Mitochondrial disease: Needs and problems of children, their parents and family. A systematic review and pilot study into the need for information of parents during the diagnostic phase

Contains fulltext : 51979.pdf (publisher's version ) (Closed access)OBJECTIVE: Firstly, this paper aims to systematically review the mitochondrial disease literature to identify studies assessing the needs and problems in the daily life of children with a mitochondrial disease and of their parents and family. The second aim is to provide more insight into the need for information by the parents of these children during the diagnostic process while in hospital. DESIGN: A systematic review and a pilot study, using a qualitative (focus group interviews; n = 7) and a quantitative (questionnaire; n = 37) design. RESULTS: Mothers reported great socioeconomic and psychoaffective strain and showed psychopathological symptoms in the two studies published with respect to this topic. The pilot study showed that parents considered an honest and interested attitude of the person who is giving the information as most important. Furthermore they wanted oral and written information and a central point where they could go with their questions at any time they felt the need. The need for information increased during the four phases of the diagnostic process and was highest in the fourth phase. CONCLUSIONS: The few studies found in the review, combined with expectations that having a mitochondrial disease must have a great impact on these children and their parents and family, call for more research in their needs and problems. Furthermore, there are gaps in the current information provision to parents of these children. A better understanding of the needs and problems of these children and their family is essential for effective care planning and might result in an improved quality of life

Oxidative switch drives mitophagy defects in dopaminergic parkin mutant patient neurons

Mutations in PRKN are the most common cause of early onset Parkinson’s disease. Parkin is an E3 ubiquitin ligase, functioning in mitophagy. Mitochondrial abnormalities are present in PRKN mutant models. Patient derived neurons are a promising model in which to study pathogenic mechanisms and therapeutic targets. Here we generate induced neuronal progenitor cells from PRKN mutant patient fibroblasts with a high dopaminergic neuron yield. We reveal changing mitochondrial phenotypes as neurons undergo a metabolic switch during differentiation. Fibroblasts from 4 controls and 4 PRKN mutant patients were transformed into induced neuronal progenitor cells and subsequently differentiated into dopaminergic neurons. Mitochondrial morphology, function and mitophagy were evaluated using live cell fluorescent imaging, cellular ATP and reactive oxygen species production quantification. Direct conversion of control and PRKN mutant patient fibroblasts results in induced neuronal progenitor and their differentiation yields high percentage of dopaminergic neurons. We were able to observe changing mitochondrial phenotypes as neurons undergo a metabolic switch during differentiation. Our results show that when pre-neurons are glycolytic early in differentiation mitophagy is unimpaired by PRKN deficiency. However as neurons become oxidative phosphorylation dependent, mitophagy is severely impaired in the PRKN mutant patient neurons. These changes correlate with changes in mitochondrial function and morphology; resulting in lower neuron yield and altered neuronal morphology. Induced neuronal progenitor cell conversion can produce a high yield of dopaminergic neurons. The mitochondrial phenotype, including mitophagy status, is highly dependent on the metabolic status of the cell. Only when neurons are oxidative phosphorylation reliant the extent of mitochondrial abnormalities are identified. These data provide insight into cell specific effects of PRKN mutations, in particular in relation to mitophagy dependent disease phenotypes and provide avenues for alternative therapeutic approaches

Succinate in dystrophic white matter: A proton magnetic resonance spectroscopy finding characteristic for complex II deficiency

A deficiency of succinate dehydrogenase is a rare cause of mitochondrial encephalomyopathy. Three patients, 2 sisters and I boy from an unrelated family, presented with symptoms and magnetic resonance imaging signs of leukoencephalopathy. Localized proton magnetic resonance spectroscopy indicated a prominent singlet at 2.40ppm in cerebral and cerebellar white matter not present in gray matter or basal ganglia. The signal was also elevated in cerebrospinal fluid and could be identified as originating from the two equivalent methylene groups of succinate. Subsequently, an isolated deficiency of complex II (succinate:ubiquinone oxidoreductase) was demonstrated in 2 patients in muscle and fibroblasts. One of the sisters died at the age of 18 months. Postmortem examination showed the neuropathological characteristics of Leigh syndrome. Her younger sister, now 12 months old, is also severely affected; the boy, now 6 years old, follows a Milder, fluctuating clinical course. Magnetic resonance spectroscopy provides a characteristic pattern in succinate dehydrogenase deficiency

The antioxidant Trolox restores mitochondrial membrane potential and Ca2+-stimulated ATP production in human complex I deficiency

Malfunction of mitochondrial complex I caused by nuclear gene mutations causes early-onset neurodegenerative diseases. Previous work using cultured fibroblasts of complex-I-deficient patients revealed elevated levels of reactive oxygen species (ROS) and reductions in both total Ca2+ content of the endoplasmic reticulum (ERCa) and bradykinin(Bk)-induced increases in cytosolic and mitochondrial free Ca2+ ([Ca2+]C; [Ca2+]M) and ATP ([ATP]C; [ATP]M) concentration. Here, we determined the mitochondrial membrane potential (Δψ) in patient skin fibroblasts and show significant correlations with cellular ROS levels and ERCa, i.e., the less negative Δψ, the higher these levels and the lower ERCa. Treatment with 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox) normalized Δψ and Bk-induced increases in [Ca2+]M and [ATP]M. These effects were accompanied by an increase in ERCa and Bk-induced increase in [Ca2+]C. Together, these results provide evidence for an integral role of increased ROS levels in complex I deficiency and point to the potential therapeutic value of antioxidant treatment

The Achilles heel of decision making system in termites

Mitochondrial beta-oxidation of long-chain fatty acids requires the concerted action of three tightly integrated membrane-bound enzymes (carnitine palmitoyltransferase I and II and carnitine/acylcarnitine translocase) that transport them into mitochondria. Neonatal onset of carnitine palmitoyltransferase II (CPT II) deficiency is an autosomal recessive, often lethal disorder of this transport. We describe a novel splice-site mutation in the CPT II gene, found in a Moroccan family, of which four out of five children have died from the neonatal form of CPT II deficiency. Mutation detection studies at the mRNA level in the CPT II gene implied that the affected children were homozygous for the previously reported 534T insertion followed by a 25-bp deletion (encompassing bases 534-558). Studies of genomic DNA, however, revealed all patients to be compound heterozygous for this 534T ins/del 25 mutation, and for a new g-->a splice-site mutation in the splice-acceptor site of intron 2. Because of these findings, prenatal diagnosis was performed in chorionic villi of three new pregnancies. This did not reveal new compound heterozygous genotypes, and, after uneventful pregnancies, all children appeared to be healthy. The new mutation is the first splice-site mutation ever identified in CPT II deficiency. The fact that it was not discovered in the patient's cDNA makes this study another example of the incompleteness of mutation detection at the mRNA level in cases where a mutation leads to aberrant splicing or nonsense-mediated messenger deca

A Drosophila Mitochondrial Complex I Deficiency Phenotype Array

Mitochondrial diseases are a group of rare life-threatening diseases often caused by defects in the oxidative phosphorylation system. No effective treatment is available for these disorders. Therapeutic development is hampered by the high heterogeneity in genetic, biochemical, and clinical spectra of mitochondrial diseases and by limited preclinical resources to screen and identify effective treatment candidates. Alternative models of the pathology are essential to better understand mitochondrial diseases and to accelerate the development of new therapeutics. The fruit fly Drosophila melanogaster is a cost- and time-efficient model that can recapitulate a wide range of phenotypes observed in patients suffering from mitochondrial disorders. We targeted three important subunits of complex I of the mitochondrial oxidative phosphorylation system with the flexible UAS-Gal4 system and RNA interference (RNAi): NDUFS4 (ND-18), NDUFS7 (ND-20), and NDUFV1 (ND-51). Using two ubiquitous driver lines at two temperatures, we established a collection of phenotypes relevant to complex I deficiencies. Our data offer models and phenotypes with different levels of severity that can be used for future therapeutic screenings. These include qualitative phenotypes that are amenable to high-throughput drug screening and quantitative phenotypes that require more resources but are likely to have increased potential and sensitivity to show modulation by drug treatment

A urinary biosignature for mitochondrial myopathy, encephalopathy, lactic acidosis and stroke like episodes (MELAS)

We used a comprehensive metabolomics approach to study the altered urinary metabolome of two mitochondrial myopathy, encephalopathy lactic acidosis and stroke like episodes (MELAS) cohorts carrying the m.3243A > G mutation. The first cohort were used in an exploratory phase, identifying 36 metabolites that were significantly perturbed by the disease. During the second phase, the 36 selected metabolites were able to separate a validation cohort of MELAS patients completely from their respective control group, suggesting usefulness of these 36 markers as a diagnostic set. Many of the 36 perturbed metabolites could be linked to an altered redox state, fatty acid catabolism and one-carbon metabolism. However, our evidence indicates that, of all the metabolic perturbations caused by MELAS, stalled fatty acid oxidation prevailed as being particularly disturbed. The strength of our study was the utilization of five different analytical platforms to generate the robust metabolomics data reported here. We show that urine may be a useful source for disease-specific metabolomics data, linking, amongst others, altered one-carbon metabolism to MELAS. The results reported here are important in our understanding of MELAS and might lead to better treatment options for the disease.Peer reviewe

Reconstructing the evolution of the mitochondrial ribosomal proteome

For production of proteins that are encoded by the mitochondrial genome, mitochondria rely on their own mitochondrial translation system, with the mitoribosome as its central component. Using extensive homology searches, we have reconstructed the evolutionary history of the mitoribosomal proteome that is encoded by a diverse subset of eukaryotic genomes, revealing an ancestral ribosome of alpha-proteobacterial descent that more than doubled its protein content in most eukaryotic lineages. We observe large variations in the protein content of mitoribosomes between different eukaryotes, with mammalian mitoribosomes sharing only 74 and 43% of its proteins with yeast and Leishmania mitoribosomes, respectively. We detected many previously unidentified mitochondrial ribosomal proteins (MRPs) and found that several have increased in size compared to their bacterial ancestral counterparts by addition of functional domains. Several new MRPs have originated via duplication of existing MRPs as well as by recruitment from outside of the mitoribosomal proteome. Using sensitive profile–profile homology searches, we found hitherto undetected homology between bacterial and eukaryotic ribosomal proteins, as well as between fungal and mammalian ribosomal proteins, detecting two novel human MRPs. These newly detected MRPs constitute, along with evolutionary conserved MRPs, excellent new screening targets for human patients with unresolved mitochondrial oxidative phosphorylation disorders