In vivo implementation of hypothalamus-specific exosomes to reverse the impact of Snord116 deletion

Funding Summary

Dr. Lee and colleagues have been investigating the use of exosomes (small vesicles released from cells) to carry PWS genes to the hypothalamus in PWS mouse models, as a first step to gene therapy for PWS.  Here they will use their engineered exosomes to test whether delivery of the PWS genes can reverse the PWS features seen in the mice.

Lay Abstract

In the first application funded by FPWR, we proposed to engineer extracellular vesicles (EVs) or exosomes to deliver SNORD116 to the brain. Exosomes are lipid-based extracellular vesicles that are secreted by cells and used to communicate with other cells via their vesicle-bound cargo, which can include RNAs, DNAs, proteins, or lipids. Exosomes have attracted much attention over the past several years as an effective pharmacological delivery system due to their relatively small size, ideally suited for the transport of RNAs and DNAs, the absence of an acute immune response that is commonly associated with other delivery systems available for clinical use, and their ability to cross the blood-brain and placental barriers readily. Also, exosomes can be modified or engineered to alter their recognition by different types of tissues and cells. Most importantly, because exosomes are not viral vectors and do not contain synthetic vector DNA, they have high translational potential in humans. We first identified protein species that may be different between PWS and control human brains. We then leveraged these findings to modify exosomes so that they expressed PWS-specific proteins on their surface. We successfully implemented this technique and showed that our modified exosomes could deliver SNORD116 to the brain of mice.
The goal for the 2023 FPWR application is simple. We propose to implement these exosomes in conditions relevant to PWS and assess whether they can mitigate or reverse the physiological and behavioral effects of Snord116 deficiency. First, by exposing the developing mouse brain to exosome-delivered Snord116, we will impede perinatal growth deficiencies observed in Snord116 deletion mice. Pregnant mice will be injected with mouse Snord116-carrying exosomes, and gene expression and physiological changes in the pups will be measured. Second, ten-week-old mice will be exposed to exosome-delivered Snord116, and their gene expression and physiological response will be measured. In both cases, exosomes can cross placental and blood-brain barriers.
Successful implementation of our exosome technology will justify its application in non-human primates and, ultimately, in PWS patients in the next several years.