Facioscapulohumeral dystrophy (FSHD) is one of the three most common muscular dystrophies in the Western world, however, its etiology remains only partially understood. Here, we provide evidence of constitutive DNA damage in in vitro cultured myoblasts isolated from FSHD patients and demonstrate oxidative DNA damage implication in the differentiation of these cells into phenotypically-aberrant myotubes. Double homeobox 4 (DUX4), the major actor in FSHD pathology induced DNA damage accumulation when overexpressed in normal human myoblasts, and RNAi-mediated DUX4 inhibition reduced the level of DNA damage in FSHD myoblasts. Addition of tempol, a powerful antioxidant, to the culture medium of proliferating DUX4-transfected myoblasts and FSHD myoblasts reduced the level of DNA damage, suggesting that DNA alterations are mainly due to oxidative stress. Antioxidant treatment during the myogenic differentiation of FSHD myoblasts significantly reduced morphological defects in myotube formation. We propose that the induction of DNA damage is a novel function of the DUX4 protein affecting myogenic differentiation of FSHD myoblasts.
Facioscapulohumeral dystrophy (FSHD) is a progressive muscular dystrophy linked to a deletion of a subset of D4Z4 macrosatellite repeats accompanied by a chromatin relaxation of the D4Z4 array on chromosome 4q. In vitro, FSHD primary myoblasts show altered expression of oxidative-related genes and are more susceptible to oxidative stress. Double homeobox 4 (DUX4) gene, encoded within each D4Z4 unit, is normally transcriptionally silenced but is found aberrantly expressed in skeletal muscles of FSHD patients. Its expression leads to a deregulation of DUX4 target genes including those implicated in redox balance. Here, we assessed DNA repair efficiency of oxidative DNA damage in FSHD myoblasts and DUX4-transfected myoblasts. We have shown that the DNA repair activity is altered neither in FSHD myoblasts nor in immortalized human myoblasts transiently expressing DUX4. DNA damage caused by moderate doses of an oxidant is efficiently repaired while FSHD myoblasts exposed for 24 h to high levels of oxidative stress accumulated more DNA damage than normal myoblasts, suggesting that FSHD myoblasts remain more vulnerable to oxidative stress at high doses of oxidants.
Human immunodeficiency virus-1 (HIV-1) Tat protein is one of the most important regulatory proteins for viral gene expression in the host cell and can modulate different cellular processes. In addition, Tat is secreted by the infected cell and can be internalized by neighboring cells; therefore, it affects both infected and uninfected cells. Tat can modulate cellular processes by interacting with different cellular structures and signaling pathways. In the nucleus, Tat might be localized either in the nucleoplasm or the nucleolus depending on its concentration. Here we review the distinct functions of Tat in the nucleoplasm and the nucleolus in connection with viral infection and HIV-induced oncogenesis.
DUX4, a double homeobox transcription factor, has been mostly studied in facioscapulohumeral dystrophy (FSHD), a pathology linked to a deletion of subtelomeric repeats on chromosome 4q.More recently, however, the gene has been associated with various sarcomas and hematological malignancies. Drugs developed for FSHD could be tested on cancer cells to develop efficient treatment strategies for both pathologies.
Skeletal muscle is a highly oxygen-consuming tissue that ensures body support and movement, as well as nutrient and temperature regulation. DNA damage induced by reactive oxygen species is present in muscles and tends to accumulate with age. Here, we present a summary of data obtained on DNA damage and its implication in muscle homeostasis, myogenic differentiation and neuromuscular disorders. Controlled and transient DNA damage appears to be essential for muscular homeostasis and differentiation while uncontrolled and chronic DNA damage negatively affects muscle health.
DUX4, a gene encoding a transcription factor involved in early embryogenesis, is heavily repressed in most somatic tissues while its aberrant expression is linked to facioscapulohumeral muscular dystrophy (FSHD). Recently, the deregulation of DUX4 expression was found in many cancers. While DUX4 role in FSHD is well studied, its relevance in cancer is less explored. Here we discuss multiple levels of control of DUX4 expression, including enhancer-promoter interactions, epigenetic modifications, non-coding RNAs and telomere positioning effect. We also connect disparate data on intrachromosomal contacts involving DUX4 and emphasize feedback loops in DUX4 regulation. Finally, we bridge data on DUX4 in FSHD and cancer and discuss prospective approaches for future FSHD therapies and the potential outcomes of DUX4 inhibition in cancer.
Triplex gene editing relies on binding a stable peptide nucleic acid (PNA) sequence to a chromosomal target, which alters the helical structure of DNA to stimulate site-specific recombination with a single-strand DNA (ssDNA) donor template and elicits gene correction. Here, we assessed whether the codelivery of PNA and donor template encapsulated in Poly Lactic-co-Glycolic Acid (PLGA)-based nanoparticles can correct sickle cell disease and x-linked severe combined immunodeficiency. However, through this process we have identified a false-positive PCR artifact due to the intrinsic capability of PNAs to aggregate with ssDNA donor templates. Here, we show that the combination of PNA and donor templates but not either agent alone results in different degrees of aggregation that result in varying but highly reproducible levels of false-positive signal. We have identified this phenomenon in vitro and confirmed that the PNA sequences producing the highest supposed correction in vitro are not active in vivo in both disease models, which highlights the importance of interrogating and eliminating carryover of ssDNA donor templates in assessing various gene editing technologies such as PNA-mediated gene editing.
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