Systematic dissection of STXBP1 3’ UTR regulation to facilitate therapeutic development

Awardee: Xuebing Wu

Institution: Columbia University

Grant Amount: $75,460.00

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

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Summary:

Most STXBP1 mutations cause diseases by inactivating one copy of the gene. A potential therapy is to increase the expression of the remaining functional copy. By systematically mutating the noncoding regulatory sequences of STXBP1, we have identified promising targets of antisense oligos (ASOs) that can potently increase STXBP1 expression. We will test these ASOs in patient-derived neurons. If successful, these ASOs will be able to treat most STXBP1 patients, regardless the identity of the mutation.

Integrative omics: A novel approach to unravelling the complexity of STXBP1 encephalopathies

Awardee: Wendy Gold

Institution: The University of Sydney

Grant Amount: $75,460.00

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

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Summary:

The paucity of any disease modifying therapeutic entering the clinic for STXBP1 is largely due to an incomplete understanding of the complex underlying disease pathophysiology and function of STXBP1 and the lack of useful clinical biomarkers. Clinical biomarkers can predict disease state, disease severity, and treatment efficacy and have the potential to enable earlier diagnosis, support novel treatments, and serve as surrogate outcome measures of improvement in key characteristics of disease and associated comorbidities in clinical trials. Through a multi-disciplinary, integrative “omics” analysis of patient blood samples, we aim to identify clinical biomarkers, disease drivers, and therapeutic targets that will contribute to improved clinical monitoring, treatment options, and outcomes for STXBP1 encephalopathies.

Fingerprinting a multiomics biomarker profile in patients with STXBP1-RD

Awardee: Pasquale Striano

Institution: University of Genoa

Grant Amount: $87,125.00

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

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Summary:

Mutations in STXBP1 gene lead to a complex and severe neurodevelopmental disorder (STXBP1-related disorders, -RD), with symptoms including intellectual disability, epilepsy, movement and behavioral disorders, and gastrointestinal (GI) symptoms. There is no cure to date, but targeted therapies for STXBP1 are under investigation. However, the variability of symptoms and severity of STXBP1-RD makes it challenging to evaluate the effect of a treatment during a clinical trial, so that we need to identify biomarkers of the disease that can be measured. We will explore these biomarkers in the metabolome and gut microbiome of patients with STXBP1-RD. Gut microbiome is the pool of microorganisms that live in our gut and constantly interacts with our organism, including with our brain (gut-brain axis). Bacteria produce a lot of substances that join our metabolome, which is the whole pool of substances present in our blood and produced or introduced in our organism. Alterations in microbiome and metabolome can be identified in many health conditions, including autism and epilepsy. We aim to identify specific alterations in the microbiome and metabolome profiles of patients with STXBP1-RD, that can be further investigated as biomarkers and as therapeutic targets.

Assessing and quantifying gait problems in patients with STXBP1-related disorders using three-dimensional gait analysis

Awardee: Sarah Weckhuysen

Institution: VIB-CMN, University of Antwerp

Grant Amount: $87,125.00

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

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Summary:

While STXBP1-related disorders (STXBP-RD) were initially described as being associated with seizures and intellectual disability (ID), the phenotypic spectrum has since then considerably broadened. We now know it includes ID without seizures, behavioral problems such as autism, and a range of movement disorders with often prominent gait problems, which all significantly impact quality of life of both the patients and their caregivers. To date, treatment of STXBP1-RD is largely limited to seizure control and there is a lack of guidelines for multidisciplinary revalidation, including motor revalidation. In this project, we aim to combine our expertise with STXBP1-RD with the available expertise in our university with gait analysis in other neurodevelopmental syndromes such as Dravet syndrome, to characterize the nature and evolution of gait abnormalities and functional mobility in patients with in STXBP-RD. We will do this in a semi-quantitative way using three-dimensional gait analysis in a cohort of 30 children and adults with STXBP-RD. We intend to use the information obtained to develop guidelines for motor revalidation for individuals with STXBP1-RD. Furthermore, the data conducted in this study will contribute to the identification of non-seizure related clinical endpoints related to motor function, a crucial step to ensure successful clinical trials in the future.

Rescue of STXBP1 encephalopathies with small molecules in mouse models in vivo

Awardee: Jacqueline Burré

Institution: Weill Medical College of Cornell University

Grant Amount: $80,070

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

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Summary:

Mutations in STXBP1 lead to nerve cell dysfunction in the brain due to a reduction in functional STXBP1 amount. We had previously identified three small molecules (4-phenylbutyrate and two novel compounds) that restore nerve cell function in cultured mouse nerve cells and in live worm disease models. Yet, if and to what extent these small molecules revert the dysfunction in a brain remains unknown. Plus, it remains unclear if there is a critical period for when treatment needs to start, necessitating studies in a mouse model. We have established a mouse line with half of STXBP1 amount and are in the process of generating two additional mouse lines with missense mutations in STXBP1. We will use these mouse models of STXBP1 disorder to test the effect of our three small molecules in living animals. We will measure changes in seizure frequency, learning and memory, anxiety, hyperactivity and general movement, in addition to brain structure and development. To reveal if there is a critical period for when treatment needs to be started, we will determine the efficiency of the three small molecules in reversing the identified dysfunction when given to mice in utero, to newborn mice or to adolescent mice. Our study is significant because it further dissects the disease mechanism in a living animal, and because of its translational importance. Importantly, our studies will go hand-in-hand with the on-going 4-phenylbutyrate clinical trial at Weill Cornell Medicine, to achieve the most effect with the least amount of drug.

A novel mouse model for developing therapeutic approaches of STXBP1 encephalopathy

Awardee: Mingshan Xue

Institution: Baylor College of Medicine

Grant Amount: $80,070

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

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Summary:

STXBP1 encephalopathy is a severe neurodevelopmental disorder caused by heterozygous pathogenic variants in syntaxin-binding protein 1 (STXBP1). Both protein haploinsufficiency and dominant-negative mutations were identified as the disease mechanisms. Models of haploinsufficiency have been developed and validated and are currently being used to test potential disease-modifying therapies. However, dominant-negative mutations may require therapeutic approaches that are different from those for haploinsufficiency. Mammalian models carrying dominant-negative mutations are currently lacking. Thus, this project aims to develop and validate a new mouse model carrying a dominant-negative missense variant to fill this critical gap. This model will provide a new tool for preclinical evaluations of different therapies of STXBP1 encephalopathy and lead to a better understanding of the disease pathogenesis.

Discovering genetic modifiers of STXBP1 protein stability

Awardee: Jimmy L. Holder, Jr.

Institution: Baylor College of Medicine

Award Amount: $71,658

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

Circuit mechanism of STXPB1-encephalopathy interrogated using human brain organoids

Awardee: Christopher Makinson

Institution: Columbia University

Award Amount: $71,658

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

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Summary:

Mutations in the gene STXBP1 are associated with multiple diseases ranging from intellectual disability to severe epilepsy and developmental delay. To understand how STXBP1 mutations impair brain development we will generate 3D cellular structures derived from patient cells, called brain organoids, that resemble in many ways the developing human brain. Since previous studies have shown that STXBP1 is important for chemical signaling between brain cells, we will examine how STXBP1 mutations affect excitatory and inhibitory chemical signaling within brain organoids. We will also apply novel high throughput approaches to measure the activity of many brain cells at one time in order to gain insights into the effects of STXBP1 mutations on cellular network activity. These approaches will allow us to determine if STXBP1 deficiency has more pronounced effects on certain parts of the brain. Importantly, we will leverage these approaches to look at multiple time points to clarify how impairments evolve throughout early development and contribute to disease. Support from this pilot grant will allow us to establish a novel human cell model of STXBP1 encephalopathy, develop novel approaches to measure cellular activity in human brain organoids, and facilitate efforts to develop novel treatments for STXBP1 encephalopathy.

Rapid and unbiased in vivo screen for lead compounds that rescue STXBP1 dysfunction and subsequent in vitro validation in human neurons

Awardee: Matthijs Verhage

Institution: Rapid and unbiased in vivo screen for lead compounds that rescue STXBP1 dysfunction and subsequent in vitro validation in human neurons

Grant Amount: $69,588

Phenylbutyrate for STXBP1 Encephalopathy – A Pilot Study

Awardee: Zachary Grinspan

Institution: Weill Cornell Medicine

Grant Amount: $69,588