CRISPR–Cas-inspired activator rescues Dravet syndrome mice

Genetic haploinsufficiency – where loss of one functional gene copy halves protein output – underlies thousands of diseases, yet few therapeutic platforms can safely restore expression, particularly in the brain. Present approaches, such as gene supplementation, transcriptional activation with CRISPR-Cas tools, and antisense oligonucleotides, each come with trade-offs. These range from cargo size constraints and the risk of permanent genomic changes to delivery challenges in neurological tissue.

The CIRTS platform evades these constraints by assembling entirely human protein components into a guide RNA-directed system, avoiding the immunogenicity and size limitations of microbial CRISPR systems while retaining programmable RNA targeting. Using systematic screening and engineering of eukaryotic initiation factor domains, the authors identified CIRTS-4GT3 – a 601-amino-acid fusion incorporating the core eIF4a- and eIF3-binding domains of human eIF4GI – that drives up to 100% increases in target protein from endogenous SCN1a, CHD2, and ARID1B transcripts in cellulo.

Crucially, CIRTS-4GT3 acts at the translational level without altering mRNA abundance, meaning protein output scales for each cell's native transcript levels. When packaged in AAV9 and delivered by intracerebroventricular injection to neonatal SCN1a-haploinsufficient mice, the activator produced a modest (~25%) NaV1.1 increase in cortical and hippocampal tissue – yet this was sufficient to reduce female mortality from 50% to 13% and raise hyperthermic seizure thresholds significantly in males. Because the system targets mRNA rather than DNA, it inherently restricts activation to cells that express the transcript, avoiding the toxicity previously reported with pan-neuronal SCN1a gene replacement.

The study was led by Riley Sinnott and Bryan Dickinson at the University of Chicago and the Chan Zuckerberg Biohub Chicago. It was published in Nucleic Acids Research on 16 February 2026.