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Gorlin-Chaudhry-Moss syndrome (GCMS) is a dysmorphic syndrome characterized by coronal craniosynostosis and severe midface hypoplasia, body and facial hypertrichosis, microphthalmia, short stature, and short distal phalanges. Variable lipoatrophy and cutis laxa are the basis for a progeroid appearance. Using exome and genome sequencing, we identified the recurrent de novo mutations c.650G>A (p.Arg217His) and c.649C>T (p.Arg217Cys) in SLC25A24 in five unrelated girls diagnosed with GCMS. Two of the girls had pronounced neonatal progeroid features and were initially diagnosed with Wiedemann-Rautenstrauch syndrome. SLC25A24 encodes a mitochondrial inner membrane ATP-Mg/P i carrier. In fibroblasts from affected individuals, the mutated SLC25A24 showed normal stability. In contrast to control cells, the probands' cells showed mitochondrial swelling, which was exacerbated upon treatment with hydrogen peroxide (H 2 O 2 ). The same effect was observed after overexpression of the mutant cDNA. Under normal culture conditions, the mitochondrial membrane potential of the probands' fibroblasts was intact, whereas ATP content in the mitochondrial matrix was lower than that in control cells. However, upon H 2 O 2 exposure, the membrane potential was significantly elevated in cells harboring the mutated SLC25A24. No reduction of mitochondrial DNA copy number was observed. These findings demonstrate that mitochondrial dysfunction with increased sensitivity to oxidative stress is due to the SLC25A24 mutations. Our results suggest that the SLC25A24 mutations induce a gain of pathological function and link mitochondrial ATP-Mg/P i transport to the development of skeletal and connective tissue., (Copyright © 2017 American Society of Human Genetics. All rights reserved.)

Mitochondrial DNA (mtDNA) mutations frequently cause neurological diseases. Modeling of these defects has been difficult because of the challenges associated with engineering mtDNA. We show here that neural progenitor cells (NPCs) derived from human induced pluripotent stem cells (iPSCs) retain the parental mtDNA profile and exhibit a metabolic switch toward oxidative phosphorylation. NPCs derived in this way from patients carrying a deleterious homoplasmic mutation in the mitochondrial gene MT-ATP6 (m.9185T>C) showed defective ATP production and abnormally high mitochondrial membrane potential (MMP), plus altered calcium homeostasis, which represents a potential cause of neural impairment. High-content screening of FDA-approved drugs using the MMP phenotype highlighted avanafil, which we found was able to partially rescue the calcium defect in patient NPCs and differentiated neurons. Overall, our results show that iPSC-derived NPCs provide an effective model for drug screening to target mtDNA disorders that affect the nervous system., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Coenzyme Q (CoQ) is a key component of the mitochondrial respiratory chain, but it also has several other functions in the cellular metabolism. One of them is to function as an electron carrier in the reaction catalyzed by sulfide:quinone oxidoreductase (SQR), which catalyzes the first reaction in the hydrogen sulfide oxidation pathway. Therefore, SQR may be affected by CoQ deficiency. Using human skin fibroblasts and two mouse models with primary CoQ deficiency, we demonstrate that severe CoQ deficiency causes a reduction in SQR levels and activity, which leads to an alteration of mitochondrial sulfide metabolism. In cerebrum of Coq9 R239X mice, the deficit in SQR induces an increase in thiosulfate sulfurtransferase and sulfite oxidase, as well as modifications in the levels of thiols. As a result, biosynthetic pathways of glutamate, serotonin, and catecholamines were altered in the cerebrum, and the blood pressure was reduced. Therefore, this study reveals the reduction in SQR activity as one of the pathomechanisms associated with CoQ deficiency syndrome., (© 2016 The Authors. Published under the terms of the CC BY 4.0 license.)

We describe two siblings who were affected with early onset focal seizures, severe progressive postnatal microcephaly, muscular hypertonia, feeding problems and bouts of apnea, only minimal psychomotor development, as well as death in infancy and childhood. We identified compound heterozygous mutations in BRAT1 exons 5 (c.638_639insA) and 8 (c.1134+1G>A) in one affected child via next-generation sequencing of the disease-associated genome followed by phenotype-driven bioinformatic analysis. Sanger sequencing confirmed the presence of these mutations in both patients and a heterozygote status of the parents. Whereas the frameshift mutation (c.638_639insA) has been described in one family, the splice-site mutation (c.1134+1G>A) is novel. In contrast to all cases published so far, one of our patients showed a considerably milder clinical course with survival into childhood. Investigation of a skeletal muscle biopsy showed a severely reduced COX enzyme histochemical staining, indicating mitochondrial dysfunction. Our data expand the clinical and mutational spectrum of the BRAT1-associated phenotype. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)

Fast neuronal network oscillations in the gamma range (~30-90 Hz) have been implicated in complex brain functions such as sensory processing, memory formation and, perhaps, consciousness, and appear to be exceptionally vulnerable to various pathologies. However, both energy demand and mitochondrial performance underlying gamma oscillations are unknown. We investigated the fundamental relationship between acetylcholine-induced gamma oscillations, mitochondrial gene expression and oxidative metabolism in hippocampal slice preparations of mouse and rat by applying electrophysiology, in situ hybridization, quantitative polymerase chain reaction, oxygen sensor microelectrode (interstitial partial oxygen pressure) and imaging of mitochondrial redox state [nicotinamide adenine dinucleotide (phosphate) and flavin adenine dinucleotide fluorescence]. We show that (i) gamma oscillation power, oxygen consumption and expression of complex I (nicotinamide adenine dinucleotide:ubiquinone oxidoreductase) subunits are higher in hippocampal subfield CA3 than in CA1 and dentate gyrus; (ii) the amount of oxygen consumption of gamma oscillations reaches that of seizure-like events; (iii) gamma oscillations are exquisitely sensitive to pharmacological complex I inhibition; and (iv) gamma oscillations utilize mitochondrial oxidative capacity near limit. These data suggest that gamma oscillations are especially energy demanding and require both high complex I expression and strong functional performance of mitochondria. Our study helps to explain the exceptional vulnerability of complex brain functions in ischaemia as well as in neurodegenerative and psychiatric disorders that are associated with mitochondrial dysfunction.

Nitric oxide associated-1 (NOA1) is an evolutionarily conserved guanosine triphosphate (GTP) binding protein that localizes predominantly to mitochondria in mammalian cells. On the basis of bioinformatic analysis, we predicted its possible involvement in ribosomal biogenesis, although this had not been supported by any experimental evidence. Here we determine NOA1 function through generation of knockout mice and in vitro assays. NOA1-deficient mice exhibit midgestation lethality associated with a severe developmental defect of the embryo and trophoblast. Primary embryonic fibroblasts isolated from NOA1 knockout embryos show deficient mitochondrial protein synthesis and a global defect of oxidative phosphorylation (OXPHOS). Additionally, Noa1⁻/⁻ cells are impaired in staurosporine-induced apoptosis. The analysis of mitochondrial ribosomal subunits from Noa1⁻/⁻ cells by sucrose gradient centrifugation and Western blotting showed anomalous sedimentation, consistent with a defect in mitochondrial ribosome assembly. Furthermore, in vitro experiments revealed that intrinsic NOA1 GTPase activity was stimulated by bacterial ribosomal constituents. Taken together, our data show that NOA1 is required for mitochondrial protein synthesis, likely due to its yet unidentified role in mitoribosomal biogenesis. Thus, NOA1 is required for such basal mitochondrial functions as adenosine triphosphate (ATP) synthesis and apoptosis.

UCP4 is a member of the mitochondrial uncoupling protein subfamily and one of the three UCPs (UCP2, UCP4, UCP5), associated with the nervous system. Its putative functions include thermogenesis, attenuation of reactive oxidative species (ROS), regulation of mitochondrial calcium concentration and involvement in cell differentiation and apoptosis. Here we investigate UCP4's subcellular, cellular and tissue distribution, using an antibody designed specially for this study, and discuss the findings in terms of the protein's possible functions. Western blot and immunohistochemistry data confirmed that UCP4 is expressed predominantly in the central nervous system (CNS), as previously shown at mRNA level. No protein was found in heart, spleen, stomach, intestine, lung, thymus, muscles, adrenal gland, testis and liver. The reports revealing UCP4 mRNA in kidney and white adipose tissue were not confirmed at protein level. The amount of UCP4 varies in the mitochondria of different brain regions, with the highest protein content found in cortex. We show that UCP4 is present in fetal murine brain tissue as early as embryonic days 12-14 (E12-E14), which coincides with the beginning of neuronal differentiation. The UCP4 content in mitochondria decreases as the age of mice increases. UCP4 preferential expression in neurons and its developmental expression pattern under physiological conditions may indicate a specific protein function, e.g. in neuronal cell differentiation.

Recently a novel family of putative nitric oxide synthases, with AtNOS1, the plant member implicated in NO production, has been described. Here we present experimental evidence that a mammalian ortholog of AtNOS1 protein functions in the cellular context of mitochondria. The expression data suggest that a candidate for mammalian mitochondrial nitric oxide synthase contributes to multiple physiological processes during embryogenesis, which may include roles in liver haematopoesis and bone development.

We report on a 25-year-old patient with isolated mitochondrial complex III deficiency and a new heteroplasmic mutation (T14849C) in the cytochrome b gene. He suffered from septo-optic dysplasia, retinitis pigmentosa, exercise intolerance, hypertrophic cardiomyopathy, and rhabdomyolysis. A HESX1 mutation was excluded as a cause of his septo-optic dysplasia. Low alpha-tocopherol concentrations in his muscles and an elevated urinary leukotriene E(4) excretion indicate increased production of reactive oxygen species.

We report the cloning of the genomic and cDNA of the human 51 kDa subunit (NDUFV1) of mitochondrial complex I. The 6 kbp NDUFV1 gene is composed of 10 exons. All intron-exon boundaries comply to the consensus sequence for splice donor and acceptor sites. Within the 5' flanking region we identified a putative binding site for NRF-2, a GATA- and GC-box element. Canonical TATA- or CCAAT-boxes were absent, the transcriptional start site, however, lies within a CpG island, which is consistent with the "housekeeping" function of the gene. Within the coding sequence we detected consensus motifs for NADH, FMN, and iron-sulfur binding sites. The amino acid sequence homology between human and cow is 96.9%. Surprisingly we found a 48 bp long complete antisense homology between the 3'UTR of the NDUFV1-mRNA and the 5'UTR of the mRNA for the gamma-interferon inducible protein precursor (IP-30). This finding is intriguing since both genes lie on different chromosomes. The exact function of IP-30 is not yet known, but it may play a role in gamma-interferon mediated immune reactions. The NDUFV1-mRNA might act as an antisense suppresser, thus restraining translation of IP-30 in tissues with high energy demand. This finding could be a molecular link between complex I deficiency and inflammatory myopathy which have been repeatedly described to occur together.