10779/crick.12657251.v1 Ilaria Dalla Rosa Ilaria Dalla Rosa Yolanda Cámara Yolanda Cámara Romina Durigon Romina Durigon Chloe F Moss Chloe F Moss Sara Vidoni Sara Vidoni Gokhan Akman Gokhan Akman Lilian Hunt Lilian Hunt Mark A Johnson Mark A Johnson Sarah Grocott Sarah Grocott Liya Wang Liya Wang David R Thorburn David R Thorburn Michio Hirano Michio Hirano Joanna Poulton Joanna Poulton Robert W Taylor Robert W Taylor Greg Elgar Greg Elgar Ramon Marti Ramon Marti Peter Voshol Peter Voshol Ian J Holt Ian J Holt Antonella Spinazzola Antonella Spinazzola MPV17 loss causes deoxynucleotide insufficiency and slow DNA replication in mitochondria The Francis Crick Institute 2020 Animals DNA Replication DNA, Mitochondrial Deoxyguanine Nucleotides Female Fibroblasts Gene Expression Regulation Humans Membrane Proteins Mice Mitochondria, Liver Signal Transduction Thymine Nucleotides Elgar FC001075 0604 Genetics Developmental Biology 2020-07-17 16:28:10 Journal contribution https://crick.figshare.com/articles/journal_contribution/MPV17_loss_causes_deoxynucleotide_insufficiency_and_slow_DNA_replication_in_mitochondria/12657251 MPV17 is a mitochondrial inner membrane protein whose dysfunction causes mitochondrial DNA abnormalities and disease by an unknown mechanism. Perturbations of deoxynucleoside triphosphate (dNTP) pools are a recognized cause of mitochondrial genomic instability; therefore, we determined DNA copy number and dNTP levels in mitochondria of two models of MPV17 deficiency. In Mpv17 ablated mice, liver mitochondria showed substantial decreases in the levels of dGTP and dTTP and severe mitochondrial DNA depletion, whereas the dNTP pool was not significantly altered in kidney and brain mitochondria that had near normal levels of DNA. The shortage of mitochondrial dNTPs in Mpv17-/- liver slows the DNA replication in the organelle, as evidenced by the elevated level of replication intermediates. Quiescent fibroblasts of MPV17-mutant patients recapitulate key features of the primary affected tissue of the Mpv17-/- mice, displaying virtual absence of the protein, decreased dNTP levels and mitochondrial DNA depletion. Notably, the mitochondrial DNA loss in the patients' quiescent fibroblasts was prevented and rescued by deoxynucleoside supplementation. Thus, our study establishes dNTP insufficiency in the mitochondria as the cause of mitochondrial DNA depletion in MPV17 deficiency, and identifies deoxynucleoside supplementation as a potential therapeutic strategy for MPV17-related disease. Moreover, changes in the expression of factors involved in mitochondrial deoxynucleotide homeostasis indicate a remodeling of nucleotide metabolism in MPV17 disease models, which suggests mitochondria lacking functional MPV17 have a restricted purine mitochondrial salvage pathway.