Bosnakovski, D. | Search bioRxiv

bioRxiv2023

Antagonism among DUX family members evolved from an ancestral toxic single homeodomain protein

Double homeobox (DUX) genes are unique to eutherian mammals and normally expressed transiently during zygotic genome activation. The canonical member, DUX4, is involved in facioscapulohumeral muscular dystrophy (FSHD) and cancer, when misexpressed in other contexts. We evaluate the 3 human DUX genes and the ancestral single homeobox gene sDUX from the non-eutherian mammal, platypus, and find that DUX4 activities are not shared with DUXA or DUXB, which lack transcriptional activation potential, but surprisingly are shared with platypus sDUX. In human myoblasts, platypus sDUX drives cytotoxicity, inhibits myogenesis, and induces DUX4 target genes, particularly those associated with zygotic genome activation (ZGA), by binding DNA as a homodimer in a way that overlaps the DUX4 homeodomain crystal structure. DUXA lacks transcriptional activity but has DNA-binding and chromatin accessibility overlap with DUX4 and sDUX, including on ZGA genes and LTR elements, and can actually be converted into a DUX4-like cytotoxic factor by fusion to a synthetic transactivation domain. DUXA competition antagonizes the activity of DUX4 on its target genes, including in FSHD patient cells. Since DUXA is an early DUX4 target gene, this activity potentiates feedback inhibition, constraining the window of DUX4 activity. The DUX gene family therefore comprises cross-regulating members of opposing function, with implications for their roles in ZGA, FSHD, and cancer. HIGHLIGHTSO_LIPlatypus sDUX is toxic and inhibits myogenic differentiation. C_LIO_LIDUXA targets overlap substantially with those of DUX4. C_LIO_LIDUXA fused to a synthetic transactivation domain acquires DUX4-like toxicity. C_LIO_LIDUXA behaves as a competitive inhibitor of DUX4. C_LI

molecular biology↗

bioRxiv2017

P53 is not necessary for DUX4 pathology

AbstractsFSHD is a genetically dominant myopathy caused by mutations that cause expression of the normally silent DUX4 gene. This transcription factor has been shown to interfere with myogenesis when misexpressed at very low levels in myoblasts, and to cause cell death when overexpressed at high levels. A previous report using adeno-associated virus to deliver high levels of DUX4 to mouse skeletal muscle demonstrated severe pathology that was suppressed on a p53 knockout background, implying that DUX4 acted through the p53 pathway. Here, we investigate the p53-dependence of DUX4 using both in vitro cellular and the transgenic iDUX4[2.7] mouse models. We find that inhibiting p53 has no effect on the cytoxicity of DUX4 in vitro. When crossed onto the p53 null background, we find no suppression of the male-specific lethality or skin phenotypes of the DUX4 transgene, and find that primary myoblasts from this mouse are still killed by DUX4 expression. These data challenge the notion that the p53 pathway is central to the pathogenicity of DUX4.\n\nSummary StatementDUX4 is thought to mediate cytopathology through p53. Here, DUX4 is shown to kill primary myoblasts and promote pathological phenotypes in the iDUX4[2.7] mouse model on the p53-null background, calling into question this notion.

genetics↗