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Alexander disease at the nanoscale in patient‐derived brain organoids

Elly Hol – University Medical Center Utrecht, The Netherlands and Marie‐Eve Tremblay – University of Victoria, Canada – ELA 2023‐017C3

Descriptif du projet

Alexander disease is a very rare brain disease. People with Alexander disease experience damage to the white matter in their brains, and they lose a lot of brain tissue. It can be diagnosed when a person is very young, even before they turn 2 years old, but sometimes it is not diagnosed until later in childhood or even adulthood. The symptoms of Alexander disease include problems with mental development, seizures, and muscle stiffness, and it ultimately leads to death. There have been about 500 cases of Alexander disease reported around the world. Unfortunately, there is currently no cure for this disease.

The disease is caused by mutations in the gene glial fibrillary acidic protein (GFAP), which codes for an astrocyte‐specific cytoskeletal protein. Astrocytes are essential for healthy brain functioning because they control many neuronal activities and homeostatic mechanisms of the brain. However, scientists still do not fully understand how this mutant GFAP protein in astrocytes causes Alexander disease.

In this project, we will closely collaborate between two teams to investigate Alexander patient‐derived human stem cell models at the ultrastructural level. We will generate miniature brain‐like structures called organoids from patient‐derived stem cells, and apply novel cell culture protocols to include white matter‐like structures. By analysing the cells in these organoids at the ultrastructural level, we will gain more knowledge on how GFAP mutations can lead to astrocyte and white matter pathology in the disease. This knowledge is essential to find new ways to treat Alexander disease.

Project financed by ELA up to: 100 000 €

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Screening of pharmacological chaperones for Megalencephalic leukoencephalopathy with subcortical cysts

Raúl Estévez – University of Barcelona, L’Hospitalet de Llobregat. Spain – ELA 2023‐013I2

Description of the project

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is type of leukodystrophy (problems in the brain white matter). Most MLC patients carry mutations in the MLC1 gene, encoding a membrane protein of unknown function. We have defined that those mutations affect to the stability of MLC1, leading to its disappearance. In this project our aim is to find compounds that might bind to MLC1 increasing its stability, and therefore increasing its function, which may eventually result in an improvement in the symptoms of MLC patients. These types of compounds have been extremely useful in other conformational diseases such as cystic fibrosis and are being used to treat patients. This project could be the first step to find a pharmacological therapy for MLC patients.

Project financed by ELA up to: 83 040 €

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Towards understanding the molecular mechanisms of hypomyelinating leukodystrophy type 16 (HLD16), caused by a dominant mutation in TMEM106B

Markus Damme – Christian‐Albrechts‐Universitaet zu Kiel, Kiel, Germany – ELA 2023‐008I3

Project abstract

Hypomyelinating leukodystrophy 16, also known as HLD16, is a rare genetic disorder that affects the development of myelin, the protective covering around nerve fibers in the brain. HLD16 is caused by a mutation in the gene TMEM106B. We genetically engineered mice in a way that they have the same mutation in TMEM106B that is found in human patients. We plan to investigate these mice to understand the disease and how the mutation in this gene, whose function is yet unknown, leads to this rare disease. This will help to develop future therapies and understand the function of TMEM106B in myelination.

Project financed by ELA up to: 97 900 €

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Study of GPR65 as a new Krabbe disease drug target

Sara Carpi – Department of Health Sciences, University ‘ Magna Græcia’ of Catanzaro, Catanzaro, Italy and Marco Cecchini – NEST, Istituto Nanoscienze ‐ CNR, Pisa, Italy – ELA 2023‐006C4

Description of the project

Krabbe disease (KD, or Globoid cell leukodystrophy) is a neurodegenerative disease caused by a deficiency of the lysosomal enzyme GALC. The early childhood form represents 85‐90% of cases and the onset of symptoms is between the 3rd and the 6th month after birth. During the advanced state, blindness and deafness show up; then a vegetative state arises which ends with death within the first 1‐2 years after birth. Unfortunately, for infants who have already developed symptoms of KD, there is no treatment that can change the course of the disease. Treatment, therefore, focuses on managing symptoms and providing supportive care.

Currently, the literature indicates that GALC‐deficiency correction might not be sufficient to cure the patients with KD, suggesting that not yet identified players could be implicated in KD pathogenesis. In this context, we identified some clear evidence pointing to the protein named GPR65 as a key factor in the pathogenesis of the disease.

Here, we propose a deep investigation of GPR65 and its evaluation as a druggable target in KD. In particular, we will evaluate GPR65 expression in patients with KD and test drugs to correct GPR65 deficiency in KD cell models. Moreover, we will explore the combination of a GPR65 mRNA‐based therapy with the GALC correction.

In case of a successful project outcome and in a forward‐looking vision, GPR65 mRNA‐based therapy might be used in combination with a main GALC‐deficiency correcting therapy, to help in achieving the complete KD phenotype rescue.

Project financed by ELA up to: 60 000 €

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Selective galactosylceramidase ablation to study the pathogenesis of Krabbe leukodystrophy

Laurence Wrabetz – SUNY Buffalo/ Hunter James Kelly Research Institute, Buffalo, USA – ELA2018-023I4

Description of the project

Krabbe leukodystrophy (KD) is a progressive and fatal neurologic lysosomal storage disorder that usually affects infants and causes death before two to three years of age. Hematopoietic Stem Cell Therapy extends the long-term survival with improved quality of life for KD patients, but it is not a cure. Using our newly developed KD animal model, we will identify which brain cell(s) needs to be efficiently cured with therapy.

Project financed by ELA up to:  71 082 €

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Preclinical studies specifically testing therapies (gene, cell, enzyme or pharmacologic therapies) for leukodystrophies

Françoise Piguet – INSERM U1169, Fontenay aux Roses, France – ELA2018-019I2

Description of the project

Metachromatic Leukodystrophy (MLD) is a rare demyelinating disease, due to arylsulfatase A (ARSA) deficiency, an enzyme involved in the catabolism of sulfatides, the main component of the myelin sheath. This deficiency leads to progressive demyelination of central nervous system and peripheral neuropathy. The most frequent form of the disease is the late infantile form of the disease which is characterized by a rapid progression of the disease, especially after the first onset of symptom. Ex vivo gene therapy develop by the group of Alessandra Biffi, and based on engraftment of lentiviral transduced hematopoietic stem cells has been shown to be effective for presymptomatic forms of MLD but not effective in early symptomatic patients, probably due to the rapid evolution and the time needed for the engrafment. On the other hand, enzyme replacement was shown as potentially effective but needed a chronic delivery. In the group, we previously proposed a gene therapy approach for MLD based on intracerebral delivery of an AAVrh.10 encoding ARSA. We had established proof of concept in mouse model of the disease and scale up study in non-human primates (NHP) leading us to propose a clinical trial which included 4 patients from 2013 to 2016. Despite ARSA expression in the brain and detection in cerebrospinal fluid (CSF) we failed to obtained any therapeutical benefits in these patients. Our point is that expressing ARSA in the CNS is fundamental to rapidly stop the disease progression, however, it could be essential also to bring back in patient healthy microglial cells. This project aim at establishing the proof of concept of rapid, sustained and important ARSA expression in the whole CNS (brain, spinal cord) and potentially also in the peripheral nerve. To achieve this aim, we propose to use a novel serotype of AAV: AAVPHP.eB that has been engineered to efficiently cross the blood brain barrier (BBB) after IV delivery. The project will be divided in two main parts, first a rapid study in the MLD mouse model both for pre and post symptomatic treatment, in order to evaluate efficiency of AAVPHP.eB-ARSA vector for biodistribution, ARSA expression, sulfatides correction, Purkinje cell prevention and behavioral testing. In a second phase, we want to test this vector in NHP thought several routes of delivery: intravenous (IV), intrathecal (IT) and intracerebroventricular (ICV), especially by potential coupling of these routes of administration to optimize CNS targeting. This with the final aim to propose a clinical trial for symptomatic MLD patients.

Project financed by ELA up to: 100 000 €

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Towards preclinical proof-of-concept for HBSL gene therapy

Matthias Klugmann – UNSW Sydney, Sydney, Australia – ELA2018-014I2

Description of the project

Hypomyelination with Brain stem and Spinal cord involvement and Leg spasticity (HBSL) is a leukodystrophy caused by defective cytoplasmic Aspartyl-tRNA synthetase (DARS). This enzyme is involved in building proteins, a fundamental biological process in bacteria and man alike. HBSL is caused by autosomal recessive mutations in the DARS gene and all point mutations identified result in neurological disease. HBSL is a potentially fatal spectrum disorder with no treatment and unclear etiology. In a pioneering effort our team at the University of New South Wales has generated the first mouse model of HBSL by introducing the same mutations causing HBSL in patients into the mouse Dars gene. Accurate animal models are the prerequisite to study the disease mechanisms and to develop and test treatments. Moreover, we have already identified that DARS expression in the brain of both mouse and man is enriched in neurons with far less expression in glia. This suggests that neurons might be the cells that a first line HBSL therapy should ideally target. In the first aim of this research proposal, we plan to engineer more mouse models that genetically mimic HBSL mutations and characterize them in order to model different forms of severity of HBSL. The second aim will be to develop a gene therapy platform for expression of a healthy copy of the DARS gene in mice. These experiments will help to identify the optimal route of delivery and the best timing for intervention. In the third aim we will perform a proof-of-concept gene therapy in the most relevant mouse model using optimized paramemters for DARS gene therapy identified in the previous aims. This project will yield an accurate animal model of HBSL that will be instrumental for preclinical testing of gene therapy or other treatment avenues. We propose that this study will generate data with high clinical relevance as our preclinical endpoints and gene therapy platform could easily be adapted for the treatment of other leukodystrophies caused by abnormal protein translation.

Project financed by ELA up to: 97 575 €

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Patient iPSC-based models for 4H leukodystrophy to identify complex neuron-glia dysfunctions

Vivi Heine and Nicole Wolf – VU university medical center, Amsterdam, The Netherlands – ELA2018-011C3

Description of the project

4H syndrome, an inherited brain white matter disorder (leukodystrophy), leads to considerable clinical handicap, ranging from mild to severe. Most patients deteriorate over time. There is no treatment yet, and we do not understand what goes wrong in the brain. There are no good animal models for this disease, hampering research. We think that besides white matter and myelin, also the nerve cells (neurons, also called grey matter) and their processes (axons) are damaged from early disease stages on. In our project, we want to explore this grey matter involvement with an innovative approach.

We are able to make white and grey matter cells from 4H patient and control fibroblasts. Earlier studies showed that 4H patient cells show affected expression of genes involved in nerve cell development. As nerve cells provide signals to white matter cells and myelination, neuronal defects could underlie abnormalities found in grey and white matter areas in 4H patient brains. We want to study co-cultures of both grey and white matter cells derived from patient cells to know how they influence each other. In the future, this might be a good model for drug screening to treat 4H.

Project financed by ELA up to: 99 565 €

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Pre-clinical testing of single and combined autophagy modulation by Lithium and Rapamycin in Globoid Cell Leukodystrophy

Ambra Del Grosso (PI: Marco Cecchini) – NEST, Istituto Nanoscienze-CNR, Pisa, Italy – ELA2018-008F2 (Fellow)

Description of the project

Globoid Cell Leukodystrophy (GLD) is a rare, hereditary disorder (with a frequency of about 1/100000 newborns) triggered by a deficit of the lysosomal enzyme galactosylceramidase (GALC) and characterized by the accumulation of galactosylsphingosine (psychosine, PSY) in the nervous system. PSY is a cytotoxic sphingolipid, which leads to the widespread degeneration of oligodendrocytes and Schwann cells, causing demyelination. Little is known about the molecular mechanisms by which PSY imparts toxicity and there is currently no cure available for GLD. The early-infantile and most widespread form of this lysosomal storage disorder (LSD) is degenerative, rapidly progressive and lethal. Bone marrow transplantation is currently the only clinically applied method to treat GLD, but gene therapy has yielded good results in experimental models. However, the recent literature strongly suggests that GALC-deficiency correction is not sufficient to completely rescue the GLD phenotype. Thus, supportive therapies
specifically addressing secondary targets of the disease might be needed to improve the final therapeutic outcome.

Autophagy, although much studied for many LSDs and neurodegenerative diseases (NDs), has been poorly investigated in GLD. Autophagy dysregulation has been only recently demonstrated, by us and others, in two in vitro GLD cell models.

Here, given our previous results and the wide data form literature showing autophagy activation as a promising therapeutic strategy for NDs and LSDs, we propose the pre-clinical testing of two autophagy activators in the naturally occurring murine model of GLD, the Twitcher mouse (TWI). Specifically, we aim to test in the TWI mouse the effects of Lithium, Rapamycin and of their combination, studying the rescue of a complete set of behavioural and biochemical parameters.

Certainly, this study will be very useful to deeply understand the role of autophagy in the molecular pathogenesis of GLD. Furthermore, in case of positive results, therapy will be readily applicable to humans for clinical testing, thanks to the fact that both tested drugs are already available as pharmaceutical preparations. Therefore, in a forward-looking vision, Lithium and/or Rapamycin could be used in combination with a main GALC-deficiency correcting therapy (as gene therapy and/or enzyme replacement therapy) to help in the achievement of a complete GLD phenotype rescue.

Project financed by ELA up to: 28 000 €

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Gene therapy for Megalencephalic leukoencephalopathy with subcortical cysts in two animal models of the disease

Assumpció Bosch – Universitat Autònoma de Barcelona, Barcelona, Spain – ELA2018-005I2

Description of the project

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare genetic disorder characterized by an abnormal head, loss of motor functions, epilepsy and mild mental decline. The disease is caused by mutations in two genes named MLC1 and GLIALCAM. There are no therapies for MLC patients, only palliative treatment. Interestingly, some patients with GLIALCAM mutations show a remitting phenotype, suggesting that it may be possible to improve the phenotype of MLC patients, even at later stages of the disease.

We present here a gene therapy preclinical therapeutic approach for MLC patients using two animal models of the disease, the Mlc1 and the GlialCAM knock-out mice. Therapeutic genes will be delivered by one-time treatment to the CNS, overcoming the difficulty of crossing the blood-brain barrier. We hope that the results of this project will be able to provide the first therapeutic tools for patients affected with MLC and may have also implications to treat other diseases affecting the myelin.

Project financed by ELA up to: 57 600 €

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