An animal model of PDH deficiency using AAV8-siRNA vector-mediated knockdown of pyruvate dehydrogenase E1α

We evaluated the feasibility of self-complementary adeno-associated virus (scAAV) vector-mediated knockdown of the pyruvate dehydrogenase complex using small interfering RNAs directed against the E1α subunit gene (PDHA1). AAV serotype 8 was used to stereotaxically deliver scAAV8-si3-PDHA1-Enhanced Green Fluorescent Protein (knockdown) or scAAV8-EGFP (control) vectors into the right striatum and substantia nigra of rats. Rotational asymmetry was employed to quantify abnormal rotation following neurodegeneration in the nigrostriatal system. By 20 weeks after surgery, the siRNA-injected rats exhibited higher contralateral rotation during the first 10 min following amphetamine administration and lower 90-min total rotations (p ≤ 0.05). Expression of PDC E1α, E1β and E2 subunits in striatum was decreased (p ≤ 0.05) in the siRNA-injected striatum after 14 weeks. By week 25, both PDC activity and expression of E1α were lower (p ≤ 0.05) in siRNA-injected striata compared to controls. E1α expression was associated with PDC activity (R2 = 0.48; p = 0.006) and modestly associated with counterclockwise rotation (R2 = 0.51;p = 0.07). The use of tyrosine-mutant scAAV8 vectors resulted in ~ 17-fold increase in transduction efficiency of rat striatal neurons in vivo. We conclude that scAAV8-siRNA vector-mediated knockdown of PDC E1α in brain regions typically affected in humans with PDC deficiency results in a reproducible biochemical and clinical phenotype in rats that may be further enhanced with the use of tyrosine-mutant vectors.