Preclinical Validation of potential GLUT1 inducing agents for GLUT1 Deficiency Syndrome (GLUT1 DS).

Awardee: Alex MacKenzie

Institution: Children’s Hospital of Eastern Ontario, University of Ottawa

Grant Amount: $61,901.00

Funding Period: February 1, 2024 - January 31, 2025

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Summary:

Glucose is an essential energy source for the growing brain; low glucose levels in the brain can result in severe delay and disruption in brain development. This is the situation in the rare genetic disorder glucose transporter 1 deficiency syndrome (GLUT1 DS). GLUT1 DS is caused by mutations in the SLC2A1 gene that makes the so called transporter protein GLUT1 which is responsible for transporting glucose from the blood into the brain. A child with GLUT1 DS has only about half the normal level of brain glucose resulting in microcephaly, the development of seizures, as well as movement, and speech disorders that get progressively worse as they age. Although in GLUT1 DS, one of the SLC2A1 genes is mutated, every person has two copies of each gene; the “turning up” of the remaining normal SLC2A1 gene to make more of the GLUT1 protein in infants and children with GLUT1 DS represents a possible treatment for this untreatable disorder. We have studied the impact of several hundred clinically approved drugs on human blood vessel cells to determine if any of them increase the expression of GLUT1; eight such drugs have been identified. The top GLUT1-inducing drugs as well as roughly an equal number of drugs with similar impact that other scientists have found and published on will be tested on a mice model that, like humans with GLUT1 DS have mutated GLUT1. We shall use a variety of approaches, including so-called PET scan, which gives read outs of actual brain glucose levels before and after drug treatment, to see which are successful in increasing glucose transport to the brain. Drugs with the capacity to increase GLUT1 levels could be used as a treatment for GLUT1 DS and will be the subject of a clinical trial.

Investigating mechanisms underlying cognitive dysfunction in Glut1 deficiency syndrome

Awardee: Maoxue Tang

Institution: Columbia University

Grant Amount: $61,855.00

Funding Period: February 1, 2023 - January 31, 2024

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Summary:

Glucose Transporter-1 deficiency syndrome (Glut1 DS) is a pediatric-onset brain disorder caused by mutations in one copy (haploinsufficiency) of the SLC2A1 (Glut1) gene and therefore low levels of the SCL2A1-coded protein, Glucose Transporter-1. Patients afflicted with Glut1 DS suffer severe epileptic seizures as children and also exhibit delayed cognitive development. Later in life, a debilitating movement disorder develops and predominates. As of yet, there is no truly effective treatment for Glut1 DS. Moreover, it is unclear how low Glut1 protein causes brain dysfunction. In this project, we wish to understand how low Glut1 results in impaired cognition. We suspect that lactate, a downstream product of brain glucose, is a key mediator of Glut1 DS disease. Low brain glucose in Glut1 DS is thought to reduce levels of brain lactate. Since brain lactate is the preferred energy substrate of cerebral neurons, these neurons are starved. Consequently, they are unable to efficiently connect and communicate with one another. These ideas will be investigated in well-established model mice we have created in the laboratory. At the end of the project, we expect to have a better understanding of how low Glut1 affects cognition and how impairments in cognition correlate with altered brain structure. The project is also expected to identify molecules that rely on adequate brain glucose (and lactate) to ensure that the cerebral circuitry is properly established. Consequently, at the conclusion of this project, we expect to be in a better position to identify therapeutic points of intervention in our quest to treat Glut1 DS effectively and safely.

Multiplex analysis of variant effects for SLC2A1 gene

Awardee: Christina Gurnett

Institution: Washington University, St Louis

Grant Amount: $64,465

Funding Period: February 1, 2022 - January 31, 2023

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Summary:

The goal of this research is to quantitatively determine the functional impact of all possible genetic variants in SLC2A1 and construct algorithms to accurately predict disease onset and severity correlating through calibration with known pathogenic and benign variants. Toward this goal, we propose to employ a high-throughput framework to assess the functional impact of genetic variants in the SLC2A1. We will introduce hundreds of SLC2A1 variants individually into the haploid cell line (HAP1) via multiplex homology-directed-repair (HDR) using CRISPR and a donor library, so that each cell obtains a single variant knocked into the endogenous SLC2A1 gene. Damaging variants that completely disrupt SLC2A1 function (and glucose uptake) will result in impaired cell growth and will drop out of a population of cells sequenced at different time points. We have preliminary data demonstrating the utility of this approach to quantify the functional effects of 15 SLC2A1 variants. We now propose to scale this assay to generate comprehensive, quantitative functional data for the entire SLC2A1 coding region.

Identification of GLUT1 Activating Compounds in a Mouse Model

Awardee: Jason Park

Institution: University of Texas Southwestern Medical Center

Award Amount: $64,200

Funding Period: February 1, 2021 - January 31, 2022

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Summary:

Glucose transporter type I deficiency (G1D) is an epilepsy syndrome that results from a mutation in the SLC2A1 gene. In normal brain function, the SLC2A1 gene makes a protein (glucose transporter type I, GLUT1) that moves glucose across the blood-brain barrier. In G1D, there is a defect in the SLC2A1 gene that results in a protein that cannot move enough glucose across the blood-brain barrier; this results in carbon deprivation of the brain and, often, seizures and other disabilities. The Million Dollar Bike Ride has funded a pilot grant to Dr. Jason Park in the Department of Pathology and the Eugene McDermott Center for Human Growth at UT Southwestern Medical Center in a study for the “Identification of GLUT1 Activating Compounds in a Mouse Model”.

Beginning in 2021, this one-year grant will fund the identification of drugs which increase the availability and/or functional activity of GLUT1. This project is in collaboration with UT Southwestern faculty member, Dr. Juan Pascual. Previously, we performed high-throughput screening of 10,000 compounds to identify GLUT1 activators in a cancer cell line model. In this project we will identify the subset of activating compounds which improve the phenotype (behavior) in G1D mice. This animal study will identify GLUT1 activating drugs for future preclinical and clinical investigation. For many years, UT Southwestern Medical Center has been at the forefront of patient care, diagnostic testing, clinical trials, patient registry, laboratory research and medical and scientific training focused on G1D. 

Defining the cellular site of action of the Glut1 protein in Glucose Transporter 1 deficiency syndrome.

Awardee: Umrao Monani

Institution: Columbia University

Award Amount: $46,858

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Final Report Summary:

Glut1 DS is a debilitating pediatric brain disorder for which there are limited treatment options.  An important aspect of our work is to explore Glut1 repletion as a means to new treatments for Glut1 DS.  We previously showed that repletion is indeed effective in treating a Glut1 DS mouse model.  Translating these findings into a treatment for the human patient requires defining precisely which cells one must target in repletion therapies.  We hypothesized that brain endothelial cells are one such cell-type.  Our results from this MDBR project suggest that this is indeed the case.  Using a mouse model of Glut1 DS we have shown that introducing a Glut1 mutation specifically in brain endothelial cells triggers all of the major disease characteristics of Glut1 DS.  Moreover, our study reveals a specific type of brain endothelial cell – the tip cell – as being especially vulnerable to Glut1 mutations.  Tip cells are important in enabling the cerebral capillaries to proliferate and develop during the early postnatal period of life.  Reduced Glut1 within them prevents them from proliferating and giving rise to new blood vessels. This effect likely explains the inability of the Glut1 DS brain to extract adequate energy (glucose) from the blood circulation to sustain the nutritional needs of brain neurons.  This, in turn, provides one plausible basis for the neurodevelopmental delay and cognitive dysfunction in Glut1 DS. 

Our study has also confirmed a previous notion of the temporal requirements for Glut1.  The transporter is especially critical in the young postnatal brain when blood capillaries proliferate and neuronal circuits are established. Once the full complement of cerebral blood vessels and neuronal circuits are established, the requirements for Glut1 wane.  These results have important implications for future therapies and imply that treatments may not have to be chronic.  Finally, our investigation has revealed an important mediator of low Glut1 in the brain.  The mediator, a neurotrophic factor that is known to be important for neuronal health and survival, is greatly reduced in the Glut1 DS brain.  Restoring this factor may therefore constitute a novel or adjunct means of treating Glut1 DS in the future. 

Exploring a novel means of regulating Glut1 expression, and its therapeutic implications.

Awardee: Umrao Monani

Institution: Columbia University

Award Amount: $48,918

Funding Period: January 1, 2018 - December 31, 2018

Exploring the postnatal requirement of the brain for the Glut1 protein

Awardee: Umrao Monani

Institution: Columbia University

Award Amount: $40,000

Funding Period: January 1, 2017 - December 31, 2017