Identification and Characterization of New RNASEH1 Mutations Associated With PEO Syndrome and Multiple Mitochondrial DNA Deletions

RNASEH1; Mitochondrial disease; MtDNARNASEH1; Malaltia mitocondrial; ADN mitocondrialRNASEH1; Enfermedad mitocondrial; ADN mitocondrialMitochondrial DNA (mtDNA) depletion and deletion syndrome encompasses a group of disorders caused by mutations in genes involved in mtDNA replication and maintenance. The clinical phenotype ranges from fatal infantile hepatocerebral forms to mild adult onset progressive external ophthalmoplegia (PEO). We report the case of a patient with PEO and multiple mtDNA deletions, with two new homozygous mutations in RNASEH1. The first mutation (c.487T>C) is located in the same catalytic domain as the four previously reported mutations, and the second (c.258_260del) is located in the connection domain, where no mutations have been reported. In silico study of the mutations predicted only the first mutation as pathogenic, but functional studies showed that both mutations cause loss of ribonuclease H1 activity. mtDNA replication dysfunction was demonstrated in patient fibroblasts, which were unable to recover normal mtDNA copy number after ethidium bromide-induced mtDNA depletion. Our results demonstrate the pathogenicity of two new RNASEH1 variants found in a patient with PEO syndrome, multiple deletions, and mild mitochondrial myopathy.This work was supported by the Spanish Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias and cofunded with ERDF funds (Grant No. FIS PI15/01428 to EG-A and FIS PI18/01574 to RM), the Spanish Ministry of Industry, Economy and Competitiveness (Grant No. SAF2017-87506-R to YC), and the Generalitat de Catalunya (a grant from the URDCat project PERIS to EG-A and RM). JT-T was funded by a fellowship granted by the Generalitat de Catalunya (PERIS program, SLT002/16/00370

Uridine Metabolism in HIV-1-Infected Patients: Effect of Infection, of Antiretroviral Therapy and of HIV-1/ART-Associated Lipodystrophy Syndrome

Background Uridine has been advocated for the treatment of HIV-1/HAART-associated lipodystrophy (HALS), although its metabolism in HIV-1-infected patients is poorly understood. Methods Plasma uridine concentrations were measured in 35 controls and 221 HIV-1-infected patients and fat uridine in 15 controls and 19 patients. The diagnosis of HALS was performed following the criteria of the Lipodystrophy Severity Grading Scale. Uridine was measured by a binary gradient-elution HPLC method. Analysis of genes encoding uridine metabolizing enzymes in fat was performed with TaqMan RT-PCR. Results Median plasma uridine concentrations for HIV-1-infected patients were 3.80 µmol/l (interquartile range: 1.60), and for controls 4.60 µmol/l (IQR: 1.8) (P = 0.0009). In fat, they were of 6.0 (3.67), and 2.8 (4.65) nmol/mg of protein, respectively (P = 0.0118). Patients with a mixed HALS form had a median plasma uridine level of 4.0 (IC95%: 3.40-4.80) whereas in those with isolated lipoatrophy it was 3.25 (2.55-4.15) µmol/l/l (P = 0.0066). The expression of uridine cytidine kinase and uridine phosphorylase genes was significantly decreased in all groups of patients with respect to controls. A higher expression of the mRNAs for concentrative nucleoside transporters was found in HIV-1-infected patients with respect to healthy controls. Conclusions HIV-1 infection is associated with a decrease in plasma uridine and a shift of uridine to the adipose tissue compartment. Antiretroviral therapy was not associated with plasma uridine concentrations, but pure lipoatrophic HALS was associated with significantly lower plasma uridine concentrations

Gene Therapy Corrects Mitochondrial Dysfunction in Hematopoietic Progenitor Cells and Fibroblasts from Coq9R239X Mice

This study has been submitted to the patent's offices at the "University of Granada" and "Fundación Progreso y Salud". Please note that the results of this manuscript have been submitted to patent protection (application number P201630630; title: “Uses of Coenzyme Q biosynthetic proteins”; date:05/16/2016).Recent clinical trials have shown that in vivo and ex vivo gene therapy strategies can be an option for the treatment of several neurological disorders. Both strategies require efficient and safe vectors to 1) deliver the therapeutic gene directly into the CNS or 2) to genetically modify stem cells that will be used as Trojan horses for the systemic delivery of the therapeutic protein. A group of target diseases for these therapeutic strategies are mitochondrial encephalopathies due to mutations in nuclear DNA genes. In this study, we have developed a lentiviral vector (CCoq9WP) able to overexpress Coq9 mRNA and COQ9 protein in mouse embryonic fibroblasts (MEFs) and hematopoietic progenitor cells (HPCs) from Coq9R239X mice, an animal model of mitochondrial encephalopathy due to primary Coenzyme Q (CoQ) deficiency. Ectopic over-expression of Coq9 in both cell types restored the CoQ biosynthetic pathway and mitochondrial function, improving the fitness of the transduced cells. These results show the potential of the CCoq9WP lentiviral vector as a tool for gene therapy to treat mitochondrial encephalopathies.This work was supported by grants from Ministerio de Economía y Competitividad (Spain) and the European Regional Development Fund (ERDF) from the European Union, to LCL through the research grants SAF2013-47761-R and SAF2015-65786-R; by Fondo de Investigaciones Sanitarias ISCIII (Spain) and the European Regional Development Fund (ERDF) from the European Union through the research grants PI12/01097 and ISCIII Red de Terapia Celular TerCel RD12/0019/0006 to FM; by the Consejería de Economía, Innovación, Ciencia y Empleo, Junta de Andalucía-FEDER/Fondo de Cohesion Europeo (FSE) de Andalucía through the research grants P10-CTS-6133 to LCL; P09-CTS-04532, PI-57069, PI-0001/2009 and PAIDI-Bio-326 to F.M.; PI-0160/2012 to KB and PI-0407/2012 to MC; by the NIH through the research P01HD080642 to LCL and by the foundation “todos somos raros, todos somos únicos” to LCL. LCL is supported by the ‘Ramón y Cajal’ National Programme, Ministerio de Economía y Competitividad, Spain (RYC-2011-07643)

Allogeneic haematopoietic stem cell transplantation for mitochondrial neurogastrointestinal encephalomyopathy

Haematopoietic stem cell transplantation has been proposed as treatment for mitochondrial neurogastrointestinal encephalomyopathy, a rare fatal autosomal recessive disease due to TYMP mutations that result in thymidine phosphorylase deficiency. We conducted a retrospective analysis of all known patients suffering from mitochondrial neurogastrointestinal encephalomyopathy who underwent allogeneic haematopoietic stem cell transplantation between 2005 and 2011. Twenty-four patients, 11 males and 13 females, median age 25 years (range 10-41 years) treated with haematopoietic stem cell transplantation from related (n = 9) or unrelated donors (n = 15) in 15 institutions worldwide were analysed for outcome and its associated factors. Overall, 9 of 24 patients (37.5%) were alive at last follow-up with a median follow-up of these surviving patients of 1430 days. Deaths were attributed to transplant in nine (including two after a second transplant due to graft failure), and to mitochondrial neurogastrointestinal encephalomyopathy in six patients. Thymidine phosphorylase activity rose from undetectable to normal levels (median 697 nmol/h/mg protein, range 262-1285) in all survivors. Seven patients (29%) who were engrafted and living more than 2 years after transplantation, showed improvement of body mass index, gastrointestinal manifestations, and peripheral neuropathy. Univariate statistical analysis demonstrated that survival was associated with two defined pre-transplant characteristics: human leukocyte antigen match (10/10 versus <10/10) and disease characteristics (liver disease, history of gastrointestinal pseudo-obstruction or both). Allogeneic haematopoietic stem cell transplantation can restore thymidine phosphorylase enzyme function in patients with mitochondrial neurogastrointestinal encephalomyopathy and improve clinical manifestations of mitochondrial neurogastrointestinal encephalomyopathy in the long term. Allogeneic haematopoietic stem cell transplantation should be considered for selected patients with an optimal donor

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE): Biochemical features and therapeutic approaches

Over the last 15 years, important research has expanded our knowledge of the clinical, molecular genetic, and biochemical features of mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). The characterization of mitochondrial involvement in this disorder and the seminal determination of its genetic cause, have opened new possibilities for more detailed and deeper studies on the pathomechanisms in this progressive and fatal disease. It has been established that MNGIE is caused by mutations in the gene encoding thymidine phosphorylase (TP), which lead to absolute or nearly complete loss of its catalytic activity, producing systemic accumulations of its substrates, thymidine (dThd) and deoxyuridine (dUrd). Findings obtained from in vitro and in vivo studies indicate that the biochemical imbalances specifically impair mitochondrial DNA (mtDNA) replication, repair, or both leading to mitochondrial dysfunction. We have proposed that therapy for MNGIE should be aimed at reducing the concentrations of these toxic nucleosides to normal or nearly normal levels. The first treatment, allogeneic stem-cell transplantation (alloSCT) reported in 2006, produced a nearly full biochemical correction of the dThd and dUrd imbalances in blood. Clinical follow-up of this and other patients receiving alloSCT is necessary to determine whether this and other therapies based on a permanent restoration of TP will be effective treatment for MNGIE. \ua9 2007 The Biochemical Society

Feeding the deoxyribonucleoside salvage pathway to rescue mitochondrial DNA

Mutations in an increasing number of nuclear genes involved in deoxyribonucleotide homeostasis cause disorders associated with somatic mitochondrial DNA (mtDNA) abnormalities. Dysfunction of the products of these genes leads to limited availability of substrates for mtDNA replication and results in mtDNA depletion, multiple deletions or point mutations; mtDNA depletion is the molecular feature linked to greatest clinical severity. In this review, we discuss recent results demonstrating that enhancement of the salvage pathways by increasing the availability of deoxyribonucleosides needed for each specific genetic defect prevents mtDNA depletion. Hence, we propose administration of selected deoxyribonucleosides and/or inhibitors of their catabolism as a pharmacological strategy to treat these diseases. Copyright \ua9 2013. Published by Elsevier Ltd

Author Correction: Resveratrol Increases Hepatic SHBG Expression through Human Constitutive Androstane Receptor: a new Contribution to the French Paradox

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper

Administration of deoxyribonucleosides or inhibition of their catabolism as a pharmacological approach for mitochondrial DNA depletion syndrome

Mitochondrial DNA (mtDNA) depletion syndrome (MDS) is characterized by a reduction in mtDNA copy number and consequent mitochondrial dysfunction in affected tissues. A subgroup of MDS is caused by mutations in genes that disrupt deoxyribonucleotide metabolism, which ultimately leads to limited availability of one or several deoxyribonucleoside triphosphates (dNTPs), and subsequent mtDNA depletion. Here, using in vitro experimental approaches (primary cell culture of deoxyguanosine kinase-deficient cells and thymidine-induced mtDNA depletion in culture as a model of mitochondrial neurogastrointestinal encephalomyopathy, MNGIE), we show that supplements of those deoxyribonucleosides (dNs) involved in each biochemical defect (deoxyguanosine or deoxycytidine, dCtd) prevents mtDNA copy number reduction. Similar effects can be obtained by specific inhibition of dN catabolism using tetrahydrouridine (THU; inhibitor of cytidine deaminase) or immucillin H (inhibitor of purine nucleoside phosphorylase). In addition, using an MNGIE animal model, we provide evidence that mitochondrial dNTP content can be modulated in vivo by systemic administration of dCtd or THU. In spite of the severity associated with diseases due to defects in mtDNA replication, there are currently no effective therapeutic options available. Only in the case of MNGIE, allogeneic hematopoietic stem cell transplantation has proven efficient as a long-term therapeutic strategy. We propose increasing cellular availability of the deficient dNTP precursor by direct administration of the dN or inhibition of its catabolism, as a potential treatment for mtDNA depletion syndrome caused by defects in dNTP metabolism