SCN2A loss of function, where a child has too little SCN2A, can lead to life-long difficulties in executing complex tasks. The first goal of this project is to determine whether similar difficulties can be observed in mice with Scn2a loss of function. Furthermore, we will evaluate whether deficits in these behaviors, as well as others we are exploring in the lab, are rescuable with gene therapy approaches that restore Scn2a levels to those found in neurotypical children. Here, our goal is to evaluate these therapies across a range of ages, with the goal of determining which aspects of behavior can be rescued later in life. This will help us understand developmental windows of opportunity for future clinical trials in children and, potentially, young adults.

Hundreds of different SCN2A genetic variants have been identified in children with autism or epilepsy. While some of them could be grouped into gain-of-function or loss-of-function variants, others are more complex. In particular, a splice-site variant of SCN2A has been identified in a child with autism. However, how this variant affects the Nav1.2 channel and neuronal activities is completely unknown, hindering the development of targeted interventions. The recent molecular and genomic revolution, including CRISPR-based genome editing technologies, offers enormous promise for treating genetic disorders like SCN2A-related disorders in an n=1 precision medicine manner. Funded by this inaugural Hodgkin-Huxley Research Award, Yang's lab will establish human-induced Pluripotent Stem Cells (hiPSCs) and rodent models of this SCN2A splice-site variant to understand disease mechanisms with clinical translation in mind. Disease phenotypes and global gene expression profiles will be studied to inform drug discovery. Yang lab will also develop cutting-edge gene therapy interventions aiming at correcting this SCN2A genetic variant in tiered model systems to bolster the translation potential of these transformative interventions. Moreover, Yang lab will be exploring next-gen chimeric mouse models with human cells to uncover in vivo phenotypes of human cells carrying SCN2A genetic variants to further increase the predictive value of preclinical disease models. These initial studies are expected to pave the way toward the ultimate clinical translation of promising interventions to improve the quality of life of individuals affected by SCN2A-related disorders.

Bridging the gap between ongoing knowledge and clinical practice – establishment of an international SCN2A database

The aim of this collaborative project between Rikke Møller's and Dennis Lal’s research teams is to establish and maintain an international SCN2A database that can be used to study genotype-phenotype relationships in SCN2A-related disorders. The database will help to record the number of individuals per pathology as well as their distribution. Furthermore, data from the database can help describing the natural history of SCN2A-related disorders, identifying outcome measures and put the basis for drug trial readiness. The specific aims of the study are: 1) To establish and maintain a database including clinical, genetic and epidemiological data of all published individuals with SCN2A-related disorders 2) Assess all reported variants and classify according to the American College of Medical Genetics and Genomics guidelines and 3) integrate all data in the existing SCN portal (scn-portal.broadinstitute.org) – an interactive website designed to provide updated and comprehensive information on SCN2A-related disorders.

Loss-of-function in the sodium channel NaV1.2 (SCN2A), where a child has too little channel function, is associated with autism spectrum disorders and intellectual disability, whereas gain-of-function in NaV1.2 is associated with seizure disorders. Surprisingly, a growing number of genetic variants in NaV1.2 seem to cause neurodevelopmental disorders without affecting electrical properties of the channel, suggesting that there are other mechanisms that could be contributing to SCN2A-related disorders. In order for neurons to function normally, NaV1.2 has to have normal functional properties and also has to be localized to the right place in the neuron. This process is controlled by a family of proteins called ankyrins, which anchor the channels in the correct place within the cell.

The goal of this project is to determine if SCN2A variants that were assumed to be associated with gain- or loss-of-function, but nevertheless appear completely normal via functional assays, hint that other channel properties, like its ability to be anchored in the membrane, are impaired. To test this, the Jenkins lab will use biochemical assays to determine the effects of five SCN2A variants with normal channel properties on their ability to bind ankyrins. Furthermore, we will use knockout-rescue-approaches in cultured mouse neurons to examine the localization of these channel variants within neurons. This work will not only shed light on mechanisms underlying important neurodevelopmental disorder-associated variants in SCN2A, but also provide insight into how rare variants could be contributing to the unique and variable phenotypes of SCN2A-associated disorders.

Dr. Samuel M. Young, Jr is a Professor and Vice Chair for Research in the Department of Anatomy and Cell Biology and is a Professor and Director of Molecular Auditory Research in the Department of Otolaryngology at the University of Iowa Carver College of Medicine. Dr. Young is an Iowa Distinguished Scholar awardee and is a member of the Iowa Neuroscience Institute and Pappajohn Biomedical Institute. Dr. Young’s research focuses on two major areas:1) the Molecular Principles of Auditory Information Processing and 2) Gene Therapy Approaches for Neurological Disorders. He published numerous high impact papers in these areas and has provisional patents filed for his gene therapy work. He serves on the editorial board for Journal of Physiology and Physiological Reviews and is a NIH standing study section member of the AUD study section. In addition, he serves as a scientific advisor to 2 biotech companies. Dr. Young is a first-generation college graduate and was a 4-year member of the Princeton University football team where he was a starting defensive tackle on the 1995 Ivy League Championship team.

Prior to joining the University of Iowa in 2017, he was an Independent Max Planck Research Group Leader of Research Group-Molecular Mechanisms for Synaptic Function at the then newly created Max Planck Florida Institute for Neuroscience (2010-2017). Dr. Young carried out 2 postdoctoral work on the biophysical and molecular mechanisms of synaptic transmission under the direction of Erwin Neher at the Max Planck Institute for Biophysical Chemistry in the Department of Membrane Biophysics in Goettingen, Germany. He carried out postdoctoral work on molecular mechanisms of synaptic transmission and the development of viral vectors for neuronal transduction under the direction of Charles F. Stevens, MD. PhD at the Howard Hughes Medical Institute and the Salk Institute in La Jolla, California. He carried out his doctoral work in the Curriculum in Genetics and Molecular Biology program at the University of North Carolina- Chapel Hill on the characterization of Adeno-associated virus type-2 site specific recombination under the direction of R. Jude Samulski, PhD in the Gene Therapy Center Dr. Young completed his undergraduate at Princeton University, graduating in 1996 with an A.B in Molecular Biology where he carried his senior thesis research on p53 cell cycle control under the direction of Arnold J. Levine, PhD.

Through the generous support of the FamilieSCN2A Foundation, my goal is to understand the neural mechanisms driving SCN2A loss of function (LOF) disorder and to develop treatments to help SCN2A LOF patients. My work focuses on modeling Scn2a loss of function in rats (Scn2a+/-), and I collaborate with other labs at UCSF (Dr. Kevin Bender and Dr. David Kastner). Together we study changes in cellular physiology, brain circuit activity patterns, and flexible learning in Scn2a+/- rats. We have found that spatial learning is impaired in Scn2a+/- rats and we are now measuring the brain activity patterns during learning in these rats. Two regions of the brain involved in spatial tasks are the hippocampus and prefrontal cortex, I am currently recording the neural activity in these two regions simultaneously during learning to identify mechanisms that underly these learning differences. We are also testing genetic rescue of Scn2a loss using a technique called CRISPR activation to increase Scn2a expression with the hopes of reversing the learning impairment in Scn2a+/- rats

Canine adenovirus type 2 (CAV-2) vectors serve as a potent tool for delivering genes of up to ~37kb in length, ensuring efficient and enduring expression of therapeutic genes. Notably, these vectors exhibit a high degree of selectivity for neuron transduction and are considered safe due to their low immunogenicity. In a collaborative effort, Ye-Eun from the Yang lab in the United States and Iria from the Kremer lab in France are working together to pioneer a novel gene delivery strategy using CAV-2 vectors containing SCN2A expression cassettes. Their research will assess the impact of this CAV-2 vector-mediated SCN2A gene delivery on rescuing behavioral and neuronal phenotypes in a mouse model of Scn2a deficiency. The anticipated outcome of this project is the development of an innovative gene delivery strategy capable of restoring SCN2A gene expression. With generous support from the FamilieSCN2A Foundation, this approach holds promise for clinical translation in future studies, offering a potential therapeutic avenue for individuals affected by SCN2A-related disorders.

The goal of the project is to understand the role a deep brain region known as the thalamus may play in the generation of epileptic episodes in SCN2A-related disorders (SRD). We will focus on the thalamus because it is known to play a central role in other types of seizure disorders, as well as in sleep, attention, and cognitive processing, which are all known to be affected in SRD patients. The central hypothesis is that a reduction in SCN2A gene function causes alterations in the neurons and neuronal circuits connecting the thalamus to the brain cortex. We will test this hypothesis by investigating the electrical properties of these neurons and circuits in mice lacking one copy of the SCN2A gene.

In children carrying SCN2A variants, impaired motor function, repetitive behaviors, social deficits, and altered sensitivity are physiological hallmarks. However, the basic cellular mechanisms that underlie these altered behaviors remain largely unknown. Xiaoling Chen, a postdoc researcher in the Yang lab, is investigating Scn2a-related disorders using in vivo calcium imaging of freely moving mice as well as brain organoids derived from human induced pluripotent stem cells. Funded by the Action Potential Award from the FamilieSCN2A Foundation, Xiaoling’s research aims to identify novel cellular targets for the development of next-generation interventions to alleviate behavioral impairments of affected children carrying SCN2A variants.

The SCN2A gene encodes the neuronal sodium channel Nav1.2, which is critical for the electrical activity of many types of neurons. Mutations in the gene alter the properties of the NaV1.2 channel, disrupting the function of single neurons and potentially leading to abnormal neuronal circuitry. Ultimately, these effects lead to epilepsy and/or ASD in affected patients. In this proposal, I will explore how alterations to the NaV1.2 channel affect the function of single neurons. Using computational models that simulate neuronal activity, we will study how each variant modulates single neuron activity and then simulate different drugs to see if they can reverse those effects.

Utilizing computational models to simulate the effects of SCN2A variants on neuronal excitability and testing potential therapeutics

NaV1.2 sodium channels encoded by SCN2A are expressed throughout the brain. One region where NaV1.2 channels are expressed at very high levels is the cerebellum. The cerebellum is involved in motor control, motor learning, and—recently identified—various aspects of social interaction typically seen in children affected by SCN2A-related disorders. With the help of the FamilieSCN2A Foundation, our goal here is to understand how cerebellar function is altered in mouse models that lack one Scn2a allele, which models aspects of loss-of-function in SCN2A. In doing so, we hope not only to gain a better understanding of how SCN2A-related disorders affect the brain, but also to develop quantitative biomarkers that can be utilized to evaluate therapeutics.

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★ $50,000 – Research Grant (1 year project)

★ Understanding cellular and behavioral effects of Scn2a haploinsufficiency in cerebellar circuits

SCN2A variants affect children in a variety of ways. In particular, SCN2A loss-of-function or nonsense variants, which lead to SCN2A deficiency, are strongly associated with neurodevelopmental disorders such as autism spectrum disorder (ASD). Yang lab has been working on a novel Scn2a deficient mouse model, aiming to study mechanisms underlying Scn2a deficiency and test for novel interventions. Muriel Eaton, a PhD candidate in Yang lab, has been exploring the Scn2a-deficient mouse model during her training, and already discovered many characteristics of this mouse model including profound social deficits and other neurodevelopmental abnormalities. For the next phase of their research, they will study how to reverse Scn2a-deficits in the mouse model and to develop potential gene therapy for SCN2A-related disorders, thanks to research funding particularly this grant from FamilieSCN2A Foundation.

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★ $50,000 – Research Grant (1 year project)

★ Advancing gene therapy in a preclinical mouse model of SCN2A deficiency

"Our lab focuses on the study of the genetics underlying epilepsy and neurodevelopmental disorders. We study which genetic variants can cause disease and how they can drive disease prognosis, comorbidity, and drug response. Specifically, our research aims to: 1) Unveil the effect of common, rare and structural genetic variation in cases and controls collected from an international collaborative network. 2) Develop tools for variant interpretation by integrating large scale data derived from patients and the general population. 3) Study epilepsy and neurodevelopmental disorders presentation in Latin America. South American countries have a higher prevalence of epilepsy, yet they are underrepresented in current genetic studies. We study Mapuche individuals, Chilean epilepsy cases and controls and patients with SCN2A-related disorders. Overall, our lab is growing a research profile focusing on interdisciplinary genomics and data science to bridge novel genetic knowledge with clinical practice – paving the way for personalized medicine with a particular focus on Latin American populations".

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★ $50,000 – Research Grant (1 year project)

★ Integrating clinical and genetic variables to model SCN2A variant pathogenicity and outcomes

*UPDATE December 2019*
In the past, anticonvulsant medications have not been tested for seizure reduction in mouse models of genetic epilepsy. Instead pre-clinical medication trials look at reduction of seizures induced with chemical or electrical stimulation. Recently Dr. Jennifer Kearney's lab at Northwestern University made a new mouse mode of SCN2A-related epilepsy. As part of her FamilieSCN2A Foundation Action Potential Grant, Dr. Sunita Misra is studying seizures in this new mouse model. Sunita's ongoing work shows that seizures in the new Scn2a mouse model are different than seizures caused by chemical or electrical stimulation. These differences may partly explain why many children with SCN2A-related early onset epilepsy have seizures that are difficult to control with current anticonvulsant medications. Further work will look at the effectiveness of FDA approved anticonvulsant medications at blocking seizures in the SCN2A mouse model.

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★ $50,000 – Research Grant (1 year project)

★ Downstream Effects of SCN2A-Related Epilepsy

SCN2A dysfunction changes the way brain cells communicate both electrically and chemically leading to epilepsy and neuropsychological comorbidities. I will use EEG to identify seizure patterns and the role of sleep on seizures in a new mouse model of SCN2A-related epilepsy. Then I will look at neurotransmitter levels in the brains of mice with SCN2A-related epilepsy. I will use drugs that target the abnormal neurotransmitter levels to improve abnormal electrical and chemical signaling in the brain. This work may identify new druggable targets for better control of epilepsy and associated comorbidities in SCN2A-related epilepsy.