Accession Numbers
The accession numbers for variants c.3G>A, c.191G>C, c.265G>T, c.309del, c.331_332del and c.355del are ClinVar: SCV000787623, SCV000787624, SCV000787625, SCV000787626, SCV000787627, and SCV000787628, respectively.

Web Resources
AlignGVGD, http://agvgd.hci.utah.edu/agvgd_input.php
CADD, http://cadd.gs.washington.edu/
ClinVar, https://www.ncbi.nlm.nih.gov/clinvar/
Ensembl, www.ensembl.org/
ExAC Browser, http://exac.broadinstitute.org/
GenBank, http://www.ncbi.nlm.nih.gov/genbank/
GeneMatcher, https://genematcher.org/
gnomAD, http://gnomad.broadinstitute.org/
GTEx Portal, https://www.gtexportal.org/home/
OMIM, http://www.omim.org/
PolyPhen-2, http://genetics.bwh.harvard.edu/pph2/
RSCB Protein Data Bank, https://www.rcsb.org/pdb/home/home.do
SIFT http://sift.bii.a-star.edu.sg/
UCSC Genome Browser, https://genome.ucsc.edu/
UniProt, www.uniprot.org/

Supplemental Data
Document S1. Figures S1–S6 and Table S1
Document S2. Article plus Supplemental Data

Acknowledgments
Work in our laboratories is supported by the Wellcome Centre for Mitochondrial Research (203105/Z/16/Z), the MRC Centre for Neuromuscular Diseases (G0601943), the NIHR Biomedical Research Centre in Age and Age Related Diseases award to the Newcastle upon Tyne Hospitals NHS Foundation, the Newcastle Molecular Pathology Node, the NHS Highly Specialised Service for Rare Mitochondrial Disorders, the Lily Foundation, the Georg August University Göttingen Faculty of Medicine research program (to M.H.), the Deutsche Forschungsgemeinschaft (SFB 815, project Z1 to I.W. and GA354/14-1 to J.G.), the Centre of Mitochondrial Biology and Pathology (Czech Science Foundation grant 14-36804G), the German Bundesministerium für Bildung und Forschung through the German Network for Mitochondrial Disorders (mitoNET, 01GM1113), the E-Rare project GENOMIT (01GM1603), the EU Horizon2020 Collaborative Research Project SOUND (633974), the Wellcome Trust (090532/Z/09/Z), and the NIHR Biomedical Research Centre Oxford. C.L.A. received a NIHR doctoral fellowship (NIHR-HCS-D12-03-04). J.P. is supported by the MRC (MR/J010448/1) and the Wellcome Trust (0948685/Z/10/Z). M.T.R. is supported by Australian National Health and Medical Research Council grant 1125390. M.G.D. is supported by the Australian Mitochondrial Disease Foundation. J.A.M. is supported by the E-Rare project GENOMIT (I 2741-B26) and Austrian Science Fonds. F.L.R., C.F., and H.D. are supported by the Rosetrees Trust, Cambridge Biomedical Research Centre, and NIHR BioResource (RG65966). We thank Jana Meisterknecht for technical assistance, Christian Mertes for helping to create Figure S2, and Anne Lombes for the MTND1 antibody. The views expressed are those of the authors and not necessarily of the NHS, NIHR, or Department of Health. Supplemental Data include six figures and one table and can be found with this article online at https://doi.org/10.1016/j.ajhg.2018.08.013.