4q35 gene transcription. This study provides insights into the biological function of repetitive sequences in regulating gene expression and shows how mutations of such elements can influence the progression of a human genetic disease.
    Full-text · Article · Apr 2012 · Cell
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    • "Loss of D4Z4 may lift repression in cis of the 4q35 region and thus the nearby genes FRG1, FRG2 and ANT1 [27], [28]. Additionally, the identification of a nuclear matrix attachment site (S/MAR) and its disassociation from the nuclear matrix in FSHD patients may change the arrangement of DNA loop domains, causing increased transcription of FRG1 and FRG2 [29], [30], [31]. Presently, it is unclear as to which or how many of these many non-exclusive mechanisms play a causal role in the pathogenesis of FSHD. "
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    ABSTRACT: Although recent publications have linked the molecular events driving facioscapulohumeral muscular dystrophy (FSHD) to expression of the double homeobox transcription factor DUX4, overexpression of FRG1 has been proposed as one alternative causal agent as mice overexpressing FRG1 present with muscular dystrophy. Here, we characterize proliferative defects in two independent myoblast lines overexpressing FRG1. Myoblasts isolated from thigh muscle of FRG1 transgenic mice, an affected dystrophic muscle, exhibit delayed proliferation as measured by decreased clone size, whereas myoblasts isolated from the unaffected diaphragm muscle proliferated normally. To confirm the observation that overexpression of FRG1 could impair myoblast proliferation, we examined C2C12 myoblasts with inducible overexpression of FRG1, finding increased doubling time and G1-phase cells in mass culture after induction of FRG1 and decreased levels of pRb phosphorylation. We propose that depressed myoblast proliferation may contribute to the pathology of mice overexpressing FRG1 and may play a part in FSHD.
    Full-text · Article · May 2011 · PLoS ONE
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    • "Our demonstration of DUX4c mRNA expression confirmed that this 4q35 gene was in a chromatin structure compatible with transcription as suggested by previous studies: its promoter was found associated with acetylated histone H4 [36] and it interacted with RNA polymerase II at slightly higher level than non-transcribed sequences [37]. Moreover, DUX4c is brought in the same chromatin loop as the enhancer-containing D4Z4 repeats in FSHD myoblasts [13], [17]; Fig. 1A) and this enhancer directly interacts with the DUX4c promoter [38]. However, these publications had failed to detect DUX4c mRNAs by RT-PCR. "
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    ABSTRACT: Facioscapulohumeral muscular dystrophy (FSHD) is a dominant disease linked to contractions of the D4Z4 repeat array in 4q35. We have previously identified a double homeobox gene (DUX4) within each D4Z4 unit that encodes a transcription factor expressed in FSHD but not control myoblasts. DUX4 and its target genes contribute to the global dysregulation of gene expression observed in FSHD. We have now characterized the homologous DUX4c gene mapped 42 kb centromeric of the D4Z4 repeat array. It encodes a 47-kDa protein with a double homeodomain identical to DUX4 but divergent in the carboxyl-terminal region. DUX4c was detected in primary myoblast extracts by Western blot with a specific antiserum, and was induced upon differentiation. The protein was increased about 2-fold in FSHD versus control myotubes but reached 2-10-fold induction in FSHD muscle biopsies. We have shown by Western blot and by a DNA-binding assay that DUX4c over-expression induced the MYF5 myogenic regulator and its DNA-binding activity. DUX4c might stabilize the MYF5 protein as we detected their interaction by co-immunoprecipitation. In keeping with the known role of Myf5 in myoblast accumulation during mouse muscle regeneration DUX4c over-expression activated proliferation of human primary myoblasts and inhibited their differentiation. Altogether, these results suggested that DUX4c could be involved in muscle regeneration and that changes in its expression could contribute to the FSHD pathology.
    Full-text · Article · Oct 2009 · PLoS ONE
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