Association of mitochondrial DNA 10398 A/G polymorphism with attention deficit and hyperactivity disorder in Korean children

Mitochondrial DNA variants, haplogroups and risk of Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

Growing evidence has shown that mitochondrial dysfunction is part of the pathogenesis of Parkinson's disease (PD). However, the role of mitochondrial DNA (mtDNA) variants on PD onset is unclear.

OBJECTIVES

The present study aims to evaluate the effect of mtDNA variants and haplogroups on risk of developing PD.

METHODS

Systematic review and meta-analysis of studies investigating associations between PD and mtDNA variants and haplogroups.

RESULTS

A total of 33 studies were eligible from 957 screened studies. Among 13,640 people with PD and 22,588 control individuals, the association with PD was consistently explored in 13 mtDNA variants in 10 genes and 19 macrohaplogroups. Four mtDNA variants were associated with PD: m.4336C (odds ratio [OR] = 2.99; 95 % confidence interval [CI] = 1.79-5.02), m.7028T (OR = 0.80; 95 % CI = 0.70-0.91), m.10398G (OR = 0.92; 95 % CI = 0.85-0.98), and m.13368A (OR = 0.74; 95 % CI = 0.56-0.98). Four mtDNA macrohaplogroups were associated with PD: R (OR = 2.25; 95 % CI = 1.92-2.65), F (OR = 1.18; 95 % CI = 1.01-1.38), H (OR = 1.12; 95 % CI = 1.06-1.18), and B (OR = 0.77; 95 % CI = 0.65-0.92).

CONCLUSIONS

Despite most studies may be underpowered by the underrepresentation of people without dominant European- and Asian-ancestry, low use of next-generation sequencing for genotyping and small sample sizes, the identification of mtDNA variants and macrohaplogroups associated with PD strengthens the link between the disease and mitochondrial dysfunction and mtDNA genomic instability.

Systematic review of mitochondrial genetic variation in attention-deficit/hyperactivity disorder

The global prevalence of attention-deficit/hyperactivity disorder (ADHD) is estimated to be between 6% and 7% in children worldwide. The pathophysiology of this heterogeneous neurodevelopmental disorder remains unknown. Mitochondrial dysfunction has been proposed as a possible contributing factor to the etiology of ADHD. There is limited literature available to help our understanding of this hypothesis, and thus we conducted a systematic review of the number and quality of studies pertaining to mitochondrial genetic alterations in ADHD. A systematic search was conducted in the relevant databases Medline (PubMed) and Embase up to March 2021. Inclusion criteria included randomized control trials, cross-sectional studies, and case-control studies. This search resulted in a total of 507 articles that emerged from the search criteria. Of these results, 10 primary research articles were selected for in depth review based on the inclusion and exclusion criteria. These studies all reported on mitochondrial genetic variation in ADHD cases such as increased copy number, single-nucleotide polymorphisms, and haplogroup associations. This initial review of the experimental literature suggests mitochondrial genetic variation, in both the mitochondrial DNA and nuclear-encoded mitochondrial genes, may indeed contribute to ADHD pathophysiology. The studies reviewed here provide promising evidence for future research to further examine the mitochondrial genetics contributing to ADHD pathophysiology. We suggest that expansion of investigations into mitochondrial mechanisms may have potential to inform new treatment options for ADHD.

Mitochondrial DNA Changes in Respiratory Complex I Genes in Brain Gliomas

Mitochondria are organelles necessary for oxidative phosphorylation. The interest in the role of mitochondria in the process of carcinogenesis results from the fact that a respiratory deficit is found in dividing cells, especially in cells with accelerated proliferation. The study included tumor and blood material from 30 patients diagnosed with glioma grade II, III and IV according to WHO (World Health Organization). DNA was isolated from the collected material and next-generation sequencing was performed on the MiSeqFGx apparatus (Illumina). The study searched for a possible relationship between the occurrence of specific mitochondrial DNA polymorphisms in the respiratory complex I genes and brain gliomas of grade II, III and IV. The impact of missense changes on the biochemical properties, structure and functioning of the encoded protein, as well as their potential harmfulness, were assessed in silico along with their belonging to a given mitochondrial subgroup. The A3505G, C3992T, A4024G, T4216C, G5046A, G7444A, T11253C, G12406A and G13604C polymorphisms were assessed as deleterious changes in silico, indicating their association with carcinogenesis.

Mitochondrial dysfunction in cognitive neurodevelopmental disorders: Cause or effect?

Mitochondria have a crucial role in brain development and neurogenesis, both in embryonic and adult brains. Since the brain is the highest energy consuming organ, it is highly vulnerable to mitochondrial dysfunction. This has been implicated in a range of brain disorders including, neurodevelopmental conditions, psychiatric illnesses, and neurodegenerative diseases. Genetic variations in mitochondrial DNA (mtDNA), and nuclear DNA encoding mitochondrial proteins, have been associated with several cognitive disorders. However, it is not yet clear whether mitochondrial dysfunction is a primary cause of these conditions or a secondary effect. Our review article deals with this topic, and brings out recent advances in mitochondria-oriented therapies. Mitochondrial dysfunction could be involved in the pathogenesis of a subset of disorders involving cognitive impairment. In these patients, mitochondrial dysfunction could be the cause of the condition, rather than the consequence. There are vast areas in this topic that remains to be explored and elucidated.

Mitochondrial DNA variants spectrum and the association with chronic Tic disorders

BACKGROUND

Tic disorders (TD) are childhood-onset neuropsychiatric disorders characterized by single or multiple sudden, rapid, recurrent, and motor tics and/or vocal tics. Several nuclear genes that involved in mitochondrial functions suggest potential role of mitochondria in tic deficit.

METHODS

To evaluate the association of mitochondrial DNA (mtDNA) variants with Tic disorders, we screened the whole mitochondrial genomes in 493 TD patients and 109 age- and sex matched healthy controls using next-generation sequencing technology.

RESULTS

A total of 1918 mtDNA variants including 1220 variants in patients only, 154 variants in controls only, and 544 variants shared by both cases and controls were identified. We found higher number of overall mtDNA variants in TD patients (P =0.00028). The variant density in MT-ATP6/8 and MT-CYB coding regions had significant difference between TD patients and controls (P=0.0025 and P=0.003, respectively). Furthermore, we observed a significant association of 15 common variants with TD based on additive model, including m.14766C>T, m.14783T>C, m.14905G>A, and m.15301G>A in MT-CYB; m.4769A>G, m.10398A>G, m.12705C>T, and m.12850A>G in MT-ND genes; m.7028C>T in MT-CO1; m.8701A>G in MT-ATP6; two noncoding variants with m.16223C>T, m.5580T>C; and three rRNA variants with m.1438A>G and m.750A>G in RNR1, and m.2352T>C in RNR2.

CONCLUSIONS

Our data provide the evidence of mtDNA variants associated with tic disorders. The accumulation of the heteroplasmic levels may increase the risk of TD. Replication studies with larger samples are necessary to understand the pathogenesis of TD.

Genetic Diversity Analysis of the Chinese Daur Ethnic Group in Heilongjiang Province by Complete Mitochondrial Genome Sequencing

Mitochondrial DNA (mtDNA) has the characteristics of maternal inheritance, high mutation rate, high copy number, and no recombination. As the most powerful tool for studying the origin and evolution of modern humans, mtDNA has great significance in the research of population genetics and evolutionary genetics. Here, we provide new insights into the maternal genetic history of the Daur ethnic group by generating complete mitochondrial genomes from a total of 146 Daur individuals in China. We also collected the published complete mitochondrial genome sequences of 5,094 individuals from 56 worldwide populations as reference data to further explore the matrilineal genetic landscape of the Daur ethnic group. First, the haplotype diversity was 0.9943 ± 0.0019 and nucleotide diversity was 0.0428 ± 0.0210. The neutrality tests of the Daur group showed significant negative values and the mismatch distribution curve was obviously distributed in a unimodal pattern. The results showed that the Daur ethnic group has high genetic diversity and may have experienced recent population expansion. In addition, the main haplogroups of the Daur population were haplogroup D (31.51%), M* (20.55%), C (10.28%), F (7.53%), and B (6.85%), all of which were prevalent in northern China. It probably implies the northern Chinese origin of the Daur population. The PCA, F_ST, and phylogenetic analysis results indicated that the Daur group formed a cluster with East Asian populations, and had few genetic differences with the populations in northern China. More importantly, we found that disease-related mutation sites of the mitochondrial genome may be related to ethnic groups, which may have important implications for the prevention and occurrence of specific diseases. Overall, this study revealed the complexity and diversity of the matrilineal genetic background of the Daur ethnic group. Meanwhile, it provided meaningful data for the research on the diversity of the human genome.

SLC25A24 gene methylation and gray matter volume in females with and without conduct disorder: an exploratory epigenetic neuroimaging study

Conduct disorder (CD), a psychiatric disorder characterized by a repetitive pattern of antisocial behaviors, results from a complex interplay between genetic and environmental factors. The clinical presentation of CD varies both according to the individual's sex and level of callous-unemotional (CU) traits, but it remains unclear how genetic and environmental factors interact at the molecular level to produce these differences. Emerging evidence in males implicates methylation of genes associated with socio-affective processes. Here, we combined an epigenome-wide association study with structural neuroimaging in 51 females with CD and 59 typically developing (TD) females to examine DNA methylation in relation to CD, CU traits, and gray matter volume (GMV). We demonstrate an inverse pattern of correlation between CU traits and methylation of a chromosome 1 region in CD females (positive) as compared to TD females (negative). The identified region spans exon 1 of the SLC25A24 gene, central to energy metabolism due to its role in mitochondrial function. Increased SLC25A24 methylation was also related to lower GMV in multiple brain regions in the overall cohort. These included the superior frontal gyrus, prefrontal cortex, and supramarginal gyrus, secondary visual cortex and ventral posterior cingulate cortex, which are regions that have previously been implicated in CD and CU traits. While our findings are preliminary and need to be replicated in larger samples, they provide novel evidence that CU traits in females are associated with methylation levels in a fundamentally different way in CD and TD, which in turn may relate to observable variations in GMV across the brain.

The Role of Mitochondria in Carcinogenesis

The mitochondria are essential for normal cell functioning. Changes in mitochondrial DNA (mtDNA) may affect the occurrence of some chronic diseases and cancer. This process is complex and not entirely understood. The assignment to a particular mitochondrial haplogroup may be a factor that either contributes to cancer development or reduces its likelihood. Mutations in mtDNA occurring via an increase in reactive oxygen species may favour the occurrence of further changes both in mitochondrial and nuclear DNA. Mitochondrial DNA mutations in postmitotic cells are not inherited, but may play a role both in initiation and progression of cancer. One of the first discovered polymorphisms associated with cancer was in the gene NADH-ubiquinone oxidoreductase chain 3 (mt-ND3) and it was typical of haplogroup N. In prostate cancer, these mutations and polymorphisms involve a gene encoding subunit I of respiratory complex IV cytochrome c oxidase subunit 1 gene (COI). At present, a growing number of studies also address the impact of mtDNA polymorphisms on prognosis in cancer patients. Some of the mitochondrial DNA polymorphisms occur in both chronic disease and cancer, for instance polymorphism G5913A characteristic of prostate cancer and hypertension.

Mitochondrial DNA copy number may be associated with attention deficit/hyperactivity disorder severity in treatment: a one-year follow-up study

OBJECTIVE

Studies on etiopathogenesis of attention deficit/hyperactivity disorder (ADHD) are increasingly focussing on mitochondrial dysfunction. Children diagnosed with ADHD who had significantly higher mitochondrial DNA (mtDNA) copy numbers than healthy children in our first study were re-examined in 1-year follow-up to investigate effects of severity and treatment of ADHD on mtDNA.

METHODS

Twenty-eight patients who participated in previous study were included in this follow-up study. Patients were equally divided into two groups according to whether they had been receiving treatment. Kiddie Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version, and Conners Parent Rating Scale (CPRS) were used. Polymerase chain reaction was performed.

RESULTS

Means of the first and second mtDNA copy were similar in all patients. mtDNA copy numbers did not change between two measurements in treated and non-treated groups. There was a correlation between CPRS ADHD index and inattention scores and mtDNA copy number in treated group. mtDNA copy number did not change in patients with ADHD over a period of 1 year regardless of treatment.

CONCLUSIONS

There may be a relationship between decreased ADHD severity with treatment and positive effects of mitochondrial functions. Mitochondrial dysfunction may play a role in pathophysiology of ADHD.KEY POINTSThis was the first study to follow up ADHD patients in order to investigate mitochondrial dysfunction by measuring mtDNA copy numbers 1 year after the initial measurements.mtDNA copy number, one of the best markers of mitochondrial dysfunction, did not change in ADHD patients over a period of 1 year regardless of treatment.Mitochondrial dysfunction may play a role in the pathophysiology of ADHD, where it may be involved with or without treatment.In the treated group, there was an association between decreased ADHD severity and reduced mtDNA copy numbers.There may be a relationship between decreased ADHD severity with treatment and the positive effects of mitochondrial functions.

Stress and Psychiatric Disorders: The Role of Mitochondria

In seeking to understand mental health and disease, it is fundamental to identify the biological substrates that draw together the experiences and physiological processes that underlie observed psychological changes. Mitochondria are subcellular organelles best known for their central role in energetics, producing adenosine triphosphate to power most cellular processes. Converging lines of evidence indicate that mitochondria play a key role in the biological embedding of adversity. Preclinical research documents the effects of stress exposure on mitochondrial structure and function, and recent human research suggests alterations constituting recalibrations, both adaptive and nonadaptive. Current research suggests dynamic relationships among stress exposure, neuroendocrine signaling, inflammation, and mitochondrial function. These complex relationships are implicated in disease risk, and their elucidation may inform prevention and treatment of stress- and trauma-related disorders. We review and evaluate the evidence for mitochondrial dysfunction as a consequence of stress exposure and as a contributing factor to psychiatric disease.

Correlation study on mtDNA polymorphisms as potential risk factors in aggressive periodontitis by NGS

OBJECTIVES

Using next-generation sequencing (NGS) to determine whether aggressive periodontitis is associated with specific mitochondrial polymorphisms.

MATERIALS AND METHODS

A total of 165 unrelated Han Chinese were enrolled in the study. We analyzed the mitochondrial DNA (mtDNA) in 97 patients with aggressive periodontitis and 68 healthy controls by NGS. The mitochondrial DNA was L-PCR-amplified and subsequently sequenced by an Illumina Genome Analyzer (NGS). Chi-square tests were used to assess the differences between the two groups. In cases of significant difference, multivariate logistic regression models were further used to analyze the association between mtDNA polymorphisms and aggressive periodontitis.

RESULTS

Significant association was observed between aggressive periodontitis and eight mitochondrial polymorphisms: "8860G-10400C" (OR = 2.828, p = .002), "8701A" (OR = 2.308, p = .005), "12705C-10398A" (OR = 2.683, p = .002), "9540C" (OR = 3.838, p = .001) and "10873T-15043G" (OR = 4.375, p = .001).

CONCLUSIONS

The pathogenesis of aggressive periodontitis is complicated, and its heredity is not well characterized. Our study was the first to use next-generation sequencing and found that 8860G-10400C, 8701A, 12705C-10398A, 9540C, and 10873T-15043G are associated with aggressive periodontitis in the Han Chinese population.

[Genetics and epigenetics of attention deficit hyperactivity disorder]

Molecular genetic studies of attention deficit hyperactivity disorder (ADHD) have demonstrated the involvement of multiple genes in the etiology of ADHD. A polygenic hypothesis of the etiopathogenesis was formulated without clear knowledge of common mechanisms of ADHD development. Twin, family and adoption studies have established the heritability of 70-80% for ADHD. Association studies have shown the relationship between ADHD and genes of dopaminergic (DRD4, DRD5, SLC6A3), serotoninergic (HTR1B, 5-HTTLPR), glutamatergic (mGluR, NDRG2) systems, metabolic pathways (SLC2A3, SLC6A4, CDH13, CFOD1, GFOD1), membrane proteins (KChIP1, ITGA1, SNAP-25) as well as tumour-suppressor (NDRG2, NF1) and cytokine genes. The marked comorbidity of ADHD with other psychiatric disorders and shared genetic risk factors were determined. Studies of a role of copy number variations (CNVs) provided more promising evidence that suggested the possible involvement of retroelements as the unifying factors of disease etiopathogenesis. Transposons, which are sensitive to stress, may cause CNVs and are key regulators of brain development and functioning. The dysregulation of transposons is thought to be important in changes in tuning of gene regulatory pathways and epigenetic regulation of neurons in ADHD that may be a common principle underlying the heterogeneous nature of ADHD. Research on noncoding RNAs will help to confirm the hypothesis and develop diagnostic algorithms of examination of ADHD patients as an important step in the implementation of personalized medicine in psychiatry.

Peripheral Mitochondrial DNA Copy Number is Increased in Korean Attention-Deficit Hyperactivity Disorder Patients

The involvement of mitochondrial dysfunction in the pathophysiology of attention-deficit hyperactivity disorder (ADHD) has been suggested in several reports. Mitochondrial DNA (mtDNA) copy number as well as methylation of the D-loop region and peroxisome-proliferator-activated receptor γ co-activator-1α (PPARGC1A) are considered biomarkers for mitochondrial dysfunction. We compared the mtDNA copy number and methylation ratio of the D-loop region and PPARGC1A between ADHD patients and controls and also among ADHD subtypes. The present study included 70 subjects with ADHD and 70 age- and gender-matched healthy controls (HCs). We measured the relative mtDNA copy number in peripheral blood cells using quantitative polymerase chain reaction (qPCR), and the methylation ratio was measured using methylation-specific PCR (MSP) after bisulfite conversion. The relative mtDNA copy number was significantly higher in ADHD patients than in HCs (p = 0.028). The mtDNA methylation ratio of PPARGC1A was decreased in ADHD patients compared with HCs (p = 0.008). After adjusting for IQ level, only the mtDNA copy number differed between the ADHD and HCs (p = 0.01). There was a significant difference in the methylation ratio of PPARGC1A among ADHD subtypes. These results suggest the possible involvement of mitochondrial dysfunction in the pathophysiology of ADHD. Further large cohort studies investigating the correlation between clinical markers and biomarkers of mitochondrial dysfunction are warranted.

Assessment of associations between mitochondrial DNA haplogroups and attention deficit and hyperactivity disorder in Korean children

Attention deficit hyperactivity disorder (ADHD) is a multifactorial disorder with multiple environmental and biological etiologies, including genetic factors. Until now, several genetic variants have been reported to be significantly associated with ADHD. Recently, the relationship between mitochondrial DNA (mtDNA) haplogroups and psychiatric disorders such as schizophrenia has also been reported. However, currently there are no reports pertaining to the genetic association between mtDNA haplogroups and ADHD. Therefore, we performed an mtDNA haplogroup analysis of a total of 472 Korean children (150 Children with ADHD and 322 controls). The 20 East Asian specific mtDNA haplogroups were determined using the SNaPshot assay. We also sequenced the displacement loop (D-loop) region, position 15,971-613. Our results showed that haplogroup B4 was significantly associated with ADHD (OR, 1.90; 95% CI, 1.055-3.429; p = 0.031). A marginally significant association was found in subjects with ADHD and haplogroup B5 (OR, 0.26; 95% CI, 0.059-1.139; p = 0.041). When stratified based on gender, an association was also observed between haplogroup B5 and boys diagnosed with ADHD (OR, 0.17; 95% CI, 0.022-1.340; p = 0.048). Compared with boys, girls with ADHD carried an excess of the haplogroup D4b (OR, 4.83; 95% CI, 1.352-17.272; p = 0.014). Stratified analysis of subtypes also showed significant results (combined: haplogroup B4, p = 0.007; inattentive: haplogroup F, p = 0.022). Our results showed a possible role of mtDNA haplogroups in the genetic etiology of ADHD and ADHD symptoms in Korean children.

Association of Monoamine Oxidase A (MAOA) Gene uVNTR and rs6323 Polymorphisms with Attention Deficit and Hyperactivity Disorder in Korean Children

Objective: Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder. The genetic cause of ADHD is still unclear, but the dopaminergic, serotonergic, and noradrenergic pathways have shown a strong association. In particular, monoamine oxidase A (MAOA) plays an important role in the catabolism of these neurotransmitters, suggesting that the MAOA gene is associated with ADHD. Therefore, we evaluated the relationship between the MAOA gene polymorphisms (uVNTR and rs6323) and ADHD. Materials and methods: We collected a total of 472 Korean children (150 ADHD cases and 322 controls) using the Korean version of the Dupaul Attention Deficit Hyperactivity Disorder Rating Scales (K-ARS). Genotyping was performed by PCR and PCR-RFLP. The Behavior Assessment System for Children Second Edition (BASC-2) was used to evaluate the problem behaviors within ADHD children. Results: We observed significant associations between the rs6323 and ADHD in girls (p < 0.05) and the TT genotype was observed as a protective factor against ADHD in the recessive model (OR 0.31, 95% CI 0.100⁻0.950, p = 0.022). The 3.5R-G haplotype showed a significant association in ADHD boys (p = 0.043). The analysis of subtype also revealed that the 4.5R allele of uVNTR was a risk factor for the development of ADHD in the combined symptom among girls (OR 1.87, 95% CI 1.014⁻3.453, p = 0.031). In the BASC-2 analysis, the MAOA uVNTR polymorphism was associated with activities of daily living in ADHD boys (p = 0.017). Conclusion: These results suggest the importance of the MAOA gene polymorphisms in the development of ADHD in Korean children. A larger sample set and functional studies are required to further elucidate of our findings.

An energetic view of stress: Focus on mitochondria

Energy is required to sustain life and enable stress adaptation. At the cellular level, energy is largely derived from mitochondria - unique multifunctional organelles with their own genome. Four main elements connect mitochondria to stress: (1) Energy is required at the molecular, (epi)genetic, cellular, organellar, and systemic levels to sustain components of stress responses; (2) Glucocorticoids and other steroid hormones are produced and metabolized by mitochondria; (3) Reciprocally, mitochondria respond to neuroendocrine and metabolic stress mediators; and (4) Experimentally manipulating mitochondrial functions alters physiological and behavioral responses to psychological stress. Thus, mitochondria are endocrine organelles that provide both the energy and signals that enable and direct stress adaptation. Neural circuits regulating social behavior - as well as psychopathological processes - are also influenced by mitochondrial energetics. An integrative view of stress as an energy-driven process opens new opportunities to study mechanisms of adaptation and regulation across the lifespan.