Proteomic and Metabolomic Analyses of Mitochondrial Complex I-deficient Mouse Model Generated by Spontaneous B2 Short Interspersed Nuclear Element (SINE) Insertion into NADH Dehydrogenase (Ubiquinone) Fe-S Protein 4 (Ndufs4) Gene

Abstract

Background: Mitochondrial complex I deficiency is a common inherited metabolic disease. Results: B2 transposable element insertion into Ndufs4 in mice causes loss of the "N assembly module" of complex I, alterations in cellular metabolites, and neurological symptoms. Conclusion: NDUFS4 subunit is required for complex I stability. Significance: Understanding the effects of oxidative phosphorylation defects is essential for the development of treatments.

Novel Insights into the Role of Neurospora crassa NDUFAF2, an Evolutionarily Conserved Mitochondrial Complex I Assembly Factor

“…A similar interaction of the human NDUFAF2 with an 830-kDa intermediate that accumulates in patients' mitochondria deficient in some nuclear complex I genes, namely, NDUFV1 (20,21), NDUFS1 (21), NDUFS4 (21), and NDUFS6 (22), was previously described. We suggest that intermediate a is the equivalent of this 830-kDa subcomplex, which also lacks the N module (19,49,50).…”

“…Mitochondria from patients and mice deficient in NDUFS4 were described as devoid of complex I activity, with accumulation of the 830-kDa intermediate associated with the NDUFAF2 assembly factor (20,21,49,50). However, it was recently reported that the absence of NDUFS4 results in increased instability of complex I leading to the accumulation of two subcomplexes, the N module and the 830-kDa intermediate, which has been found to be associated with two assembly factors (49,50). Furthermore, complex I activity was detected in different tissues of homozygous ndufs4 mutant mice, consistent with our results from nuo21 mutant.…”

Whole Exome Sequencing Identifies the Genetic Basis of Late-Onset Leigh Syndrome in a Patient with MRI but Little Biochemical Evidence of a Mitochondrial Disorder

“…In our experience, patients and mice with mutations in these genes often show an apparently more severe impact on the amount of fully assembled CI on BN-PAGE than on spectrophotometric CI activity or functional analyses such as ATP synthesis (Leong et al 2012). This is likely due to the amount of fully assembled CI in the intact inner membrane being higher than implied by BN-PAGE and enzyme studies where the membrane has been disrupted by detergent, freeze-thawing or sonication (Leong et al 2012), destabilising the assembled CI. All four of these CI subunit genes are expressed ubiquitously, but the impact on CI enzyme activity and function also varies between tissues (Bird et al 2014).…”

“…Among these components, disease-causing mutations in 14 nuclear-encoded structural subunits of CI (NDUFS1, NDUFS2, NDUFS3, NDUFS4, NDUFS7, NDUFS8, NDUFV2, NDUFS6, NDUFV1, NDUFA1, NDUFA2, NDUFA9, NDUFA10, NDUFA12), four assembly factor defects (NDUFAF2, NDUFAF5, NDUFAF6, FOXRED1) and 6 mtDNA subunits have previously been linked with Leigh syndrome (Ogilvie et al 2005;Mimaki et al 2012;Lemire 2015;Lake et al 2015). Mutations in four CI subunits (NDUFV1, NDUFS1, NDUFS4 and NDUFS6), all located in the matrix arm (N-module) of CI, lead to CI subassembly complexes of about 830 kDa on BN-PAGE analysis that appear to have lost the matrix arm of CI (Mimaki et al 2012;Ogilvie et al 2005;Tuppen et al 2010;Leong et al 2012). In our experience, patients and mice with mutations in these genes often show an apparently more severe impact on the amount of fully assembled CI on BN-PAGE than on spectrophotometric CI activity or functional analyses such as ATP synthesis (Leong et al 2012).…”

“…Mutations in four CI subunits (NDUFV1, NDUFS1, NDUFS4 and NDUFS6), all located in the matrix arm (N-module) of CI, lead to CI subassembly complexes of about 830 kDa on BN-PAGE analysis that appear to have lost the matrix arm of CI (Mimaki et al 2012;Ogilvie et al 2005;Tuppen et al 2010;Leong et al 2012). In our experience, patients and mice with mutations in these genes often show an apparently more severe impact on the amount of fully assembled CI on BN-PAGE than on spectrophotometric CI activity or functional analyses such as ATP synthesis (Leong et al 2012). This is likely due to the amount of fully assembled CI in the intact inner membrane being higher than implied by BN-PAGE and enzyme studies where the membrane has been disrupted by detergent, freeze-thawing or sonication (Leong et al 2012), destabilising the assembled CI.…”