A Phenotype-Driven Approach to Generate Mouse Models with Pathogenic mtDNA Mutations Causing Mitochondrial Disease

Kauppila, Johanna H.K.; Baines, Holly L.; Bratić, Ana; Simard, Marie‐Lune; Freyer, Christoph; Mourier, Arnaud; Stamp, Craig; Filograna, Roberta; Larsson, Nils‐Göran; Greaves, Laura C.; Stewart, James B.

doi:10.1016/j.celrep.2016.08.037

Cited by 110 publications

(149 citation statements)

References 48 publications

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“…The observed level of accumulation of variants present in blood should not be seen as a baseline level, caused by an absence of purifying selection. As a matter of fact, the low number of variants detected in blood samples could be due to selection that acts during life thanks to the rapid turnover of this cell type as already reported in previously published works (Larsson et al, 1990;Ciafaloni et al, 1991;Rajasimha et al, 2008;Pallotti et al, 2014;Kauppila et al, 2016). Interestingly, between PBs, the intra-individual approach indicated unequal accumulation as one thousand times more likely (BF = 9.2e −04 ), but when looking across individuals the result was inverted, and equal accumulation was five times more likely (BF = 5.03).…”

Section: Quality and Quantity Of Mtdna Variants Across Cell Typesmentioning

confidence: 85%

Intra-individual purifying selection on mitochondrial DNA variants during human oogenesis

Vicario

Lang

et al. 2017

Human Reproduction

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STUDY QUESTION: Does selection for mtDNA mutations occur in human oocytes?SUMMARY ANSWER: We provide statistical evidence in favor of the existence of purifying selection for mtDNA mutations in human oocytes acting between the expulsion of the first and second polar bodies (PBs).WHAT IS KNOWN ALREADY: Several lines of evidence in Metazoa, including humans, indicate that variation within the germline of mitochondrial genomes is under purifying selection. The presence of this internal selection filter in the germline has important consequences for the evolutionary trajectory of mtDNA. However, the nature and localization of this internal filter are still unclear while several hypotheses are proposed in the literature.STUDY DESIGN, SIZE, DURATION: In this study, 60 mitochondrial genomes were sequenced from 17 sets of oocytes, first and second PBs, and peripheral blood taken from nine women between 38 and 43 years of age.PARTICIPANTS/MATERIALS, SETTING, METHODS: Whole genome amplification was performed only on the single cell samples and Sanger sequencing was performed on amplicons. The comparison of variant profiles between first and second PB sequences showed no difference in substitution rates but displayed instead a sharp difference in pathogenicity scores of protein-coding sequences using three different metrics (MutPred, Polyphen and SNPs&GO).MAIN RESULTS AND THE ROLE OF CHANCE: Unlike the first, second PBs showed no significant differences in pathogenic scores with blood and oocyte sequences. This suggests that a filtering mechanism for disadvantageous variants operates during oocyte development between the expulsion of the first and second PB. LIMITATIONS, REASONS FOR CAUTION:The sample size is small and further studies are needed before this approach can be used in clinical practice. Studies on a model organism would allow the sample size to be increased.

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Section: Quality and Quantity Of Mtdna Variants Across Cell Typesmentioning

confidence: 85%

Intra-individual purifying selection on mitochondrial DNA variants during human oogenesis

Vicario

Lang

et al. 2017

Human Reproduction

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“…mtDNA mutations can be introduced into mouse germ cells (Inoue et al, 2000), or they can be induced to occur as a consequence of a proofreading-deficient DNA polymerase gamma (Kauppila et al, 2016). However, the generated mouse models cannot recapitulate the heteroplasmy or tissue specificity of mtDNA disorders.…”

Section: Introductionmentioning

confidence: 99%

Human iPSC-Derived Neural Progenitors Are an Effective Drug Discovery Model for Neurological mtDNA Disorders

et al. 2017

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SUMMARYMitochondrial DNA (mtDNA) mutations frequently cause neurological diseases. Modeling of these defects has been difficult because of the challenges associated with engineering mtDNA. We show here that neural progenitor cells (NPCs) derived from human induced pluripotent stem cells (iPSCs) retain the parental mtDNA profile and exhibit a metabolic switch toward oxidative phosphorylation. NPCs derived in this way from patients carrying a deleterious homoplasmic mutation in the mitochondrial gene MT-ATP6 (m.9185T>C) showed defective ATP production and abnormally high mitochondrial membrane potential (MMP), plus altered calcium homeostasis, which represents a potential cause of neural impairment. High-content screening of FDA-approved drugs using the MMP phenotype highlighted avanafil, which we found was able to partially rescue the calcium defect in patient NPCs and differentiated neurons. Overall, our results show that iPSC-derived NPCs provide an effective model for drug screening to target mtDNA disorders that affect the nervous system.

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“…Surf1 knockout mice are reported to suffer a loss between 30% and 50% of COX activity , whereas mtDNA mutator mice lose around 25–30% . Mice harbouring the mt‐tRNA ALA mutation show only sparse COX impairment . The NBTx assay revealed that in these mouse models, qualitative levels of formazan crystal deposition correlated with the reported mitochondrial COX deficiency (Figure ).…”

Section: Resultsmentioning

confidence: 93%

A novel histochemistry assay to assess and quantify focal cytochrome c oxidase deficiency

Simard

Mourier

Greaves

et al. 2018

The Journal of Pathology

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Defects in the respiratory chain, interfering with energy production in the cell, are major underlying causes of mitochondrial diseases. In spite of this, the surprising variety of clinical symptoms, disparity between ages of onset, as well as the involvement of mitochondrial impairment in ageing and age‐related diseases continue to challenge our understanding of the pathogenic processes. This complexity can be in part attributed to the unique metabolic needs of organs or of various cell types. In this view, it remains essential to investigate mitochondrial dysfunction at the cellular level. For this purpose, we developed a novel enzyme histochemical method that enables precise quantification in fresh‐frozen tissues using competing redox reactions which ultimately lead to the reduction of tetrazolium salts and formazan deposition in cytochrome c oxidase‐deficient mitochondria. We demonstrate that the loss of oxidative activity is detected at very low levels – this achievement is unequalled by previous techniques and opens up new opportunities for the study of early disease processes or comparative investigations. Moreover, human biopsy samples of mitochondrial disease patients of diverse genotypic origins were used and the successful detection of COX‐deficient cells suggests a broad application for this new method. Lastly, the assay can be adapted to a wide range of tissues in the mouse and extends to other animal models, which we show here with the fruit fly, Drosophila melanogaster. Overall, the new assay provides the means to quantify and map, on a cell‐by‐cell basis, the full extent of COX deficiency in tissues, thereby expending new possibilities for future investigation. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

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A Phenotype-Driven Approach to Generate Mouse Models with Pathogenic mtDNA Mutations Causing Mitochondrial Disease

Cited by 110 publications

References 48 publications

Intra-individual purifying selection on mitochondrial DNA variants during human oogenesis

Intra-individual purifying selection on mitochondrial DNA variants during human oogenesis

Human iPSC-Derived Neural Progenitors Are an Effective Drug Discovery Model for Neurological mtDNA Disorders

A novel histochemistry assay to assess and quantify focal cytochrome c oxidase deficiency

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