Transcriptional and cytopathological hallmarks of FSHD in chronic DUX4-expressing mice
Darko Bosnakovski, … , Dawn A. Lowe, Michael Kyba
Darko Bosnakovski, … , Dawn A. Lowe, Michael Kyba
Published April 6, 2020
Citation Information: J Clin Invest. 2020;130(5):2465-2477. https://doi.org/10.1172/JCI133303.
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Research Article Muscle biology Neuroscience Article has an altmetric score of 10

Transcriptional and cytopathological hallmarks of FSHD in chronic DUX4-expressing mice

Abstract

Facioscapulohumeral muscular dystrophy (FSHD) is caused by loss of repression of the DUX4 gene; however, the DUX4 protein is rare and difficult to detect in human muscle biopsies, and pathological mechanisms are obscure. FSHD is also a chronic disease that progresses slowly over decades. We used the sporadic, low-level, muscle-specific expression of DUX4 enabled by the iDUX4pA-HSA mouse to develop a chronic long-term muscle disease model. After 6 months of extremely low sporadic DUX4 expression, dystrophic muscle presented hallmarks of FSHD histopathology, including muscle degeneration, capillary loss, fibrosis, and atrophy. We investigated the transcriptional profile of whole muscle as well as endothelial cells and fibroadiopogenic progenitors (FAPs). Strikingly, differential gene expression profiles of both whole muscle and, to a lesser extent, FAPs, showed significant overlap with transcriptional profiles of MRI-guided human FSHD muscle biopsies. These results demonstrate a pathophysiological similarity between disease in muscles of iDUX4pA-HSA mice and humans with FSHD, solidifying the value of chronic rare DUX4 expression in mice for modeling pathological mechanisms in FSHD and highlighting the importance FAPs in this disease.

Authors

Darko Bosnakovski, Ahmed S. Shams, Ce Yuan, Meiricris T. da Silva, Elizabeth T. Ener, Cory W. Baumann, Angus J. Lindsay, Mayank Verma, Atsushi Asakura, Dawn A. Lowe, Michael Kyba

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Figure 4

Compromised muscle vasculature in iDUX4pA-HSA mice.

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Compromised muscle vasculature in iDUX4pA-HSA mice. (A) Representative F...
(A) Representative FACS profile for CD45–CD31+ and CD45–CD146+CD31+ cells in the pool of muscles (gastrocnemius, quadriceps, pectoralis) of WT and iDUX4pA-HSA mice at 3 months after induction with a 10× serial dilution of doxycycline. (B) FACS analyses for CD45–CD31+, CD45–CD146+, and CD45–CD31+CD146+ cells presented in A. Data are shown as mean ± SEM; *P < 0.05; ***P < 0.001; ****P < 0.0001 by 1-way ANOVA, n = 4. (C) Immunofluorescence staining for CD31 (green), laminin (red), and nuclei (DAPI, blue) in quadriceps at 6 months after induction with chow containing 625 mg/kg doxycycline. Scale bar: 100 μm. (D) Quantification of CD31+ myofibers in sections presented in C. ****P < 0.0001. (E) 3D render and maximum intensity projections (MIP) of TA muscle from WT and iDUX4pA-HSA mice at 6 months. Disorganized vasculature with nonperfused segments of the vasculature (indicated by arrows) in iDUX4pA-HSA muscle. Scale bar: 100 μm. (F) Heatmap of differentially expressed genes in CD45–Pdgfrα–CD31+ FACS-sorted cells from control (n = 3) and iDUX4pA-HSA (n = 4) mice after 6 months induction with doxycycline. (G) The DUX4 score shows no enrichment of DUX4 early target genes in CD31+ cells from iDUX4pA-HSA mice. (H) MA plot showing the fold change of gene expression on samples presented in F. (I) KEGG pathway analyses showing the most enriched affected processes in CD31 cells from iDUX4pA-HSA mice.