An isogenetic myoblast expression screen identifies DUX4-mediated FSHD-associated molecular pathologies.
Facioscapulohumeral muscular dystrophy (FSHD) is caused by an unusual deletion with neomorphic activity. This deletion derepresses genes in cis; however which candidate gene causes the FSHD phenotype, and through what mechanism, is unknown. We describe a novel genetic tool, inducible cassette exchange, enabling rapid generation of isogenetically modified cells with conditional and variable transgene expression. We compare the effects of expressing variable levels of each FSHD candidate gene on myoblasts. This screen identified only one gene with overt toxicity: DUX4 (double homeobox, chromosome 4), a protein with two homeodomains, each similar in sequence to Pax3 and Pax7. DUX4 expression recapitulates key features of the FSHD molecular phenotype, including repression of MyoD and its target genes, diminished myogenic differentiation, repression of glutathione redox pathway components, and sensitivity to oxidative stress. We further demonstrate competition between DUX4 and Pax3/Pax7: when either Pax3 or Pax7 is expressed at high levels, DUX4 is no longer toxic. We propose a hypothesis for FSHD in which DUX4 expression interferes with Pax7 in satellite cells, and inappropriately regulates Pax targets, including myogenic regulatory factors, during regeneration.
Bosnakovski
Darko
D
Lillehei Heart Institute and Department of Pediatrics, University of Minnesota, MN 55455, USA.
Xu
Zhaohui
Z
Gang
Eun Ji
EJ
Galindo
Cristi L
CL
Liu
Mingju
M
Simsek
Tugba
T
Garner
Harold R
HR
Agha-Mohammadi
Siamak
S
Tassin
Alexandra
A
Coppée
Frédérique
F
Belayew
Alexandra
A
Perlingeiro
Rita R
RR
Kyba
Michael
M
D000818:Animals; D002454:Cell Differentiation; D003001:Cloning, Molecular; D017353:Gene Deletion; D005786:Gene Expression Regulation; D005978:Glutathione / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D020391:Muscular Dystrophy, Facioscapulohumeral / Q000378:metabolism / Q000473:pathology*; D032446:Myoblasts / Q000378:metabolism*; D010084:Oxidation-Reduction; D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor / Q000378:metabolism; D051761:Paired Box Transcription Factors / Q000378:metabolism; D010641:Phenotype; D019076:Transgenes
C532958:Dux4 protein, mouse; D018398:Homeodomain Proteins; D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor; D051761:Paired Box Transcription Factors; C497322:Pax7 protein, mouse; C068686:Pax3 protein, mouse; D005978:Glutathione