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Nat Med. 2015 Dec;21(12):1455-63. doi: 10.1038/nm.3990. Epub 2015 Nov 16.

Dystrophin expression in muscle stem cells regulates their polarity and asymmetric division.

Author information

1
Sprott Center for Stem Cell Research, Ottawa Hospital Research Institute, Regenerative Medicine Program, Ottawa, Ontario, Canada.
2
Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.

Abstract

Dystrophin is expressed in differentiated myofibers, in which it is required for sarcolemmal integrity, and loss-of-function mutations in the gene that encodes it result in Duchenne muscular dystrophy (DMD), a disease characterized by progressive and severe skeletal muscle degeneration. Here we found that dystrophin is also highly expressed in activated muscle stem cells (also known as satellite cells), in which it associates with the serine-threonine kinase Mark2 (also known as Par1b), an important regulator of cell polarity. In the absence of dystrophin, expression of Mark2 protein is downregulated, resulting in the inability to localize the cell polarity regulator Pard3 to the opposite side of the cell. Consequently, the number of asymmetric divisions is strikingly reduced in dystrophin-deficient satellite cells, which also display a loss of polarity, abnormal division patterns (including centrosome amplification), impaired mitotic spindle orientation and prolonged cell divisions. Altogether, these intrinsic defects strongly reduce the generation of myogenic progenitors that are needed for proper muscle regeneration. Therefore, we conclude that dystrophin has an essential role in the regulation of satellite cell polarity and asymmetric division. Our findings indicate that muscle wasting in DMD not only is caused by myofiber fragility, but also is exacerbated by impaired regeneration owing to intrinsic satellite cell dysfunction.

PMID:
26569381
PMCID:
PMC4839960
DOI:
10.1038/nm.3990
[Indexed for MEDLINE]
Free PMC Article

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