Biology subjects

Lee, Y. i.

Publications and source records attributed to Lee, Y. i..

6 recordsLinked to original sources

bioRxiv2025

Functional and structural pathologies in skeletal muscle of a rat model of Duchenne muscular dystrophy

BackgroundDuchenne muscular dystrophy (DMD) is a lethal pediatric degenerative muscle disease for which there is no cure. Robust preclinical models that recapitulate major clinical features of DMD are required to investigate efficacy of potential DMD therapeutics. Rat models of DMD have emerged as promising small animal models to accomplish this; however, there have been no comprehensive studies investigating the functional skeletal muscle decrements associated with the modeling of DMD in rats. MethodsCRISPR/Cas9 gene editing was used to generate a dystrophin-deficient Sprague-Dawley muscular dystrophy rat (MDR). Biochemical and immunofluorescent analyses were performed to confirm loss of dystrophin in striated muscles of this rat model. In situ and ex vivo muscle function was assessed in wild-type (WT) and MDR muscles at 3, 6, and 12 months of age, followed by histopathological analyses. ResultsMDR muscle tissues exhibited loss of full-length dystrophin and reduced content of other dystrophin glycoprotein complex members. MDR extensor digitorum longus (EDL) muscles and diaphragms displayed pronounced and progressive muscle weakness beginning at 3 months of age, compared to WT littermates. EDLs also exhibit susceptibility to eccentric contraction-induced damage. Functional deficits in soleus muscles were less severe and were associated with a right shift in force-frequency relationship and a muscle fiber-type shift. MDR muscles display progressive histopathology including degenerative lesions, fibrosis, regenerative foci, and modest adipose deposition. ConclusionsMDR is a preclinical model of DMD that exhibits many translational features of the human disease, including a large dynamic range of muscle decrements, that has high utility for the evaluation of potential therapeutics for DMD.

physiology↗

bioRxiv2025

Dual S100A1 and ARC gene therapy as a treatment for DMD cardiomyopathy

Duchenne muscular dystrophy (DMD) is a lethal pediatric striated muscle disease caused by loss of dystrophin for which there is no cure. Cardiomyopathy is the leading cause of death amongst individuals with DMD, and effective therapeutics to treat DMD cardiomyopathy are a major unmet clinical need. This work investigated adeno-associated viral (AAV) gene therapy approaches to treat DMD cardiomyopathy by overexpression of the calcium binding proteins S100A1 and apoptosis repressor with caspase recruitment domains (ARC). Using the severe D2.mdx mouse model of DMD, we identified that S100A1 gene therapy improves the diastolic dysfunction associated with DMD cardiomyopathy, whereas ARC gene therapy prolongs survival. The combination of both S100A1 and ARC in a single bicistronic vector improves the long-term cardiac outcome of D2.mdx mice, development of heart failure caused by micro-dystrophin expression, and exhibits safety via intracoronary delivery in a canine model of DMD. Furthermore, S100A1-ARC gene therapy provides functional benefits when expressed in D2.mdx skeletal muscle. Together, these findings indicate that S100A1-ARC gene therapy represents an effective treatment for DMD cardiomyopathy and may be effective in treating other forms of cardiomyopathy and muscle pathologies. SIGNIFICANCE STATEMENTCardiomyopathy is the leading cause of death amongst individuals with Duchenne muscular dystrophy (DMD). Effective therapeutics to treat DMD cardiomyopathy represent a major unmet clinical need. This work identifies the dual gene therapy approach of S100A1 and ARC as an effective treatment that improves long-term cardiac function and life-expectancy in severe mouse model of DMD. Intracoronary delivery of this AAV-based gene therapy also exhibits safety and evidence of efficacy in dystrophic canines. Furthermore, functional benefits in skeletal muscle are also incurred via S100A1-ARC expression in striated muscle. These findings indicate that S100A1-ARC therapy is an effective treatment for DMD cardiomyopathy whose benefits may be applicable for other forms of cardiac and muscle disease.

molecular biology↗

bioRxiv2023

How Myosin VI Traps its Off-State, is Activated and Dimerizes

Myosin VI (Myo6) is the only minus-end directed nanomotor on actin, allowing it to uniquely contribute to numerous cellular functions. As for other nanomotors, proper functioning of Myo6 relies on precise spatio-temporal control of motor activity via a poorly defined off-state and interactions with partners. Our structural, functional, and cellular studies reveal key features of myosin regulation and indicate that not all partners can activate Myo6. TOM1 and Dab2 cannot bind the off-state while, GIPC1 binds Myo6, releases its auto-inhibition and triggers proximal dimerization. Myo6 partners thus differentially recruit Myo6. We solved a crystal structure of the proximal dimerization domain, and show that its disruption compromises endocytosis in HeLa cells, emphasizing the importance of Myo6 dimerization. Finally, we show that the L926Q deafness mutation disrupts Myo6 auto-inhibition and indirectly impairs proximal dimerization. Our study thus demonstrates the importance of partners in the control of Myo6 auto-inhibition, localization, and activation.

biochemistry↗

bioRxiv2022

Potential limitations of micro-dystrophin gene therapy for Duchenne muscular dystrophy

Adeno-associated viruses (AAVs) expressing versions of truncated dystrophin (micro-dystrophins) are being delivered at high doses to patients with Duchenne muscular dystrophy (DMD) in clinical trials. We examined this strategy with two different micro-dystrophins, similar to those currently in clinical trials, in a severe mouse model of DMD, the D2.mdx mouse, using doses of AAV comparable to those used in the clinical trials. We achieved high levels of micro-dystrophin expression in striated muscle with cardiac expression [~]10 fold higher than that observed in skeletal muscle. Significant, albeit incomplete, correction of the skeletal muscle disease is observed. Surprisingly, a lethal acceleration of cardiac disease progression occurs with one of the micro-dystrophins, while the second appears to benefit the heart. The detrimental impact on the heart in the first case appears to be caused by the high levels of micro-dystrophin in the heart resulting in competition between micro-dystrophin and utrophin at the cardiomyocyte membrane. While the significance of these observations for patients currently being treated with AAV-micro-dystrophin therapies is unclear since the levels of expression being achieved in the DMD hearts are unknown, it suggests that micro-dystrophin treatments may need to be carefully titrated to avoid high levels of expression in the heart.

pharmacology and toxicology↗

bioRxiv2022

Evaluation of the DBA/2J mouse as a potential background strain for genetic models of cardiomyopathy

The potential use of the D2.mdx mouse (the mdx mutation on the DBA/2J genetic background) as a preclinical model of the cardiac aspects of Duchenne muscular dystrophy (DMD) has been criticized based on speculation that the DBA/2J genetic background displays an inherent hypertrophic cardiomyopathy phenotype. Accordingly, the goal of the current study was to further examine the cardiac status of this mouse strain over a 12-month period. DBA/2J mice have been scrutinized for the presence of cardiac lesions, however, in the current study we find that DBA/2J mice contain equivalent amounts of left ventricular collagen as healthy canine and human samples. In a longitudinal echocardiography study, neither sedentary or exercised DBA/2J mice demonstrated left ventricular wall thickening or cardiac functional deficits. In summary, we find no evidence of hypertrophic cardiomyopathy, or any other cardiac pathology, and thus propose that it is an appropriate background strain for genetic modeling of cardiac diseases, including the cardiomyopathy associated with DMD.

physiology↗

bioRxiv2021

Filopodia powered by class X myosin promote fusion of mammalian myoblasts

Skeletal muscle fibers are multinucleated cellular giants formed by the fusion of mononuclear myoblasts. Several molecules involved in myoblast fusion have been discovered, and finger-like projections coincident with myoblast fusion have also been implicated in the fusion process. The role of these cellular projections in muscle cell fusion was investigated herein. We demonstrate that these projections are filopodia generated by class X myosin (Myo10), an unconventional myosin motor protein specialized for filopodia. We further show that Myo10 is highly expressed by differentiating myoblasts, and Myo10 ablation inhibits both filopodia formation and myoblast fusion in vitro. In vivo, Myo10 labels regenerating muscle fibers associated with Duchenne muscular dystrophy and acute muscle injury. Conditional loss of Myo10 from muscle-resident stem cells, known as satellite cells, severely impairs postnatal muscle regeneration. Furthermore, the muscle fusion proteins Myomaker and Myomixer are detected in myoblast filopodia. These data demonstrate that Myo10-driven filopodia facilitate multi-nucleated mammalian muscle formation.

cell biology↗