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Lookup NU author(s): Professor Grainne Gorman, Dr Hue Hornig - Do, Dr Helen Tuppen, Dr Laura Greaves, Dr Langping He, Angela Baker, Gavin Falkous, Jane Newman, Professor Mike TrenellORCiD, Emeritus Professor Doug Turnbull, Professor Bobby McFarlandORCiD, Professor Robert Taylor
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Complex I (CI) is the largest of the five multi-subunit complexes constituting the human oxidative phosphorylation (OXPHOS) system. Seven of its catalytic core subunits are encoded by mitochondrial DNA (ND (NADH dehydrogenase) 1-6, ND4L (NADH dehydrogenase subunit 4L)), with mutations in all seven having been reported in association with isolated CI deficiency. We investigated two unrelated adult patients presenting with marked exercise intolerance, persistent lactic acidaemia and severe muscle-restricted isolated CI deficiency associated with sub-sarcolemmal mitochondrial accumulation. Screening of the mitochondrial genome detected novel mutations in the MTND1 (NADH dehydrogenase subunit 1) gene, encoding subunit of CI [ Patient 1, m.3365T>C predicting p.(Leu20Pro); Patient 2, m.4175G>A predicting p.(Trp290*)] at high levels of mitochondrial DNA heteroplasmy in skeletal muscle. We evaluated the effect of these novel MTND1 mutations on complex assembly showing that CI assembly, although markedly reduced, was viable in the absence of detectable ND1 signal. Real-time PCR and Western blotting showed overexpression of different CI assembly factor transcripts and proteins in patient tissue. Together, our data indicate that the mechanism underlying the expression of the biochemical defect may involve a compensatory response to the novel MTND1 gene mutations, promoting assembly factor up-regulation and stabilization of respiratory chain super-complexes, resulting in partial rescue of the clinical phenotype.
Author(s): Gorman GS, Blakely EL, Hornig-Do HT, Tuppen HAL, Greaves LC, He LP, Baker A, Falkous G, Newman J, Trenell MI, Lecky B, Petty RK, Turnbull DM, McFarland R, Taylor RW
Publication type: Article
Publication status: Published
Journal: Clinical Science
Year: 2015
Volume: 128
Issue: 12
Pages: 895-904
Print publication date: 01/06/2015
Online publication date: 27/01/2015
Acceptance date: 27/01/2015
Date deposited: 13/08/2015
ISSN (print): 0143-5221
ISSN (electronic): 1470-8736
Publisher: Portland Press Ltd
URL: http://dx.doi.org/10.1042/CS20140705
DOI: 10.1042/CS20140705
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