April 2019 Funded Mircrogrants

April 2019 Funded Microgrants

3107 - Development of antisense oligonucleotides to treat giant axonal neuropathy

Giant axonal neuropathy (GAN) is a rare and devastating genetic disease characterized by difficulty coordinating movements (called ataxia). Some patients also lose sensation, strength, and reflexes in their arms and legs. In addition, visual and hearing problems occur in some patients. Furthermore, they may experience problems with the release of urine, constipation, heat intolerance, and reduction or loss of the ability to sweat. As the disease progresses, some experience paralysis, seizures, and a gradual loss in mental function (dementia). Most patients do not survive past their twenties. GAN is a very rare disease; only 50 affected families have been identified in the world.

We propose to develop a new therapy using small DNA-like molecules (antisense oligonucleotides, AONs). These molecules are designed to target the mutated gene products called RNA and correct the effects of the miswritten genetic code. We will examine the efficacy of newly designed DNA-like molecules in GAN patient cells. We expect AONs correct the effects of the miswritten genetic code and restore the protein production in AON cells. We envision that successful completion of this study will eventually lead to human clinical trials. Therefore, this study will provide a significant positive impact on the lives of GAN patients.

3141 - Setting stage for a personalised approach to treat creatine transporter (SLC6A8) deficiency

Cerebral creatine transporter deficiency is a genetic cause of intellectual disability. Affecting the uptake of creatine to the brain, patients have almost undetectable levels of this important substance in their nervous system. Current treatment with creatine supplements has only limited therapeutic effects. Therefore the development of new treatments is urgently needed.

We recently have diagnosed a male patient with this condition. He has a unique genetic mutation which has not been observed thus far. We have developed a lab method that allowed further characterization of this patient’s mutation. Our method is based on the measurement of electrical signals that are produced when creatine is transported across cell membranes. In our patient’s mutation no electrical signals could be detected indicating a severe loss of function of his creatine transporter.

We are asking the Rare Disease Foundation for funding to continue our research. Our particular aim is to test whether the deleterious effects of our patient’s mutation can be corrected with particular compounds such as creatine salts, or with drugs which potentially could rescue the defective transporter’s function (4-phenylbutyrate).

If one of the tested compounds shows an effect in our test system, we will aim to apply this treatment in our patient and evaluate the clinical effects on an individualized basis. This is an example of personalized precision medicine for a rare potentially treatable condition. If we are successful in this patient, we hope to expand our research and make it available for a greater number of patients.

3091 - Oncological correlates and underlying genetic factors of inflammation in malignant meningiomas

Meningiomas are brain tumors that occur in 2 to 7.5 people per 100,000 in the general population.3,15,19 While the majority of meningiomas are benign, 1-3% are classified as malignant (grade III) by the World Health Organization.19,21 These rare malignant meningiomas display aggressive behavior and predispose patients to poor long-term outcomes including increased rates of recurrence and reduced survival. Currently, the biological features that make a subset of meningiomas malignant are not well understood. There is a critical need to identify biological substrates that result in malignancy to identify potential targets for drug therapies. The role of inflammation in meningiomas is inadequately described in the literature, and there is a critical need to characterize inflammatory response in these tumors. Inflammation has been implicated in tumor growth in various diseases 1,6,22, however, a quantitative analysis of inflammatory cell infiltration has not yet been performed in malignant meningiomas. This analysis could have significant implications for current treatment standards for patients with malignant meningiomas by i) identifying inflammatory biomarkers associated with aggressive tumor behavior and ii) identifying biological targets for drug therapies. We believe that the proposed study could also benefit the study of many other rare diseases in addition to malignant meningiomas. The role of inflammation is increasingly recognized in the development of many neurological diseases including psychiatric illness9,17, rare tumors2, trigeminal neuralgia8, and Huntingdon’s disease14. This study may benefit various other rare diseases by i) establishing a robust methodology by which immune cells are quantified and correlated with DNA sequencing and disease outcomes, and ii) providing preliminary data to describe the role of inflammation in malignant meningiomas that may be similar in other rare brain tumors such as glioblastoma and medulloblastoma.

3101 - Adrenergic Arrhythmias in SCN5A Mutation Carriers

Sudden cardiac death (SCD) is a devastating event for the affected families and places a significant financial burden on the health care system. Many cases of SCD are unexpected and are caused by previously undiagnosed cardiac arrhythmias. An arrhythmia is when the heart beat is irregular. With genetic screening becoming more affordable, it is increasingly possible to detect potential cases of SCD before a catastrophic event. SCD may arise from structural or electrical defects in the heart. Although structural defects are the most common cause of SCD, more and more electrical defects are being found, thanks again to genetic screening. One protein in the heart responsible for electrical activity is the sodium channel, NaV1.5. The gene that forms NaV1.5 is called SCN5A. Genetic irregularities in SCN5A are known to cause two main forms of arrhythmias: long-QT syndrome and Brugada syndrome. Recently, however, a new and far more rare form of arrhythmia associated with SCN5A was identified. This arrhythmia can cause SCD and is associated with adrenergic stimulation of the heart – the fight-or-flight response. We recently studied one irregular sodium channel from a patient with this disease, but there are other families with the same symptoms but different genetic irregularities. We seek to study those irregular sodium channels in an effort to help our clinical colleagues understand, diagnose, and treat their patients, and prevent more cases of SCD. Only by understanding the fundamental properties of these irregular sodium channels can proper treatment protocols and lifestyle changes be recommended for the patients whose hearts harbor the hidden time bomb that causes unexpected sudden cardiac death. Our research has the potential to save lives, improve the lives of those with these genetic irregularities, and relieve the economic and emotional burden of this devastating disease.

3137 - Development of a Blood-based Diagnostic for Viral Myocarditis through Novel Biomarkers

Myocarditis is a rare disease characterized by inflammation and injury of the heart muscle. Myocarditis is a major cause of sudden and unexpected death in children and young adults. Viruses that infect the heart are a common cause of myocarditis. The damage is significant because injured heart muscle cells cannot contract effectively, and individuals afflicted with myocarditis may develop failure of the heart pump that requires medical or surgical intervention, including heart transplantation or artificial heart pumps, for survival.

Early diagnosis is required to minimize devastating outcomes. The current gold standard (the most certain way) of diagnosing myocarditis involves examining snipped tissue from the heart for evidence of inflammation and damage. Not all parts of the heart, however, will be equally involved by the disease, so the biopsy may miss the inflammation and damage. Correct diagnosis using this invasive process can be made in fewer than 30% of the patients who actually have myocarditis, which is not sufficiently sensitive.

To achieve a more accurate diagnosis for myocarditis, our laboratory is learning from valuable mouse models of viral myocarditis, and applying that knowledge to human myocarditis diagnostic development. We discovered that increased amounts of certain proteins are associated with heart failure during viral infection in mice when compared to the hearts of healthy uninfected mice. Further, this pattern of increased protein expression appears to be specific to viral myocarditis as compared to other causes of heart failure. Our preliminary work in human heart muscle has revealed increased amounts of the same proteins in human myocarditis, suggesting that they are biomarkers of viral myocarditis, or biological hallmarks of this particular disease state. We are now examining whether detection of these proteins provides for improved diagnosis in myocarditis. These new insights may lead to better management and outcomes for patients.

3096 - Evaluating the efficacy of a novel inhibitor of retinoic acid catabolism in a model of Fibrodysplasia Ossificans Progressiva

Fibrodysplasia Ossificans Progressiva (FOP) affects only 1 in 1.6million people, but its impact on patients and their families is devastating, and few treatment options are available. Patients appear normal at birth apart from a hallmark big toe abnormality. However, symptoms advance in early childhood, whereby muscles and ligaments become progressively replaced by bone. Any minor trauma, such as immunizations, dental work, or blunt muscle trauma from bumps, bruises and falls can trigger soft tissues to calcify. The result is painful and debilitating. Most FOP individuals are confined to wheelchairs by age 30, and the disease is fatal by around 45 years of age. Our lab studies the role of vitamin A in health and disease. We have recently designed a new drug that is able to block calcification in a cell culture model of bone formation. We would now like to test this drug candidate in a mouse model of FOP to see if it would be useful in limiting the debilitating excess bone formation in these patients. Moreover, there are non-FOP patients who suffer from inappropriate bone growth following invasive surgeries (estimated up to 10% of all surgeries) and this drug may also prove useful for those patients.

3131 - Development and screening of base editing systems for treatment of the mucopolysaccharidoses

The mucopolysaccharidoses are rare genetic lysosomal diseases, which result from the progressive accumulation of glycosaminoglycans, a cellular waste product. The MPS disorders result from essential lysosomal enzymes becoming non-functional, often due to a single DNA mutation. Severe neuronopathic forms of MPS result in a significant reduction in lifespan and quality of life. Currently, treatment of MPS is limited due to a protective barrier between the brain and the body that blocks access for enzyme replacement therapies, a common treatment of other related diseases. Genome editing technologies, which work like ‘molecular scissors’ to cut DNA, target and remove the disease-causing mutation and are promising potential therapeutics for MPS disorders2,3. Recently, a modified genome editing system, base editing, has been shown to be more efficient and accurate in targeting single disease-causing mutations in human stem cells4. Our group has determined that 57% of known mutations in MPS disorders are targets for base editing. If successful, correction of these mutations in stem cells derived from patients with MPS would allow for the production of functional enzyme. We propose the use of base editing to target and edit 13 different MPS-causing mutations. Through transplantation of genome edited cells back into the patient, a long-term supply of functional enzyme would be produced within the brain5. This would result in a reduction of disease symptoms and an increased quality of life for patients with neuronopathic MPS.

3068 - Incorporation of high-resolution 3D spectroscopic 7-Tesla MRI into intraoperative neuronavigation for resection of glioblastoma

Glioblastoma (GBM) is a rare (prevalence <10/100,000) but highly aggressive form of brain cancer that can occur in people of all ages. At present, treatment involves surgically removing as much of the tumor as possible followed by giving medications along with radiation therapy. Although this is the best treatment, one of the biggest barriers to improving patients’ survival is that it is often not possible to remove the entire tumor since there are frequently tiny GBM cells throughout the brain that cannot be seen during surgery or on standard MRI scans. However, recent research has shown that GBM cells produce larger amounts of specific substances while making smaller amounts of other molecules. We can detect these patterns and thus use them to pinpoint the location of GBM cells with a special type of scan called magnetic resonance spectroscopic imaging (MRSI), even though they might not be seen on a normal MRI scan. Our center has recently obtained a new, more powerful MRI scanner and we hypothesize that by using this machine to identify GBM cells through MRSI, surgeons will be able to take out more of the tumor and improve these patients’ survival.

3113 - Examining the effects on mitochondria of genetic mutation in the gene called DNM1L, that causes severe epilepsy and neurological disease in children

Mitochondria is the energy or power generating system in every human cell. Mitochondrial disease in children usually causes a severe clinical picture, most of the time affecting development and brain function, causing severe epilepsy and it can be fatal early in the neonatal period or infancy. Unfortunately it does not have a satisfactory treatment and most patients will do poorly. We follow several patients with severe neurological disorders, who have genetic changes that alter the mitochondrial function and one change in particular caused in one patient a very severe and rapidly declining disease.

This gene, called DNM1L, helps mitochondria to divide and keep their normal shape. If mutations occur in this gene, the mitochondria will remain fused, longer than normal and its function will be compromised. Since mitochondria is where all the energy production happens in all types of cell, their dysfunction will affect most organ systems and especially the high energy organs, such as the brain. Calcium is an element that has a very important role in all functions of a cell, including the mitochondria. We would like to examine how the mutation described in DNM1L gene in one of our patients presenting with severe neurological disorder, causes too much or too little calcium on this system. We will perform experiments in control cells where we mutate this gene, mimicking what happens in patients and compare it to control cells. The results will help us understand what happens in this genetic condition, why our patient was so severely affected, but it also may show us some possibilities, especially if we manipulate the calcium levels, that can be used to treat this condition.

3078 - Mechanistic studies into an ultrarare GRID2 mutation involved in spinocerebellar ataxia

Characterized by progressive and irreversible neurodegeneration and loss of coordination of hands, speech, and gait, spinocerebellar ataxia (SCA) is a heterogenous genetic disease with no cure. Research into certain forms of SCA are well-funded, such as Friedreich ataxia and ataxia telangiectasia, but many rare forms are not. We have a Canadian patient with early-onset ataxia, developmental delay, and recurrent seizures. Using state-of-the-art sequencing technology, we found the genetic mutation responsible for this patient’s SCA. Unfortunately, this mutation is so rare that there has only been one other case reported in the literature (published in 2017). Our lab specializes in molecular studies of the protein which this patient has a mutation in. We wish to conduct the first mechanistic studies into the disease biology for this ultrarare mutation using the microgrant. This will provide a platform for us to identify ways to reverse the disease using novel drug compounds.

3097 - Creating family friendly information resources for rare diseases

In this project, we will develop and disseminate family friendly information resources for newly identified childhood genetic disorders which are rare diseases (<1/2000 people in the United Kingdom affected (UK)). New genetic sequencing technologies used in the UK wide Deciphering Developmental Disorders and 100 000 genomes projects have identified dozens of new childhood genetic conditions. Many of these new genetic conditions are associated with co-occurrence of neurodevelopmental conditions such as Rolandic epilepsy, ADHD, motor impairment or sleep problems. This is because the genetic variant causes alterations to multiple parts of the developing brain. Most of these genetic developmental disorders are individually rare and have only been identified as distinct medical conditions very recently by modern genetic sequencing technology. The symptoms associated with these newly discovered developmental disorders are reported in scientific papers, but these are usually not useful for families. This means that the information available to the families on how the condition will progress/affect the child is limited. To address this unmet need we will produce family friendly information leaflets (using understandable lay language) for 5 new genetic disorders we have characterised in our research. We will perform a special type of scientific interviewing (qualitative interviewing) to understand in detail the symptoms of these rare genetic conditions to provide the most useful information for our leaflets. A focus group will be held to allow families to comment on these resources and suggest modifications. These information leaflets will be made freely available via the Unique website (www.rarechromo.org).

3077 - Investigating the role of lipid metabolism in congenital muscular dystrophy

Congenital muscular dystrophy type 1A (MDC1A) is caused by genetic mutations in a gene called LAMA2, which encodes LAMA2 protein, an integral component in muscle and nerve cells. The lack of LAMA2 protein leads to muscle degeneration and peripheral nerve abnormalities. There is currently no therapy for MDC1A patients, although many researchers, including our group are currently working on a variety of therapeutic interventions.

In the past few years, we have made an interesting observation, whereby targeting only the skeletal muscles is not enough to ameliorate the disease phenotypes in mice. Instead, it is important to also target the peripheral nerves to improve the overall motor functions.

A major component of the peripheral nerves is myelin, which is a lipid-rich (fatty) substance produced by Schwann cells. To better understand the molecular mechanisms underlying the defect in MDC1A peripheral nerves, we will (1) evaluate the lipid composition in the nerves, (2) develop cellular assay to study myelination process, and (3) test the effect of lipid supplementation. Successful completion of this project will lead to a better understanding of MDC1A etiology and inform future therapeutic developments, which may be translated to other rare diseases with impairment in peripheral nerve structures.

3061 - Seizure disorder in cardiofaciocutaneous syndrome: Clinical characteristics, therapeutics and impact on quality of life

Cardiofaciocutaneous syndrome (CFC) is a rare neurogenetic disease that occurs in approximately 1:810,000 births [1] and is associated with heart disease, characteristic facial features, skin anomalies, and varying degrees of developmental delay. [2] Individuals with CFC are at significantly heightened risk for neurological complications including seizures, hydrocephalus, and intellectual disability. [3] Anecdotal reports from caregivers of children with CFC have indicated that seizures can significantly impact life quality in this population, and that there is a significant risk of sudden death in epilepsy among these patients. Nevertheless, no previous studies have provided a comprehensive characterization of the clinical presentation of seizures in CFC. Further, the impact of seizures and anticonvulsant therapies on the neuropsychological functioning of affected patients is poorly understood. Our research will investigate neurological comorbidities of CFC, with an emphasis on seizure disorder and associated anticonvulsant treatments. We will examine how neurological comorbidities affect neuropsychological function, life quality and risk for mortality in CFC. Results of this study not only will be submitted for scientific publication, but will also be used to create an informational brochure for caregivers outlining the study results. The brochure will provide information regarding seizure type and frequency, reported efficacy of therapeutic approaches reported among study participants, and relevant resources for families and physicians.

3100 - Defining the genetic etiology of mitochondrial myopathy patients.

Next-generation DNA-sequencing has largely contributed to gene discoveries in rare diseases. However, many rare diseases are still without a molecular cause due to heterogeneity and limitations of the approach. In the case of mitochondrial myopathies, it is estimated that between 40% and 70% still lack a molecular diagnosis after exhaustive clinical and genetic evaluation. The combination of multiple omic approaches is now necessary to identify the molecular cause in these unresolved cases. In the proposed project, we will combine the sequencing data from DNA- and RNA-sequencing in order to uncover the genetic defects leading to the pathology. The combination of both approaches will identify variation at the DNA level and their possible functional impact on the transcriptome on both the nuclear and mitochondrial genome. RNA-sequencing data will provide a more in-depth analysis by identifying aberrant splicing event and differential expression. Our project will have a direct impact of patients affected with a mitochondrial myopathy and their family. Obtaining a molecular diagnosis will allow a proper genetic counseling, better risk assessment and clinical management as well as reducing the psychological hardship associated with the long diagnostic odyssey. In addition, defining the genetic etiology of mitochondrial myopathies will contribute towards a better understanding of biological processes underlying these diseases and could ultimately result in the identification of biomarkers and viable therapeutic targets. Research on rare diseases has had implications that have shaped the medical biology field for decades, by shedding light on normal and abnormal physiology as well as contributing to our understanding of common disorders. More specifically, the study of rare mitochondrial myopathies has the potential to increase the knowledge of normal muscle and mitochondrial functions and provides insight in more common defects.

3134 - Identification of Rejection-Resistant Fibroblasts for use in Bio-Engineered Skin Substitutes

Approximately 1:100,000 individuals are affected by a major burn covering more than 20% of their total body surface area (%TBSA).1 These burns are difficult to treat and mortality rates increase up to 50% for patients with a 90% TBSA burn.2 The standard treatment for deep burns is skin grafting, whereby a thin layer of skin is removed from a healthy area and placed on a burned area. However, patients with extensive burns (>40% TBSA) have limited unburned skin for skin grafts. Bio-engineered skin substitutes are being researched as a solution to this problem. Bio-engineered skin is artificial skin grown in a lab from skin cells. It is ideal to use the patient’s own cells, obtained from a skin biopsy, for this process; however, the 4 to 8 weeks needed to grow the skin leads to treatment delays. Using cells from a donor may reduce the skin manufacturing time, but comes with the risk of skin transplant rejection, whereby the patient’s immune system attacks the donor cells.

Fibroblasts are the main cells in the dermis of the skin, and thus make up a large component of tissue engineered skin. In this study, we will build on the results of our earlier studies that identified a specific type of mouse fibroblasts that are resistant to transplant rejection. Using skin samples obtained during the planned removal of excess tissue (e.g. extra digits and ear tags), we seek to identify human fibroblasts that also resist rejection.

3126 - Gene Therapy for POLR3-Related Hypomyelinating Leukodystrophies

Leukodystrophies are a group of rare genetic diseases affecting previously healthy children, leading to progressive disability and death. Unfortunately, no treatment is available for most of these children. Leukodystrophies are characterized by abnormalities in the white matter of the brain, whose main component, myelin, is needed to insulate brain cells (neurons), protect them, and allow fast electric conduction necessary in the nervous system, similar to insulation on electrical wires in a household. Leukodystrophies are classified as hypomyelinating (lack of myelin formation) and non-hypomyelinating (unhealthy myelin) based on distinguishing features seen in brain scans.

Our lab has identified that errors (mutations) in several genes cause a form of leukodystrophy called POLR3-related Hypomyelinating Leukodystrophy (POLR3-HLD), including the genes POLR3A, POLR3B and POLR1C. Now we are trying to understand why mutations in these genes lead to disease, and how we might fix it. This proposal aims to address the latter; specifically, how in vivo gene therapy may be used to address hypomyelination caused by defects in POLR3-HLD genes.

In our lab, we have designed a genetically modified mouse with a severe mutation in Polr3a that will be activated just before myelination starts and only in the brain cells generating myelin. Mice with this specific Polr3a defect will display hypomyelination and can then be treated with viruses designed to target myelin cells and transfer a working copy of the gene to them. In this manner, we can test if transferring a working copy of Polr3a to the brain will be a safe and effective way to redress myelin defects caused by loss of Polr3a function during myelination.

3142 - Determining Leucine tolerance in a patient with Maple Syrup Urine Disease (MSUD) using novel stable isotope methods

Maple syrup Urine Disease (MSUD) is a rare inherited disorder of the 3 branched chain amino acids (BCAA), with a 1:185,000 incidence. MSUD, if untreated can lead to coma and death. The cornerstone of MSUD treatment is a protein restricted diet with limited intake of BCAA (leucine, isoleucine and valine), supplemented with medical formula while maintaining plasma leucine levels within the recommended treatment range, as leucine is the key regulator of BCAA metabolism.

This study proposes the use of L-1-13C-Leucine (a stable isotope of leucine) and it’s catabolism to 13CO2 to help determine leucine tolerance of a patient (A) with MSUD, followed at Biochemical Diseases Clinic. This patient is an 8 y old diagnosed with MSUD in the neonatal period, who has had excellent metabolic control based on his monitoring blood work. However, recent blood work performed following a 4 h fast revealed leucine level below the normal reference range. Leucine is an essential amino acid can be elevated in plasma following a longer overnight fast, due to endogenous breakdown, therefore masking truly low levels in a patient. In light of this, determining the true individual leucine tolerance will be key to optimizing patient management and optimizing growth and development. Furthermore this approach can be utilised in other MSUD patients followed in the Biochemical Diseases clinic ensuring their optimized metabolic management.

3125 - Oligodendrocyte Dysfunction in POLR3-Related Hypomyelinating Leukodystrophies

Leukodystrophies are a group of rare genetic diseases affecting previously healthy children, leading to progressive disability and death. Unfortunately, no treatment is available for most of these children. Leukodystrophies are characterized by abnormalities in the white matter of the brain, whose main component, myelin, is needed to insulate brain cells (neurons), protect them, and allow fast electric conduction necessary in the nervous system, similar to insulation on electrical wires in a household. Leukodystrophies are classified as hypomyelinating (lack of myelin formation) and non-hypomyelinating (unhealthy myelin) based on distinguishing features seen in brain scans.

Dr. Bernard’s group has identified that errors (mutations) in several genes cause a form of leukodystrophy called POLR3-related Hypomyelinating Leukodystrophy (POLR3-HLD), including the genes POLR3A, POLR3B and POLR1C. Now we are trying to understand why mutations in these genes lead to disease, and how we might fix it. This proposal aims to address the former; specifically, how POLR3A mutations leads to defects in myelin cell function and how they are different than other cells harboring mutations in POLR3A.

In our lab, we have designed a genetically modified mouse with a severe mutation in Polr3a that can be activated in myelin cells when we administer a drug. Using this system, we can isolate these cells from the brain and study them in a dish. We can then compare their functions in normal conditions with those when Polr3a is lost to identify the specific problems that Polr3a causes in myelin cells. Furthermore, we can compare myelin cells with other types of cells to identify what makes them more vulnerable to the mutations causing disease in patients. By ascertaining the so-called mechanism of this disease we can better understand how to treat it, making this project of critical importance to patients who currently have no therapeutic options.

3081 - Probing the cause of atypical immune deficiency arising in adolescence

At the age of 13, a boy suddenly developed fevers every few weeks that were accompanied by a soar throat, ulcers around the mouth, poor appetite, slow growth and fatigue. At around the same time, he developed a progressive skin condition on his arms. He has been hospitalized many times over the last few years. His blood tests show he has low immune cells, particularly neutrophils which are important as the first line of defense against infections and tissue damage. Also, his T cells and B cells, which are part of the immune system that provide memory against specific bugs, were found to be mostly immature. He was tested for the 283 known causes of primary immunodeficiency, which came out negative. Up until age 13, he was very healthy – with no previous notable increased risk of infections and no skin diseases.

Further genetic testing revealed a rare version of a gene, RECQL4. The significance of this finding is unknown – but it is assumed that it is unlikely the cause of this boy’s recent health issues. However, RECQL4 makes an enzyme that plays a role in DNA repair and regulation, so it cannot be completely ruled out that the version of this gene the boy has plays any role in the decline of his health or whether his condition was independently induced by an environmental trigger – such as an infection. The research team aims to define the nature of the immune problem this teen has. They have planned experiments to test the response of his immune cells to different types of stress to determine if exposure to stressors causes death or damage to his immune cells. If so, they will test if this can be prevented. Boys of the same age with no sign of immune deficiency will be used as comparisons. The scientists will also assess the type of microbiome (the community of bacteria) present in his diseased skin. They hope this line of experiments will provide insight to help this boy and his family get the answers they seek about his condition and ultimately its treatment.

3130-Improving the Diagnostic Yield for Inborn Errors of Metabolism Using RNA Sequencing

Next Generation Sequencing (NGS) testing by Focused Panels, Whole Exome or Whole Genome sequencing has revolutionized the molecular genetics of Mendelian disorders particularly the rare and ultra-rare ones and is rapidly becoming the standard of clinical care. Despite its impact, 25–50% of the patients do not receive a molecular diagnosis following testing. Currently, many disease-causing variants are classified as variants of unknown significance (VUS) or they are not reported at all because they are not prioritized. Many of these VUS are missense, synonymous or non-coding variants that may affect RNA abundance or isoform but cannot be prioritized due to our poor understanding of their significance. The goal of this proposal is the validation of RNA sequencing for the diagnosis of Inborn Errors of Metabolism in a clinical laboratory.

3120 - Implication of DNMT3A mutations in the Pathogenesis of Tatton-Brown-Rahman Syndrome

Tatton-Brown-Rahman syndrome (TBRS) is a rare genetic disorder characterized by tall stature, intellectual disability and dysmorphic facial features. This disorder is associated to a functional mutation in DNMT3A, an enzyme responsible for establishing DNA methylation modifications implicated in gene regulation, and vital for development and cellular identity. Currently, we do not know how functional mutations in the DNMT3A protein can be at the origin of the neurodevelopmental and other associated problems observed in patients with TBRS. Thus, there is an urgent need to develop human model systems to understand the molecular and cellular causes of TBRS, in order to find potential and specific treatments for patients. With the collaboration of clinical geneticists, we have identified 2 TBRS patients, carrying a single mutation in the functional methyltransferase domain of DNMT3A. Using cells from TBRS patients, we derived induced-pluripotent stem cells (iPSC), a technology allowing us to transform the cells into stem cells, and reprogrammed these cells into neural progenitors and terminally differentiated neurons to establish the first preclinical model of TBRS to specify the deleterious impacts of functional DNMT3A mutations on neurodevelopment gene regulatory networks. Overall, this project will uncover the functional impact of DNMT3A mutations on the transcription profiles during brain cell development, and provide a patient-derived model to test new therapeutic avenues to treat patients with TBRS.

3128 - Characterization of rare variants in CACNA1C identified in patients with neurodevelopmental disorder

The gene CACNA1C encodes a calcium channel with important functions in the heart and brain. Mutations in a specific part of the CACNA1C gene cause a condition called Timothy syndrome, where individuals have autism and learning disability in association with long QT cardiac arrhythmia. Other types of mutations in CACNA1C may be associated with autism, psychiatric disease and seizures. However, it is still difficult to identify which mutations in this gene are actually disease causing, and also difficult to predict what health and learning problems are associated with any particular mutation. We will investigate rare genetic variants of uncertain significance in CACNA1C that have been found in individuals with autism and intellectual disability. We will try to determine how these variants impact the function of the calcium channel and if this can provide insight into what health issues (such as epilepsy, or cardiac arrhythmia) may be expected for a given mutation. This study may help the patients involved in the study, including two patients from Calgary with unclear variants who have inspired this project, come to a clearer genetic diagnosis and understanding of their disease.


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