Archives: projects

Duchenne muscular dystrophy (DMD) is a devastating muscle disease that affects ~1 in 3500 boys. DMD is caused by the absence of dystrophin protein in skeletal muscle, leading to chronic degeneration of muscle fibres. Muscle degeneration is initially counteracted by muscle stem cell (MuSC)-dependent muscle repair. However, chronic cycles of muscle degeneration and regeneration lead to MuSC exhaustion, which precedes the onset of progressive muscle degeneration. The resulting muscle weakness severely limits mobility and ultimately respiration of patients. until they succumb to disease in their third decade of life. Therapeutic strategies to increase or ‘expand’ MuSC populations hold significant promise to both alleviate and treat DMD. Expansion of donor MuSCs, both in culture and after engraftment, will facilitate cell-based therapies for DMD. Moreover, expansion of MuSCs in a DMD patient would be expected to prevent their exhaustion and further delay progression of disease. Our team has previously identified a major regulatory pathway for protein synthesis as a pharmacological target to expand MuSCs ex vivo. We showed that inhibition of this pathway with a small molecule, named ‘Sal003’, enables MuSC expansion. We will further improve the potency of Sal003 with the overall goal to expand MuSCs within skeletal muscle, with therapeutic implications for both cell based therapies, and new strategies that slow MuSC exhaustion in DMD and potentially other muscle disease.

Neuromuscular disorders are a large group of diseases that affect the proper functioning of muscles. With the revolution in gene discovery for these disorders, and the prohibitively long time needed to develop accurate mammalian models for each new variant discovered, simpler animal models are needed to bridge the gap and help guide the development of higher models. Dr. Parker’s team uses the nematode C. elegans with its powerful genetics and rapid behavioural methodologies to model aspects of human neurodegenerative diseases. Charcot-Marie Tooth (CMT) disease is a hereditary peripheral motor and sensory neuropathy, and many of the genes involved are conserved throughout evolution. Dr. Parker’s team has developed a high throughput in vivo drug screening platform using C. elegans that has led to clinical trials for human neurodegenerative diseases. Here Dr. Parker’s team are now developing C. elegans models for CMT to be used for drug discovery and development.

Myotonic dystrophy type 1 (DM1) is the most common form of muscular dystrophy found in adults and currently there is no cure for this disease. DM1 is a multisystemic disease that affects several tissues including skeletal muscles, heart and brain. There are two major clinical manifestations of DM1: the classical adult form and congenital/childhood form. While the causes for skeletal muscle abnormalities in adulthood DM1 are established, the mechanisms responsible for the brain aspects of the congenital/childhood forms of DM1 remain largely unknown. The congenital form of DM1 is maternally transmitted and is characterized by reduced fetal movements, severe hypotonia and weakness at birth, often-respiratory insufficiency, feeding difficulties and talipes. Recent advances in stem cell technology now, will allow establishing stem cell lines from patients with adult and CDM1/childhood forms of the disease with the possibility to guide the differentiation of these stem cells into brain cells. Using the latest technology in disease modeling using 2 and 3D neuronal cultures), will speed up new discoveries on how we can reverse brain abnormalities in these patients.

Impact: Understanding the DM1 disease mechanism will help neurologists and other healthcare providers to improve the current diagnosis, monitor the disease progression and eventually improve treatment.

We are developing non-viral vehicles for delivery of genome editing machinery with specific emphasis on targeting skeletal muscle cells associated with Duchenne muscular dystrophy (DMD). Clustered regularly interspaced palindromic repeats (CRISPR)-CRISPR associated protein 9 (Cas9) is a powerful new gene editing tool. Our objective focuses on generating novel degradable and biocompatible nanoparticles (BNPs), using our U of T patented polyurethane technology. These carriers address limitations with current CRISPR/Cas9 delivery platforms, specifically eliminating use of immune reactive virus; enables co-delivery of a specific targeting tool; and reduces potential off-target tissue damage; . Studies will evaluate the therapeutic corrective capacity of nanoparticles in a DMD mouse model, and establish a technology to enable novel therapies for DMD patients in Canada and abroad.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a hereditary neurological disorder presenting with pyramidal (i.e. lower limbs spasticity), cerebellar (i.e. incoordination) and neuropathic (i.e. distal muscle weakness) impairments. Our previous research studies have shown that people with ARSACS have major impairments in regard to upper and lower limbs coordination, upper limbs dexterity, walking speed/endurance and balance control, ultimately leading to participation restrictions and difficulty to perform activities of daily living. No cure exists for ARSACS; at the moment we can only alleviate deficits. Some study conducted in degenerative ataxia other than ARSACS have documented positive effects of physical therapy on balance, gait and performance of daily living activities. However, currently, there is limited knowledge about rehabilitation interventions for ARSACS.

The objective of this pilot project is to document the effects of a re-entrainment program aiming to increase trunk and lower limb motor control on walking capacities, balance and accomplishment of daily activities in people with ARSACS.

There is little in the medical literature to guide the management of pregnant patients with myasthenia gravis (MG). Existing guides are based on small series and expert opinion, rather than population-based or prospective data.

Objective: To determine if pregnant MG patients are at increased risk of perinatal compilation (including fetal and maternal complications), in comparison with healthy controls matched on age, geographic region, and year. Month of delivery.

Study Design Retrospective, population-based, cohort study using administrative health databases housed at ICES (Institute for Clinical Evaluative Sciences).

Significance: This study provides a unique opportunity to study a relatively rare disease using province-wide health services data. The results of the study should both inform clinical practice and form the basis of future prospective studies.

Boys with glucocorticoid (GC)-treated Duchenne muscular dystrophy (DMD) are at risk for vertebral and long bone fractures due to osteoporosis. Vertebral fractures in DMD cause chronic back pain and spine deformity, while leg fractures can lead to premature, permanent loss of ambulation. Prevalence studies have shown that 20-60% of boys will sustain long bone fractures and up to 30% will have painful vertebral fractures. Fractures have also been linked in DMD to fat embolus syndrome causing acute respiratory distress and sudden death. The goal of this study, a pilot trial, is to evaluate the safety and feasibility of a novel therapy in the treatment of osteoporosis (denosumab) compared to our standard of care approach (intravenous bisphosphonate therapy, zoledronic acid) in boys with DMD. Denosumab is a human monoclonal antibody that inactivates RANKL, thereby inhibiting bone resorption and increasing bone strength at both trabecular (spine) and cortical (long bone) sites. A large study on close to 8,000 women with post-menopausal osteoporosis (the FREEDOM trial) showed that denosumab reduced vertebral and hip fracture risks without an increased frequency of side effects compared to placebo. The use of this agent is particularly compelling in the DMD setting, since studies in a murine model of DMD by co-investigator J. Frenette have shown that RANKL inhibition protects against DMD muscle dysfunction, degeneration and inflammation.

Variability in the characteristic symptoms of a disorder or phenotype is observed in many diseases and neuromuscular disorders are not an exception. In many cases the spectrum of how these disorders present is an obstacle to our understanding the causes and thus is hindering the development of valuable treatments. RYR1-related disorders are a good example of extremely variable neuromuscular disorders with phenotype ranging from a severe neonatal myopathy to malignant hyperthermia susceptibility. Our study cohort, composed of individuals carrying the same novel RYR1 heterozygous missense variant and extremely diverse phenotype, represents a unique and powerful example of the variable expressivity associated with RYR1 mutations. This cohort is therefore ideal for investigating the molecular causes of this phenomenon. We are proposing to look at transcriptomic and epigenomic signatures that could be associated with variability.

Our findings will hold the potential to improve diagnosis, help evaluate disease progression, offer a better risk management to patients and ultimately lead to new therapeutic avenues.

A critical, unmet clinical need is the identification of effective therapies for Duchenne muscular dystrophy (DMD) and myotonic dystrophy type 1 (DM1). When a protein in our muscles called AMP-activated protein kinase (AMPK) is turned on, it reduces disease severity in mice with DMD and DM1. However, AMPK-activating drugs in previous muscular dystrophy studies are neither safe for long-term human use, nor particularly potent. The use of better compounds to activate AMPK, those that are safe, effective, and able to be taken orally, would greatly increase their clinical impact for DMD and DM1 patients. Here, we will employ a new strategy to target AMPK for the treatment of muscular dystrophy. Specifically, we will investigate whether stimulation of AMPK with a practical, next-generation compound improves the health of mice with DMD and DM1, which would provide a better outlook for applicability in muscular dystrophy patients. We will focus on the ability of the AMPK-activating drug to restore the proper structure and function of dystrophic muscles, as well as explore the molecular mechanisms of its action. There is no better time than the present to perform this study since this drug is in clinical trials for treating diabetes. This proposal will determine the therapeutic potential of a novel AMPK-stimulating compound for the most prevalent muscular dystrophies in children and adults in Canada.

Current research in spinal muscular atrophy (SMA) focuses primarily on severe patients and on severe pre-clinical models. It is important to also cater research to milder patients who are already living with the disorder. Mild SMA has been challenging to model in mice for reasons that are not altogether clear. Therefore, a clear need exists in the field for a model to study the mild forms of the disease (SMA type III/IV). This proposal aims to characterize a novel mouse model generated in our laboratory to help study defects in mild SMA patients. It will allow for better characterization of molecular changes within skeletal muscle and motor neurons, and determine whether these differ in any way to those identified in the models of more severe SMA. The work will also assess whether biomarkers identified for the severe form of the disease will be useful in mild SMA.

This new model will allow for the understanding of the most susceptible pathogenic molecular changes in motor neurons, and investigation of the effects of SMN depletion in milder forms of the disease. In addition, it will also provide guidance for the currently aging SMA patient population treated with anti-sense oligonucleotides or gene therapy.

Collectively, the proposed studies will substantially inform the diagnosis, biology and treatment of mild SMA.