DUX4 in Cells and Mice

Bosnakovski, Darko and Kyba, Michael (2008) DUX4 in Cells and Mice. In: Facioscapulohumeral Muscular Dystrophy International Research Consortium 2008, 11 Nov 2008, Philadelphia.

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By targeting each FSHD candidate gene to a doxycycline-inducible locus in murine C2
myoblasts, we have shown that DUX4 is uniquely toxic, that this toxicity is caused by sensitizing cells
to oxidative stress, and that both Pax3 and Pax7 act as dominant inhibitors of the DUX4 phenotype. At
low, non-toxic, levels of expression, DUX4 interferes with the expression of myogenic regulators and
inhibits differentiation, a feature shared by DUX4c. Using a set of deletion and frameshift mutants, we
show that both repression of MyoD and inhibition of differentiation require translation of the
homeodomains but not the c-terminus, while toxicity requires translation of both the homeodomains
and the c-terminus. Based on these results, we introduced DUX4, in the context of the terminal D4Z4
repeat, into mouse ES cells downstream of a doxycycline-inducible promoter on the X chromosome,
proximal to the ubiquitously-expressed HPRT locus. We had previously tried, unsuccessfully, to
generate transgenic mice carrying DUX4 and D4Z4 in various constructs by pronuclear injection
(random integration) without success. Using the X-linked inducible locus, we have now derived
strains carrying D4Z4/DUX4, however surprisingly, the D4Z4/DUX4 X chromosome (XD) is malespecific
lethal, even without dox. Female carriers are fertile but suffer a growth disadvantage and a
severe skin phenotype. Although they do not display an obvious muscular dystrophy, these are the
first mice to carry phenotypically active D4Z4 sequences. We hypothesize that D4Z4 sequences
interact with our basal promoter, resulting in DUX4 expression, and consequent growth defects. We
interpret previous failures to generate mice carrying active D4Z4 repeats to be due to strong selection
against D4Z4 integrations into open chromatin where DUX4 may be expressed. Females may be
partially protected from the dominant-lethal gene by X-inactivation, an unintended consequence of our
X-linked approach. We discuss these results in the context of developing an animal model for FSHD.

Item Type: Conference or Workshop Item (Speech)
Subjects: Medical and Health Sciences > Basic medicine
Divisions: Faculty of Medical Science
Depositing User: Darko Bosnakovski
Date Deposited: 03 Sep 2013 10:33
Last Modified: 03 Sep 2013 10:33
URI: https://eprints.ugd.edu.mk/id/eprint/7049

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