Search

Leber’s hereditary optic neuropathy (LHON) is one of the most common mitochondrial diseases caused by point mutations in mitochondrial DNA (mtDNA). The majority of diagnosed LHON cases are caused by a point mutation at position 11,778 in the mitochondrial genome. LHON mainly affects young men in their 20s and 30s with usually poor visual prognosis. It remains unexplained why men are more likely to develop the disease and why only retinal ganglion cells are affected. In this study, a cell model was used for the first time to investigate the influence of testosterone on the cell death mechanism apoptosis and on an autophagy/mitophagy. Cells with m.11778G > A were found to be significantly more susceptible to nucleosome formation and effector caspase activation that serve as hallmarks of apoptotic cell death. Cells having this mutation expressed higher levels of mitophagic receptors BNIP3 and BNIP3L/Nix in a medium with testosterone. Moreover, cells having the mutation exhibited greater mitochondrial mass, which suggests these cells have a decreased cell survival. The observed decrease in cell survival was supported by the observed increase in apoptotic cell death. Autophagy was analyzed after inhibition with Bafilomycin A1 (Baf A1). The results indicate impairment in autophagy in LHON cells due to lower autophagic flux supported by observed lower levels of autophagosome marker LC3-II. The observed impaired lower autophagic flux in mutant cells correlated with increased levels of BNIP3 and BNIP3L/Nix in mutant cells.

Rodzinne wystepowanie ataksji jest wskazaniem do poglebiania diagnostyki w ramach badan genetycznych. Obecnośc objawow wśrod rodzenstwa, a jednocześnie ich brak u rodzicow moze sugerowac dziedziczenie autosomalne recesywne. Przypadki przedstawione w niniejszej pracy wskazują na zasadnośc uwzglednienia w diagnostyce roznicowej chorob mitochondrialnych. Mimo ze są one związane z wariantami mitochondrialnego DNA (mtDNA), niektore z nich mogą byc dziedziczone w sposob autosomalny, tak jak w przypadku spektrum chorob wynikających z zaburzenia funkcjonowania mitochondrialnej polimerazy DNA gamma. W przedstawionej pracy korelacja obrazu klinicznego oraz hiperintensywnośc w obrebie wzgorza w badaniu rezonansu magnetycznego byly przeslankami do wysuniecia podejrzenia zespolu ataksja–neuropatia spowodowanego wariantami w obrebie genu POLG kodującego podjednostke katalityczną polimerazy gamma (POLG).

This comprehensive case analysis aimed to identify the features enabling a runner to achieve championship in 24-h ultramarathon (UM) races. A 36-year-old, multiple medalist of the World Championships in 24-h running, was assessed before, one and 10 days after a 24-h run. Results of his extensive laboratory and cardiological diagnostics with transthoracic echocardiography (TTE) and a one-time cardiopulmonary exercise test (CPET) were analyzed. After 12 h of running (approximately 130 km), the athlete experienced an increasing pain in the right knee. His baseline clinical data were within the normal range. High physical efficiency in CPET (VO2max 63 mL/kg/min) was similar to the average achieved by other ultramarathoners who had significantly worse results. Thus, we also performed genetic tests and assessed his psychological profile, body composition, and markers of physical and mental stress (serotonin, cortisol, epinephrine, prolactin, testosterone, and luteinizing hormone). The athlete had a mtDNA haplogroup H (HV0a1 subgroup, belonging to the HV cluster), characteristic of athletes with the highest endurance. Psychological studies have shown high and very high intensity of the properties of individual scales of the tools used mental resilience (62–100% depending on the scale), openness to experience (10th sten), coherence (10th sten), positive perfectionism (100%) and overall hope for success score (10th sten). The athlete himself considers the commitment and mental support of his team to be a significant factor of his success. Body composition assessment (%fat 13.9) and the level of stress markers were unremarkable. The tested athlete showed a number of features of the champions of ultramarathon runs, such as: inborn predispositions, mental traits, level of training, and resistance to pain. However, none of these features are reserved exclusively for “champions”. Team support’s participation cannot be underestimated. The factors that guarantee the success of this elite 24-h UM runner go far beyond physiological and psychological explanations. Further studies are needed to identify individual elements of the putative “mosaic theory of being a champion”.

Mitochondrial encephalomyopathies comprise a group of heterogeneous disorders resulting from impaired oxidative phosphorylation (OxPhos). Among a variety of symptoms progressive external ophthalmoplegia (PEO) seems to be the most common. The aim of this study is to present clinical and genetic characteristics of Polish patients with PEO. Clinical, electrophysiological, neuroradiological, and morphological data of 84 patients were analyzed. Genetic studies of mitochondrial DNA (mtDNA) were performed in all patients. Among nuclear DNA (nDNA) genes POLG was sequenced in 41 patients, TWNK (C10orf2) in 13 patients, and RNASEH1 in 2 patients. Total of 27 patients were included in the chronic progressive external ophthalmoplegia (CPEO) group, 24 in the CPEO+ group. Twenty-six patients had mitochondrial encephalomyopathy (ME), six patients Kearns&ndash, Sayre syndrome (KSS), and one patient sensory ataxic neuropathy, dysarthria, ophthalmoparesis (SANDO) syndrome. Genetic analysis of nDNA genes revealed the presence of pathogenic or possibly pathogenic variants in the POLG gene in nine patients, the TWNK gene in five patients and the RNASEH1 gene in two patients. Detailed patients&rsquo, history and careful assessment of family history are essential in the diagnostic work-up. Genetic studies of both mtDNA and nDNA are necessary for the final diagnosis of progressive external ophthalmoplegia and for genetic counseling.

Leber hereditary optic neuropathy (LHON) is a mitochondrial disorder with symptoms limited to a single tissue, optic nerve, resulting in vision loss. In the majority of cases it is caused by one of three point mutations in mitochondrial DNA (mtDNA) but their presence is not sufficient for disease development, since ~50% of men and ~10% women who carry them are affected. Thus additional modifying factors must exist. In this study, we use next generation sequencing to investigate the role of whole mtDNA variation in male Polish patients with LHON and m.11778G > A, the most frequent LHON mutation. We present a possible association between mtDNA haplogroup K and variants in its background, a combination of m.3480A > G, m.9055G > A, m.11299 T > C and m.14167C > T, and LHON mutation. These variants may have a negative effect on m.11778G > A increasing its penetrance and the risk of LHON in the Polish population. Surprisingly, we did not observe associations previously reported for m.11778G > A and LHON in European populations, particularly for haplogroup J as a risk factor, implying that mtDNA variation is much more complex. Our results indicate possible contribution of novel combination of mtDNA genetic factors to the LHON phenotype. Electronic supplementary material The online version of this article (10.1007/s11011-020-00605-3) contains supplementary material, which is available to authorized users.

Choroby mitochondrialne wynikają z nieprawidłowej funkcji mitochondrialnego systemu fosforylacji oksydacyjnej: łańcucha oddechowego i syntazy ATP, produkującego energię komórkową w formie ATP. Jest to zróżnicowana grupa chorób dziedzicznych o szerokim spektrum objawów klinicznych mogących pojawić się w każdym wieku. Mogą one być wynikiem mutacji zarówno w mitochondrialnym DNA, jak i DNA jądrowym. Duża zmienność fenotypu pacjentów utrudnia ich diagnozowanie. Ostatnie osiągnięcia w dziedzinie diagnostyki i badań genetycznych oraz nowe metody reprodukcyjne są ogromną szansą na poprawę diagnostyki, leczenia i ograniczenie chorób mitochondrialnych. W tej pracy przedstawiono nowe zagadnienia pozwalające lepiej zrozumieć etiologię tych chorób oraz postęp w ich diagnozowaniu.

Background. Leber’s hereditary optic neuropathy (LHON) is a disease associated with pathogenetic mutations of mitochondrial DNA which affects predominantly young adult males and leads to loss of central vision, low visual acuity and unstable fixation. The purpose of this study was to allow the patient to establish the best possible fixation in the best area of retinal sensitivity in LHON patient with central scotoma. Methods. A 17 years old patient with confirmed mitochondrial LHON 11778G > A mutation was included in the study. The patient underwent 16 visual rehabilitation sessions — two for each of 8 weeks using the training module available in the equipment — MAIA microperimeter. Visual acuity and standrad microperimetry examination were performed before and 8 weeks period of training. To measure the fixation stability with MAIA microperimeter, P1, P2 and Bivariate Contour Ellipse Area (BCEA) parameters were used. Results. Visual acuity of the trained better eye was 0.08 at the baseline versus 0.063 after 8 weeks training. Fixation stability parameter was P1-21%, P2-64% at the first session versus P1-60%, P2-90% at the last session. BCEA values 29.2°˛ before and 14.2°˛ after training, respectively. Conclusions. Visual training via microperimetry could potentially be a method that improves the fixation stability in patients with LHON.

Mitochondrial diseases are defined by a respiratory chain dysfunction and in most of the cases manifest as multisystem disorders with predominant expression in muscles and nerves and may be caused by mutations in mitochondrial (mtDNA) or nuclear (nDNA) genomes. Most of the proteins involved in respiratory chain function are nuclear encoded, although 13 subunits of respiratory chain complexes (together with 2 rRNAs and 22 tRNAs necessary for their translation) encoded by mtDNA are essential for cell function. nDNA encodes not only respiratory chain subunits but also all the proteins responsible for mtDNA maintenance, especially those involved in replication, as well as other proteins necessary for the transcription and copy number control of this multicopy genome. Mutations in these genes can cause secondary instability of the mitochondrial genome in the form of depletion (decreased number of mtDNA molecules in the cell), vast multiple deletions or accumulation of point mutations which in turn leads to mitochondrial diseases inherited in a Mendelian fashion. The list of genes involved in mitochondrial DNA maintenance is long, and still incomplete.

Huntington disease (HD) is an inherited neurodegenerative disorder caused by mutations in the huntingtin gene. Involvement of mitochondrial dysfunctions in, and especially influence of the level of mitochondrial DNA (mtDNA) on, development of this disease is unclear. Here, samples of blood from 84 HD patients and 79 controls, and dermal fibroblasts from 10 HD patients and 9 controls were analysed for mtDNA levels. Although the type of mitochondrial haplogroup had no influence on the mtDNA level, and there was no correlation between mtDNA level in leukocytes in HD patients and various parameters of HD severity, some considerable differences between HD patients and controls were identified. The average mtDNA/nDNA relative copy number was significantly higher in leukocytes, but lower in fibroblasts, of symptomatic HD patients relative to the control group. Moreover, HD women displayed higher mtDNA levels in leukocytes than HD men. Because this is the largest population analysed to date, these results might contribute to explanation of discrepancies between previously published studies concerning levels of mtDNA in cells of HD patients. We suggest that the size of the investigated population and type of cells from which DNA is isolated could significantly affect results of mtDNA copy number estimation in HD. Hence, these parameters should be taken into consideration in studies on mtDNA in HD, and perhaps also in other diseases where mitochondrial dysfunction occurs. Electronic supplementary material The online version of this article (doi:10.1007/s11011-017-0026-0) contains supplementary material, which is available to authorized users.

Introduction Migraine is a common neurological disorder characterized by a particular phenotype, complex pathophysiology and a heterogeneous genetic background. Among several heritable forms, familial hemiplegic migraine is the best described one. In the majority of cases it is caused by mutations in one of three different genes. Case report Clinical symptoms of a 47 year old proband (and independently described in his 20 year old son) as well as differential diagnosis are discussed in the presented report. The most characteristic were recurrent attacks of blurred vision, paresthesias and hemiparesis often accompanied by speech disturbances and followed by severe headache with vomiting. Advanced morphological and genetic procedures were required to exclude MELAS, CADASIL and Call-Fleming syndrome. Finally, the definite diagnosis was possible after the application of the whole exome sequencing technique. It confirmed, for the first time in the Polish population, a heterozygous T666M mutation (c.1997C>T; p.Thr666Met) in the CACNA1A gene in the proband, the proband's son and in several other family members. Conclusion The presented report provides clinical and genetic insight into familial hemiplegic migraine 1 resulting from a mutation in the CACNA1A gene.

RNase H1 is able to recognize DNA/RNA heteroduplexes and to degrade their RNA component. As a consequence, it has been implicated in different aspects of mtDNA replication such as primer formation, primer removal, and replication termination, and significant differences have been reported between control and mutant RNASEH1 skin fibroblasts from patients. However, neither mtDNA depletion nor the presence of deletions have been described in skin fibroblasts while still presenting signs of mitochondrial dysfunction (lower mitochondrial membrane potential, reduced oxygen consumption, slow growth in galactose). Here, we show that RNase H1 has an effect on mtDNA transcripts, most likely through the regulation of 7S RNA and other R-loops. The observed effect on both mitochondrial mRNAs and 16S rRNA results in decreased mitochondrial translation and subsequently mitochondrial dysfunction in cells carrying mutations in RNASEH1.

RNase H1 is able to recognize DNA/RNA heteroduplexes and to degrade their RNA component. As a consequence, it has been implicated in different aspects of mtDNA replication such as primer formation, primer removal, and replication termination, and significant differences have been reported between control and mutant RNASEH1 skin fibroblasts from patients. However, neither mtDNA depletion nor the presence of deletions have been described in skin fibroblasts while still presenting signs of mitochondrial dysfunction (lower mitochondrial membrane potential, reduced oxygen consumption, slow growth in galactose). Here, we show that RNase H1 has an effect on mtDNA transcripts, most likely through the regulation of 7S RNA and other R-loops. The observed effect on both mitochondrial mRNAs and 16S rRNA results in decreased mitochondrial translation and subsequently mitochondrial dysfunction in cells carrying mutations in RNASEH1.

Diseases related to DNA polymerase gamma dysfunction comprise of heterogeneous clinical presentations with variable severity and age of onset. Molecular screening for the common POLG variants: p.Ala467Thr, p.Trp748Ser, p.Gly848Ser, and p.Tre251Ile has been conducted in a large population cohort (n = 3123) and in a clinically heterogeneous group of 1289 patients. Recessive pathogenic variants, including six novel ones were revealed in 22/26 patients. Infantile Alpers-Huttenlocher syndrome and adulthood ataxia spectrum were the most common found in our group. Distinct molecular profile identified in the Polish patients with significant predominance of p.Trp748Ser variant (50% of mutant alleles) reflected strikingly low population frequency of the three remaining variants and slightly higher p.Trp748Ser allele frequency in the general Polish population as compared to the non-Finish European population.

POLG2 associated disorders belong to the group of mitochondrial DNA (mtDNA) diseases and present with a heterogeneous clinical spectrum, various age of onset, and disease severity. We report a 39-year old female presenting with childhood-onset and progressive neuroophthalmic manifestation with optic atrophy, mixed polyneuropathy, spinal and cerebellar ataxia and generalized chorea associated with mtDNA depletion. Whole-exome sequencing identified an ultra-rare homozygous missense mutation located at Chr17: 062474101-C > A (p.Asp433Tyr) in nuclear POLG2 gene encoding PolγB, an accessory subunits of mitochondrial polymerase γ responsible for mtDNA replication. The healthy parents and 2 sisters of the patient were heterozygous for the variant. To our best knowledge, this is the first case of homozygous variant in the POLG2 gene resulting in mitochondrial depletion syndrome in an adult patient and its clinical manifestations extend the clinical spectrum of POLG2 associated diseases.

Glaucoma is one of the leading causes of visual impairment and blindness worldwide. However, the cause of retinal ganglion cell loss and damage of the optic nerve in its pathogenesis is largely unknown. The high energy demands of these cells may reflect their strong dependence on mitochondrial function and thus sensitivity to mitochondrial defects. To address this issue, we studied whole mitochondrial genome variation in normal tension glaucoma patients and control individuals from the Polish population using next generation sequencing. Our findings indicate that few features of mitochondrial DNA variation are different for glaucoma patients and control subjects. New insights into normal tension glaucoma development are discussed. We provide also a comprehensive approach for mitochondrial DNA analysis and variant evaluation.

Mitochondrial diseases are caused by dysfunction of the mitochondrial oxidative phosphorylation system and can be the result of mutations both in mitochondrial DNA and in nuclear DNA. Mitochondrial diseases collectively describe a diverse group of heritable disorders, which may present at any age and have a wide spectrum of clinical manifestations. This leads to highly variable presentations, making the diagnosis of mitochondrial diseases challenging. Recent advances in genetic testing and novel reproductive options hold great promise for improving the clinical identification and treatment of mitochondrial diseases. In this work we discuss what is new in understanding and diagnosis of mitochondrial diseases.Choroby mitochondrialne wynikają z nieprawidłowej funkcji mitochondrialnego systemu fosforylacji oksydacyjnej: łańcucha oddechowego i syntazy ATP, produkującego energię komórkową w formie ATP. Jest to zróżnicowana grupa chorób dziedzicznych o szerokim spektrum objawów klinicznych mogących pojawić się w każdym wieku. Mogą one być wynikiem mutacji zarówno w mitochondrialnym DNA, jak i DNA jądrowym. Duża zmienność fenotypu pacjentów utrudnia ich diagnozowanie. Ostatnie osiągnięcia w dziedzinie diagnostyki i badań genetycznych oraz nowe metody reprodukcyjne są ogromną szansą na poprawę diagnostyki, leczenia i ograniczenie chorób mitochondrialnych. W tej pracy przedstawiono nowe zagadnienia pozwalające lepiej zrozumieć etiologię tych chorób oraz postęp w ich diagnozowaniu.

Background During the last few years, the correlation between mitochondrial disorders and autoimmune diseases has been reported. Autoimmune polyneuropathies were concomitant with symptoms related to the polymerase γ (POLG) mutations. POLG is involved in mitochondrial DNA (mtDNA) replication and maintenance. Material and methods We present a case of a16-year-old girl with W748S mutation of POLG region with a 1,5-year history of slowly progressive walking difficulties. Results In the neurological examination the girl had ataxic gait with sensory disturbances in lower extremities with areflexia. Nerve conduction studies (NCS) demonstrated axonal–demyelinating sensorimotor polyneuropathy of the lower limbs. Additionally, magnetic resonance imaging (MRI) of the lumbar spine revealed gadolinium enhancement of the spinal roots and an examination of cerebrospinal fluid showed dissemination. The immunomodulatory treatment with intravenous methylprednisolone and intravenous immunoglobulin (IVIg) was started. Conclusions The IVIg and IVMP treatment led to marked improvement of her abnormal gait and improved resolution of abnormalities of touch, temperature sensation and improved proprioception. The W748S mutations were commonly reported and associated with variable phenotypes, most often Alpers syndrome, but also polyneuropathy. However, electrodiagnostic features and partial response to immunomodulatory therapy suggest the autoimmune etiology of the patients’ subacute symptoms. We hypothesize that oxidative stress caused by impaired mitochondria function may trigger an autoimmune response.

Summary Mitochondrial DNA was found to be highly mutated in colorectal cancer cells. One of the key molecules involved in the maintenance of the mitochondrial genome is the nuclear-encoded polymerase gamma. The aim of our study was to determine if there is a link between polymorphisms within the polymerase gamma gene (POLG) and somatic mutations within the mitochondrial genome in cancer cells. We investigated POLG sequence variability in 50 colorectal cancer patients whose complete mitochondrial genome sequences were determined. Relative mtDNA copy number was also determined. We identified 251 sequence variants in the POLG gene. Most of them were germline-specific (∼92%). Twenty-one somatic changes in POLG were found in 10 colorectal cancer patients. We have found no association between the occurrence of mtDNA somatic mutations and the somatically occurring variants in POLG. MtDNA content was reduced in patients carrying somatic variants in POLG or germline nucleotide variants located in the region encoding the POLG polymerase domain, but the difference did not reach statistical significance. Our findings suggest that somatic mtDNA mutations occurring in colorectal cancer are not a consequence of somatic mutations in POLG. Nevertheless, POLG nucleotide variants may lead to a decrease in mtDNA content, and consequently result in mitochondrial dysfunction.

Purpose. To analyse visual field (VF) defects obtained using semiautomated kinetic perimetry (SKP) in patients suffering from Leber hereditary optic neuropathy (LHON). Methods. Twenty-two eyes of eleven consecutive LHON male patients with confirmed mitochondrial 11778G>A DNA mutation were prospectively examined with the V4e stimulus of SKP in both eyes. The mean time after the onset of LHON was one year. The area of obtained isopters was measured in square degrees (deg2). Additionally, static automated perimetry (SAP) within 30° was performed. Results. Visual acuity ranged from counting fingers to 50 cm to 0.4. VFs obtained with SKP showed central scotomas in 18 eyes (82%); the periphery of the VF in these eyes remained intact. The mean area of central scotoma was 408.8 deg2, and the mean area of the peripheral VF was 12291.1 deg2; SAP also revealed central scotoma in these patients. In four eyes (18%) with the worst visual acuity, only the residual central island of VF was found using SKP (mean area 898.4 deg2). SAP was difficult to obtain in these patients. Conclusions. SKP provides additional clinical information in regard to the visual function of LHON patients. SKP enables the quantification of the area of central scotoma, preserved peripheral VF, and residual central island of vision. Using V4 stimulus is especially useful in LHON patients with poor visual acuity, when SAP is difficult to obtain.

Numerous studies of mitochondrial DNA (mtDNA) in cancer have shown differences between mtDNA sequences in tumor and normal tissue and at various stages of cancer treatment in the same patient. However, there is little data on acute lymphoblastic leukemia (ALL), the most common type of leukemia in children. In this study we compared mitochondrial sequence variation in the D-loop region and in 5 genes of mtDNA in bone marrow samples of 6 pediatric patients with ALL at various stages of therapy. We found several common polymorphisms and one variant at position 3688 whose level varied during leukemia treatment. Our results suggest that mitochondrial DNA mutations, whose levels change during patient treatment, could be potential biomarkers for monitoring treatment efficacy and disease progression.

Mitochondrial diseases may cause a wide range of central and peripheral nervous system disorders, as well as muscle disorders. The diagnostic workup routinely includes electrophysiological, morphological, neuroimaging and genetic studies. In some cases, the diagnosis may be ascertained only when mitochondrial DNA (mtDNA) examination in the muscle is performed. We report on a case of a 24-year-old woman, with a 7-year history of slowly progressive cerebellar syndrome and bilateral ptosis. Mitochondrial encephalomyopathy was suspected, based on the clinical picture and results of examinations, but the typical red ragged fibers were not found in the muscle biopsy. The results of molecular analysis of mtDNA showed a mtDNA deletion in the muscle and, on a level detectable only with polymerase chain reaction method, in blood leukocytes. This case emphasizes the important role of mtDNA studies in muscle in nonspecific multisystem mitochondrial disorders, even without clinical muscle involvement.

Deletions in mitochondrial DNA are a common cause of mitochondrial disorders. The molecular diagnosis of mtDNA deletions for years was based on Southern hybridization later replaced by PCR methods such as PCR with primers specific for a particular deletion (mainly the so-called common deletion of 4977 bp) and long PCR. In order to evaluate the usefulness of MLPA (Multiplex Ligation-dependent Probe Amplification) in molecular diagnosis of large scale mtDNA deletions we compare four diagnostic methods: Southern hybridization, PCR, long-PCR and MLPA in a group of 16 patients with suspected deletions. Analysis was performed on blood, muscle and in one case hepatic tissue DNA. The MLPA was not able to confirm all the deletions detected by PCR methods, but due to its relative ease of processing, minimal equipment, low costs and the additional possibility to detect frequent point mtDNA mutations in one assay it is worth considering as a screening method. We recommend to always confirm MLPA results by PCR methods.

Men and women not only look different, but they have different risks of multiple diseases like migraine, neurodegenerative disorders or numerous cancers. Even the nerve cells may die in different ways and exhibit different sensitivity to pro-apoptotic factors. Some of the differences can be explained by the action of sex hormones, but the experiments on four core genotype mouse model, in which XX and XY mice can be of either sex showed that not all differences are due to hormones. An example of a disease with no simple explanation of sex bias is Leber hereditary optic neuropathy, a mitochondrial disease with about 4:1 male to female ratio. The apoptotic death of retinal ganglion cells forming an optic disc is a proposed mechanism of the disease pathophysiology. The mechanisms causing different sensitivity of the nerve cells of male and female subjects may be responsible for the gender bias in LHON and merit further studies.

Mutations in NADH dehydrogenase (ND) subunits of complex I lead to mitochondrial encephalomyopathies associated with various phenotypes. This report aims to present the patient’s clinical symptomatology in the context of a very rare 13042G>A de novo mutation and with an emphasis on changing phenotypic expression and pronounced, long-standing response to levetiracetam. Electronic supplementary material The online version of this article (doi:10.1007/s11011-014-9645-x) contains supplementary material, which is available to authorized users.

There are many theories of aging and a number of them encompass the role of mitochondria in this process. Mitochondrial DNA mutations and deletions have been shown to accumulate in many tissues in mammals during aging. However, there is little evidence that these mutations could affect the functioning of aging tissues.

Mitochondrial haplogroups can differ in frequency of occurrence in those who are 100 years old and in the rest of the population. These differences are not universally observed; moreover, they are population-specific. We analyzed the haplogroups in 97 Polish 100-year-olds and compared them with those of more than 145 people who served as controls. No statistically significant differences were observed. In additions, we checked D-loop sequences in 31 controls and in some of the centenarians. Statistically significant differences were found for sites 73 and 152 in the D-loop.

Mitochondrial DNA point mutations are associated with various syndromes, among which mitochondrial myopathy, encephalopathy, lactic acidosis and stroke (MELAS) and myoclonic epilepsy with ragged red fibres (MERRF) are the most common.1 Here we present a case report of a young man with a mitochondrial encephalomyopathy caused by a mutation in the ND5 gene (13042A>G), which has been described previously.1 A 21-year-old man presented with a 2-year history of recurrent generalised epileptic seizures and myoclonus with no family history. Neurological examination revealed discrete nystagmus and multifocal myoclonus in the upper limbs, ataxia and focal dystonia presenting as writer's cramp. Neuropsychological examination showed slight working memory impairment and slowed learning of both verbal and visual material. Follow-up examinations conducted 18 and 33 months later did not show evidence of progression of the deficits. The patient exhibited anosodiaphoria throughout the observation period. Laboratory studies showed a normal serum lactic acid level of 9.45 mg% with an abnormal lactic acid curve during ischaemic muscle exercise. Creatine kinase activity was within the normal range. A 50 min video EEG disclosed a pattern characteristic of myoclonic epilepsy. Visual evoked potentials showed delayed P100 responses. Electromyography and nerve conduction studies were within normal ranges. MRI showed hyperintensive lesions on T2 and FLAIR images in the right cerebral peduncle, close to the occipital horns of the lateral ventricles, in the left temporal lobe as well as …

Mitochondrial DNA was found to be highly mutated in colorectal cancer cells. One of the key molecules involved in the maintenance of the mitochondrial genome is the nuclear-encoded polymerase gamma. The aim of our study was to determine if there is a link between polymorphisms within the polymerase gamma gene (POLG) and somatic mutations within the mitochondrial genome in cancer cells. We investigated POLG sequence variability in 50 colorectal cancer patients whose complete mitochondrial genome sequences were determined. Relative mtDNA copy number was also determined. We identified 251 sequence variants in the POLG gene. Most of them were germline-specific (∼92%). Twenty-one somatic changes in POLG were found in 10 colorectal cancer patients. We have found no association between the occurrence of mtDNA somatic mutations and the somatically occurring variants in POLG. MtDNA content was reduced in patients carrying somatic variants in POLG or germline nucleotide variants located in the region encoding the POLG polymerase domain, but the difference did not reach statistical significance. Our findings suggest that somatic mtDNA mutations occurring in colorectal cancer are not a consequence of somatic mutations in POLG. Nevertheless, POLG nucleotide variants may lead to a decrease in mtDNA content, and consequently result in mitochondrial dysfunction.

Leber hereditary optic neuropathy (LHON) is a genetic, maternally inherited disease caused by point mutations in the mitochondrial genome. LHON patients present with sudden, painless and usually bilateral loss of vision caused by optic nerve atrophy. The first clinical description of the disease was made by Theodor Leber, a German ophthalmologist, in 1871. Here we present his thorough notes about members of four families and their pedigrees. We also provide insights into the current knowledge about LHON pathology, genetics and treatment in comparison with Leber's findings.

Over 90% of Leber's hereditary optic neuropathy (LHON) is caused by one of three mtDNA mutations (m.11778A>G, m.3460G>A, m.14484T>C). The remaining cases are due to rare mutations in different genes encoding subunits of the respiratory chain. The proband is a 17-year-old male with symptoms of optic nerve atrophy. No common LHON mutations were found, but detailed sequencing identified a rare, homoplasmic mutation m.3635G>A in the ND1 gene.

Current state-of-the-art anti-angiogenic therapies target the VEGF pathway, which is the main essential signaling pathway for angiogenesis, including pathological angiogenesis in cancer and eye disease. Ranibizumab (Lucentis) and VEGF-Trap (aflibercept) represent two different approaches to inhibiting angiogenesis by targeting VEGF family signaling. The former is a relatively short monoclonal antibody fragment, which binds VEGF-A on the basis of antigen recognition by the variable region of an antibody, while aflibercept is not an monoclonal antibody, but a decoy receptor, binding VEGF-A on the basis of the molecular interaction between the ligand (VEGF) and its cognate cellular receptor (VEGFR-1 and VEGFR-2). VEGF-Trap has therefore a broader specificity, recognizing and binding VEGF-B and PIGF in addition to VEGF-A, following the specificity of VEGFR-1 and VEGFR-2. This broader specificity is considered as beneficial in cancer treatment and could be also beneficial in treatment of nAMD, this claim should, however, be backed by clinical studies. The presence of an Fc fragment in VEGF-Trap is also an important difference; even though this fragment does not participate in the recognition of the target molecule, it can influence the biological properties of the fusion protein. The relative merits of both approaches will become clear only after long-term laboratory and clinical testing, as their biological activity is also likely to differ. Given the clear differences in the mechanism of target molecule recognition, biochemical and biophysical properties (including molecular weight) and specificity, they cannot be considered as equivalent, unless extensive long-term clinical studies prove otherwise.

Vulvar squamous cell carcinoma (VSCC) is a rare female genital neoplasm. Although numerous molecular changes have been reported in VSCC, biomarkers of clinical relevance are still lacking. On the other hand, there is emerging evidence on the use of mtDNA as a diagnostic tool in oncology. In order to investigate mtDNA status in VSCC patients, haplogroup distribution analysis and D-loop sequencing were performed. The results were compared with available data for the general Polish population, cancer free-centenarians as well as patients with endometrial and head and neck cancer. The obtained data were also compared with the current status of mitochondrial databases. Significant differences in haplogroup distribution between VSCC cohort, general Polish population and cancer-free centenarians cohort were found. Moreover, a correlation between the VSCC patients haplogroup and HPV status was observed. Finally, a specific pattern of mtDNA polymorphisms was found in VSCC. Our results suggest that the mitochondrial genetic background may influence the risk of VSCC occurrence as well as susceptibility to HPV infection.

Mitochondrial cytopathies are heterogeneous disorders affecting multiple systems but most commonly involving the skeletal muscle and central nervous system. The variety of symptoms and signs requires biochemical, morphological and genetic evaluation. The results of genetic studies indicate that there is no direct correlation between genotype and phenotype in mitochondrial cytopathies. This study is the first such analysis of a group of Polish patients with mitochondrial cytopathies. Its aim is to define the clinical features of mitochondrial cytopathies in relation to their genetic defects.In a retrospective study, 46 patients with final diagnosis of mitochondrial cytopathy were evaluated clinically and electrophysiologically. Each patient underwent electromyography, electroneurography, and some patients were also assessed using electroencephalography. Clinical diagnoses were confirmed through the histopathological evaluation of muscle biopsies. In 36 cases mitochondrial DNA (mtDNA) testing was performed.Eight different clinical syndromes were diagnosed among the evaluated patients. In the skeletal muscle biopsy, ragged-red fibres, which are a significant symptom for these disorders, were present in the majority of cases (93%). The presence of specific gene mutations was confirmed in 9 out of the 36 cases in which mtDNA was examined.The results of our study confirm the remarkable clinical heterogeneity of mitochondrial cytopathies. Final diagnosis in many cases could only be confirmed by detection of the genetic defects. Molecular diagnosis may in the future have a significant impact on new therapeutic approaches.

Three mutations in mitochondrial DNA complex I genes are responsible for over 90% of Leber hereditary optic neuropathy (LHON) cases in Europe. A family with two LHON mutations--practically homoplasmic 11778G>A and varying levels of 3460G>A--was found during analysis of Polish patients. DNA and visual acuity was analyzed in four affected brothers and their unaffected sister and mother as well as in their step brother. Four male patients experienced vision loss around the age of 20 while for their step brother the onset was late--at the age of 33. No additional neurological symptoms were observed and both women were completely asymptomatic. The mutation occurred in a haplogroup H background, the most common one in both the Polish population and among patients. Double LHON mutations are extremely rare, and this particular combination has not been previously described in the literature.

Polymorphisms in mitochondrial DNA (mtDNA) were analyzed in 152 samples from the Polish population using restriction enzymes AvaI, BamHI, HaeII, HpaI and PstI. Additionally, each sample was classified into the appropriate haplogroup. When required, appropriate fragments were sequenced to establish the exact polymorphic sites. We found one new morph for PstI and six new morphs for AvaII. Some detected morphs have previously been described as population specific morphs in different regions of the world. All polymorphisms were classified into 31 different haplotypes. 21 of them were detected in single individuals. The Polish population was compared with other populations from different regions. Moreover, we have obtained evidence for mutation hot spots in the mtDNA coding region. Our results indicate that AvaII morph and haplogroup composition of the Polish population is similar to other European populations and has a distribution typical for this part of the world. However, statistically significant differences in haplogroup composition were found between the Polish population and Italian and Finnish populations.

termini: -CCAtrinucleotide is added to mt-tRNAs, whilst mt-rRNAs and mt-mRNAs are oligo- or polyadenylated,respectively. The cis-acting elements, enzymes and indeed the mechanisms involved in these processesare still largely uncharacterized. Further, the function of polyadenylation in promoting stability, translation ordecay of human mt-mRNA is unclear. A microdeletion has been identified in a patient presenting with mtDNAdisease. Loss of these two residues removes the termination codon for MTATP6 and sets MTCO3immediately in frame. Accurate processing at this site still occurs, but there is a markedly decreased steady-state level of RNA14, the ATPase 8- and 6-encoding bi-cistronic mRNA unit, establishing that an mtDNAmutation can cause dysregulation of mRNA stability. Analysis of the polyadenylation profile of the processedRNA14 at steady state revealed substantial abnormalities. The majority of mutated RNA14 terminated withshort poly (A) extensions and a second, partially truncated population, was also present. Initial maturation ofmutated RNA14 was unaffected, but deadenylation occurred rapidly. Inhibition of mitochondrial proteinsynthesis showed that the deadenylation was dependent on translation. Finally, deadenylation was shown toenhance mRNA decay, explaining the decrease in steady-state RNA14. An hypothesis is presented todescribe how an mtDNA mutation that results in the loss of a termination codon causes enhanced mt-mRNAdecay by translation-dependent deadenylation.INTRODUCTIONHuman mtDNA, a circular duplex of 16569bp, is present inmulticopy in all nucleated cells of the body. It encodes 13polypeptides, all of which are believed to be essential com-ponents of the enzymatic complexes that couple cellularrespiration to ATP synthesis. In addition, the genome encodes22 tRNA and 2 rRNA molecules that are required for intra-mitochondrial protein synthesis. Mitochondrial transfection inmammals remains intractable and in the absence of faithfulreconstitution systems many aspects of mitochondrial geneexpressionarenotwellunderstood.Ithasbeenknownforover20years that the genome is almost fully transcribed from bothstrands (1). These polycistronic RNA units are rapidly processedinto discrete RNA species, which are immediately maturedto produce mt-rRNAs and mt-mRNAs that are oligo- andpolyadenylated, or mt-tRNA species that carry a 3

MELAS (mitochondrial myopathy, lactic acidosis and stroke-like episodes) is one of the most common mitochondrial encephalomyopathies.We present four children with A3243G MELAS mtDNA mutation and give a summary of clinical MELAS symptoms reported in the literature. Serum lactate elevation, mosaic pattern of COX deficit and decreased activity of complex I and IV in the muscle biopsy were found in all cases. RRFs were recognized in three out of four.The main features seen in all our patients were poor growth and fatigability with muscle weakness. All presented epileptic jerks of various character, some deformation features (recurrent pretibial and peritarsal edema, large swollen-looking hands and feet, hypertelorism and protruding ears) and some cutaneous lesions (atopic dermatitis, local melanoderma, asymmetric vascular dilatation). Stroke-like episodes, multihormonal hypopituitarism, sensorineural hypoacusis, pigmentary retinal degeneration, intracranial calcification, heart involvement, recurrent vomiting or abdominal pain were seen only in individual cases. The homonymous hemianopia frequently reported in the literature was not a feature of our patients. One of them suffered from nonspecific sialoadenitis never mentioned in the literature.Morphological, enzymatic and molecular investigations of a muscle biopsy sample should be undertaken to improve early MELAS detection in patients with any multiorgan disease associated with serum lactate elevation.

To describe a patient with genetically confirmed POLG mutation and partially treatment-responsive chronic immune demyelinating polyneuropathy. Patient and methods: A 16 years old girl with predominantly sensory neuropathy, dysarthria and ataxia. Case description together with nerve conduction study, evoked potentials and MRI results are presented. She had history of 1.5 years of slowly progressive walking difficulties. Developmental milestones were normal, but she was never good at sports. On admission she had ataxic gait, proprioceptive sensation disturbances, high arched feet, dysarthria, pansensory loss in lower extremities up to her knees, areflexia, positive Romberg sign. Nerve conduction studies demonstrated sensory-motor polyneuropathy of lower limbs. Evoked potentials studies confirmed disturbances of visual, brain stem and somatosensory pathways. Magnetic resonance imaging (MRI) of lumbar spine revealed gadolinium enhancement of spinal roots She had elevated CSF protein with normal leukocyte count. Preliminary diagnosis of chronic immune demyelinating neuropathy was made. Immunomodulatory treatment with methylprednisolone and IVIG led to marked improvement of gait, resolution of abnormalities of touch, temperature sensation, improved proprioception. Several weeks later she developed action-exacerbated myoclonus of her left lower extremity, partially responsive to treatment with clonazepam and levetiracetam. Myoclonus limited her ability to walk. MR Spectroscopy with voxel placed in lateral ventricle demonstrated increased lactate in CSF. DNA testing revealed heterozygous mutation of POLG, with paternally inherited W748S, and maternally inherited V1106A mutation of an evolutionary conserved POLG region. The case raises the question if mitochondrial disease triggered additional immune disease, or autoimmune polyneuropathy affected the clinical course of this rare hereditary disorder.

Replication of the mitochondrial genome depends on the single DNA polymerase (pol gamma). Mutations in the POLG gene, encoding the catalytic subunit of the human polymerase gamma, have been linked to a wide variety of mitochondrial disorders that show remarkable heterogeneity, with more than 200 sequence variants, often very rare, found in patients. The pathogenicity and dominance status of many such mutations remain, however, unclear. Remarkable structural and functional conservation of human POLG and its S. cerevisiae ortholog (Mip1p) led to the development of many successful yeast models, enabling to study the phenotype of putative pathogenic mutations. In a group of patients with suspicion of mitochondrial pathology, we identified five novel POLG sequence variants, four of which (p.Arg869Ter, p.Gln968Glu, p.Thr1053Argfs*6, and p.Val1106Ala), together with one previously known but uncharacterised variant (p.Arg309Cys), were amenable to modelling in yeast. Familial analysis indicated causal relationship of these variants with disease, consistent with autosomal recessive inheritance. To investigate the effect of these sequence changes on mtDNA replication, we obtained the corresponding yeast mip1 alleles (Arg265Cys, Arg672Ter, Arg770Glu, Thr809Ter, and Val863Ala, respectively) and tested their effect on mitochondrial genome stability and replication fidelity. For three of them (Arg265Cys, Arg672Ter, and Thr809Ter), we observed a strong, partially dominant phenotype of a complete loss of functional mtDNA, whereas the remaining two led to partial mtDNA depletion and significant increase in point mutation frequencies. These results show good correlation with the severity of symptoms observed in patients and allow to establish these variants as pathogenic mutations. Electronic supplementary material The online version of this article (doi:10.1007/s00439-015-1578-x) contains supplementary material, which is available to authorized users.