mtDNA 4977-bp Deletion Research Articles

Evaluation of mtDNA common deletion in esophageal squamous cell carcinoma.

Mitochondrial defects are thought to play a role in cancer initiation and progression for a long time. Because of the absence of protective histones and an inefficiency in the DNA repair process, mitochondrial DNA is known to be prone to mutations. The deletion of 4977bp is one of the most common mutations in human cancers. This study aimed to investigate the relationship between 4977bp common deletion and Esophageal Squamous Cell Carcinoma Disease (SCC) to provide prognostic information. By using a PCR protocol, this study identified the 4977bp deletion of mtDNA. A PCR method was used on tumor samples from 41 squamous cell carcinoma patients and blood samples from 50 healthy individuals to detect DNA. Among the 41 tumor samples (80.5%), 33 were found to have the 4977bp deletion, while none of the blood samples from healthy individuals contained it. It is shown that the deletion of 4977bp of mtDNA correlates significantly with SCC in this study. A 4977bp deletion could be used as an effective cancer screening indicator and biomarker for early diagnosis and prevention of cancer.

Associations of mitochondrial DNA copy number and deletion rate with early pregnancy loss

Early pregnancy loss (EPL) is a common event worldwide. Previous studies show that mitochondrial DNA (mtDNA) copy number (CN) is associated with semen parameters and preimplantation embryo viability, indicating the predictive potential of mtDNA CN for ongoing pregnancy outcomes. However, no relevant study has assessed the relationship between mtDNA CN and EPL. Thus, we aimed to determine whether mtDNA CN and mtDNA 4977-bp deletion rate (DR) in chorionic villous tissue are associated with EPL. Chorionic villous tissue total DNA was extracted from 75 EPL cases and 75 healthy controls. Chromosomal analysis was conducted using copy number variation (CNV) sequencing. The mtDNA CN and DR were measured in samples without pathogenic CNVs. The association between mtDNA CN or DR and EPL risk were estimated using logistic regression. The EPL group had a significantly different mtDNA CN (P < 0.001) and DR (P = 0.005) compared to the control group. Both biomarkers were independent risk factors for EPL (CN odds ratio 1.71, 95% confidence interval 1.17 to 2.49, P = 0.005; DR odds ratio 1.07, 95% confidence interval 1.02 to 1.12, P = 0.006). These results suggest that higher mtDNA CN and DR levels are strongly associated with EPL and represent independent risk factors for EPL. Further studies validating these findings and exploring the underlying biological mechanisms are warranted.

OR03-04 The Study of Cell Senescence in Cortisol-Producing Adrenocortical Adenomas

Introduction Aging is associated with the pathogenesis of many endocrine disorders such as cardiovascular diseases and diabetes. Cell senescence has been reported as one of their mechanisms. In addition, stress responsiveness has been reported to be associated with cell senescence. In addition, some genetic abnormalities such as mitochondrial DNA (mtDNA) damages or telomere shortening, have been detected in some endocrine disorders. Cortisol is a well-known stress-induced hormone and closely associated with aging. We previously reported that cortisol-producing adenoma (CPA) more abundantly expressed cell senescent markers such as p16 and p21 than other hormone-producing adrenocortical adenomas. However, the detailed pathophysiology of cell senescence and its association with histological features in CPAs have remained virtually unknown. Therefore, we analyzed cell senescent markers (telomere length, mtDNA copy number, mtDNA deletion and p16 and p21 immunoreactivity) and analyzed their correlation with clinicopathological factors in CPA patients. Methods & Materials Forty CPA cases was immunohistochemically evaluated. Twenty CPA, ten adjacent ZF and six non-functional adenoma (NFA) were examined for mtDNA abnormalities. mtDNA deletion was evaluated by nested-PCR and mtDNA copy number and telomere length were measured using real-time PCR. Results p21 immunoreactivity was significantly higher in CPA than that of adjacent ZF (P=0.0001) and significantly inversely correlated with tumor size (P=0.0004). Telomere length was much longer in CPA than that in adjacent ZF(P=0.0038), and NFA (P=0.0018). mtDNA copy number of NFA was significantly higher than that of CPA and adjacent ZF (P=0.0038). mtDNA copy number of compact cells was significantly higher than that of clear cells (P=0.0432). mtDNA copy number of compact cells was positively correlated with urinary free cortisol (UFC) (P=0.0428) and plasma cortisol (F) (P=0.0609). mtDNA copy number of clear cells were inversely correlated with F (0.0497). 4977 bp mtDNA deletion was more frequently detected in CPA (54%) and in adjacent ZF (50%) than in NFA (17%). Discussion Results of our present study did reveal that CPA harbored more senescent phenotype as demonstrated by abundant p16 and p21, marked telomere shortening, frequent mtDNA 4977bp deletion and relatively low mtDNA copy number, possibly caused by long-term exposure of excessive cortisol in situ compared to NFA. In addition, clear tumor cells could represent more senescent histological phenotype because of their lower mtDNA copy numbers. This is the first study to demonstrate that compact tumor cells were biologically more active than clear tumor cells and could reflect clinical cortisol biosynthesis, resulting in marked functional intratumoral heterogeneity in CPAs.

The mitochondrial DNA 4977-bp deletion and copy number alteration in Han Chinese samples with uterine fibroids.

Uterine fibroids (UFs) are the most common benign neoplasms, but their pathogenesis is not completely understood. Thus far, alterations in the mitochondrial DNA (mtDNA) content and the mtDNA 4977-bp deletion level in UFs, as well as the corresponding nontumorous tissue, have remained elusive. To test whether large mtDNA deletions and mtDNA content are involved in the pathogenesis of UFs, a total of 309 UF tissues and 28 paired adjacent myometrium from 270 UF patients were enrolled for the analysis of large mtDNA deletions and mtDNA content through the use of nested PCR and qPCR techniques, respectively. In our samples, a 4977-bp deletion was identified: 36 out of 309 UF tissues (11.56%) and 15 out of 28 (53.57%) paired adjacent myometrium were detected to harbor the 4977-bp deletion. In addition, a novel 4838-bp mtDNA deletion was identified in three UF tissues, and other different sizes of deleted fragments (4910, 4926, 5135-bp) were also found in UFs for the first time. Furthermore, older age was significantly associated with an mtDNA large deletion in the paired adjacent myometrium. We also found that increased mtDNA content and higher expression of ND1 occurred in solitary fibroids compared to adjacent myometrium. In conclusion, we identified a lower frequency of mtDNA large deletions and some novel large deletion in UFs for the first time. Furthermore, there was a general increase of mtDNA copy number during solitary UF development. Although the definite mechanism by which mtDNA was altered is supposed to be further confirmed, it will be helpful for further studies on the pathological mechanism of UFs.

Hearing impairments, presbycusis and the possible therapeutic interventions

The hearing is an important sensation of all living organism to maintain his or her life mainly in human. Any distortion to it leads to hearing impairment. Hearing loss (HL) can be congenital or acquired. It can be syndromic; HL associated with other abnormalities or non-syndromic, HL is not associated with any other anomalies. Hearing impairment have mostly autosomal recessive loci, but can be autosomal dominant, X-linked, and mitochondrial. Acquired HL can be genetic or environmental factors based. Age-related HL is acquired hearing loss occur in aged population. Its prevalence rate increases with age. Genetic of presbycusis is not well-known, but NAT2*6A polymorphism, SNPs in KCNQ4, grainy head-like 2 gene, Glutamate receptor-7 gene, 4977-bp mt-DNA deletion in human and 4834-bp mtDNA deletion in rodents were identified. Different strains of mice are developed like C57BL/6J, CBA/CaJ, DBA/2J, BALB/cJ and Fisher 344 albino rats mainly used as models to study HL and presbycusis. Like other disorders have complete treatment, but HL cannot be completely treated. However some attempts can be made for its betterment by using hearing aid devices, surgical and pharmaceutical treatments. In future stem cells and gene therapy will be the affective methods to treat congenital hearing impairment and presbycusis.

Mitochondrial DNA deletion Δ4977 in peptic ulcer disease

Reactive oxygen species (ROS) play a critical role in peptic ulcer disease (PUD). Due to the high rate of ROS production and limited capacity for DNA repair within mitochondria, mtDNA is susceptible to oxidative damage and mutations. mtDNA deletion Δ4977 is one of the most common deletion events identified in mitochondria. We examined the association of 4977-bp mtDNA deletion with PUD. Genotypes were determined in bioptic samples of 150 PUD patients and 190 controls. The 4977-bp mtDNA deletion was found more frequently among patients with PUD (52%) than among controls (22.63%). The strong association between the mtDNA 4977-bp deletion and PUD was confirmed (OR = 3.7; 95% CI, 2.32-5.91; P = 0.0001). The 4977-bp deletion in mitochondrial DNA may be a risk factor for PUD, or may reflect an increase in oxidative stress that commonly accompanies underlying PUD disease. Larger population-based studies are needed to uncover the possible causal relationship between this deletion and peptic ulcer disease.

A novel large-scale deletion of the mitochondrial DNA of spermatozoa of men in north iran.

To investigate the level of correlation between large-scale deletions of the mitochondrial DNA (mtDNA) with defective sperm function. In this analytic study, a total of 25 semen samples of the nor- mozoospermic infertile men from North of Iran were collected from the IVF center in an infertility clinic. The swim-up procedure was performed for the separation of spermatozoa into two groups; (normal motility group and abnormal motility group) by 2.0 ml of Ham's F-10 medium and 1.0 ml of semen. After total DNA extraction, a long-range polymerase chain reaction (PCR) technique was used to determine the mtDNA deletions in human spermatozoa. The products of PCR analysis showed a common 4977 bp deletion and a novel 4866 bp deletion (flanked by a seven-nucleotide direct repeat of 5΄-ACCCCCT-3΄ within the deleted area) from the mtDNA of spermatozoa in both groups. However, the frequency of mtDNA deletions in abnormal motility group was significantly higher than the normal motility group (56, and 24% for 4866 bp-deleted mtDNA and, 52, and 28% for 4977 bp-deleted mtDNA, respectively). It is suggested that large-scale deletions of the mtDNA is associated with poor sperm motility and may be a causative factor in the decline of fertility in men.

Folate deficiency is not associated with increased mitochondrial genomic instability: results from dietary intake and lymphocytic mtDNA 4977-bp deletion in healthy young women in Italy

The mitochondrial DNA (mtDNA) 4977-bp deletion is a biomarker of mitochondrial genomic instability. It is frequently detected in a number of sporadic diseases, and it accumulates in many tissues during aging. Folic acid plays an important role in the maintenance of genomic stability in mammals. The aim of the present cross-sectional study was to characterise the levels of the mtDNA deletion in the lymphocytes of healthy young women, taking into account folate intake, red blood cell (RBC) folate levels and the distribution of the methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism. Folate intake was estimated by a food frequency questionnaire. Determination of the MTHFR C677T polymorphism and of the mtDNA deletion was performed by real-time polymerase chain reaction analysis. A total of 476 women were enrolled. Low levels of deletion were found (mean ΔCt = 1.24). After multivariate analysis, results did not show any significant relationship between age, smoking habits, pregnancy status, nutritional status, inadequate folate intake, folate deficiency, use of folic acid supplements, MTHFR C677T polymorphism and mtDNA 4977-bp deletions. The lack of association between inadequate folate intake, folate deficiency and mitochondrial genomic instability was confirmed also considering reference values of folate based on DNA damage prevention. Our results indicate that mtDNA 4977-bp deletions are maintained at low levels in lymphocytes of young healthy women despite the wide range of variation of folate intakes and folate status. Future studies, carefully designed to address limits and methodological issues related to variation of this biomarker as an effect of different dietary patterns and of folate status, could provide further insight on the specific mechanisms that are acting in lymphocytes of healthy subjects under observed folate intake.

Mitochondrial Genome Changes As a Measure Of Iron-Induced Mitochondrial Stress In Transfusion-Dependent Thalassemia

IntroductionIron overload is a consequence of chronic blood transfusions to treat severe forms of thalassemia. While patient outcomes have improved with advances in iron overload assessment and chelation therapy, iron toxicity continues to be the primary determinant of morbidity. Mitochondrial dysfunction is of central importance in iron overload. However, clinical assessment of mitochondrial damage has not been feasible because current methods require invasive tissue sampling. MethodsNovel bioassays were used to assess changes in the mitochondrial genome from a small amount of peripheral blood. We studied the relationship between mitochondrial DNA (mtDNA), mitochondrial respiratory complexes, and clinical measures of iron overload. Real-time PCR-based assays were used to measure mtDNA copy number per nuclear DNA copy (mtDNA:nDNA) and the frequency of the mtDNA 4977-bp deletion (ΔmtDNA4977). The quantity of mitochondrial respiratory complex I and IV in blood was measured using ELISA and expressed as a percentage of quantity in HepG2 cells. Results44 individuals with thalassemia (median age 34.9 years, range 14 to 52.4 years) and 27 healthy controls (median age 22 years, range 19 to 39 years) were studied in this analysis. The median liver iron concentration (LIC) in thalassemia was 11.0 mg/g dry-weight (2.3-59.4 mg/g dry-weight), while the median ferritin was 2220 mcg/L (308-9470 mcg/L). The median cardiac T2* was 28.7 ms (6.5-45.8 ms).The mtDNA:nDNA was estimated and the median mtDNA copy number was 249.8 (87.6-738.3) in thalassemia, compared with 225.4 (101.9-348.7) in controls. The mtDNA copy number was significantly elevated in thalassemia (p=0.033, Mann-Whitney test). The mtDNA copy number increased with age in thalassemia (r=0.45, p=0.005), but no correlation with age was observed in the control group (r=0.06, p=n.s.). Myocardial iron deposition influenced the mtDNA copy number as evidenced by an inverse relationship with T2* (r= -0.45, p=0.006). The frequency of the ΔmtDNA4977deletion was analyzed in a subset of subjects and was found to be 8-fold higher in thalassemia versus controls (p=0.012). The median quantity of complex IV in thalassemia was 3.4% (0 to 104.2) compared with 2.5% (range 0 to 18.67) in controls. The median complex I activity in thalassemia was 6.3% (range 0 to 161.4) compared with 17.86% (range 0 to 55.0) in controls. These differences were not statistically significantly between the two groups. Higher values of mtDNA copy number were associated with increased quantity of complex IV (r=0.515, p=0.10) in thalassemia, but not in controls. No correlation of mtDNA copy number was observed with complex I activity. LIC, ferritin, and platelet count did not influence the mtDNA:nDNA ratios. InterpretationAlterations in mtDNA can be measured in blood samples of patients with thalassemia and iron overload. Increases in mitochondrial genome copy number and ΔmtDNA4977 deletion frequency may be a reflection of iron-induced mitochondrial stress. This hypothesis is supported by an increase in mtDNA copy number with age in thalassemia, but not in controls. The relation between mtDNA changes and myocardial iron suggests that this assay may possess physiological relevance. These preliminary results support the potential application of these non-invasive assays for the assessment of iron-induced organ damage. Disclosures:No relevant conflicts of interest to declare.

Mitochondrial DNA 4977-bp deletion in endometriosis

Endometriosis is a multifactorial gynecological condition characterized by the presence of ectopic endometrial and stromal tissue outside the uterus. Free radicals and Oxidative stress have been proposed to be involved in the pathogenesis of the endometriosis. It has been shown that mitochondrial DNA (mtDNA) is particularly susceptible to oxidative damage and mutations due to the high rate of reactive oxygen species production and limited DNA repair capacity in mitochondria. While a number of deletions can occur, the most commonly studied in human is a 4977-bp deletion that removes all or parts of the genes for NADH dehydrogenase subunits 3, 4, 4L and 5, cytochrome C oxidase subunit III and ATP synthase subunits 6 and 8.” We evaluated whether mtDNA common deletion is related with the susceptibility to endometriosis in northern Iran. In this study 80 endometriosis cases and 100 controls were enrolled. Total DNA was extracted from endometrial tissue samples. The mitochondrial common deletion was determined by Gap- polymerase chain reaction (Gap-PCR). It was found that the mitochondrial common deletion was more likely to be present in patients with endometriosis. Assessing indicate that 60 % of patients and 8 % of controls show mtDNA 4977-bp deletion (Odds Ratio [OR] = 17.25, P < 0.0001, confidence interval [CI] = 5.18–57.36). The mtDNA 4977 deletion may play a role in endometriosis. Further studies with larger numbers of patients are required for further evaluation and confirmation of our finding.

4977-bp mitochondrial DNA deletion in infertile patients with varicocele

Varicocele is the abnormal inflexion and distension of veins of the pampiniform plexus within spermatic cord and is one of the amendable causes of male infertility. It can increase reactive oxygen species (ROS) production in semen and cause oxidative stress. The purpose of this study was to analyse spermatozoa mtDNA 4977-bp deletion in infertile men with varicocele. To detect 4977-bp deletion in spermatozoa mtDNA, semen samples of 60 infertile patients with clinical varicocele and 90 normal men from northern Iran were prepared. After extraction of spermatozoa total DNA, Gap polymerase chain reaction (Gap PCR) was performed. 4977-bp deletion was observed in 81.66% of patients with varicocele, while approximately 15.55% of controls had this deletion. As spermatozoa from patients with varicocele had a high frequency of occurrence of 4977-bp deletion in mtDNA [OR = 24.18, 95% confidence interval (CI) = 10.15-57.57, P < 0.0001], varicocele may induce mtDNA deletion in spermatozoa and cause infertility in north Iranian men. However, to determine the relation between sperm mtDNA 4977-bp deletion and varicocele-induced infertility, larger population-based studies are needed. It is concluded that there is an association between sperm mtDNA 4977-bp deletion and varicocele-induced infertility in the population studied.

The effect of overexpression of PGC-1α on the mtDNA4834 common deletion in a rat cochlear marginal cell senescence model

Aging is a natural process usually defined as a progressive loss of function with an accumulation of senescent cells. The clinical manifestations of this process include age-related hearing loss (AHL)/presbycusis. Several investigations indicated the association between a mitochondrial common deletion (CD) (mtDNA 4977-bp deletion in humans, corresponding to 4834-bp deletion in rats) and presbycusis. Previous researches have shown that peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) is a key regulator of mitochondrial biogenesis and energy metabolism. However, the expression of PGC-1α in the inner ear and the possible effect of PGC-1α on presbycusis are not clear. Our data demonstrated the distribution of PGC-1α and its downstream transcription factors nuclear respiratory factor-1 (NRF-1), mitochondrial transcription factor A (Tfam) and nuclear factor κB (NF-κB) in marginal cells (MCs) for the first time. To explore the role of PGC-1α in cellular senescence, we established a model of marginal cell senescence harboring the mtDNA4834 common deletion induced by d-galactose. We also found that PGC-1α and its downstream transcription factors compensatorily increased in our cell senescence model. Furthermore, the overexpression of PGC-1α induced by transfection largely increased the expression levels of NRF-1 and TFAM and significantly decreased the expression level of NF-κB in the cell senescence model. And the levels of CD, senescent cells and apoptotic cells in the cell model decreased after PGC-1α overexpression. These results suggested that PGC-1α might protect MCs in this cell model from senescence through a nuclear-mitochondrial interaction and against apoptosis. Our study may shed light on the pathogenesis of presbycusis and provide a new therapeutic target for presbycusis.

Increases in Mitochondrial DNA Content and 4977-bp Deletion upon ATM/Chk2 Checkpoint Activation in HeLa Cells

Activation of the Mec1/Rad53 damage checkpoint pathway influences mitochondrial DNA (mtDNA) content and point mutagenesis in Saccharomyces cerevisiae. The effects of this conserved checkpoint pathway on mitochondrial genomes in human cells remain largely unknown. Here, we report that knockdown of the human DNA helicase RRM3 enhances phosphorylation of the cell cycle arrest kinase Chk2, indicating activation of the checkpoint via the ATM/Chk2 pathway, and increases mtDNA content independently of TFAM, a regulator of mtDNA copy number. Cell-cycle arrest did not have a consistent effect on mtDNA level: knockdown of cell cycle regulators PLK1 (polo-like kinase), MCM2, or MCM3 gave rise, respectively, to decreased, increased, or almost unchanged mtDNA levels. Therefore, we concluded that the mtDNA content increase upon RRM3 knockdown is not a response to delay of cell cycle progression. Also, we observed that RRM3 knockdown increased the levels of reactive oxygen species (ROS); two ROS scavengers, N-acetyl cysteine and vitamin C, suppressed the mtDNA content increase. On the other hand, in RRM3 knockdown cells, we detected an increase in the frequency of the common 4977-bp mtDNA deletion, a major mtDNA deletion that can be induced by abnormal ROS generation, and is associated with a decline in mitochondrial genome integrity, aging, and various mtDNA-related disorders in humans. These results suggest that increase of the mitochondrial genome by TFAM-independent mtDNA replication is connected, via oxidative stress, with the ATM/Chk2 checkpoint activation in response to DNA damage, and is accompanied by generation of the common 4977-bp deletion.

Mitochondrial transcription factor A overexpression and base excision repair deficiency in the inner ear of rats with d‐galactose‐induced aging

Oxidative damage to mtDNA is associated with excessive reactive oxygen species production. The mitochondrial common deletion (mtDNA 4977-bp and 4834-bp deletion in humans and rats, respectively) is the most typical and frequent form of mtDNA damage associated with aging and degenerative diseases. The accumulation of the mitochondrial common deletion has been proposed to play a crucial role in age-related hearing loss (presbycusis). However, the mechanisms underlying the formation and accumulation of mtDNA deletions are still obscure. In the present study, a rat mimetic aging model induced by D-Gal was used to explore the origin of deletion mutations and how mtDNA repair systems modulate this process in the inner ear during aging. We found that the mitochondrial common deletion was greatly increased and mitochondrial base excision repair capacity was significantly reduced in the inner ear in D-Gal-treated rats as compared with controls. The overexpression of mitochondrial transcription factor A induced by D-Gal significantly stimulated mtDNA replication, resulting in an increase in mtDNA copy number. In addition, an age-related loss of auditory sensory cells in the inner ear was observed in D-Gal-treated rats. Taken together, our data suggest that mitochondrial base excision repair capacity deficiency and an increase in mtDNA replication resulting from mitochondrial transcription factor A overexpression may contribute to the accumulation of mtDNA deletions in the inner ear during aging. This study also provides new insights into the development of presbycusis.

Correlation analysis between mtDNA 4977-bp deletion and ageing

Mitochondrial DNA 4977-bp deletion (common deletion) has been associated with ageing human tissues and a few studies have demonstrated their presence in breast cancer patients too; however, no previous publication evaluated both topics in the same samples group. First, when analyzing 95 breast cancer patients, we found a higher percentage of cases carrying the deletion in non-tumoral tissue 73.68% (70/95) than in the tumoral counterparts 45.26% (43/95), showing that the 4977-bp deletion is a phenomenon which commonly appear first in the non-tumoral breast tissue rather than tumoral tissue. Secondly, we analyzed and compared the ageing related distribution of the common deletion rates, in a control group of 199 samples (ages ranging from 10 to 80 years), with those found in cancer patients. Significant correlation was observed in control cases, between individual age ranges and rates of deletion (chi2: 23.21 and p < 0.01). In contrast, non-tumoral breast tissue did not show a pattern of correlation, chi2: 0.042 and p: 0.837. However, interestingly, we found that the risk of having deleted mtDNAs was higher for non-tumoral breast samples than for the control group samples, OR: 2.32 [1.22–4.42, 95% CI]; this could be reflecting that other mechanisms are involved in mitochondrial genome deletion increased rate detected in breast cancer cases, than the normal ageing process.

Activation of PKCδ and ERK1/2 in the sensitivity to UV-induced apoptosis of human cells harboring 4977 bp deletion of mitochondrial DNA

The 4977 bp deletion of mitochondrial DNA (mtDNA), often found in patients with chronic progressive external ophthalmoplegia (CPEO), has been demonstrated to increase the susceptibility to apoptosis of human cells. We investigated the mechanism underlying the apoptotic susceptibility of the Δ4977 cybrid harboring about 80% 4977 bp-deleted mtDNA. The production of hydrogen peroxide (H 2O 2) and phosphorylation of PKCδ and ERK1/2 were increased in the Δ4977 cybrid, which was more susceptible to UV-induced apoptosis. Moreover, treatment with N-acetyl- l-cysteine (NAC) or blocking of activation of PKCδ by rottlerin or PKCδ-siRNA, and inhibition of ERK1/2 by PD98059 or ERK1/2-siRNA significantly attenuated the susceptibility of the Δ4977 cybrid to apoptosis. Furthermore, the increase of PKCδ expression in the Δ4977 cybrid also amplified the apoptotic signal through caspase 3-mediated proteolytic activation of PKCδ. In addition, PKCδ and ERK1/2 were hyperphosphorylated in skin fibroblasts of CPEO patients harboring 4977 bp-deleted mtDNA. We suggest that the activation of PKCδ and ERK1/2 elicited by 4977 bp-deleted mtDNA-induced oxidative stress plays a role in the susceptibility of the mutant cells to apoptosis. This may explain, at least in part, the degenerative manifestation of brain and muscle in patients with mitochondrial encephalomyopathies such as CPEO syndrome.

Frequency of the mitochondrial DNA 4977bp deletion in oesophageal mucosa during the progression of Barrett’s oesophagus

Purpose The mechanisms of the progression of Barrett’s oesophagus (BO) to oesophageal adenocarcinoma (OA) are poorly understood. The frequency of the 4977bp deletion in mitochondrial DNA (mtDNA) was investigated in specimens ranging from normal oesophageal tissue to OA in order to investigate whether this deletion represents a useful biomarker of disease progression. Methods The presence of the 4977bp deletion was screened by PCR amplification from 70 specimens in total. Results The frequency of specimens with the 4977bp deletion increased in relation to the degree of dysplasia (8.3% in normal squamous epithelium; 15.4% in BO; 40% in low grade dysplasia (LGD); 69.2% in high-grade dysplasia and 90% in para-tumoural tissue). However, the frequency of the deletion reduced sharply in OA specimens (16.7%; p < 0.001). Conclusion The mtDNA 4977bp deletion may be useful as a biomarker to detect the severity of dysplasia but not the presence of OA.

Quantitative analysis of the 4977-bp common deletion of mitochondrial DNA in postmortem frontal cortex from patients with bipolar disorder and schizophrenia

Several reports have suggested a role for mitochondrial dysfunction in the pathophysiology of bipolar disorder and schizophrenia. We have focused on the relationship between deleted mitochondrial DNA (mtDNA) and bipolar disorder. To investigate this relationship, we developed a methodology for quantification of the common 4977-bp deletion of mtDNA based on real-time polymerase chain reaction with SYBR Green. In this study, we assessed accumulation of the common deletion in postmortem frontal cortex from 147 individuals (48 controls, 49 patients with bipolar disorder, 50 patients with schizophrenia). We demonstrated age-dependent accumulation of the common deletion of mtDNA (p=1.09E-10). Females showed significantly higher accumulation of the deletion than did males (p=0.002). There was no significant association between accumulation and the two studied major mental disorders in the frontal cortex (p>0.2). However, there was no statistically significant correlation between the common deletion and aging in female patients with bipolar disorder (p=0.133), and no significant sex difference in patients with bipolar disorder (p=0.509). These results indicate that aging and sex have effect on accumulation of the common deletion of mtDNA in the prefrontal cortex depending on the diagnosis.

Prevalence of 4977bp Deletion in Mitochondrial DNA from Patients with Chronic Kidney Disease Receiving Conservative Treatment or Hemodialysis in Southern Brazil

Background. Damage to mitochondrial DNA (mtDNA) has been described in patients with chronic kidney disease (CKD). The presence of mtDNA 4977bp deletion in many different tissues can serve as a marker of this damage. However, no attempt has been made to detect the presence of mtDNA 4977bp in blood cells of patients with CKD. Methods. Polymerase chain reaction techniques (PCR) were used to detect mtDNA 4977bp deletion in blood samples of 94 CKD patients. Results. The prevalence of 4977bp deletion in mtDNA was 73.1% (38/52) in patients with CKD undergoing hemodialysis, 57.1% (27/42) in patients with CKD receiving conservative treatment, and 27.8% (15/54) in control samples (p < 0.001). Higher prevalence of this mutation was not associated with patient age (p = 0.54) or time on hemodialysis (p = 0.70). Conclusion. The higher prevalence of mtDNA 4977bp deletion in patients in this study indicates that the CKD can induce damage to mtDNA in blood cells and could be exacerbated by hemodialysis.

Quantitative analysis of mitochondrial DNA 4977-bp deletion in sporadic breast cancer and benign breast diseases

The mitochondrial DNA (mtDNA) 4977-bp deletion (DeltamtDNA(4977) mutation) is one of the most frequently observed mtDNA mutations in human tissues and may play a role in carcinogenesis. Only a few studies have evaluated DeltamtDNA(4977) mutation in breast cancer tissue, and the findings have been inconsistent, which may be due to methodological differences. In this study, we developed a quantitative real-time PCR assay to assess the level of the DeltamtDNA(4977) mutation in tumor tissue samples from 55 primary breast cancer patients and 21 patients with benign breast disease (BBD). The DeltamtDNA(4977) mutation was detected in all of the samples with levels varying from 0.000149% to 7.0%. The DeltamtDNA(4977) mutation levels were lower in tumor tissues than in adjacent normal tissues in both breast cancer and BBD subjects. The differences, however, were not statistically significant. No significant difference between breast cancer and BBD patients was found in the DeltamtDNA(4977) mutation levels of tumor tissues and adjacent normal tissues. The DeltamtDNA(4977) mutation levels were not significantly associated with clinicopathological characteristics (age, histology, tumor stage, and ER/PR status) in breast cancer or BBD patients. These results do not support the notion that the mitochondrial DNA 4977-bp deletion plays a major role in breast carcinogenesis.