Mitochondrial Gene Therapy Improves Respiration, Biogenesis, and Transcription in G11778A Leber's Hereditary Optic Neuropathy and T8993G Leigh's Syndrome Cells

Abstract

Many incurable mitochondrial disorders result from mutant mitochondrial DNA (mtDNA) and impaired respiration. Leigh's syndrome (LS) is a fatal neurodegenerative disorder of infants, and Leber's hereditary optic neuropathy (LHON) causes blindness in young adults. Treatment of LHON and LS cells harboring G11778A and T8993G mutant mtDNA, respectively, by > 90%, with healthy donor mtDNA complexed with recombinant human mitochondrial transcription factor A (rhTFAM), improved mitochondrial respiration by *1.2-fold in LHON cells and restored > 50% ATP synthase function in LS cells. Mitochondrial replication, transcription, and translation of key respiratory genes and proteins were increased in the short term. Increased NRF1, TFAMB1, and TFAMA expression alluded to the activation of mitochondrial biogenesis as a mechanism for improving mitochondrial respiration. These results represent the development of a therapeutic approach for LHON and LS patients in the near future.

Leber's Hereditary Optic Neuropathy Associated with the m.10197G>A Mutation

“…The mtND3*10197A (m.10197G>A) mutation has been identified as the novel causative gene in Chinese patients with LHON and dystonia [1]. The m.10197G>A mutation also has been detected in patients with bilateral basal ganglia lesions and Leigh syndrome [2][3][4]. This mutation substitutes a threonine for an alanine at codon 47 of MTND3.…”

Mitochondrial Genetic Manipulation

“…With this strategy, the mitochondriadeficient phenotype of Parkinson's disease cybrids was reportedly rescued upon colocalization of MTD-TFAM carrying human mtDNA with mitochondria (Keeney et al 2009). Also, partial restoration of organelle function in human cells carrying mitochondrial mutations was achieved by targeting healthy donor mtDNA loaded on MTD-TFAM (Iyer et al 2012a). However, the MTD-TFAM protein alone promoted a similar boosting of mitochondrial functions in cell cultures and mice Keeney et al 2009;Thomas et al 2011).…”

Mitochondrial disorders: aetiologies, models systems, and candidate therapies

“…Other cell types have been utilised to generate cellular models of mitochondrial disease, including primary cells such as fibroblasts from skin biopsies [43,44] or induced pluripotent stem (iPS) cells, thereby recapitulating mitochondrial disorders in patient-derived cells [45]. Although there are many applications for iPS cells, which are stem cells that have undergone exogenously directed reprogramming from nonpluripotent cells and that can subsequently be differentiated into cell types relevant to particular disease pathologies, limitations with the technology are evident.…”

“…The recombinant human mitochondrial transcription factor A protein (TFAM), which itself stimulates mitochondrial biogenesis, has been used to deliver mtDNA to mitochondria, a strategy termed 'protofection'. Wild type mtDNA was delivered to near homoplasmic mutant mtDNA cybrid lines generated using platelets from patients with LHON or PD and primary fibroblasts from a patient with Leigh syndrome [44,68], resulting in significant improvements in mitochondrial respiration, biogenesis, and transcription in treated cells.…”

“…For some mitochondrial disorders, including LHON, mtDNA mutations are often homoplasmic, making such an approach inappropriate. As outlined above, delivery of wild type mtDNA also represents a rational therapeutic strategy being pursued [44] and may be used to modulate levels of heteroplasmy.…”