Phenotypic characterization of FSHD-like FLExDUX4 minipigs
Investigator: Peter L. Jones, PhD, University of Nevada, Reno School of Medicine
All forms of FSHD are caused by misexpression of DUX4 (double homeobox protein 4) in skeletal muscles; thus, the primary therapeutic targets in FSHD are the DUX4 gene, DUX4-fl mRNA and DUX4-FL protein. In addition, cell therapy may be applicable for boosting muscle mass and replacement in those affected, either on its own or in combination with a DUX4-targeted therapy.
Therefore, with the burgeoning development of DUX4-targeted therapeutics and cell therapy approaches, there is a pressing need for a large animal model of FSHD to translate efficacious dosing and durability of experimental therapeutics while assessing toxicity and immune responses. Indeed, failure to properly translate effective dosing from mouse models, with 1/1500-1/5500 the body mass of humans and very different physiology, can lead to failure of a clinical trial at one extreme, and severe adverse events at the other.
Fortunately, miniature pigs (minipigs) have come to fill this gap in large animal human disease modeling, rapidly becoming established in translational research because they offer lower operating costs, are more ethically acceptable, and, most importantly, they share many similarities to humans in terms of size, physiology, anatomy, metabolic profile, and lifespan. Therefore, we chose the Göttingen minipig as the best model system for creating large animal models of FSHD for use in preclinical testing of potential therapeutics.
Building on our development of the first phenotypic FSHD-like transgenic FLExDUX4 mouse models, we have successfully generated the first transgenic FLExDUX4 minipigs. We have confirmed that the cells engineered for this model produce viable minipigs that express DUX4 mRNA, protein, and porcine target genes in skeletal muscles upon tamoxifen induction. However, beyond proof-of-concept that our transgenic approach is functional in vivo, there are still a number of variables (e.g., transgene copy number, gender, etc…) that have not been addressed.
In addition, we need to determine the experimental conditions for generating reproducible phenotype, determine the short-term natural history of the DUX4-mediated pathology, develop the metrics for assessing the model, and characterize the model so it can be properly utilized for preclinical testing of DUX4-targeted and cell-based therapeutics.
Thus, the goal of this proposal is to help generate the animals and data necessary to begin to properly validate the FLExDUX4 minipig as a reproducible FSHD-like model suitable for therapeutic development and preclinical testing.