Validating tRNA Viruses to Target SCN2A-Related Autism Phenotypes
Abstract
The SCN2A gene encodes a protein called a sodium channel that regulates the balance of excitatory activity in the human brain. Mutations in SCN2A are associated with autism spectrum disorders (ASD). SCN2A was one of the earliest genes associated with ASD, and up to half of patients with SCN2A mutations are autistic. Mutations in the SCN2A gene can put in the wrong type of amino acid, resulting in dysfunctional sodium channel protein, or they can put in a stop signal that introduces an abnormal premature termination codon (PTC) within the channel’s reading frame, much like a misplaced period in the middle of a sentence. Making less than the entire protein (due to the stop signal) reduces the amount of functional protein so much that it causes widespread abnormal brain activity. This results in abnormal brain development, autism, and seizures. Unfortunately, there are no available mouse models of SCN2A PTC mutations that could help spur a better understanding of autism and the development of therapeutic strategies for clinical management. Furthermore, existing small molecule (daily pill) therapies for PTC-associated diseases replace the stop signal with a wrong amino acid (which is not tolerated by SCN2A) and are clinically ineffective. Gene editing approaches like CRISPR can target unintended genes, and any such effort would require specific validation for each of the many individual PTC mutations, which is an onerous task. New tools and therapeutic strategies are needed for the treatment of autism-associated SCN2A PTCs. Our group at the University of Iowa has developed a novel gene-correction approach which uses a genetically engineered transfer RNA (ACE tRNA) to repair PTCs. Our highly innovative method works at the source of the mutation to correct the mistaken genetic code and put the correct amino acid in the correct place in the protein. We have identified ACE tRNA sequences for the repair of every known human PTC, a potentially game-changing discovery. We have made two new mouse models of SCN2A PTCs, Y84X and R1626X, which match mutations found in autistic SCN2A patients. We will analyze the sodium channel activity and behaviors of these mice, including both male and female mice, since there are known sex differences in autism symptoms and in co-occurring conditions. We will then determine whether we can correct SCN2A PTCs in neurons from these mice. We will also test whether we can correct PTCs in human neurons generated from autistic SCN2A patients. This project addresses three FY22 ARP Idea Development Award Area(s) of Interest: (1) mechanisms underlying sex differences in ASD; (2) mechanisms underlying conditions co-occurring with ASD; and (3) assessment of novel therapeutics using valid preclinical models. This project will have multiple high-impact outcomes for ASD research and, hopefully, for the lives of autistic individuals and their families. For basic scientists, our SCN2A PTC mice will be an invaluable resource for the ASD research community. These models will advance our understanding of the molecules and brain circuits that underlie ASD and will serve as a preclinical testbed for future treatments. In the short term, our studies of mice carrying human SCN2A patient mutations will help us understand how ASD develops in the context of these mutations and may help reveal some of molecular basis for sex differences in ASD manifestation, as well as some of the co-occurring conditions frequently observed alongside ASD, specifically sleep disturbances and seizures. Similarly, our studies in human-derived neurons will help us understand on a basic level what goes wrong when these mutations occur, and develop a novel method to fix them. -In the long term, our experiments will provide the proof-of-concept data necessary to move forward with clinical trials using ACE tRNA as a gene therapy. This work will enable the development of delivery modes for the correction of autism-a
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 04, 2024
- Source ID
- HT94252310279
Entities
People
- Aislinn Williams
Organizations
- United States Army
- University of Iowa