Regulated coexpression of PrP from different species in mice impacts the replication and host range properties of prion strains

Authors: DEFRANCO, JOSEPH - Colorado State University; Bian, Jifeng; KIM, SEHUN - Colorado State University; ATKINSON, ZOE - Colorado State University; CROWELL, JENNA - Colorado State University; KANG, HAE-EUN - Animal And Plant Quarantine Agency; BODROGI, HANNAH - Colorado State University; CHRISTIANSEN, JEFFREY - Animal And Plant Health Inspection Services (APHIS), National Wildlife Center; DIAZ-DOMINGUEZ, CARLOS - Colorado State University; TELLING, GLENN - Colorado State University

Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2025
Publication Date: 11/26/2025
Citation: Defranco, J.P., Bian, J., Kim, S., Atkinson, Z.N., Crowell, J., Kang, H., Bodrogi, H.O., Christiansen, J.R., Diaz-Dominguez, C.M., Telling, G.C. 2025. Regulated coexpression of PrP from different species in mice impacts the replication and host range properties of prion strains. Proceedings of the National Academy of Sciences (PNAS). https://doi.org/10.1073/pnas.2515284122.
DOI: https://doi.org/10.1073/pnas.2515284122

Interpretive Summary: Prion diseases are caused by a misfolded version of a normal protein in the body. This misfolded form, called a prion, can trigger other normal proteins to also misfold, spreading disease in the brain like Chronic Wasting Disease (CWD) in cervids and Creutzfeldt-Jakob Disease in humans. Stopping this chain reaction is key to developing treatments, but we still don’t fully understand how the normal protein changes into the harmful form. To tackle this, we developed a unique platform using gene-targeted (Gt) mice. These mice express prion proteins from different species—such as mouse, deer, or elk—but under identical genetic and physiological conditions. This lets us study the effects of protein sequence alone, without the confounding variables of different genetic backgrounds. We then created hybrid mice that co-express two versions of the prion protein, like mouse and deer or mouse and elk. This gave us a way to observe how these proteins interact in a living system. What we found was striking: in some cases, the mouse prion protein seemed to interfere with the disease-causing version from deer or elk. One line of hybrid mice was even completely resistant to infection with CWD. This tells us that certain combinations of prion protein sequences can actually block disease, acting as a kind of natural defense. Our work not only uncovers new insights into how prion diseases begin, but also opens up the possibility of using these dominant-negative combinations as the basis for future therapies. It's a promising step toward stopping prion diseases at their source.

Technical Abstract: Prions are conformationally altered, infectious counterparts of host-encoded proteins. Designing therapeutics requires impeding the conversion of the cellular prion protein (PrPC) to the disease-causing isoform, PrPSc; however, the underlying mechanisms controlling this process are still poorly understood. We have developed an innovative platform to assess the prion conversion efficiencies within mice that express different PrPC primary structures. Our approach rests on the creation of gene-targeted (Gt) mice in which physiological expression of PrPC from various species, including mouse, deer, and elk, is accurately controlled by the endogenous mouse Prnp gene in an invariant inbred genetic background. Interbreeding these Gt lines results in offspring that coexpress different PrP primary structures allowing to explore their cooperative or antagonistic effects during prion infection. Here we describe the results of our initial studies in which we developed Gt hybrids expressing mouse and either deer or elk PrP, referred to as GtQ/M and GtE/M, respectively. Infections of GtE/M and GtQ/M mice with cervid and mouse strains not only demonstrate proof of principle for our approach but leveraging these in vivo studies with species-specific antibodies and cell infection studies provide remarkable new insights into prion conformational conversion. Additionally, the coexpression mouse PrPC rendered GtQ/M completely resistant to deer/moose CWD, demonstrating that Gt mice can be used to screen for dominant-negative PrP combinations for therapeutic purposes.