Nouraein, S. | bioRxiv Science

bioRxiv2023

Acoustically Targeted Noninvasive Gene Therapy in Large Brain Regions

Focused Ultrasound Blood-Brain Barrier Opening (FUS-BBBO) can deliver adeno-associated viral vectors (AAVs) to treat genetic disorders of the brain. However, such disorders often affect large brain regions. Moreover, the applicability of FUS-BBBO in the treatment of brain-wide genetic disorders has not yet been evaluated. Herein, we evaluated the transduction efficiency and safety of opening up to 105 sites simultaneously. Increasing the number of targeted sites increased gene delivery efficiency at each site. We achieved transduction of up to 60% of brain cells with comparable efficiency in the majority of the brain regions. Furthermore, gene delivery with FUS-BBBO was safe even when all 105 sites were targeted simultaneously without negative effects on animal weight, neuronal loss, or astrocyte activation. To evaluate the application of multi-site FUS-BBBO for gene therapy, we used it for gene editing using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated 9 (Cas9) system, and found effective gene editing, but also a loss of neurons at the targeted sites. Overall, this study provides a brain-wide map of transduction efficiency and the first example of gene editing after site-specific noninvasive gene delivery to a large brain region.

bioengineering↗

bioRxiv2022

Engineered Serum Markers for Noninvasive Monitoring of Gene Expression in the Brain

Noninvasive efforts to map brain gene expression have been hampered by low sensitivity and limited access to the brain. Here, we introduce a new platform that enables multiplexed, noninvasive, and site-specific monitoring of brain gene expression through a novel class of engineered reporters called Released Markers of Activity (RMAs). Instead of detecting gene expression in the less accessible brain, RMA reporters exit from a known brain region into the blood, where they can be easily measured with biochemical techniques. Expressing RMAs at a single brain site, typically covering [~]1% of the brain volume, provides up to a 39,000-fold signal increase over the baseline in vivo. Further, expression of RMAs in as few as several hundred neurons was sufficient for their reliable detection. When placed under a promoter upregulated by neuronal activity, RMAs could be used to measure neuronal activity in specific brain regions with a simple blood draw. We found that chemogenetic activation of cells expressing Fos-responsive RMA increased serum levels of RMA over 4-fold compared to non-activated controls. By contrast, a control RMA expressed under a constitutive neuronal promoter did not show such upregulation, demonstrating multiplexed ratiometric measurement with RMAs and proving specificity of neuronal activity discrimination. Together, our study pioneers a new noninvasive paradigm for repeatable and multiplexed monitoring of gene expression in an intact brain with sensitivity that is currently unavailable through other noninvasive gene expression reporter systems.

neuroscience↗