Rectifying METTL4-Mediated N6-Methyladenine Excess in Mitochondrial DNA Alleviates Heart Failure.

BACKGROUND: Myocardial mitochondrial dysfunction underpins the pathogenesis of heart failure (HF), yet therapeutic options to restore myocardial mitochondrial function are scarce. Epigenetic modifications of mitochondrial DNA (mtDNA), such as methylation, play a pivotal role in modulating mitochondrial homeostasis. However, their involvement in HF remains unclear. METHODS: Experimental HF models were established through continuous angiotensin II and phenylephrine (AngII/PE) infusion or prolonged myocardial ischemia/reperfusion injury. The landscape of N6-methyladenine (6mA) methylation within failing cardiomyocyte mtDNA was characterized using high-resolution mass spectrometry and methylated DNA immunoprecipitation sequencing. A tamoxifen-inducible cardiomyocyte-specific Mettl4 knockout mouse model and adeno-associated virus vectors designed for cardiomyocyte-targeted manipulation of METTL4 (methyltransferase-like protein 4) expression were used to ascertain the role of mtDNA 6mA and its methyltransferase METTL4 in HF. RESULTS: METTL4 was predominantly localized within adult cardiomyocyte mitochondria. 6mA modifications were significantly more abundant in mtDNA than in nuclear DNA. Postnatal cardiomyocyte maturation presented with a reduction in 6mA levels within mtDNA, coinciding with a decrease in METTL4 expression. However, an increase in both mtDNA 6mA level and METTL4 expression was observed in failing adult cardiomyocytes, suggesting a shift toward a neonatal-like state. METTL4 preferentially targeted mtDNA promoter regions, which resulted in interference with transcription initiation complex assembly, mtDNA transcriptional stalling, and ultimately mitochondrial dysfunction. Amplifying cardiomyocyte mtDNA 6mA through METTL4 overexpression led to spontaneous mitochondrial dysfunction and HF phenotypes. The transcription factor p53 was identified as a direct regulator of METTL4 transcription in response to HF-provoking stress, thereby revealing a stress-responsive mechanism that controls METTL4 expression and mtDNA 6mA. Cardiomyocyte-specific deletion of the Mettl4 gene eliminated mtDNA 6mA excess, preserved mitochondrial function, and mitigated the development of HF upon continuous infusion of AngII/PE. In addition, specific silencing of METTL4 in cardiomyocytes restored mitochondrial function and offered therapeutic relief in mice with preexisting HF, irrespective of whether the condition was induced by AngII/PE infusion or myocardial ischemia/reperfusion injury. CONCLUSIONS: Our findings identify a pivotal role of cardiomyocyte mtDNA 6mA and the corresponding methyltransferase, METTL4, in the pathogenesis of mitochondrial dysfunction and HF. Targeted suppression of METTL4 to rectify mtDNA 6mA excess emerges as a promising strategy for developing mitochondria-focused HF interventions.

Subtype-Specific Association of Mitochondrial DNA Copy Number With Poststroke/TIA Outcomes in 10†241 Patients in China.

BACKGROUND: Mitochondrial DNA copy number (mtDNA-CN) is associated with the severity and mortality in patients with stroke, but the associations in different stroke subtypes remain unexplored. METHODS: We conducted an observational prospective cohort analysis on patients with ischemic stroke or transient ischemic attack enrolled in the Third China National Stroke Registry. We applied logistic models to assess the association of mtDNA-CN with functional outcome (modified Rankin Scale score, 3-6 versus 0-2) and Cox proportional hazard models to assess the association with stroke recurrence (treating mortality as a competing risk) and mortality during a 12-month follow-up, adjusting for sex, age, physical activity, National Institutes of Health Stroke Scale at admission, history of stroke and peripheral artery disease, small artery occlusion, and interleukin-6. Subgroup analyses stratified by age and stroke subtypes were conducted. RESULTS: The Third China National Stroke Registry enrolled 15 166 patients, of which 10 241 with whole-genome sequencing data were retained (mean age, 62.2 [SD, 11.2] years; 68.8% men). The associations between mtDNA-CN and poststroke/transient ischemic attack outcomes were specific to patients aged ≤65 years, with lower mtDNA-CN significantly associated with stroke recurrence in 12 months (subdistribution hazard ratio, 1.15 per SD lower mtDNA-CN [95% CI, 1.04-1.27]; P=5.2×10-3) and higher all-cause mortality in 3 months (hazard ratio, 2.19 [95% CI, 1.41-3.39]; P=5.0×10-4). Across subtypes, the associations of mtDNA-CN with stroke recurrence were specific to stroke of undetermined cause (subdistribution hazard ratio, 1.28 [95% CI, 1.11-1.48]; P=6.6×10-4). In particular, lower mtDNA-CN was associated with poorer functional outcomes in stroke of undetermined cause patients diagnosed with embolic stroke of undetermined source (odds ratio, 1.53 [95% CI, 1.20-1.94]; P=5.4×10-4), which remained significant after excluding patients with recurrent stroke (odds ratio, 1.49 [95% CI, 1.14-1.94]; P=3.0×10-3). CONCLUSIONS: Lower mtDNA-CN is associated with higher stroke recurrence rate and all-cause mortality, as well as poorer functional outcome at follow-up, among stroke of undetermined cause, embolic stroke of undetermined source, and younger patients.

A case of exacerbated encephalopathy with stroke-like episodes and lactic acidosis triggered by metformin in a patient with MELAS.

Mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is a maternally inherited multisystemic disorder caused by mutations in mitochondrial DNA that result in cellular energy deficiency. MELAS affects the most metabolically active organs, including the brain, skeletal muscles, cochlea, retina, heart, kidneys, and pancreas. As a result, about 85% of carriers of m.3243A > G, the most common mutation in MELAS, develop diabetes by the age of 70. Although metformin is the most widely prescribed drug for diabetes, its usefulness in mitochondrial dysfunction remains controversial. Here, we present the case of a 32-year-old Korean patient diagnosed with MELAS who presented with exacerbated stroke-like episodes and lactic acidosis triggered by metformin.

Heteroplasmy of Wild-Type Mitochondrial DNA Variants in Mice Causes Metabolic Heart Disease With Pulmonary Hypertension and Frailty.

BACKGROUND: In most eukaryotic cells, the mitochondrial DNA (mtDNA) is transmitted uniparentally and present in multiple copies derived from the clonal expansion of maternally inherited mtDNA. All copies are therefore near-identical, or homoplasmic. The presence of >1 mtDNA variant in the same cytoplasm can arise naturally or result from new medical technologies aimed at preventing mitochondrial genetic diseases and improving fertility. The latter is called divergent nonpathologic mtDNA heteroplasmy (DNPH). We hypothesized that DNPH is maladaptive and usually prevented by the cell. METHODS: We engineered and characterized DNPH mice throughout their lifespan using transcriptomic, metabolomic, biochemical, physiologic, and phenotyping techniques. We focused on in vivo imaging techniques for noninvasive assessment of cardiac and pulmonary energy metabolism. RESULTS: We show that DNPH impairs mitochondrial function, with profound consequences in critical tissues that cannot resolve heteroplasmy, particularly cardiac and skeletal muscle. Progressive metabolic stress in these tissues leads to severe pathology in adulthood, including pulmonary hypertension and heart failure, skeletal muscle wasting, frailty, and premature death. Symptom severity is strongly modulated by the nuclear context. CONCLUSIONS: Medical interventions that may generate DNPH should address potential incompatibilities between donor and recipient mtDNA.

Extracellular Tuning of Mitochondrial Respiration Leads to Aortic Aneurysm.

BACKGROUND: Marfan syndrome (MFS) is an autosomal dominant disorder of the connective tissue caused by mutations in the FBN1 (fibrillin-1) gene encoding a large glycoprotein in the extracellular matrix called fibrillin-1. The major complication of this connective disorder is the risk to develop thoracic aortic aneurysm. To date, no effective pharmacologic therapies have been identified for the management of thoracic aortic disease and the only options capable of preventing aneurysm rupture are endovascular repair or open surgery. Here, we have studied the role of mitochondrial dysfunction in the progression of thoracic aortic aneurysm and mitochondrial boosting strategies as a potential treatment to managing aortic aneurysms. METHODS: Combining transcriptomics and metabolic analysis of aortas from an MFS mouse model (Fbn1c1039g/+) and MFS patients, we have identified mitochondrial dysfunction alongside with mtDNA depletion as a new hallmark of aortic aneurysm disease in MFS. To demonstrate the importance of mitochondrial decline in the development of aneurysms, we generated a conditional mouse model with mitochondrial dysfunction specifically in vascular smooth muscle cells (VSMC) by conditional depleting Tfam (mitochondrial transcription factor A; Myh11-CreERT2Tfamflox/flox mice). We used a mouse model of MFS to test for drugs that can revert aortic disease by enhancing Tfam levels and mitochondrial respiration. RESULTS: The main canonical pathways highlighted in the transcriptomic analysis in aortas from Fbn1c1039g/+ mice were those related to metabolic function, such as mitochondrial dysfunction. Mitochondrial complexes, whose transcription depends on Tfam and mitochondrial DNA content, were reduced in aortas from young Fbn1c1039g/+ mice. In vitro experiments in Fbn1-silenced VSMCs presented increased lactate production and decreased oxygen consumption. Similar results were found in MFS patients. VSMCs seeded in matrices produced by Fbn1-deficient VSMCs undergo mitochondrial dysfunction. Conditional Tfam-deficient VSMC mice lose their contractile capacity, showed aortic aneurysms, and died prematurely. Restoring mitochondrial metabolism with the NAD precursor nicotinamide riboside rapidly reverses aortic aneurysm in Fbn1c1039g/+ mice. CONCLUSIONS: Mitochondrial function of VSMCs is controlled by the extracellular matrix and drives the development of aortic aneurysm in Marfan syndrome. Targeting vascular metabolism is a new available therapeutic strategy for managing aortic aneurysms associated with genetic disorders.

Mitochondrial DNA Heteroplasmy of Hair Shaft Using HID Ion GeneStudioTM S5 Sequencing System.

ABSTRACT: Objective To study the heteroplasmy of the whole mitochondrial genome genotyping result of hair shaft samples using HID Ion GeneStudioTM S5 Sequencing System. Methods The buccal swabs and blood of 8 unrelated individuals, and hair shaft samples from different parts of the same individual were collected. Amplification of whole mitochondrial genome was performed using Precision ID mtDNA Whole Genome Panel. Analysis and detection of whole mitochondrial genome were carried out using the HID Ion GeneStudioTM S5 Sequencing System. Results The mitochondrial DNA sequences in temporal hair shaft samples from 2 individuals showed heteroplasmy, while whole mitochondrial genome genotyping results of buccal swabs, blood, and hair samples from the other 6 unrelated individuals were consistent. A total of 119 base variations were observed from the 8 unrelated individuals. The numbers of variable sites of the individuals were 29, 40, 38, 35, 13, 36, 40 and 35, respectively. Conclusion Sequence polymorphism can be fully understood using HID Ion GeneStudioTM S5 Sequencing system.

Changes in peripheral mitochondrial DNA copy number in metformin-treated women with polycystic ovary syndrome: a longitudinal study.

BACKGROUND: Patients with polycystic ovarian syndrome (PCOS) are associated with known alterations in mitochondria DNA copy number (mtDNA-CN). The aim of this study is to study the change in mtDNA-CN in patients with PCOS who were treated with metformin. METHODS: This is a prospective cohort of patients with PCOS, who received metformin for one year. From 2009 to 2015, 88 women diagnosed with PCOS, based on the Rotterdam criteria, were enrolled. Serial measurements of mtDNA-CN, 8-hydroxydeoxyguanosine (8-OHdG), anthropometric, metabolic, endocrine, and inflammatory markers were obtained before and after 3, 6, and 12 months of treatment. RESULTS: A significant decrease in mtDNA-CN was seen over the course of one year. Other markers, including 8-OHdG, testosterone, free androgen index, blood pressure and liver enzymes, also decreased in the same interval. On regression analysis, there was a significant association between the change in mtDNA-CN and serum total testosterone, and no association between mtDNA-CN and metabolic factors. CONCLUSIONS: Treatment with metformin is associated with a time-dependent decrease in mtDNA-CN in patients with PCOS who are treated over the course of one year. This may signify a reduction in mitochondria dysfunction. The change in mtDNA-CN corresponds to a similar change in serum total testosterone, and suggests a possible relationship between mtDNA-CN and testosterone. TRIAL REGISTRATION: ClinicalTrials.gov , NCT00172523 . Registered September 15, 2005.

The heart in m.3243A>G carriers.

OBJECTIVES: Little is known about cardiac involvement in m.3243A>G variant carriers. Thus, this study aimed to assess type and frequency of cardiac disease in symptomatic and asymptomatic m.3243A>G carriers. METHODS: Systematic literature review. RESULTS: The m.3243A>G variant may manifest phenotypically as mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), maternally inherited diabetes and deafness (MIDD), myoclonic epilepsy with ragged red fiber (MERRF), Leigh syndrome, or MELAS/KSS (Kearns-Sayre syndrome) overlap. Only few systematic studies which prospectively investigated m.3243A>G carriers for cardiac involvement were found. Cardiac abnormalities reported in m.3243A>G carriers include myocardial abnormalities, arrhythmias, or conduction defects. Myocardial abnormalities include myocardial thickening, hypertrophic cardiomyopathy, dilated cardiomyopathy, noncompaction, myocardial fibrosis, systolic dysfunction, heart failure, or arterial hypertension. Arrhythmias reported in m.3243A>G carriers include paroxysmal supraventricular or ventricular arrhythmias, including sinus tachycardia, atrial fibrillation and nonsustained ventricular tachycardia, and sudden cardiac death. Conduction defects in this group of patients include Wolff-Parkinson-White syndrome and left/right bundle branch block. Asymptomatic m.3243A>G carriers usually do not develop clinical or subclinical cardiac disease. CONCLUSIONS: Cardiac involvement in m.3243A>G carriers has been only rarely systematically studied, which is perhaps why the incidence of cardiac diseases in MELAS is lower than would be expected. Myocardial abnormalities are much more frequent than arrhythmias or conduction defects. All symptomatic and asymptomatic m.3243A>G carriers should be systematically investigated for cardiac disease.

Application of Multiple Genetic Markers in Determination of Full and Half Sibling Relationship： A Case Report.

ABSTRACT: Objective To investigate the application of the comprehensive use of multiple genetic markers in full and half sibling relationship testing through the identification of a case of suspected sibling relationship. Methods Genomic DNA were extracted from bloodstain samples from 4 subjects （ZHANG-1, ZHANG-2, male; ZHANG-3, ZHANG-4, female）. Autosomal STR loci, X-STR, Y-STR loci and polymorphisms of mtDNA HV-Ⅰ and Ⅱwere genotyped by EX20 STR kit, X19 kit, Data Y24 STR kit, and Sanger sequencing, respectively. Results According to autosomal STR based IBS scoring results, full sibling relationships were indicated among ZHANG-2, ZHANG-3 and ZHANG-4, but those were not indicated between ZHANG-1 and ZHANG-2 or ZHANG-3 or ZHANG-4. According to autosomal STR based FSI and HSI, with ITO method and discriminant function method, full sibling relationships among ZHANG-2, ZHANG-3 and ZHANG-4 were indicated, and half sibling relationships between ZHANG-1 and ZHANG-2 or ZHANG-3 or ZHANG-4 were also indicated. X-STR and mtDNA sequencing results showed that all the 4 samples came from a same maternal line, and Y-STR results showed that ZHANG-1 and ZHANG-2 did not come from a same paternal line, which supported the half sibling relationship between ZHANG-1 and ZHANG-2 or ZHANG-3 or ZHANG-4, verified by parental genotype reconstruction based on autosomal STR genotyping. Conclusion For the identification of sibling relationships, it is effective to have reliable results with the mutual verification and support of multiple genetic markers （autosomal STR, sex chromosomal STR and mtDNA sequence） and calculations （IBS, ITO, discriminant function method and family reconstruction）.

Mitochondrial Oxidative Stress Promotes Atherosclerosis and Neutrophil Extracellular Traps in Aged Mice.

RATIONALE: Mitochondrial oxidative stress (mitoOS) has been shown to be increased in various cell types in human atherosclerosis and with aging. However, the role of cell type-specific mitoOS in atherosclerosis in the setting of advanced age and the molecular mechanisms remains to be determined in vivo. OBJECTIVE: The aim of this study was to examine the role of myeloid cell mitoOS in atherosclerosis in aged mice. APPROACH AND RESULTS: Lethally irradiated low-density lipoprotein receptor-deficient mice (Ldlr-/-) were reconstituted with bone marrow from either wild-type or mitochondrial catalase (mCAT) mice. mCAT transgenic mice contain ectopically expressed human catalase gene in mitochondria, which reduces mitoOS. Starting at the age of 36 weeks, mice were fed the Western-type diet for 16 weeks. We found that mitoOS in lesional myeloid cells was suppressed in aged mCAT→Ldlr-/- chimeric mice compared with aged controls, and this led to a significant reduction in aortic root atherosclerotic lesion area despite higher plasma cholesterol levels. Neutrophil extracellular traps (NETs), a proinflammatory extracellular structure that contributes to atherosclerosis progression, were significantly increased in the lesions of aged mice compared with lesions of younger mice. Aged mCAT→Ldlr-/- mice had less lesional neutrophils and decreased NETs compared with age-matched wild-type→Ldlr-/- mice, whereas young mCAT→ and wild-type→Ldlr-/- mice had comparable numbers of neutrophils and similar low levels of lesional NETs. Using cultured neutrophils, we showed that suppression of mitoOS reduced 7-ketocholesterol-induced NET release from neutrophils of aged but not younger mice. CONCLUSIONS: MitoOS in lesional myeloid cells enhanced atherosclerosis development in aged mice, and this enhancement was associated with increased lesional NETs. Thus, mitoOS-induced NET formation is a potentially new therapeutic target to prevent atherosclerosis progression during aging.

STING-IRF3 Triggers Endothelial Inflammation in Response to Free Fatty Acid-Induced Mitochondrial Damage in Diet-Induced Obesity.

OBJECTIVE: Metabolic stress in obesity induces endothelial inflammation and activation, which initiates adipose tissue inflammation, insulin resistance, and cardiovascular diseases. However, the mechanisms underlying endothelial inflammation induction are not completely understood. Stimulator of interferon genes (STING) is an important molecule in immunity and inflammation. In the present study, we sought to determine the role of STING in palmitic acid-induced endothelial activation/inflammation. APPROACH AND RESULTS: In cultured endothelial cells, palmitic acid treatment activated STING, as indicated by its perinuclear translocation and binding to interferon regulatory factor 3 (IRF3), leading to IRF3 phosphorylation and nuclear translocation. The activated IRF3 bound to the promoter of ICAM-1 (intercellular adhesion molecule 1) and induced ICAM-1 expression and monocyte-endothelial cell adhesion. When analyzing the upstream signaling, we found that palmitic acid activated STING by inducing mitochondrial damage. Palmitic acid treatment caused mitochondrial damage and leakage of mitochondrial DNA into the cytosol. Through the cytosolic DNA sensor cGAS (cyclic GMP-AMP synthase), the mitochondrial damage and leaked cytosolic mitochondrial DNA activated the STING-IRF3 pathway and increased ICAM-1 expression. In mice with diet-induced obesity, the STING-IRF3 pathway was activated in adipose tissue. However, STING deficiency (Stinggt/gt ) partially prevented diet-induced adipose tissue inflammation, obesity, insulin resistance, and glucose intolerance. CONCLUSIONS: The mitochondrial damage-cGAS-STING-IRF3 pathway is critically involved in metabolic stress-induced endothelial inflammation. STING may be a potential therapeutic target for preventing cardiovascular diseases and insulin resistance in obese individuals.

[A study of clinical and genetic characteristics of a Leber hereditary optic neuropathy family with the heteroplasmic m.14484T>C mutation].

Objective: To study clinical and genetic characteristics of a Leber hereditary optic neuropathy (LHON) family with the heteroplasmic m.14484T>C mutation. Methods: A cross-sectional study. The objects of the study included a 31-year-old male LHON patient with the heteroplasmic m.14484T>C mutation (the proband) who visited Department of Ophthalmology in the Affiliated Central Hospital of Qingdao University in March 2015 and other 36 matrilineal relatives in a four-generation family (12 males and 24 females aged 2-81 years, median 27 years). The visual acuity, intraocular pressure, fundus, color vision, visual field, visual evoked potential and optical coherence tomography were evaluated in maternal members. The mitochondrial DNA (mtDNA) sequence of fragments including m.14484 loci was detected by Sanger sequencing in 33 members. The sequencing peaks were analyzed by QSVanalyzer software to get the heteroplasmy levels of m.14484T>C mutation. The mtDNA of the proband was amplified by PCR and sequenced. Assembled sequence of mtDNA was compared with the updated consensus Cambridge sequence. The differences in visual evoked potential, optical coherence tomography and heteroplasmy levels were compared between two groups by the t-test, and among multiple groups by the single factor variance analysis. Results: Among the 33 maternal members of the family, 4 patients, 28 carriers and 1 person without a mutation were confirmed. The penetrance was 12.5% (4/32) . In addition to 4 patients with obvious abnormality on the ophthalmic examination, 5 carriers also appeared anomaly on the electrophysiological and visual function examinations. Compared to carriers, the amplitude of P100 was obviously decreased in the LHON patients[ (5.6±2.6) µV vs. (15.6±9.6) µV, t=2.880, P=0.006]. Significantly reduced values were seen in the average retinal nerve fiber layer thickness[ (71±17) µm vs. (99±11) µm, t=5.969, P< 0.001], in each side of the sub-area macular thickness, and in the nasal side of the lateral sub-area macular thickness [ (260±16) µm vs. (291±12) µm, t=5.593, P<0.001] between the LHON patients and carriers. The heteroplasmic levels were 80%±3% in the LHON patients, and 27%±18% in the unaffected members;the difference was significant (t=-8.395, P<0.001). The average degree of heteroplasmy had no difference between male and female members (48%±34% vs. 35%±28%, t=-1.147, P=0.258). The average mutation load was 29%±14% in the second generation members, 36%±29% in the third generation members, and 51%±36% in the fourth generation members;the differences were not statistically significant (F=1.152, P=0.330). The difference in the heteroplasmic levels was not statistically significant between mothers and their offspring (31%±25% vs. 42%±32%, t=1.165, P=0.251). Compared to Cambridge consensus sequence, 41 mutations was found in mtDNA of the proband, of which, 10 were missense mutations, including mutations m.4216T>C and m.3394T>C. According to the phylogenetic tree, the haplotype of the proband was M9a (M9a1a1c1a). Conclusions: In the family with the heteroplasmic m.14484T>C mutation, clinical manifestations of LHON appear in the individuals whose heteroplasmic level is more than 75%, and all of patients show typical chronic optic atrophy on the ophthalmic examination. The carriers with the m.14484T>C mutation also appear anomaly on the electrophysiological and visual function examinations. The heteroplasmic level of m.14484T>C mutation has a tendency to increase during the transmission in the family. The primary mutation m.14484T>C coordinate mutations m.4216T>C and m.3394T>C to increase the penetrance and incidence of abnormal visual function in carriers. (Chin J Ophthalmol, 2018, 54: 526-534).

[Clinical research progress of gene therapy for Leber hereditary optic neuropathy].

Leber hereditary optic neuropathy (LHON) is a mitochondria hereditary eye disease that involves with retinal ganglion cells (RGCs) resulting eventually in degeneration and atrophy of optic nerve. The three mitochondrial DNA mutations (ND4 G11778A, ND1G3460A, ND6T14484C) have been recognized as the primary mutation locus of LHON. Currently there is no effective therapy for LHON. The result of a clinical trial launched in 2007 indicated that intraocular injection of the recombination of adeno-associated virus and target gene is an effective and safe cure for Leber's Congenital Amaurosis (LCA), which brings hope of treating other hereditary eye diseases with gene therapy. Since LHON mainly involves with RGCs, the target gene can be delivered directly to RGCs with the means of injecting the recombination into vitreous cavity, therefore resulting in less damage to retina as compared to other gene therapy for LCA which require the drug to be injected under the retina. This article summarizes the research progress of the clinical trial relevant to gene therapy for LHON. (Chin J Ophthalmol, 2018, 54: 636-640).

Mitochondrial genome of Plasmodium vivax/simium detected in an endemic region for malaria in the Atlantic Forest of Espírito Santo state, Brazil: do mosquitoes, simians and humans harbour the same parasite?

BACKGROUND: The transmission of malaria in the extra-Amazonian regions of Brazil, although interrupted in the 1960s, has persisted to the present time in some areas of dense Atlantic Forest, with reports of cases characterized by particular transmission cycles and clinical presentations. Bromeliad-malaria, as it is named, is particularly frequent in the state of Espírito Santo, with Plasmodium vivax being the parasite commonly recognized as the aetiologic agent of human infections. With regard to the spatial and temporal distances between cases reported in this region, the transmission cycle does not fit the traditional malaria cycle. The existence of a zoonosis, with infected simians participating in the epidemiology, is therefore hypothesized. In the present study, transmission of bromeliad-malaria in Espírito Santo is investigated, based on the complete mitochondrial genome of DNA extracted from isolates of Plasmodium species, which had infected humans, a simian from the genus Allouata, and Anopheles mosquitoes. Plasmodium vivax/simium was identified in the samples by both nested PCR and real-time PCR. After amplification, the mitochondrial genome was completely sequenced and compared with a haplotype network which included all sequences of P. vivax/simium mitochondrial genomes sampled from humans and simians from all regions in Brazil. RESULTS: The haplotype network indicates that humans and simians from the Atlantic Forest become infected by the same haplotype, but some isolates from humans are not identical to the simian isolate. In addition, the plasmodial DNA extracted from mosquitoes revealed sequences different from those obtained from simians, but similar to two isolates from humans. CONCLUSIONS: These findings strengthen support for the hypothesis that in the Atlantic Forest, and especially in the state with the highest frequency of bromeliad-malaria in Brazil, parasites with similar molecular backgrounds are shared by humans and simians. The recognized identity between P. vivax and P. simium at the species level, the sharing of haplotypes, and the participation of the same vector in transmitting the infection to both host species indicate interspecies transference of the parasites. However, the intensity, frequency and direction of this transfer remain to be clarified.

Aging Reversal and Healthy Longevity is in Reach: Dependence on Mitochondrial DNA Heteroplasmy as a Key Molecular Target.

Recent trends in biomedical research have highlighted the potential for effecting significant extensions in longevity with enhanced quality of life in aging human populations. Within this context, any proposed method to achieve enhanced life extension must include therapeutic approaches that draw upon essential biochemical and molecular regulatory processes found in relatively simple single cell organisms that are evolutionarily conserved within complex organ systems of higher animals. Current critical thinking has established the primacy of mitochondrial function in maintaining good health throughout plant and animal phyla. The mitochondrion represents an existentially defined endosymbiotic model of complex organelle development driven by evolutionary modification of a permanently enslaved primordial bacterium. Cellular mitochondria are biochemically and morphologically tailored to provide exponentially enhanced ATP-dependent energy production accordingly to tissue- and organ-specific physiological demands. Thus, individual variations in longevity may then be effectively sorted according to age-dependent losses of single-cell metabolic integrity functionally linked to impaired mitochondrial bioenergetics within an aggregate presentation of compromised complex organ systems. Recent empirical studies have focused on the functional role of mitochondrial heteroplasmy in the regulation of normative cellular processes and the initiation and persistence of pathophysiological states. Accordingly, elucidation of the multifaceted functional roles of mitochondrial heteroplasmy in normal aging and enhanced longevity will provide both a compelling genetic basis and potential targets for therapeutic intervention to effect meaningful life extension in human populations.

[Relationship between mitochondrial DNA copy number, membrane potential of human embryo and embryo morphology].

Objective: To explore the relationship between the embryo with the different morphological types in the third day and its mitochondrial copy number, the membrane potential. Methods: Totally 117 embryos with poor development after normal fertilization and were not suitable transferred in the fresh cycle and 106 frozen embryos that were discarded voluntarily by infertility patients with in vitro fertilization-embryo transfer after successful pregnancy were selected. According to evaluation of international standard in embryos, all cleavage stage embryos were divided into class Ⅰ frozen embryo group (n=64), class Ⅱ frozen embryo group (n=42) and class Ⅲ fresh embryonic group (not transplanted embryos; n=117). Real-time PCR and confocal microscopy methods were used to detect mitochondrial DNA (mtDNA) copy number and the mitochondrial membrane potential of a single embryo. The differences between embryo quality and mtDNA copy number and membrane potential of each group were compared. Results: The copy number of mtDNA and the mitochondrial membrane potential in class Ⅲ fresh embryonic group [(1.7±1.0)×10(5) copy/µl, 1.56±0.32] were significantly lower than those in class Ⅰ frozen embryo group [(3.4±1.7)×10(5) copy/µl, 2.66±0.21] and class Ⅱ frozen embryo group [(2.6±1.2)×10(5) copy/µl, 1.80±0.32; all P<0.05]. The copy number of mtDNA and the mitochondrial membrane potential in classⅠ frozen embryo group were significantly higher than those in classⅡ frozen embryo group (both P<0.05). Conclusion: The mtDNA copy number and the mitochondrial membrane potential of embryos of the better quality embryo are higher.

[Whole Genome Sequencing of Human mtDNA Based on Ion Torrent PGM™ Platform].

OBJECTIVES: To analyze and detect the whole genome sequence of human mitochondrial DNA （mtDNA） by Ion Torrent PGM™ platform and to study the differences of mtDNA sequence in different tissues. METHODS: Samples were collected from 6 unrelated individuals by forensic postmortem examination, including chest blood, hair, costicartilage, nail, skeletal muscle and oral epithelium. Amplification of whole genome sequence of mtDNA was performed by 4 pairs of primer. Libraries were constructed with Ion Shear™ Plus Reagents kit and Ion Plus Fragment Library kit. Whole genome sequencing of mtDNA was performed using Ion Torrent PGM™ platform. Sanger sequencing was used to determine the heteroplasmy positions and the mutation positions on HVⅠ region. RESULTS: The whole genome sequence of mtDNA from all samples were amplified successfully. Six unrelated individuals belonged to 6 different haplotypes. Different tissues in one individual had heteroplasmy difference. The heteroplasmy positions and the mutation positions on HVⅠ region were verified by Sanger sequencing. After a consistency check by the Kappa method, it was found that the results of mtDNA sequence had a high consistency in different tissues. CONCLUSIONS: The testing method used in present study for sequencing the whole genome sequence of human mtDNA can detect the heteroplasmy difference in different tissues, which have good consistency. The results provide guidance for the further applications of mtDNA in forensic science.

Mitochondrial DNA Haplogroups and Neurocognitive Impairment During HIV Infection.

BACKGROUND: Neurocognitive impairment (NCI) remains an important complication in persons infected with human immunodeficiency virus (HIV). Ancestry-related mitochondrial DNA (mtDNA) haplogroups have been associated with outcomes of HIV infection and combination antiretroviral therapy (CART), and with neurodegenerative diseases. We hypothesize that mtDNA haplogroups are associated with NCI in HIV-infected adults and performed a genetic association study in the CNS HIV Antiretroviral Therapy Effects Research (CHARTER) cohort. METHODS: CHARTER is an observational study of ambulatory HIV-infected adults. Haplogroups were assigned using mtDNA sequence, and principal components were derived from ancestry-informative nuclear DNA variants. Outcomes were cross-sectional global deficit score (GDS) as a continuous measure, GDS impairment (GDS ≥ 0.50), and HIV-associated neurocognitive disorder (HAND) using international criteria. Multivariable models were adjusted for comorbidity status (incidental vs contributing), current CART, plasma HIV RNA, reading ability, and CD4 cell nadir. RESULTS: Haplogroups were available from 1027 persons; median age 43 years, median CD4 nadir 178 cells/mm(3), 72% on CART, and 46% with HAND. The 102 (9.9%) persons of genetically determined admixed Hispanic ancestry had more impairment by GDS or HAND than persons of European or African ancestry (P < .001 for all). In multivariate models including persons of admixed Hispanic ancestry, those with haplogroup B had lower GDS (ß = -0.34; P = .008) and less GDS impairment (odds ratio = 0.16; 95% confidence interval, .04, .63; P = .009) than other haplogroups. There were no significant haplogroup associations among persons of European or African ancestry. CONCLUSIONS: In these mostly CART-treated persons, mtDNA haplogroup B was associated with less NCI among persons of genetically determined Hispanic ancestry. mtDNA variation may represent an ancestry-specific factor influencing NCI in HIV-infected persons.

Divergent mitochondrial biogenesis responses in human cardiomyopathy.

BACKGROUND: Mitochondria are key players in the development and progression of heart failure (HF). Mitochondrial (mt) dysfunction leads to diminished energy production and increased cell death contributing to the progression of left ventricular failure. The fundamental mechanisms that underlie mt dysfunction in HF have not been fully elucidated. METHODS AND RESULTS: To characterize mt morphology, biogenesis, and genomic integrity in human HF, we investigated left ventricular tissue from nonfailing hearts and end-stage ischemic (ICM) or dilated (DCM) cardiomyopathic hearts. Although mt dysfunction was present in both types of cardiomyopathy, mt were smaller and increased in number in DCM compared with ICM or nonfailing hearts. mt volume density and mtDNA copy number was increased by ≈2-fold (P<0.001) in DCM hearts in comparison with ICM hearts. These changes were accompanied by an increase in the expression of mtDNA-encoded genes in DCM versus no change in ICM. mtDNA repair and antioxidant genes were reduced in failing hearts, suggestive of a defective repair and protection system, which may account for the 4.1-fold increase in mtDNA deletion mutations in DCM (P<0.05 versus nonfailing hearts, P<0.05 versus ICM). CONCLUSIONS: In DCM, mt dysfunction is associated with mtDNA damage and deletions, which could be a consequence of mutating stress coupled with a peroxisome proliferator-activated receptor γ coactivator 1α-dependent stimulus for mt biogenesis. However, this maladaptive compensatory response contributes to additional oxidative damage. Thus, our findings support further investigations into novel mechanisms and therapeutic strategies for mt dysfunction in DCM.

Mitochondrial DNA mutations in Medulloblastoma.

To date, several studies on genomic events underlying medulloblastoma (MB) biology have expanded our understanding of this tumour entity and led to its division into four groups-WNT, SHH, group 3 (G3) and group 4 (G4). However, there is little information about the relevance of pathogenic mitochondrial DNA (mtDNA) mutations and their consequences across these. In this report, we describe the case of a female patient with MB and a mitochondriopathy, followed by a study of mtDNA variants in MB groups. After being diagnosed with G4 MB, the index patient was treated in line with the HIT 2000 protocol with no indications of relapse after five years. Long-term side effects of treatment were complemented by additional neurological symptoms and elevated lactate levels ten years later, resulting in suspected mitochondrial disease. This was confirmed by identifying a mutation in the MT-TS1 gene which appeared homoplasmic in patient tissue and heteroplasmic in the patient's mother. Motivated by this case, we explored mtDNA mutations across 444 patients from ICGC and HIT cohorts. While there was no statistically significant enrichment of mutations in one MB group, both cohorts encompassed a small group of patients harbouring potentially deleterious mtDNA variants. The case presented here highlights the possible similarities between sequelae caused by MB treatment and neurological symptoms of mitochondrial dysfunction, which may apply to patients across all MB groups. In the context of the current advances in characterising and interpreting mtDNA aberrations, recognising affected patients could enhance our future knowledge regarding the mutations' impact on carcinogenesis and cancer treatment.