Adeno-associated Virus 9 Mediated FKRP Gene Therapy Restores Functional Glycosylation of α-dystroglycan and Improves Muscle Functions

Abstract

Mutations in the FKRP gene are associated with a wide range of muscular dystrophies from mild limb-girdle muscular dystrophy (LGMD) 2I to severe Walker-Warburg syndrome and muscle-eye-brain disease. The characteristic biochemical feature of these diseases is the hypoglycosylation of α-dystroglycan (α-DG). Currently there is no effective treatment available. In this study, we examined the adeno-associated virus serotype 9 vector (AAV9)-mediated gene therapy in the FKRP mutant mouse model with a proline to leucine missense mutation (P448L). Our results showed that intraperitoneal administration of AAV9-FKRP resulted in systemic FKRP expression in all striated muscles examined with the highest levels in cardiac muscle. Consistent with our previous observations, FKRP protein is localized in the Golgi apparatus in myofibers. Expression of FKRP consequently restored functional glycosylation of α-DG in the skeletal and cardiac muscles. Significant improvement in dystrophic pathology, serum creatine kinase levels and muscle function was observed. Only limited FKRP transgene expression was detected in kidney and liver with no detectable toxicity. Our results provided evidence for the utility of AAV-mediated gene replacement therapy for FKRP-related muscular dystrophies.

Adeno-Associated Virus-Mediated Overexpression of LARGE Rescues α-Dystroglycan Function in Dystrophic Mice with Mutations in the Fukutin-Related Protein

“…S2), confirming the localization of LARGE in the Golgi apparatus (Brockington et al, 2005;Grewal et al, 2005). The same series of experiments was carried out for AAV9-mediated FKRP expression, elucidating similar results reported previously (Xu et al, 2013) (Supplementary Fig. S3).…”

“…We have previously constructed an AAV9-FKRP recombinant vector expressing wild-type codon-optimized FKRP (Xu et al, 2013). Local and systemic delivery of AAV9-FKRP mediated effective expression of FKRP in both skeletal and, more notably, cardiac muscle of the FKRP P448L mutant mice.…”

B4GALNT2 (GALGT2) Gene Therapy Reduces Skeletal Muscle Pathology in the FKRP P448L Mouse Model of Limb Girdle Muscular Dystrophy 2I

“…However, this was not evident on most treated myofibers by immunostaining, as would be expected, for example, in FKRP gene replacement therapies. 64,65 Nevertheless, changed functional glycosylation of a dystroglycan may still also be a factor in the therapeutic mechanism of GALGT2.…”

The potential of adeno-associated viral vectors for gene delivery to muscle tissue

“…Moreover, rAAV9 following intravenous injection leads to robust and sustained whole body skeletal muscle transduction in neonatal dogs without pharmacological intervention or immune suppression [44]. The systemic muscle gene transfer by rAAV8 and rAAV9 vectors has shown great promise in the treatment of several muscle diseases in animal models, such as DMD [45,46], LGMD [47] and Pompe disease [48]. In addition, rAAV9 more efficiently transduces cardiac muscle than rAAV serotypes 4, 6, 7 and 8 after intravenous injection to mice, leading to the highest transgene expression in heart [49,50].…”