Muscle Stem Cells & Myopathies - PDF

Muscle degeneration and myopathies Natasha Chang Department of Biochemistry [email protected] ANAT 416 March 14, 2024 Overview: 2. Muscle degeneration and myopathies - Aging - Duchenne muscular dystrophy (DMD) - Dystrophin mediates satellite cell fate Sustaining muscle regenerative capacity Ch...

Muscle degeneration and myopathies Natasha Chang Department of Biochemistry [email protected] ANAT 416 March 14, 2024 Overview: 2. Muscle degeneration and myopathies - Aging - Duchenne muscular dystrophy (DMD) - Dystrophin mediates satellite cell fate Sustaining muscle regenerative capacity Chang et al., Trends Mol Med (2016) https://doi.org/10.1016/j.molmed.2016.04.002 Muscle stem cells and aging https://www.huffpost.com/entry/not-sofast-3-ways-to-slo_b_12661378 Decline of tissue regenerative potential is a hallmark of aging Age-related changes in both extrinsic (niche and systemic factors) and intrinsic (cell autonomous) factors Blau et al, Nature (2015) https://doi.org/10.1038/nm.3918 Age-dependent changes – satellite cell and niche -niche stiffness -niche mediated signaling -global epigenome changes -cell signaling molecules -metabolism Hwang and Brack, Curr Topics in Dev Biol (2018) https://doi.org/10.1016/bs.ctdb.2017.08.008 Muscle regeneration & satellite cell numbers are reduced with age 14 days post injury they don’t see major difference between injured and non injured young mice BUT they do see a big difference with aged muscle and the more they age, the cross sectional area is a lot lower Han et al, Science Advances (2018) https://doi.org/10.1126/sciadv.aar4008 Brack et al, J of Cell Sci (2005) https://doi.org/10.1242/jcs.02602 Increasing age negatively impacts satellite cell engraftment is there a functional issue w aged satellite cells? - they induced an injury into a recipient mouse (using a Muscular Dystrophy Model) and transplanting s Price et al, Nature Medicine (2014) https://doi.org/10.1038/nm.3655 JAK-STAT signaling is enhanced in aged satellite cells A B C Elevated JAK-STAT signaling reduces symmetric cell divisions and promotes asymmetric cell divisions Inhibiting JAK-STAT rescues symmetric divisions in satellite cells from old mice Price et al, Nature Medicine (2014) https://doi.org/10.1038/nm.3655 Inhibiting JAK-STAT enhances engraftment A siRNA or small molecules B Price et al, Nature Medicine (2014) https://doi.org/10.1038/nm.3655 Loss of stem cell quiescence A Regenerative decline of geriatric muscle stem cells B C D E Enhanced markers of senescence Reduced activation/proliferation Sousa-Victor et al, Nature (2014) https://doi.org/10.1038/nature13013 Loss in stem cell quiescence Li and Izpisua Belmonte, Nature (2014) https://doi.org/10.1038/nature13058 Autophagy maintains stemness by preventing senescence autophagy pathway is disregulated in aged cells the potein gets inserted into the aurophagosome membrane - they Chang, Front Cell Dev Biol (2020) https://doi.org/10.3389/fcell.2020.00138 Impaired basal autophagy in aged satellite cells Garcia-Prat et al, Nature (2016) https://doi.org/10.1038/nature16187 A B Genetic deletion of autophagy in satellite cells induces senescence, mitochondrial dysfunction and increased ROS Restoring autophagy with rapamycin or genetic expression of Atg7 prevents senescence Garcia-Prat et al, Nature (2016) https://doi.org/10.1038/nature16187 Stem cell rejuvenation Heterochronic parabiosis Conboy et al, Nature (2005) ; https://doi.org/10.1038/nature03260 Myopathies Diseases of muscle: musculoskeletal and neuromuscular disorders Wang et al, Pathobiology of Human Disease (2014) Muscular Dystrophy Duchenne and Becker EmeryDreifuss limb girdle facioscapulahumeral Heterogenous group of inherited disorders characterized by progressive muscle wasting and weakness distal oculopharyngeal Emery, BMJ (1998) https://doi.org/10.1136/bmj.317.7164.991 Duchenne Muscular Dystrophy (DMD) - Affects ~1/3500 boys Dystrophin-associated - Progressive muscle wasting Glycoprotein Complex (DGC) - Mutations in the DMD gene really suseptible to mutations bc it is a really encoding dystrophin a lethal disease, succumb to the end of life at 2—30 years, die bc of the diagphragm problems long gene Netter’s Neurology, 2nd ed. (2011) they affect the translation of the dystrophin protein - sits at the muscle-fiber membrane and is important for maintaining its integrity currently there is no cure for DMD - even tho we know the genetic Wang of Human Disease (2014) cause ofet it, al, andPathobiology the genes responsible Animal and Cell Models of DMD McGreevy et al, Dis Mod & Mech (2015); https://doi.org/10.1242/dmm.018424 DMD is also a muscle stem cell disease - Dystrophin is expressed in satellite cells - Dystrophin regulates cell polarity and asymmetric cell division - Dystrophin-mediated cell polarity is perturbed in mdx satellite cells Dumont et al, Nature Med (2015) https://doi.org/10.1038/nm.3990 Chang et al, Trends Mol Med (2016) https://doi.org/10.1016/j.molmed.2016.04.002 Dystrophin is expressed in satellite cells Mice Zebrafish Human fetal myoblasts Pax7 DMD DAPI W e yp t ild r e b fi Satellite cells r ibe f hic p ro t s Dy Dumont et al, Nat Med (2015) Gurevich et al, Science (2016) Alexander et al, Cell Stem Cell (2016) Dystrophin mediates cell polarity through the polarity effector Par1b to regulate asymmetric cell divisions C. Elegans asymmetric division (PAR6 – PAR2) https://goehringlab.crick.ac.uk/images-movies/polarizing-par-proteins.html Dumont et al, Nature Med (2015) https://doi.org/10.1038/nm.3990 Dystrophin-deficiency leads to impaired cell polarity and defective asymmetric cell division A B Dumont et al, Nature Med (2015) https://doi.org/10.1038/nm.3990 Altered mitotic spindle orientation and mitotic abnormalities they then wanted to know whats the functoinal concequence of altering orientation of myofibers: Impaired differentiation of myoblasts WT they saw a significant inhibition in turning on the myogenic factors mdx Dumont et al, Nature Med (2015) https://doi.org/10.1038/nm.3990 Dumont et al, Nature Med (2015) https://doi.org/10.1038/nm.3990 Dystrophin-mediated regulation of satellite cell fate ? ? ? p38g ? p38g Carm1 P-Carm1 (cytoplasmic) nuclear translocation Carm1 Carm1 Pax7 Pax7 cytoplasm Pax7me:MLL complex activates transcription nucleus H3K43me modification of Myf5 promoter Phosphorylation of CARM1 by p38g prevents nuclear localization Carm1f/f myoblasts Dystrophin-mediated regulation of satellite cell fate ? ? ? p38g ? p38g Carm1 P-Carm1 (cytoplasmic) nuclear translocation Carm1 Carm1 Pax7 Pax7 cytoplasm Pax7me:MLL complex activates transcription nucleus H3K43me modification of Myf5 promoter p38g interacts with the DGC in mature myofibers Dumont et al., Nature Med (2015) p38g interacts with the DGC via b1-Syntrophin we see them colocalize EDL myofibers cultured for 36h HEK 293T cells p38g interacts with the DGC via b1-Syntrophin have PLA signal showing that PLA/ syntrophin are interacting Proximity ligation assay (PLA) EDL myofibers cultured for 36h Dysregulated phosphorylation of CARM1 in dystrophin-deficient satellite cells Proximity ligation assay (PLA) EDL myofibers cultured for 36h **p ≤ 0.01 Reduced binding of CARM1 to PAX7 in dystrophin-deficient satellite cells p38g CARM1 x PAX7 Proximity ligation assay (PLA) EDL myofibers cultured for 36h ***p ≤ 0.0001 Reduced levels of H3K4me3 at Myf5 in mdx myoblasts H3K4me3 ChIP Primary myoblasts n ≥ 3, *p ≤ 0.05, **p ≤ 0.01 Epigenetic changes in dystrophin-deficient cells result in decreased Myf5 transcription Myf5 qPCR Satellite cells Primary myoblasts n ≥ 3, *p ≤ 0.05, **p ≤ 0.01 p38g depletion results in induction of Myf5 mRNA WT / mdx Isolation of satellite cells n=3, **p £ 0.01, ***p £ 0.001 - The DGC regulates the the epigenetic activation of Myf5 following asymmetric cell division - The p38g/CARM1 signaling axis is dysregulated in dystrophindeficient satellite cells - Provides a molecular explanation for the stem cell dysfunction in DMD and new avenues for therapy Chang et al, Cell Stem Cell (2018) https://doi.org/10.1016/j.stem.2018.03.022 Filippelli and Chang, Cells Tissues Organs (2021) https://doi.org/10.1159/000514305 Filippelli and Chang, Cells Tissues Organs (2021) https://doi.org/10.1159/000514305 Molecular mechanisms leading to stem cell dysfunction? How can we restore stem cell regenerative capacity and improve endogenous muscle regeneration? Summary Muscle stem cell dysfunction is an underlying cause of muscle degeneration and aging Extrinsic niche-related and intrinsic impairment in satellite cell functions occur during aging and contribute to the agerelated decline in muscle regenerative capacity DMD is a muscle degenerative disease that is caused by the lack of dystrophin in the muscle fiber as well as the muscle satellite stem cell Dystrophin and the DGC regulate satellite cell fate through the p38g/CARM1 signaling axis