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Bi-allelic Mutations in NDUFA6 Establish Its Role in Early-Onset Isolated Mitochondrial Complex I Deficiency

Lookup NU author(s): Dr Charlotte Alston, Lucie Taylor, Ruth Glasgow, Professor Bobby McFarland, Professor Robert Taylor

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved. Isolated complex I deficiency is a common biochemical phenotype observed in pediatric mitochondrial disease and often arises as a consequence of pathogenic variants affecting one of the ∼65 genes encoding the complex I structural subunits or assembly factors. Such genetic heterogeneity means that application of next-generation sequencing technologies to undiagnosed cohorts has been a catalyst for genetic diagnosis and gene-disease associations. We describe the clinical and molecular genetic investigations of four unrelated children who presented with neuroradiological findings and/or elevated lactate levels, highly suggestive of an underlying mitochondrial diagnosis. Next-generation sequencing identified bi-allelic variants in NDUFA6, encoding a 15 kDa LYR-motif-containing complex I subunit that forms part of the Q-module. Functional investigations using subjects' fibroblast cell lines demonstrated complex I assembly defects, which were characterized in detail by mass-spectrometry-based complexome profiling. This confirmed a marked reduction in incorporated NDUFA6 and a concomitant reduction in other Q-module subunits, including NDUFAB1, NDUFA7, and NDUFA12. Lentiviral transduction of subjects' fibroblasts showed normalization of complex I. These data also support supercomplex formation, whereby the ∼830 kDa complex I intermediate (consisting of the P- and Q-modules) is in complex with assembled complex III and IV holoenzymes despite lacking the N-module. Interestingly, RNA-sequencing data provided evidence that the consensus RefSeq accession number does not correspond to the predominant transcript in clinically relevant tissues, prompting revision of the NDUFA6 RefSeq transcript and highlighting not only the importance of thorough variant interpretation but also the assessment of appropriate transcripts for analysis.


Publication metadata

Author(s): Alston CL, Heidler J, Dibley MG, Kremer LS, Taylor LS, Fratter C, French CE, Glasgow RIC, Feichtinger RG, Delon I, Pagnamenta AT, Dolling H, Lemonde H, Aiton N, Bjornstad A, Henneke L, Gartner J, Thiele H, Tauchmannova K, Quaghebeur G, Houstek J, Sperl W, Raymond FL, Prokisch H, Mayr JA, McFarland R, Poulton J, Ryan MT, Wittig I, Henneke M, Taylor RW

Publication type: Article

Publication status: Published

Journal: American Journal of Human Genetics

Year: 2018

Volume: 103

Issue: 4

Pages: 592-601

Print publication date: 04/10/2018

Online publication date: 20/09/2018

Acceptance date: 22/08/2018

Date deposited: 26/10/2018

ISSN (print): 0002-9297

ISSN (electronic): 1537-6605

Publisher: Cell Press

URL: https://doi.org/10.1016/j.ajhg.2018.08.013

DOI: 10.1016/j.ajhg.2018.08.013

PubMed id: 30245030


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