Mechanisms of altered skeletal muscle action potentials in the R6/2 mouse model of Huntington’s disease

Huntington’s disease (HD) patients suffer from progressive and debilitating motor dysfunction for which only palliative treatment is currently available. Previously, we discovered reduced skeletal muscle Cl− channel (ClC-1) and inwardly rectifying K+ channel (Kir) currents in R6/2 HD transgenic mice. To further investigate the role of ClC-1 and Kir currents in HD skeletal muscle pathology, we measured the effect of reduced ClC-1 and Kir currents on action potential (AP) repetitive firing in R6/2 mice using a two-electrode current clamp. We found that R6/2 APs had a significantly lower peak amplitude, depolarized maximum repolarization, and prolonged decay time compared with wild type (WT). Of these differences, only the maximum repolarization was accounted for by the reduction in ClC-1 and Kir currents, indicating the presence of additional ion channel defects. We found that both KV1.5 and KV3.4 mRNA levels were significantly reduced in R6/2 skeletal muscle compared with WT, which explains the prolonged decay time of R6/2 APs. Overall, we found that APs in WT and R6/2 muscle significantly and progressively change during activity to maintain peak amplitude despite buildup of Na+ channel inactivation. Even with this resilience, the persistently reduced peak amplitude of R6/2 APs is expected to result in earlier fatigue and may help explain the motor impersistence experienced by HD patients. This work lays the foundation to link electrical changes to force generation defects in R6/2 HD mice and to examine the regulatory events controlling APs in WT muscle.

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Altered Ca2+ signaling in skeletal muscle fibers of the R6/2 mouse, a model of Huntington’s disease

The Journal of General Physiology ◽

10.1085/jgp.201411255 ◽

2014 ◽

Vol 144 (5) ◽

pp. 393-413 ◽

Cited By ~ 15

Author(s):

Peter Braubach ◽

Murat Orynbayev ◽

Zoita Andronache ◽

Tanja Hering ◽

Georg Bernhard Landwehrmeyer ◽

...

Keyword(s):

Skeletal Muscle ◽

Huntington's Disease ◽

Huntington’S Disease ◽

Voltage Clamp ◽

Trinucleotide Repeat ◽

Transport Model ◽

Muscle Fibers ◽

Muscle Pathology ◽

Release Flux ◽

Inward Currents

Huntington’s disease (HD) is caused by an expanded CAG trinucleotide repeat within the gene encoding the protein huntingtin. The resulting elongated glutamine (poly-Q) sequence of mutant huntingtin (mhtt) affects both central neurons and skeletal muscle. Recent reports suggest that ryanodine receptor–based Ca2+ signaling, which is crucial for skeletal muscle excitation–contraction coupling (ECC), is changed by mhtt in HD neurons. Consequently, we searched for alterations of ECC in muscle fibers of the R6/2 mouse, a mouse model of HD. We performed fluorometric recordings of action potentials (APs) and cellular Ca2+ transients on intact isolated toe muscle fibers (musculi interossei), and measured L-type Ca2+ inward currents on internally dialyzed fibers under voltage-clamp conditions. Both APs and AP-triggered Ca2+ transients showed slower kinetics in R6/2 fibers than in fibers from wild-type mice. Ca2+ removal from the myoplasm and Ca2+ release flux from the sarcoplasmic reticulum were characterized using a Ca2+ binding and transport model, which indicated a significant reduction in slow Ca2+ removal activity and Ca2+ release flux both after APs and under voltage-clamp conditions. In addition, the voltage-clamp experiments showed a highly significant decrease in L-type Ca2+ channel conductance. These results indicate profound changes of Ca2+ turnover in skeletal muscle of R6/2 mice and suggest that these changes may be associated with muscle pathology in HD.

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A mouse model of Huntington’s disease shows altered ultrastructure of transverse tubules in skeletal muscle fibers

The Journal of General Physiology ◽

10.1085/jgp.202012637 ◽

2021 ◽

Vol 153 (4) ◽

Author(s):

Shannon H. Romer ◽

Sabrina Metzger ◽

Kristiana Peraza ◽

Matthew C. Wright ◽

D. Scott Jobe ◽

...

Keyword(s):

Electron Microscopy ◽

Skeletal Muscle ◽

Huntington's Disease ◽

Huntington’S Disease ◽

Muscle Fibers ◽

Membrane Capacitance ◽

Mrna Levels ◽

Primary Role ◽

Ec Coupling ◽

Skeletal Muscle Fibers

Huntington’s disease (HD) is a fatal and progressive condition with severe debilitating motor defects and muscle weakness. Although classically recognized as a neurodegenerative disorder, there is increasing evidence of cell autonomous toxicity in skeletal muscle. We recently demonstrated that skeletal muscle fibers from the R6/2 model mouse of HD have a decrease in specific membrane capacitance, suggesting a loss of transverse tubule (t-tubule) membrane in R6/2 muscle. A previous report also indicated that Cav1.1 current was reduced in R6/2 skeletal muscle, suggesting defects in excitation–contraction (EC) coupling. Thus, we hypothesized that a loss and/or disruption of the skeletal muscle t-tubule system contributes to changes in EC coupling in R6/2 skeletal muscle. We used live-cell imaging with multiphoton confocal microscopy and transmission electron microscopy to assess the t-tubule architecture in late-stage R6/2 muscle and found no significant differences in the t-tubule system density, regularity, or integrity. However, electron microscopy images revealed that the cross-sectional area of t-tubules at the triad were 25% smaller in R6/2 compared with age-matched control skeletal muscle. Computer simulation revealed that the resulting decrease in the R6/2 t-tubule luminal conductance contributed to, but did not fully explain, the reduced R6/2 membrane capacitance. Analyses of bridging integrator-1 (Bin1), which plays a primary role in t-tubule formation, revealed decreased Bin1 protein levels and aberrant splicing of Bin1 mRNA in R6/2 muscle. Additionally, the distance between the t-tubule and sarcoplasmic reticulum was wider in R6/2 compared with control muscle, which was associated with a decrease in junctophilin 1 and 2 mRNA levels. Altogether, these findings can help explain dysregulated EC coupling and motor impairment in Huntington’s disease.

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Skeletal muscle pathology in Huntington's disease

Frontiers in Physiology ◽

10.3389/fphys.2014.00380 ◽

2014 ◽

Vol 5 ◽

Cited By ~ 54

Author(s):

Daniel Zielonka ◽

Izabela Piotrowska ◽

Jerzy T. Marcinkowski ◽

Michal Mielcarek

Keyword(s):

Skeletal Muscle ◽

Huntington's Disease ◽

Huntington’S Disease ◽

Muscle Pathology

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Long-Term Efficacy and Safety of Deutetrabenazine for Chorea in Huntington’s Disease: Results From the ARC-HD Open-label Study

CNS Spectrums ◽

10.1017/s1092852920002655 ◽

2021 ◽

Vol 26 (2) ◽

pp. 164-165

Author(s):

Samuel Frank ◽

Claudia M. Testa ◽

David Stamler ◽

Elise Kayson ◽

David Oakes ◽

...

Keyword(s):

Huntington's Disease ◽

Huntington’S Disease ◽

Rating Scale ◽

Study Drug ◽

Motor Dysfunction ◽

Open Label ◽

Entire Treatment Period ◽

End Of Treatment ◽

Pharmaceutical Industries

AbstractBackgroundChorea is a prominent motor dysfunction in Huntington’s disease (HD). Deutetrabenazine, a vesicular monoamine transporter 2 (VMAT2) inhibitor, is FDA-approved for the treatment of chorea in HD. In the pivotal, 12-week First-HD trial, deutetrabenazine treatment reduced the Unified Huntington’s Disease Rating Scale (UHDRS) total maximal chorea (TMC) score versus placebo. ARC-HD, an open-label extension study, evaluated long-term safety and efficacy of deutetrabenazine dosed in a response-driven manner for treatment of HD chorea.MethodsPatients who completed First-HD (Rollover) and patients who converted overnight from a stable dose of tetrabenazine (Switch) were included. Safety was assessed over the entire treatment period; exposure-adjusted incidence rates (EAIRs; adverse events [AEs] per person-year) were calculated. A stable, post-titration time point of 8 weeks was chosen for efficacy analyses.ResultsOf 119 patients enrolled (Rollover, n=82; Switch, n=37), 100 (84%) completed ≥1 year of treatment (mean [SD] follow-up, 119 [48] weeks). End of study EAIRs for patients in the Rollover and Switch cohorts, respectively, were: any AE, 2.6 and 4.3; serious AEs, 0.13 and 0.14; AEs leading to dose suspension, 0.05 and 0.04. Overall, 68% and 73% of patients in Rollover and Switch, respectively, experienced a study drug–related AE. Most common AEs possibly related to study drug were somnolence (17% Rollover; 27% Switch), depression (23%; 19%), anxiety (9%; 11%), insomnia (10%; 8%), and akathisia (9%; 14%). Rates of AEs of interest include suicidality (9%; 3%) and parkinsonism (6%; 11%). In both cohorts, mean UHDRS TMC score and total motor score (TMS) decreased from baseline to Week 8; mean (SD) change in TMC score (units) was –4.4 (3.1) and –2.1 (3.3) and change in TMS was –7.1 (7.3) and –2.4 (8.7) in Rollover and Switch, respectively. While receiving stable dosing from Week 8 to 132 (or end of treatment), patients showed minimal change in TMC score (0.9 [5.0]), but TMS increased compared to Week 8 (9.0 [11.3]). Upon drug withdrawal, there were no remarkable AEs and TMC scores increased 4.4 (3.7) units compared to end of treatment.ConclusionsThe type and severity of AEs observed in long-term deutetrabenazine exposure are consistent with the previous study. Efficacy in reducing chorea persisted over time. There was no unexpected worsening of HD or chorea associated with HD upon deutetrabenazine withdrawal.FundingTeva Pharmaceutical Industries Ltd., Petach Tikva, Israel

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Early Motor Dysfunction and Striosomal Distribution of Huntingtin Microaggregates in Huntington's Disease Knock-In Mice

Journal of Neuroscience ◽

10.1523/jneurosci.22-18-08266.2002 ◽

2002 ◽

Vol 22 (18) ◽

pp. 8266-8276 ◽

Cited By ~ 156

Author(s):

Liliana B. Menalled ◽

Jessica D. Sison ◽

Ying Wu ◽

Melisa Olivieri ◽

Xiao-Jiang Li ◽

...

Keyword(s):

Huntington's Disease ◽

Huntington’S Disease ◽

Motor Dysfunction

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Skeletal muscle regeneration is altered in the R6/2 mouse model of Huntington's disease

10.1101/2022.01.11.475914 ◽

2022 ◽

Author(s):

Sanzana Hoque ◽

Marie Sjogren ◽

Valerie Allamand ◽

Kinga Gawlik ◽

Naomi Franke ◽

...

Keyword(s):

Skeletal Muscle ◽

Huntington's Disease ◽

Huntington’S Disease ◽

Muscle Damage ◽

Satellite Cell ◽

Mouse Models ◽

Satellite Cells ◽

Muscle Fibers ◽

Cag Repeat ◽

Skeletal Muscle Regeneration

Huntington's disease (HD) is caused by CAG repeat expansion in the huntingtin (HTT) gene. Skeletal muscle wasting alongside central pathology is a well-recognized phenomenon seen in patients with HD and HD mouse models. HD muscle atrophy progresses with disease and affects prognosis and quality of life. Satellite cells, progenitors of mature skeletal muscle fibers, are essential for proliferation, differentiation, and repair of muscle tissue in response to muscle injury or exercise. In this study, we aim to investigate the effect of mutant HTT on the differentiation and regeneration capacity of HD muscle by employing in vitro mononuclear skeletal muscle cell isolation and in vivo acute muscle damage model in R6/2 mice. We found that, similar to R6/2 adult mice, neonatal R6/2 mice also exhibit a significant reduction in myofiber width and morphological changes in gastrocnemius and soleus muscles compared to WT mice. Cardiotoxin (CTX)-induced acute muscle damage in R6/2 and WT mice showed that the Pax7+ satellite cell pool was dampened in R6/2 mice at 4 weeks post-injection, and R6/2 mice exhibited an altered inflammatory profile in response to acute damage. Our results suggest that, in addition to the mutant HTT degenerative effects in mature muscle fibers, expression of mutant HTT in satellite cells might alter developmental and regenerative processes to contribute to the progressive muscle mass loss in HD. Taken together, the results presented here encourage further studies evaluating the underlying mechanisms of satellite cell dysfunction in HD mouse models.

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B12 Longitudinal view of mitochondrial bioenergetics in skeletal muscle of premanifest transgenic minipig model for huntington’s disease

10.1136/jnnp-2018-ehdn.64 ◽

2018 ◽

Author(s):

Marie Rodinova ◽

Jana Krizova ◽

Hana Stufkova ◽

Bozena Bohuslavova ◽

Georgina Askeland ◽

...

Keyword(s):

Skeletal Muscle ◽

Huntington's Disease ◽

Huntington’S Disease ◽

Mitochondrial Bioenergetics ◽

Longitudinal View

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The longevity-associated variant of BPIFB4 improves a CXCR4-mediated striatum–microglia crosstalk preventing disease progression in a mouse model of Huntington’s disease

Cell Death and Disease ◽

10.1038/s41419-020-02754-w ◽

2020 ◽

Vol 11 (7) ◽

Cited By ~ 2

Author(s):

Alba Di Pardo ◽

Elena Ciaglia ◽

Monica Cattaneo ◽

Anna Maciag ◽

Francesco Montella ◽

...

Keyword(s):

Mouse Model ◽

Huntington's Disease ◽

Huntington’S Disease ◽

Neurodegenerative Disorder ◽

Motor Dysfunction ◽

Cag Repeats ◽

Huntingtin Protein ◽

Human Microglia

Abstract The longevity-associated variant (LAV) of the bactericidal/permeability-increasing fold-containing family B member 4 (BPIFB4) has been found significantly enriched in long-living individuals. Neuroinflammation is a key player in Huntington’s disease (HD), a neurodegenerative disorder caused by neural death due to expanded CAG repeats encoding a long polyglutamine tract in the huntingtin protein (Htt). Herein, we showed that striatal-derived cell lines with expanded Htt (STHdh Q111/111) expressed and secreted lower levels of BPIFB4, when compared with Htt expressing cells (STHdh Q7/7), which correlated with a defective stress response to proteasome inhibition. Overexpression of LAV-BPIFB4 in STHdh Q111/111 cells was able to rescue both the BPIFB4 secretory profile and the proliferative/survival response. According to a well-established immunomodulatory role of LAV-BPIFB4, conditioned media from LAV-BPIFB4-overexpressing STHdh Q111/111 cells were able to educate Immortalized Human Microglia—SV40 microglial cells. While STHdh Q111/111 dying cells were ineffective to induce a CD163 + IL-10high pro-resolving microglia compared to normal STHdh Q7/7, LAV-BPIFB4 transduction promptly restored the central immune control through a mechanism involving the stromal cell-derived factor-1. In line with the in vitro results, adeno-associated viral-mediated administration of LAV-BPIFB4 exerted a CXCR4-dependent neuroprotective action in vivo in the R6/2 HD mouse model by preventing important hallmarks of the disease including motor dysfunction, body weight loss, and mutant huntingtin protein aggregation. In this view, LAV-BPIFB4, due to its pleiotropic ability in both immune compartment and cellular homeostasis, may represent a candidate for developing new treatment for HD.

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