Mutant mitochondrial helicase Twinkle causes multiple mtDNA deletions and a late-onset mitochondrial disease in mice

Abstract

Defects of mitochondrial DNA (mtDNA) maintenance have recently been associated with inherited neurodegenerative and muscle diseases and the aging process. Twinkle is a nuclear-encoded mtDNA helicase, dominant mutations of which cause adult-onset progressive external ophthalmoplegia (PEO) with multiple mtDNA deletions. We have generated transgenic mice expressing mouse Twinkle with PEO patient mutations. Multiple mtDNA deletions accumulate in the tissues of these mice, resulting in progressive respiratory dysfunction and chronic late-onset mitochondrial disease starting at 1 year of age. The muscles of the mice faithfully replicate all of the key histological, genetic, and biochemical features of PEO patients. Furthermore, the mice have progressive deficiency of cytochrome c oxidase in distinct neuronal populations. These ''deletor'' mice do not, however, show premature aging, indicating that subtle accumulation of mtDNA deletions and progressive respiratory chain dysfunction are not sufficient to accelerate aging. This model is a valuable tool for therapy development and testing for adult-onset mitochondrial disorders. mouse model ͉ progressive external ophthalmoplegia ͉ mitochondrial DNA replication

Restoring mitochondrial DNA copy number preserves mitochondrial function and delays vascular aging in mice

“…Twinkle unwinds short stretches of dsDNA in the 5′–3′ direction in preparation for mtDNA replication, and alterations in Twinkle expression lead to changes in mtCN (Jemt et al., 2011). Twinkle ‐/‐ mice show multiple mtDNA deletions and develop progressive respiratory dysfunction and chronic late‐onset mitochondrial disease (Tyynismaa et al., 2005). In contrast, mice overexpressing Twinkle show increased mtCN (Tyynismaa et al., 2004), which could potentially increase mitochondrial respiration.…”

Tissue- and cell-type–specific manifestations of heteroplasmic mtDNA 3243A>G mutation in human induced pluripotent stem cell-derived disease model

“…Primary antibodies were against Tra1-60 (1:40, ab90232, Millipore), SSEA4 (1:1,000, ab90231, Millipore), Nanog Western blot analysis was done from protein lysates from cells with precast TGX gradient gels (BioRad) according to the manufacturer's protocol. COX-SDH histochemical activity analyses from cryosections were done as previously published (24).…”

“…Heteroplasmic mice carrying two normal mtDNA variants (18) or randomly occurring mutations isolated from somatic tissues (19)(20)(21)(22) have been generated by cytoplast fusion to zygotes. Further, random mtDNA mutagenesis has been induced by manipulating nuclear-encoded mtDNA maintenance genes (23)(24)(25)(26). However, transgenic mice, carrying human disease-associated mt-tRNA mutations, do not exist.…”

MtDNA mutagenesis impairs elimination of mitochondria during erythroid maturation leading to enhanced erythrocyte destruction

“…Several hypotheses could account for the effect: (1) the causative mtDNA mutation is selected against in proliferating cells, as occurs in Pearson syndrome patients that survive the anaemia; (2) mtDNA mutagenesis is slowly progressive and/or does not affect the erythroid cells (adult-onset mtDNA maintenance disorders) (3) the specific mitochondrial pathway is redundant 11,12 . For example, Deletor mice 12 carry a mutation in the nuclear-encoded replicative Twinkle helicase, leading to subtle progressive accumulation of secondary multiple mtDNA deletions after 1 year of age. These mice only show mtDNA mutagenesis in postmitotic tissues, not in SSCs, and accordingly do not develop anaemia 9 .…”