Mitochondrial Transfer of the Mutant Human ND6T14484C Gene Causes Visual Loss and Optic Neuropathy

Purpose: To evaluate the long-term effects of mitochondrial gene transfer of mutant human NADH ubiquinone oxidoreductase subunit VI (hND6T14484C) in the mouse eye.

Methods: Adult mice were injected intravitreally with mitochondrial-targeted adeno-associated virus carrying either hND6T14484C or mitochondrial encoded mCherry. The delivery and expression of the interest gene were detected by polymerase chain reaction (PCR), quantitative PCR (qPCR), and immunostaining. The pathologic effects of the mutant gene in live mice were assessed with RNA-seq, serial spectral domain optical coherence tomography (SD-OCT), and pattern electroretinogram (PERG).

Results: Delivered hND6 was found 30-fold greater than endogenous mouse ND6 in microdissected retinal ganglion cells of hND6-injected mice. Compared to controls injected with mCherry, PERG amplitude of hND6 mice dropped significantly at 3 (P = 0.0023), 6 (P = 0.0058), and 15 (P = 0.031) months after injection. SD-OCT revealed swelling of the optic nerve head followed by the progressive retinal and optic nerve atrophy in hND6 mice. Furthermore, RNA-seq data showed a change in 381 transcripts' expression in these mice compared to mCherry mice. Postmortem analysis showed hND6 mice had marked atrophy of the entire optic nerve, from the globe to the optic chiasm, and a significant loss of retinal ganglion cells compared to age-matched control mice (P = 1.7E-9).

Conclusions: Delivered hND6T14484C induces visual loss and optic neuropathy in mice, the hallmarks of human Leber's hereditary optic neuropathy (LHON).

Translational relevance: Results from this study will help establish a novel strategy not only to generate an LHON animal model but also to provide a potential to treat this or any other mitochondrial diseases.