Novel Missense Mitochondrial ND4L Gene Mutations in Friedreich's Ataxia

AbstractObjective(s)The mitochondrial defects in Friedreich's ataxia have been reported in many researches. Mitochondrial DNA is one of the candidates for defects in mitochondrion, and complex I is the first and one of the largest catalytic complexes of oxidative phosphorylation (OXPHOS) system. Materials and MethodsWe searched the mitochondrial ND4L gene for mutations by TTGE and sequencing on 30 FRDA patients and 35 healthy controls.ResultsWe found 3 missense mutations [m.10506A>G (T13A), m.10530G>A (V21M), and m.10653G>A (A62T)] in four patients whose m.10530G>A and m.10653G>A were not reported previously. In two patients, heteroplasmic m.10530G>A mutation was detected. They showed a very early ataxia syndrome. Our results showed that the number of mutations in FRDA patients was higher than that in the control cases (P= 0.0287).ConclusionAlthough this disease is due to nuclear gene mutation, the presence of these mutations might be responsible for further mitochondrial defects and the increase of the gravity of the disease. Thus, it should be considered in patients with this disorder

The study of mitochondrial ATP6, ND3 and COX3 gene nucleotide variations in Iranian patients with atherosclerosis by PCR-SSCP

Background and aims: Atherosclerosis is a complex arterial disease that is caused due to the interaction of genetic and environmental factors. Mutations in the mitochondrial genome have probably a direct effect on increased oxidative stress and thereby cause progression of the disease. The aim of the current study was to identify the possible nucleotide changes in the mitochondrial ATP6, ND3 and COX3 genes in Iranian patients with atherosclerosis. Methods: In this case-control study, DNA was extracted from peripheral blood of 90 patients with atherosclerosis and 95 healthy individuals by standard method. The regions of the mitochondrial genome including ATP6, ND3 and COX3 genes were studied by PCR-SSCP; and banding shift specimens were sequenced to determine the exact nucleotide changes. The obtained data were analyzed using the Fisher's exact test and GraphPad prism software. Results: The results of SSCP and DNA sequencing lead to the detection of three nucleotide changes in ATP6 gene including a synonymous polymorphism at position m.9034 G>A, and an SNP at position m.9055 G>A, in which alanine is converted to tyrosine and synonymous hetroplasmic variant at m. 9162C>T. Also, it was found three homoplasmic nucleotide variations including synonymous m.9602A>G, m.9899T>C related to histidine amino acid and homoplasmic variant m.9929C>A that resulted in changing of tyrosine to stop codon. Conclusion:. Since it has been proven, m.9055G>A variant increases the risk of developing breast cancer, and on the other hand, this polymorphism has also been reported in the Caucasian population of Parkinson's; Therefore, it can be said that the combination of this mutation with other predisposing factors increases the severity of coronary heart disease. Investigating other mitochondrial genes could be regarded important in order to find the the relationship between nucleotide changes of mitochondrial genes cardiovascular diseases

Novel Point Mutations in Frataxin Gene in Iranian Patients with Friedreich’s Ataxia

How to Cite This Article: Heidari MM , Khatami M, Pourakrami J. Novel Point Mutations in Frataxin Gene in Iranian Patients withFriedreich’s Ataxia. Iran J Child Neurol. 2014 Winter; 8(1):32-36. ObjectiveFriedreich’s ataxia is the most common form of hereditary ataxia with autosomal recessive pattern. More than 96% of patients are homozygous for GAA repeat extension on both alleles in the first intron of FXN gene and the remainingpatients have been shown to be heterozygous for a GAA extension in one allele and point mutation in other allele.Materials & MethodsIn this study, exons of 1, 2, 3, and 5 of frataxin gene were searched by single strand conformation polymorphism polymerase chain reaction (PCR-SSCP) in 5 patients with GAA extension in one allele. For detection of exact mutation,samples with band shifts were sent for DNA sequencing.Results Three novel point mutations were found in patients heterozygous for the GAA repeat expansion, p.S81A, p.Y123D, and p.S192C. ConclusionOur results showed that these point mutations in one allele with GAA extension in another allele are associated with FRDA signs. Thus, these results emphasize the importance of performing molecular genetic analysis for point mutations inFRDA patients. References:Delatycki MB, Williamson R, Forrest SM. Friedreich ataxia: an overview. J Med Genet 2000;37(1):1-8.Harding AE, Zilkha KJ. ‘Pseudo-dominant’ inheritance in Friedreich’s ataxia. J Med Genet 1981;18(4):285-7.Schulz JB, Boesch S, Burk K, Durr A, Giunti P, Mariotti C, et al. Diagnosis and treatment of Friedreich ataxia: a European perspective. Nat Rev Neurol 2009;5(4):222-34.Campuzano V, Montermini L, Lutz Y, Cova L, Hindelang C, Jiralerspong S, et al. Frataxin is reduced in Friedreich ataxia patients and is associated with mitochondrial membranes. Hum Mol Genet 1997;6(11):1771-80.Sharma R, De Biase I, Gomez M, Delatycki MB, Ashizawa T, Bidichandani SI. Friedreich ataxia in carriers of unstable borderline GAA triplet-repeat alleles. Ann Neurol 2004;56(6):898-901.Durr A, Cossee M, Agid Y, Campuzano V, Mignard C, Penet C, et al. Clinical and genetic abnormalities in patients with Friedreich’s ataxia. N Engl J Med 1996;17;335(16):1169-75.Filla A, De Michele G, Cavalcanti F, Pianese L, Monticelli A, Campanella G, et al. The relationship between trinucleotide (GAA) repeat length and clinical features in Friedreich ataxia. Am J Hum Genet 1996;59(3):554-60.Lamont PJ, Davis MB, Wood NW. Identification and sizing of the GAA trinucleotide repeat expansion of Friedreich’s ataxia in 56 patients. Clinical and genetic correlates. Brain 1997;120 ( Pt 4):673-80.Montermini L, Richter A, Morgan K, Justice CM, Julien D, Castellotti B, et al. Phenotypic variability in Friedreich ataxia: role of the associated GAA triplet repeat expansion. Ann Neurol 1997;41(5):675-82.Monros E, Molto MD, Martinez F, Canizares J, Blanca J, Vilchez JJ, et al. Phenotype correlation and intergenerational dynamics of the Friedreich ataxia GAA trinucleotide repeat. Am J Hum Genet 1997;61(1):101-10.Zuhlke CH, Dalski A, Habeck M, Straube K, Hedrich K, Hoeltzenbein M, et al. Extension of the mutation spectrum in Friedreich’s ataxia: detection of an exon deletion and novel missense mutations. Eur J Hum Genet 2004;12(11):979-82.Heidari MM, Houshmand M, Hosseinkhani S, Nafissi S, Scheiber-Mojdehkar B, Khatami M. A novel mitochondrial heteroplasmic C13806A point mutation associated with Iranian Friedreich’s ataxia. Cell Mol Neurobiol 2009;29(2):225-33.Heidari MM, Houshmand M, Hosseinkhani S, Nafissi S, Scheiber-Mojdehkar B, Khatami M. Association between trinucleotide CAG repeats of the DNA polymerase gene (POLG) with age of onset of Iranian Friedreich’s ataxia patients. Neurol Sci 2008; 29(6):489-93.Heidari MM, Houshmand M, Hosseinkhani S, Nafissi S, Khatami M. Complex I and ATP content deficiency in lymphocytes from Friedreich’s ataxia. Can J Neurol Sci 2009;36(1):26-31.Campuzano V, Montermini L, Molto MD, Pianese L, Cossee M, Cavalcanti F, et al. Friedreich’s ataxia: autosomal recessive disease caused by an intronic GAA triplet repeat expansion. Science 1996;271(5254):1423-7.Sambrook J, Russel DW. Chapter 13: Detection of Mutations by Single-strand Conformational Polymorphism and Heteroduplex Analysis. Molecular cloning: a laboratory manual. 3eded. New York: Cold Spring Harborn Laboratory Press; 2001. P.49-59.Kyte J, Doolittle RF. A simple method for displaying the hydropathic character of a protein. J Mol Biol 1982;157(1):105-32.Harding AE, Hewer RL. The heart disease of Friedreich’s ataxia: a clinical and electrocardiographic study of 115 patients, with an analysis of serial electrocardiographic changes in 30 cases. Q J Med 1983;52(208):489-502.Cavalier L, Ouahchi K, Kayden HJ, Di Donato S, Reutenauer L, Mandel JL, et al. Ataxia with isolated vitamin E deficiency: heterogeneity of mutations and phenotypic variability in a large number of families. Am J Hum Genet 1998;62(2):301-10.Anheim M, Mariani LL, Calvas P, Cheuret E, Zagnoli F, Odent S, et al. Exonic deletions of FXN and early-onset Friedreich ataxia. Arch Neurol 2012;69(7):912-6.Li H, Gakh O, Smith DYt, Ranatunga WK, Isaya G. Missense mutations linked to friedreich ataxia have different but synergistic effects on mitochondrial frataxin isoforms. J Biol Chem 2013;288(6):4116-27.Evans-Galea MV, Corben LA, Hasell J, Galea CA, Fahey MC, du Sart D, et al. A novel deletion-insertion mutation identified in exon 3 of FXN in two siblings with a severe Friedreich ataxia phenotype. Neurogenetics 2011;12(4):307-13.

Novel and heteroplasmic mutations in mitochondrial tRNA genes in Brugada syndrome

  Background: Brugada syndrome (BrS) is a rare cardiac arrhythmia characterized by sudden death associated with electrocardiogram patterns characterized by incomplete right bundle-branch block and ST-segment elevations in the anterior precordial leads. This syndrome predominantly is seen in younger males with structurally normal hearts. Mitochondrial variants particularly mt-tRNA mutations, are hot spots that lead to cardiological disorders. Previous studies have shown that mutations in mitochondrial tRNA genes play an important causal or modifying role in BrS. The present study aims to evaluate the involvement of mitochondrial tRNA genes in arrhythmogenic BrS. Methods: In this study, 40 Iranian patients were investigated for the presence of the mutations in 6 mitochondrial tRNA genes (tRNA Ile, Met, Gln, Asn, Ala and Trp) by PCR-SSCP analysis. Results: There were 4 mutations in tRNA genes, that for first time, were found in BrS patients and these mutations were not in controls. Three of them were heteroplasmic and located in tRNAGln (T4377A) and tRNAMet (G4407A and C4456T) which were assessed as pathogenic mutations. A homo­plasmic variant (5580T > C) in tRNATrp gene was located within the junction region between tRNATrp and tRNAAla genes. This mutation may disturb the processing of mt-tRNATrp. Conclusions: The results of this study suggest that mutations in mitochondrial tRNA genes might lead to deficiencies in translational process of critical proteins of the respiratory chain and potentially lead to BrS in Iranian subjects. (Cardiol J 2018; 25, 1: 113–119

The POLG Polyglutamine Tract Variants in Iranian Patients with Multiple Sclerosis

How to Cite This Article: Khatami M, Heidari MM, Mansouri R, Mousavi F. The POLG Polyglutamine Tract Variants in Iranian Patients with Multiple Sclerosis. Iran J Child Neurol. 2015 Winter; 9(1):37-41.AbstractObjectiveMultiple Sclerosis (MS) is a common disease of the central nervous system. The interaction between inflammatory and neurodegenerative processes typically results in irregular neurological disturbances followed by progressive disability.Mitochondrial dysfunction has been implicated in neurodegenerative disorders. The DNA polymerase-gamma (POLG) gene, which encodes the catalytic subunit of enzyme responsible for directing mtDNA replication, contains a poly glutamine tract (poly-Q) in the N-terminal, encoded by a CAG sequence in exon 2.Materials & MethodsWe analyzed the POLG trinucleotide repeats in 40 Iranian patients with MS (27 females and 13 males with an age range of 18–55); and 47 healthy age, gender, and ethnic matched controls were chosen by PCR-SSCP analysis. ResultsOur results indicated that the most common allele in patients had 10 consecutive CAG repeats (10Q). Other alleles of 11and 12 trinucleotide repeats were detected.We did not find any difference between the CAG repeat length distribution in controls and MS patients.ConclusionNo correlation was observed in the POLG gene CAG repeat with pathogenesis of MS, but it looks that other point mutations in POLG gene may have an important role in the disease’s pathogenesis and produced more significant results.ReferencesBaranzini SE. Revealing the genetic basis of multiple sclerosis: are we there yet? Curr Opin Genet Dev. 2011 Jun; 21(3):317-24.Hoffjan S, Akkad DA. The genetics of multiple sclerosis: an update 2010. Mol Cell Probes. 2010 Oct; 24(5):237-43.Disanto G, Berlanga AJ, Handel AE, Para AE, Burrell AM, Fries A, et al. Heterogeneity in multiple sclerosis: scratching the surface of a complex disease. Autoimmune Dis. 2010; 2011:932351.International Multiple Sclerosis Genetics C, Wellcome Trust Case Control C, Sawcer S, Hellenthal G, Pirinen M, Spencer CC, et al. Genetic risk and a primary role for cell-mediated immune mechanisms in multiple sclerosis. Nature. 2011 Aug 11; 476(7359):214-9.Mao P, Reddy PH. Is multiple sclerosis a mitochondrial disease? Biochimica et biophysica acta. 2010 Jan; 1802(1):66-79.Inarrea P, Alarcia R, Alava MA, Capablo JL, Casanova A, Iniguez C, et al. Mitochondrial complex enzyme activities and cytochrome C expression changes in multiple sclerosis. Mol Neurobiol. 2014 Feb; 49(1):1-9.Schaller A, Hahn D, Jackson CB, Kern I, Chardot C, Belli DC, et al. Molecular and biochemical characterization of a novel mutation in POLG associated with Alpers syndrome. BMC Neurology. 2011; 11(1):4.Milone M, Brunetti-Pierri N, Tang LY, Kumar N, Mezei MM, Josephs K, et al. Sensory ataxic neuropathy with ophthalmoparesis caused by POLG mutations. Neuromuscul Disord. 2008 Aug; 18(8):626-32.Azrak S, Ayyasamy V, Zirpoli G, Ambrosone C, Bandera EV, Bovbjerg DH, et al. CAG repeat variants in the POLG1 gene encoding mtDNA polymerase-gamma and risk of breast cancer in African-American women. PLoS One. 2012; 7(1):e29548.Eerola J, Luoma PT, Peuralinna T, Scholz S, Paisan-Ruiz C, Suomalainen A, et al. POLG1 polyglutamine tract variants associated with Parkinson’s disease. Neurosci Lett. 2010 Jun 14; 477(1):1-5.Rovio A, Abel J, Ahola A, Andres A, Bertranpetit J, Blancher A, et al. A prevalent POLG CAG microsatellite length allele in humans and African great apes. Mammalian genome. 2004; 15(6):492-502.Spelbrink JN, Toivonen JM, Hakkaart GA, Kurkela JM, Cooper HM, Lehtinen SK, et al. In vivo functional analysis of the human mitochondrial DNA polymerase POLG expressed in cultured human cells. Journal of Biological Chemistry. 2000; 275(32):24818-28.Williams AJ, Paulson HL. Polyglutamine neurodegeneration: protein misfolding revisited. Trends in neurosciences. 2008; 31(10):521-8.Luoma P, Eerola J, Ahola S, Hakonen A, Hellström O, Kivistö K, et al. Mitochondrial DNA polymerase gamma variants in idiopathic sporadic Parkinson disease. Neurology. 2007; 69(11):1152-9.Heidari MM, Houshmand M, Hosseinkhani S, Nafissi S, Scheiber-Mojdehkar B, Khatami M. Association between trinucleotide CAG repeats of the DNA polymerase gene (POLG) with age of onset of Iranian Friedreich’s ataxia patients. Neurol Sci. 2008 Dec; 29(6):489-93.Heidari MM, Khatami M, Talebi AR. The POLG Gene Polymorphism in Iranian Varicocele-Associated Infertility Patients. Iran J Basic Med Sci. 2012 Mar; 15(2):739-44.Jensen M, Leffers H, Petersen JH, Nyboe Andersen A, Jorgensen N, Carlsen E, et al. Frequent polymorphism of the mitochondrial DNA polymerase gamma gene (POLG) in patients with normal spermiograms and unexplained subfertility. Hum Reprod. 2004 Jan; 19(1):65-70.Taanman JW, Schapira AH. Analysis of the trinucleotide CAG repeat from the DNA polymerase gamma gene (POLG) in patients with Parkinson’s disease. Neurosci Lett. 2005 Mar 7; 376(1):56-9.Wong LJ, Naviaux RK, Brunetti-Pierri N, Zhang Q, Schmitt ES, Truong C, et al. Molecular and clinical genetics of mitochondrial diseases due to POLG mutations. Hum Mutat. 2008 Sep; 29(9):E150-72.Kumleh HH, Riazi GH, Houshmand M, Sanati MH, Gharagozli K, Shafa M. Complex I deficiency in Persian multiple sclerosis patients. Journal of the Neurological Sciences. 2006 4/15/; 243(1–2):65-9.Ebers GC, Sadovnick AD, Dyment DA, Yee IML, Willer CJ, Risch N. Parent-of-origin effect in multiple sclerosis: observations in half-siblings. The Lancet. 2004; 363(9423):1773-4.Harding A, Sweeney M, Miller D, Mumford C, Kellar-Wood H, Menard D, et al. Occurrence of a multiple sclerosis-like illness in women who have a Leber’s hereditary optic neuropathy mitochondrial DNA mutation. Brain: a journal of neurology.1992; 115(4):979-89.Ahari SE, Houshmand M, Panahi MS, Kasraie S, Moin M, Bahar MA. Investigation on mitochondrial tRNA (Leu/Lys), NDI and ATPase 6/8 in Iranian multiple sclerosis patients. Cell Mol Neurobiol. 2007 Sep; 27(6):695-700.Mahad DJ, Ziabreva I, Campbell G, Lax N, White K, Hanson PS, et al. Mitochondrial changes within axons in multiple sclerosis. Brain: a journal of neurology. 2009 May; 132(Pt 5):1161-74

Manganese-Induced Nephrotoxicity Is Mediated through Oxidative Stress and Mitochondrial Impairment

Manganese (Mn) is an essential element that is incorporated in various metabolic pathways and enzyme structures. On the other hand, a range of adverse effects has been described in association with Mn overexposure. Mn is a well-known neurotoxic agent in mammals. Renal injury is another adverse effect associated with Mn intoxication. No precise mechanism for Mn nephrotoxicity has been identified so far. The current study was designed to evaluate the potential mechanisms of Mn-induced renal injury. Rats were treated with Mn (20 and 40 mg/mL, respectively, in drinking water) for 30 consecutive days. Markers of oxidative stress, as well as several mitochondrial indices, were assessed in the kidney tissue. Renal injury was evident in Mn-treated animals, as judged by a significant increase in serum BUN and creatinine. Moreover, urinalysis revealed a significant increase in urine glucose, phosphate, and protein in Mn-treated rats. Kidney histopathological alterations, including tubular atrophy, interstitial inflammation, and necrosis, were also detected in Mn-treated animals. Biomarkers of oxidative stress, including an increment in reactive oxygen species (ROS), lipid peroxidation, and oxidized glutathione (GSSG), were detected in Mn-treated groups. On the other hand, kidney glutathione (GSH) stores and total antioxidant capacity were depleted in Mn groups. Mn exposure was associated with significant mitochondrial depolarization, decreased mitochondrial dehydrogenases activity, mitochondrial permeabilization, and depletion of adenosine triphosphate (ATP) content. These data highlight oxidative stress and mitochondrial impairment as potential mechanisms involved in Mn-induced renal injury

Synthesis, structure characterization, DNA binding, and cleavage properties of mononuclear and tetranuclear cluster of copper(II) complexes

Two copper(II) complexes, cluster 1, and mononuclear 2, have been synthesized by reacting acetylacetone and benzohydrazide (1:1 ratio for 1 and 1:2 ratio for 2) with CuCl2 in a methanol solution. In 2, which is a new complex, the ligand acts as a tetradentate which binds the metal ion via two amide-O atoms and two imine-N atoms providing an N2O2 squa-re-planar around the copper(II) ion. The absorption spectra data evidence strongly suggested that the two copper(II) compounds could interact with CT-DNA (intrinsic binding constant, Kb = 0.45 × 10⁴ M⁻¹ for 1 and Kb = 2.39 × 10⁴ M⁻¹ for 2). The super coiled plasmid pBR322 DNA cleavage ability was studied with 1 and 2 in the presence and absence of H₂O₂ as an oxidant. In both the absence and the presence of an oxidizing agent, complex 2 exhibited no nuclease activity. However, even in the absence of an oxidant, complex 1 exhibited significant DNA cleavage activity.The authors are grateful to the Yazd University and the Australian National University for partial support of this work

Epidemiology and Outcome of Patients with Acute Kidney Injury in Emergency Department; a Cross-Sectional Study

Introduction: Elimination of preventable deaths due to acute kidney injury (AKI) in low-income countries by 2025 is an important healthcare goal at the international level. The present study was designed with the aim of evaluating the prevalence and outcome of AKI in patients presenting to emergency department.Methods: The present cross-sectional, retrospective study was performed on patients that presented to the emergency departments of 3 major teaching hospitals, Tehran, Iran, between 2005 and 2015 and were diagnosed with AKI. Patient selection was done using consecutive sampling and required data for this study was extracted by referring to the medical profiles of the patients and filling out a checklist designed for the study.Results: 770 AKI patients with the mean age of 62.72 ± 19.79 (1 – 99) years were evaluation (59.1% male). 690 (89.61%) cases of AKI causes were pre-renal or renal. Among the pre-renal causes, 74 (73.3%) cases were due to different types of shock (p < 0.001). The most common etiologic causes of AKI in pre-renal group were hypotension (57.3%) and renal vascular insufficiency (31.6%). In addition, regarding the renal types, rhabdomyolysis (35.0%), medication (17.5%) and chemotherapy (15.3%) and in post-renal types, kidney stone (34.5%) were the most common etiologic causes. 327 (42.5%) patients needed dialysis and 169 (21.9%) patients died. Sex (p = 0.001), age over 60 years (p = 0.001), blood urea nitrogen level (p < 0.001), hyperkalemia (p < 0.001), metabolic acidosis (p < 0.001), cause of failure (p = 0.001), and type of failure (p = 0.009) were independent risk factors of mortality.Conclusion: The total prevalence of AKI in emergency department was 315 for each 1000000 population and preventable mortality rate due to AKI was estimated to be 28.2 cases in each 1000000 population. The most important preventable AKI causes in the pre-renal group included shock, sepsis, and dehydration; in the renal group they included rhabdomyolysis and intoxication; and stones in the post-renal group

The association between TNP2 gene polymorphisms and Iranian infertile men with varicocele: A case-control study

Background: Numerous researches have provided great evidence that revealed the relationship between varicocele and sperm DNA damage. Objective: Because of the crucial role of nuclear transition proteins (TPs) in sperm DNA condensation and integrity, this case-control study was designed to study TNP2 gene nucleotide variations in Iranian patients with varicocele. Materials and Methods: PCR-SSCP and DNA sequencing were used to search for mutations in exons 1 & 2 of the TNP2 gene in 156 infertile patients with varicocele and 150 fertile men. Results: The results of sequencing showed three variants at positions c.301C > T (p.R101C), c.391C > T (p.R131 W), and g.IVS1-26G >C (rs8043625) of TNP2 gene. It was found that varicocele risk in men who have the CC genotype of g.IVS1-26G >C SNP is higher than those who don’t have these genotypes (according to Co-dominant model, Dominant model, Recessive model, and Over-dominant model). The haplotype-based analysis showed that (C/C/T) and (C/T/T) haplotypes were a risk factor of in patients with varicocele compared to controls (OR = 3.278, p = 0.000 and OR= 9.304, p = 0.038, respectively). Conclusion: Because of the significant difference in the genotype and allele frequencies of g.IVS1-26G >C SNP in the intronic region of TNP2 in patients with varicocele compared with controls and also because of the high conservation of this SNP position during evolution, this SNP may be involved in some important processes associated with the expression of this gene like mRNA splicing, but the exact mechanism is not clear