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Assessment of ataxic movements is usually based on clinical judgment. Technical devices can be employed in the quantification of ataxic movements in addition to clinical evaluation. The effect of maximal speed in upper limb movements in ataxia patients has not been quantified. The aim was to quantify upper limb movements in patients with hereditary or idiopathic ataxia and to find features of movement that are characteristic for ataxia. We examined 19 patients with degenerative ataxia and 21 healthy controls. An ad hoc system comprising a touch screen, an accelerometer, and a gyroscope was used to measure speed, angular acceleration, consistency, and accuracy of upper limb movements. The movements were quantified during finger-to-nose test that the patients were asked to perform at their own pace and as fast as possible. Disease severity was estimated by using the Scale for the Assessment and Rating of Ataxia (SARA). The mean SARA score of the patients was 13.5. Compared to the controls the performance of the patients was slow (p < 0.001) and arrhythmic (p < 0.001), but end-point accuracy on the touch screen was intact. The SARA score correlated with the standard deviation of amplitude of angular acceleration in Z-axis (F(1,17) = 15.00, p < 0.001 with R2 = 0.47). Upper limb movements of the patients with degenerative ataxia were slower and more arrhythmic than those in the controls. The patients retained spatial end-point accuracy. [ABSTRACT FROM AUTHOR]

Background: Leber's hereditary optic neuropathy (LHON) is a common form of mitochondrial disease. The typical clinical presentation of LHON is subacute, painless loss of vision resulting from bilateral optic nerve atrophy. Moreover, extra-ocular manifestations such as cardiac conduction abnormalities and neurological manifestations such as multiple sclerosis (MS) like disease or parkinsonism are encountered in some patients. Abnormal findings in spinal cord MR imaging or in the cerebrospinal fluid (CSF) have been observed in previous cases of LHON-associated myelopathy. Case presentation: We report a male patient with LHON who developed symptoms of myelopathy including gait unsteadiness, enhanced deep tendon reflexes and sensory loss of the lower extremities. Imaging of the brain and spinal cord, CSF analysis, as well as neurography and electromyography did not disclose any abnormalities. The somatosensory evoked potential (SEP) findings were suggestive of dorsal column dysfunction. Conclusions: The patient case demonstrates that myelopathy associated with LHON can present without abnormal findings in central nervous system MR imaging or in the CSF, and without evidence suggestive of multiple sclerosis or MS-like disease. The dorsal column seems to be particularly vulnerable to myelopathy changes in LHON. Evoked potential investigations may assist in confirming the diagnosis, when clinical features are in line with myelopathy but findings in CSF analysis and central nervous system imaging are normal. [ABSTRACT FROM AUTHOR]

Occipital stroke and occipital epilepsy are possible manifestations of mitochondrial diseases. A previous study in northern Finland suggested a frequency of 10% for mitochondrial disorder in young patients with stroke. Here we studied the epidemiology of occipital brain infarcts in a defined population in southwestern Finland. Patients diagnosed with brain infarct or visual field defect with onset at the ages of 18–45 years were identified from the discharge files at the Turku University Hospital. We further ascertained those patients with an occipital brain infarct in brain imaging or homonymous hemianopia with no signs of other etiology in brain imaging. We reviewed the clinical data for known stroke risk factors and analyzed samples for the m.3243A > G and m.8344A > G mutations in mitochondrial DNA (mtDNA), and determined mtDNA haplogroups and five common mutations in the gene encoding polymerase γ ( POLG1). Migraine was more common in young patients with occipital brain infarct than in the general population, especially among women. None of the patients harboured the m.3243A > G or m.8344A > G mutation in mtDNA or any of the five common mutations in POLG1. Interestingly, 17% of the men and 33% of the women belonged to the mtDNA haplogroup Uk, while its frequency in the general population is 17%. Our results suggest that mtDNA haplogroup Uk is associated with increased risk of occipital stroke in young women. POLG1 mutations have been associated with occipital epilepsy, but we did not find the common mutations in patients with occipital stroke. [ABSTRACT FROM AUTHOR]

OBJECTIVE--To study insulin sensitivity and perfusion in skeletal muscle together with the β-cell function in subjects with the m.3243A>G mutation in mitochondrial DNA, the most common cause of mitochondrial diabetes. RESEARCH DESIGN AND METHODS--We measured skeletal muscle glucose uptake and perfusion using positron emission tomography and 2-[[sup 18]F]fluoro-2-deoxyglucose and [[sup 15]O]H[sub 2]O during euglycemic hyperinsulinemia in 15 patients with m.3243A>G. These patients included five subjects with no diabetes as defined by the oral glucose tolerance test (OGTT) (group 1), three with GHb <6.1% and newly found diabetes by OGTT (group 2), and seven with a previously diagnosed diabetes (group 3). Control subjects consisted of 13 healthy individuals who were similar to the carriers of, m.3243A>G with respect to age and physical activity. β-Cell function was assessed using the OGTT and subsequent mathematical modeling. RESULTS--Skeletal muscle glucose uptake was significantly lower in groups 1, 2, and 3 than in the control subjects. The glucose sensitivity of β-cells in group 1 patients was similar to that of the control subjects, whereas in group 2 and 3 patients, the glucose sensitivity was significantly lower. The insulin secretion parameters correlated strongly with the proportion of m.3243A>G mutation in muscle. CONCLUSIONS---Our findings show that subjects with m.3243A >G are insulin resistant in skeletal muscle even when β-cell function is not markedly impaired or glucose control compromised. We suggest that both the skeletal muscle insulin sensitivity and the β-cell function are affected before the onset of the mitochondrial diabetes caused by the m.3243A>G mutation. Diabetes 58:543-549, 2009 [ABSTRACT FROM AUTHOR]

A letter to the editor is presented about the association of mitochondrial DNA variation with complex traits.

Differences in ACTN3 (alpha-actinin 3) genotypes have been reported among endurance and power athletes. Elite athletic performance in endurance sports should also depend on mitochondrial oxidative phosphorylation (OXPHOS) that produces ATP for muscle metabolism. We determined mitochondrial DNA (mtDNA) and ACTN3 genotypes in Finnish elite endurance (n=52) and sprint (n=89) athletes, and found that the frequencies of mtDNA haplogroups differed significantly between the two groups. Most notably, none of the endurance athletes belonged to haplogroup K or subhaplogroup J2, both of which have previously been associated with longevity. The frequency of ACTN3 XX genotype was higher and that of RR was lower among Finnish endurance athletes, and, in addition, none of the top Finnish sprinters had the XX genotype. Lack of mtDNA haplogroup K and subhaplogroup J2 among elite endurance athletes suggests that these haplogroups are ‘uncoupling genomes’. Such genomes should not be beneficial to endurance-type athletic performance but should be beneficial to longevity, since uncoupling of OXPHOS reduces the production of ATP, reduces the release of reactive oxygen species and generates heat.European Journal of Human Genetics (2005) 13, 965–969. doi:10.1038/sj.ejhg.5201438; published online 11 May 2005 [ABSTRACT FROM AUTHOR]

Deleterious point mutations in mitochondrial DNA (mtDNA) have been found in many human populations and always at a low frequency suggesting that they are under strong negative selection. It is assumed that this selection is caused by reduced genetic fitness of mutation carriers, but the fitness of carriers of any mtDNA mutation has not been determined. We estimated the reproductive disadvantage caused by the mitochondrial DNA mutation 3243A > G in a population-based group of female carriers (n = 32). The person-years method, Kaplan-Meier survival analysis and population statistics were used to estimate net reproduction rates of the mutation carriers and the general population. We found that women with 3243A > G reproduced at the same rate as women in the general population, suggesting that on average host-level selection against women harbouring the 3243A > G mutation is not strong. [ABSTRACT FROM AUTHOR]

The enzymatically catalyzed formation of 4-hydroxyproline plays a key role in the intracellular biosynthesis of collagen, since a critical number of 4-hydroxyprolyl residues is required for synthesis and secretion of triple-helical procollagen molecules under physiologic conditions. The enzyme catalyzing the conversion of prolyl residues to 4-hydroxyproline, prolyl 4-hydroxylase, requires ferrous ion, α-ketoglutarate, and ascorbate for its activity. 3,4-Dihydroxybenzoic acid has been known to act as potent competitive inhibitor of purified prolyl 4-hyroxylase with respect to one or several of the cofactors or cosubstrates of the enzyme. 3,4-Dihydroxybenzoic acid, however, is a poor inhibitor of prolyl hydroxylation in intact cells, probably due to its polarity not allowing it to enter the cells. In this study, several hydrophobic modifications of 3,4-dihydzoxybenzoic acid were tested in human skin fibroblast cultures for their efficacy to inhibit the synthesis of 4-hydroxyproline. The results indicated that the ethylester of 3,4-dihydroxybenzoic acid was an efficient inhibitor of prolyl hydroxylation in fibroblast cultures, with Ki of ∼0.4 mM. Ethyl 3,4-dihydroxybenzoate had little, if any, effect on the hydroxylation of lysyl residues, and it did not affect total protein synthesis or DNA replication in these cells. To test the hypothesis that ethyl 3,4-dihydroxybenzoate might serve as a potential antifibrotic agent, its efficacy in inhibiting prolyl hydroxylation in scleroderma fibroblasts was also tested. The results indicated that the synthesis of 4-hydroxyproline in scleroderma cell cultures was similarly reduced by ethyl 3,4-dihydroxy- benzoate. Thus, structural analogs of the cofactors or co- substrates of prolyl 4-hydroxylase, such as ethyl 3,4- dihydroxybeuzoate tested here or its further modifications, may serve as inhibitors of posttranslational hydroxylation of prolyl residues also in vivo. [ABSTRACT FROM AUTHOR]

The structure and function of the 2-oxoglutarate binding site prolyl 4-hydroxylase was studied by assaying the inhibitory potential of 24 selected aliphatic or aromatic compounds. All except one of them inhibited the enzyme competitively with respect to 2-oxoglutarate and noncompetitively with respect to Fe2+, the KIvalue ranging from 0.8 µM to over 15 mM. The K1 values for the two most effective inhibitors, pyridine 2,5-dicarboxylate and 2,4-dicarboxylate, were about 0.8µM and 2µM, these compounds being the most potent inhibitors of prolyl 4-hydroxylase with respect to 2-oxoglutarate known so far. Only one of the compounds tested, 2-oxodiopinate, was able to support hydroxylation by replacing 2-oxoglutarate as a cosubtrate. The data suggest that the 2-oxoglutarate binding site can be divided into three district subsites. Subsite I, is probably a positively charged side chain of the enzyme that ionically binds the C5 carboxyl group of the 2-oxoglutarate, subsite II consists of two cis-positioned equatorial coordination sites of the enzyme-bound ferrous ion and is chelated by the C2-C2 moiety, while subsite III involves a hydrophobic binding site in the C3-C4 region of the cosubstrate. The sp3 rehybridization of C2 within the chelating moiety of the cosubstrate appears to be a crucial event during decarboxylation that proceed in the form of a ligand reaction inside the Fe2+coordination sphere. [ABSTRACT FROM AUTHOR]

Abstract: Charcot–Marie–Tooth disease (CMT), which is the eponym for hereditary motor and sensory neuropathy (HMSN), affects ∼1 in 2500 individuals. The most common subtype of X-linked CMT, CMTX1, is caused by mutations in GJB1, the gene encoding connexin 32, a gap junction protein in myelinated Schwann cells. We report a woman, who presented at the age of 56years with gait unsteadiness and tingling in her feet. Clinical investigation revealed impaired sensation to pinprick, light touch and vibration in her distal lower limbs. Ankle reflexes were bilaterally absent. Sequencing revealed a novel heterozygous c.712C>T (p.R238C) mutation in the GJB1 gene. This mutation is predicted to result in the loss of disulfide bonds and thus in abnormal protein structure. In this woman, the reported novel GJB1 mutation resulted in sensory abnormalities, slowly progressive loss of distal lower limb strength, and notable loss of balance, with onset of symptoms late in adult age. [Copyright &y& Elsevier]

Background and Purpose: The biallelic repeat expansion (AAGGG)exp in the replication factor C subunit 1 gene (RFC1) is a frequent cause of cerebellar ataxia, neuropathy and vestibular areflexia syndrome (CANVAS) as well as late‐onset ataxia. The clinical spectrum of RFC1 disease has expanded since the first identification of biallelic (AAGGG)exp and includes now various nonclassical phenotypes. Biallelic (AAGGG)exp in RFC1 in patients with clinically confirmed Parkinson's disease (PD) has recently been found. Methods: A nationwide cohort of 273 Finnish patients with early‐onset PD was examined for the biallelic intronic expansion in RFC1. The expansion (AAGGG)exp was first screened using extra long polymerase chain reactions (Extra Large‐PCRs) and flanking multiplex PCR. The presence of biallelic (AAGGG)exp was then confirmed by repeat‐primed PCR and, finally, the repeat length was determined by long‐read sequencing. Results: Three patients were found with the biallelic (AAGGG)exp in RFC1 giving a frequency of 1.10% (0.23%–3.18%; 95% confidence interval). The three patients fulfilled the diagnostic criteria of PD, none of them had ataxia or neuropathy, and only one patient had a mild vestibular dysfunction. The age at onset of PD symptoms was 40–48 years and their disease course had been unremarkable apart from the early onset. Conclusions: Our results suggest that (AAGGG)exp in RFC1 is a rare cause of early‐onset PD. Other populations should be examined in order to determine whether our findings are specific to the Finnish population. [ABSTRACT FROM AUTHOR]

Comments on a study of mtDNA genotypes in patients who had an occipital stroke and a history of migraine. The inclusion of patients with A3243G, a point mutation of a nucleotide; Analysis of informative polymorphisms to determine mtDNA genotypes in blood DNA; Polymorphic sites defining mtDNA haplogroups found in different populations by continent; Suggestion that mtDNA haplogroup U constitutes a risk genome that may harbor mutations in the pathogenesis of migraine-associated stroke.

Objectives Mutations in mitochondrial DNA cause a variety of clinical phenotypes ranging from a mild hearing impairment ( HI) to severe encephalomyopathy. The MT- TS1 gene is a hotspot for mutations causing HI. The m.7510T>C mutation in MT- TS1 has been previously associated with non-syndromic HI in four families from different ethnic backgrounds. Materials and Methods We describe the clinical, genetic, and histopathological findings in a Finnish family with the heteroplasmic m.7510T>C mutation in mitochondrial DNA. Results The family proband presented with a progressive mitochondrial disease phenotype including migraine, epilepsy, mild ataxia, and cognitive impairment in addition to HI. One young adult presented with HI only. Other family members had a mild phenotype comprising ataxia and tremor in addition to HI. Mutation heteroplasmy was 90% in the blood of maternal grandmother and ≥99% in the muscle and blood of the three other family members. Muscle histology was consistent with mitochondrial myopathy in three family members. The mitochondrial haplogroup of the family was a different branch of the haplogroup H than in the previous reports of this mutation. Conclusion Our results suggest that, in addition to sensorineural HI, the m.7510T>C mutation is associated with a spectrum of mitochondrial disease clinical features including migraine, epilepsy, cognitive impairment, ataxia, and tremor, and with evidence of mitochondrial myopathy. [ABSTRACT FROM AUTHOR]

Background: Many features of Huntington's disease (HD) make these patients susceptible to subdural hematomas (SDH), but there are no previous reports on the epidemiology of SDH in this population. We investigated the incidence and risk factors of chronic SDH. Methods: A national cohort of 192 Finnish patients with HD was investigated. Information was gathered from medical records and administrative registries. Results: The incidence rate of SDH was 68.3/100,000 person-years among the 192 patients. Seven patients were identified with a chronic SDH at or after the diagnosis of HD. Their age was 58.5 ± 15.0 years (mean ± SD) at the time of diagnosis of HD and 60.9 ± 14.1 years at the time of diagnosis of SDH. The incidence rate of chronic SDH after the diagnosis of HD was 4.7/1000 person-years and by 8.3 years of follow-up the cumulative risk was 5.4 %. Review of the patient charts revealed only a few of the common risk factors for chronic SDH, but the rate of reoperations was high. Conclusions: The incidence of chronic SDH was higher in patients with HD than that in the general population. Incidence of chronic SDH began to increase at the time of expected motor onset of HD. Common risk factors of SDH were scarce aside from fall-related head injuries. [ABSTRACT FROM AUTHOR]

Introduction: The biallelic repeat expansion (AAGGG)exp in RFC1 causes cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS). Recently, cognitive impairment has been reported in patients with CANVAS and a broader neurodegenerative process associated with RFC1 has been suggested. Furthermore, rare cases of multiple system atrophy, Parkinson's disease, amyotrophic lateral sclerosis or CANVAS with features of dementia with Lewy bodies have been found.Objective: We hypothesized that the biallelic (AAGGG)exp is associated with neurodegeneration manifested as cognitive symptoms and that atypical RFC1 disease may be found among patients with cognitive disorder.Methods: Clinical data on nine patients with biallelic (AAGGG)exp were reviewed and 564 patients with Alzheimer's disease or frontotemporal dementia (FTD) were investigated for biallelic RFC1 (AAGGG)exp.Results: Five patients with biallelic (AAGGG)exp were found with a cognitive impairment and in four of them the phenotype resembled FTD. However, biallelic (AAGGG)exp was not detected among patients with Alzheimer's disease or FTD.Conclusion: Cognitive impairment is a feature in patients with the biallelic (AAGGG)exp, but the pathogenic expansion seems to be rare in patients with dementia. Studies on patients with diverse phenotypes would be useful to further explore the involvement of RFC1 in neuronal degeneration and to identify atypical phenotypes, which should be taken into account in clinical practice. [ABSTRACT FROM AUTHOR]

Background: Seizures are common in juvenile Huntington's disease (HD), but considered to be rare in adult-onset HD. We studied the occurrence of epilepsy and seizures in a nationwide cohort of Finnish patients with adult-onset HD.Methods: Patients with HD and their diagnoses of epilepsy or seizures were identified by a search into a nationwide registry. Cases were verified in a subsequent review of patient charts.Results: Three out of 114 HD patients alive on prevalence date had been diagnosed with epilepsy giving a prevalence of 2.6% (95% CI, 0.6-7.5). In addition, one patient with a single unprovoked seizure, one patient with a medication-induced seizure and two patients with transient nonspecific attacks were identified. Epilepsy was not associated with clinical severity of HD and seizures were controlled with antiepileptic medications (AEDs). Generalized tonic-clonic seizures (GTCs) were the most common seizure type.Conclusions: Prevalence of epilepsy is similar in patients with adult-onset HD compared to general population. Seizures are easily controlled with AEDs. [ABSTRACT FROM AUTHOR]

Background: Inflammatory mechanisms have an acknowledged role in the progression of chronic subdural hematoma (CSDH) and in tissue response after subarachnoid hemorrhage (SAH). The participation of extracellular matrix, especially glycosaminoglycans, in the cellular events during tissue repair is known to be important. We studied the production of glycosaminoglycans after two types of meningeal injury-one caused by rupture of the dural border cell layer after head injury, and the other caused by SAH. Methods: Patients with CSDH ( n = 28), subdural effusion ( n = 8), and SAH ( n = 33) were included in the study. Samples from subdural fluid or cerebrospinal fluid (CSF) were assayed for hyaluronic acid (HA) with an enzyme-linked assay and for sulfated glycosaminoglycans (sGAGs) with a dye-binding assay. Results: The median HA concentration was 3021 (range, 408-14,012) ng/ml in the CSDH fluid, 668 (392-3607) ng/ml in the effusion fluid, and 21.7 (5.8-195) ng/ml in the serum. In lumbar CSF after SAH, the median HA concentration was 246 (47-3686) ng/ml being 1.5-fold higher than that in control CSF. The median sGAG concentration was 52.8 (0-144) μg/ml in CSDH fluid, but only 5.32 (0-20.5) μg/ml in the effusion fluid, where the concentration was similar to that in the serum. Conclusions: We found high, but variable, concentrations of sGAGs and HA in the CSDH and effusion fluid after head injury and HA in the CSF after SAH. Our results show that HA and sGAGs are induced after meningeal injury and that these proteins may participate in a reactive process. [ABSTRACT FROM AUTHOR]

We aimed to provide a detailed phenotypic description of status epilepticus (SE) in a large cohort of patients with POLG disease and identify prognostic biomarkers to improve the management of this life-threatening condition. In a multinational, retrospective study with data on patients with POLG disease from seven European countries, we identified those who had SE. The age of SE onset, accompanying clinical, laboratory, imaging and genetic findings were analysed. One hundred and ninety-five patients with genetically confirmed POLG disease were recruited, of whom 67% (130/194) had epilepsy. SE was identified in 77% (97/126), with a median age of SE onset of 7 years. SE was the presenting symptom of the disease in 43% (40/93) of those with SE, while 57% (53/93) developed SE during the disease course. Convulsive SE was reported in 97% (91/94) followed by epilepsia partialis continua in 67% (56/84). Liver impairment 78% (74/95), ataxia 69% (60/87), stroke-like episodes 57% (50/88), were the major comorbidities. In the majority (66%; 57/86) with SE this became refractory or super-refractory. The presence of seizures was associated with significantly higher mortality compared to those without (P ≤ 0.001). The median time from SE debut to death was 5 months. SE is a major clinical feature of POLG disease in early and juvenile to adult-onset disease and can be the presenting feature or arise as part of a multisystem disease. It is associated with high morbidity and mortality, with the majority of patients with SE going on to develop refractory or super-refractory SE. [ABSTRACT FROM AUTHOR]

Abstract: MFN2 mutations are a major cause of the axonal form of Charcot–Marie–Tooth disease (CMT2). MFN2 encodes mitofusin 2, a mitochondrial fusion protein that is critical for mitochondrial DNA integrity and function. Here we describe CMT2 in a Finnish man and his son, with disease onset in young adulthood, slow progression, and prominent sensory as well as autonomic dysfunction. Molecular analysis revealed in both subjects a previously unreported heterozygous MFN2 mutation c.708G>A that is predicted to abolish a donor splice site for exon 7 of the MFN2 gene. An incorrectly spliced transcript without exon 7 was detected in RT-PCR analysis. The lack of exon 7 creates frameshift and, consequently, premature termination within exon 8. We demonstrated the presence of the aberrant mRNA suggesting either dominant-negative or toxic gain-of-function effect of the heterozygous c.708G>A mutation. This novel mutation adds to the few previously reported pathogenic MFN2 splice site mutations causing CMT2. [Copyright &y& Elsevier]

Mitochondrial diabetes and deafness (MIDD) is a subtype of diabetes mellitus (DM) that most commonly results from the m.3243A > G mutation in mitochondrial DNA (mtDNA). Sensorineural hearing loss is a typical accompanying feature. Previous studies have suggested a prevalence of ~1-1.5 % for MIDD. We studied the molecular epidemiology of MIDD among young (aged 18-45 years) adults in a defined population in southwestern Finland. Of the identified cohort of 1,532 patients with DM, we received blood samples of 299 patients and analyzed them for the m.3243A > G mutation and for mtDNA haplogroups. We found three DM patients (1.0 %) with the m.3243A > G mutation. All the three patients with DM and m.3243A > G also had severe hearing impairment that required use of hearing aid. MtDNA haplogroup U was more prevalent among patients with maternal family history of DM. We conclude that among young adults, ~1 % of all DM is associated with the m.3243A > G mutation. We suggest that all patients with both DM and hearing impairment, at least in this age group, should undergo investigation for this mutation. Furthermore, our results suggest that mtDNA haplogroup U is associated with maternal family history of DM. [ABSTRACT FROM AUTHOR]

Leukoencephalopathy with brainstem and spinal cord involvement and elevated lactate (LBSL) is clinically characterized by progressive pyramidal and cerebellar dysfunction, dorsal column dysfunction and sometimes with axonal neuropathy. Magnetic resonance imaging of brain and the spinal cord reveals characteristic findings. LBSL is caused by mutations in the DARS2 gene that encodes the mitochondrial aspartyl-tRNA synthetase. The presentation and clinical course of LBSL is not uniform, and there is lack of longitudinal data on these patients. In addition, the existing data on the prevalence and characteristics of cognitive abnormalities in patients with LBSL are scarce and somewhat conflicting. Here we report long-term data of neurological and cognitive functioning in three non-related adult patients with LBSL. Cognitive impairment seems to be common among patients with LBSL and DARS2 mutations. The cognitive profile in LBSL shares similarities with that reported in multiple sclerosis, as information-processing speed and working memory are especially affected. In addition, our results and the previously reported carrier frequencies of common pathogenic DARS2 mutations suggest that LBSL may be underdiagnosed in the population. [ABSTRACT FROM AUTHOR]

Abstract: Leigh syndrome is a mitochondrial disease with considerable clinical and genetic variation. We present a 16-year-old boy with Leigh-like syndrome and broad developmental retardation, parkinsonism and hypogonadism. Sequencing of the entire mitochondrial DNA from blood revealed the m.4296G>A mutation in the MT-TI gene. The mutation was heteroplasmic with a 95% proportion of the mutant genome, while the proportion was 58% in the blood of the patient''s clinically healthy mother. Our results suggest that m.4296G>A is pathogenic in humans, and that the phenotype related to this change includes Leigh-like syndrome in adolescence with parkinsonism and hypogonadism, in addition to the previously reported early infantile Leigh syndrome. [Copyright &y& Elsevier]

Objective: To investigate the prevalence of ear diseases, other otological risk factors potentially affecting hearing, and noise exposure among adults. Furthermore, subject-related factors possibly associated with hearing impairment (HI), i.e. handedness, eye color, and susceptibility to sunburn, were studied. Design: A cross-sectional, unscreened, population-based, epidemiological study among adults. Study sample: The subjects (n = 850), aged 54-66 years, were randomly sampled from the population register. A questionnaire survey, an otological examination, and pure-tone audiometry were performed. Results: Chronic middle-ear disease (both active and inactive) was the most common ear disease with a prevalence of 5.3%, while the prevalence of otosclerosis was 1.3%, and that of Ménière's disease, 0.7%. Noise exposure was reported by 46% of the subjects, and it had no effect on hearing among those with no ear disease or other otological risk factors for HI. Dark eye color and non-susceptibility to sunburn were associated with HI among noise-exposed subjects. Conclusions: Common ear diseases and other otological risk factors constitute a major part of the etiologies of HI among adults. Contrary to previous studies, noise exposure turned out to have only marginal effect on hearing among those with no otological risk factors. [ABSTRACT FROM AUTHOR]

Abstract Objective: There are only a few population-based epidemiological studies on audiogram configurations among adults. The aim of this study was to investigate the prevalence of different audiogram configurations among older adults. In addition, audiogram configurations among subjects reporting hearing problems were examined. Design: Cross-sectional, population-based, unscreened epidemiological study among older adults. Study sample: The subjects (n == 850), aged 54-66 years, were randomly sampled from the population register. A questionnaire survey, an otological examination, and pure-tone audiometry were performed. Results: The most prevalent audiogram configuration among men was high-frequency steeply sloping (65.3% left ear, 51.2% right ear) and among women, high-frequency gently sloping (33.0% left ear, 31.5% right ear). There were significantly more flat configurations among women than among men. Unclassified audiograms were common especially among women (17.5%). Subjects reporting hearing difficulties, difficulties in following conversation in noise, or tinnitus, more often had a high-frequency steeply sloping configuration than those not reporting. Conclusions: High-frequency sloping audiogram configurations were common among older adults, and a high-frequency steeply sloping configuration was common among those reporting hearing problems. Sumario Objetivo: Existen pocos estudios epidemiológicos poblacionales sobre la configuración de los audiogramas en adultos. El objetivo de este estudio fue investigar la prevalencia de diferentes configuraciones audiométricas entre los adultos mayores. Además se examinaron las configuraciones audiométricas de los sujetos que reportaban problemas auditivos. Diseño: Estudio epidemiológico transversal basado en población no tamizada entre adultos mayores. Muestra: Los sujetos (n == 850), con edades entre 54 y 66 años fueron escogidos al azar de un registro poblacional. Se les aplicó un cuestionario y se realizó un examen otológico y una audiometría tonal. Resultados: la configuración audiométrica más prevalente en hombres fue la de caída abrupta en frecuencias agudas (65.3% oído izquierdo, 51.2% oído derecho) y entre las mujeres fue la caída suave en frecuencias agudas (33% oído izquierdo y 31.5% oído derecho). La configuración plana fue significativamente más frecuente en mujeres que en hombres. Los audiogramas no clasificados fueron comunes, especialmente entre las mujeres (17.5%). Los sujetos que reportaban dificultades auditivas, dificultad para seguir una conversación en ruido o acúfeno presentaban con mayor frecuencia una caída abrupta en frecuencias agudas que aquellos que no lo reportaban. Conclusiones: Las configuraciones audiométricas con caída abrupta en frecuencias agudas fueron más comunes entre quienes reportaron problemas auditivos. [ABSTRACT FROM AUTHOR]

Background: There are not many population-based epidemiological studies on the association between self-reported hearing problems and measured hearing thresholds in older adults. Previous studies have shown that the relationship between self-reported hearing difficulties and measured hearing thresholds is unclear and, according to our knowledge, there are no previous population-based studies reporting hearing thresholds among subjects with hyperacusis. Purpose: The aim was to investigate the prevalence of self-reported hearing problems, that is, hearing difficulties, difficulties in following a conversation in noise, tinnitus, and hyperacusis, and to compare the results with measured hearing thresholds in older adults. Research Design: Cross-sectional, population-based, and unscreened. Study Sample: Random sample of subjects (n=850) aged 54-66 yr living in the city of Oulu (Finland) and the surrounding areas. Data Collection and Analysis: Otological examination, pure tone audiometry, questionnaire survey Results: The prevalence of self-reported hearing problems was 37.1% for hearing difficulties, 43.3% for difficulties in following a conversation in noise, 29.2% for tinnitus, and 17.2% for hyperacusis. More than half of the subjects had no hearing impairment, or HI (BEHL[better ear hearing level]0.5-4 kHz <20 dB HL) even though they reported hearing problems. Subjects with self-reported hearing problems, including tinnitus and hyperacusis, had significantly poorer hearing thresholds than those who did not report hearing problems. Self-reported hearing difficulties predicted hearing impairment in the pure-tone average at 4, 6, and 8 kHz, and at the single frequency of 4 kHz. Conclusions: The results indicate that self-reported hearing difficulties are more frequent than hearing impairment defined by audiometric measurement. Furthermore, self-reported hearing difficulties seem to predict hearing impairment at high frequencies (4-8 kHz) rather than at the frequencies of 0.5--4 kHz, which are commonly used to define the degree of hearing impairment in medical and legal issues. [ABSTRACT FROM AUTHOR]

Abstract There are only a few large, population-based epidemiological studies on hearing impairment (HI) in adults. The objective of this study was to investigate the prevalence of HI and possible differences between ears in older adults. The subjects (n = 850), aged 54-66 years, were randomly sampled from the population register. A questionnaire survey, an otological examination, and pure-tone audiometry were performed. Another questionnaire was mailed to collect information on non-participants. The prevalence of HI averaged over the frequencies of 0.5, 1, 2, and 4 kHz for the better ear ≥20 dB HL was 26.7% (men: 36.8%, women: 18.4%). There was no difference between left and right ear pure-tone averages over the frequencies 0.5, 1, 2, and 4 kHz (PTA0.5-4 kHz), but a significant difference of −0.8 dB HL was found for the low frequencies 0.125, 0.25, and 0.5 kHz (PTA0.125-0.5 kHz), and 4.4 dB HL for the high frequencies over 4, 6, and 8 kHz (PTA4-8 kHz). In conclusion, HI was a highly prevalent finding in this age group. Sumario Existen pocos estudios epidemiológicos grandes, basados en la población, sobre impedimentos auditivos (HI) en adultos. El objetivo de este estudio fue investigar la prevalencia de HI y posibles diferencias entre los oídos de adultos mayores. La muestra de sujetos (n = 850), con edades de 54-66 años, se hizo al azar, a partir de registros de población. Se aplicó un cuestionario y se realizó un examen otológico y una audiometría de tonos puros. Otro cuestionario fue enviado por correo para colectar información de los no participantes. La prevalencia de HI promediada en las frecuencias de 0.5, 1, 2, y 4 kHz en el mejor oído, >20 dB HL, fue de 26.7% (hombres: 36.8%; mujeres: 18.4%). No hubo diferencia entre los promedios con tonos puros en oídos derecho o izquierdo en las frecuencias de 0.5, 1, 2, y 4 kHz (PTA 0.5-4 kHz), pero si una diferencia significativa de -0.8 dB HL, encontrada en las frecuencias graves de 0.125, 0.25 y 0.5 kHz (PTA 0.125-0.5 kHz), y 4.4 dB HL en las frecuencias agudas de 4, 6 y 8 kHz (PTA 4-8 kHz). En conclusión, el HI fue un hallazgo altamente prevalente en este grupo de edad. [ABSTRACT FROM AUTHOR]

Background: Mitochondrial dysfunction, oxidative damage and the accumulation of somatic mutations in mitochondrial DNA (mtDNA) have been associated with certain neurodegenerative disorders. Previous studies have also provided controversial results on the association of mtDNA haplogroups with susceptibility to Alzheimer's disease (AD), but possible relationships between mtDNA and frontotemporal lobar degeneration (FTLD) have been less frequently studied. Methods: We analysed the role of mtDNA and its maintenance enzymes in 128 early-onset AD (eoAD) and in 66 FTLD cases. Patients and 99 controls were collected from a defined region of Finland, that of Northern Ostrobothnia, for the determination of mtDNA haplogroups and the analysis of two common mtDNA mutations (m.3243A>G, m.8344A>G). In addition, screening was performed for five common POLG1 mutations (T251I, A467T, P587L, W748S and Y955C) and all the coding exons of the PEO1 and ANT1 genes were screened for mutations. Results: The frequency of haplogroup cluster IWX was 2.3 fold higher among the FTLD cases than in the controls (OR 2.69, 95% CI 1.09-6.65, p = 0.028). The frequency of mtDNA haplogroups or clusters did not differ between the eoAD cases and controls. The two mtDNA mutations and five POLG1 mutations were absent in the eoAD and FTLD patients. No pathogenic mutations were found in the PEO1 or ANT1 genes. Conclusions: We conclude that the haplogroup cluster IWX was associated with FTLD in our cohort. Further studies in other ethnically distinct cohorts are needed to clarify the contribution of mtDNA haplogroups to FTLD and AD. [ABSTRACT FROM AUTHOR]

To study the hypothesis that concentrations of procollagen propeptides of type I and III collagens (PICP and PIIINP, respectively) and the carboxyterminal telopeptide of type I collagen (ICTP) in subdural haematoma increase in a time-dependent manner as a sign of dural collagen synthesis after head injury. Thirty-six patients with subdural haematoma were operated. Subdural haematoma fluid samples were assayed for the concentrations of PICP, PIIINP and ICTP by specific radioimmunoassays. High concentrations of PICP, PIIINP and ICTP were found in subdural haematoma. The mean concentration of PICP in the 36 subdural haematoma samples was 11.8 (SD 9.27) mg/l, the concentration of PIIINP 590 (SD 302) μg/l and that of ICTP 32.0 (SD 12.1) μg/l. The time elapsed from the alleged head injury to operation could be defined in 30 patients. The concentrations of PICP, PIIINP and ICTP in subdural haematoma increased rapidly during the first two weeks after head injury and then stayed high for at least three months. High concentrations of procollagen propeptides were found in subdural haematoma samples of different haematoma age. Concentrations of these propeptides seem to follow a timedependent course. The elevation of the concentrations of procollagen propeptides in subdural haematoma may be regarded as a sign of sustained dural collagen synthesis after head injury. [ABSTRACT FROM AUTHOR]

Background: The genetics of cerebellar ataxia is complex. Hundreds of causative genes have been identified, but only a few cause more than single cases. The spectrum of ataxia-causing genes differs considerably between populations. The aim of the study was to investigate the molecular epidemiology of ataxia in the Finnish population.Patients and Methods: All patients in hospital database were reviewed for the diagnosis of unspecified ataxia. Acquired ataxias and nongenetic ataxias such as those related to infection, trauma or stroke were excluded. Sixty patients with sporadic ataxia with unknown etiology and 36 patients with familial ataxia of unknown etiology were recruited in the study. Repeat expansions in the SCA genes (ATXN1, 2, 3, 7, 8/OS, CACNA1A, TBP), FXN, and RFC1 were determined. Point mutations in POLG, SPG7 and in mitochondrial DNA (mtDNA) were investigated. In addition, DNA from 8 patients was exome sequenced.Results: A genetic cause of ataxia was found in 33 patients (34.4%). Seven patients had a dominantly inherited repeat expansion in ATXN8/OS. Ten patients had mitochondrial ataxia resulting from mutations in nuclear mitochondrial genes POLG or RARS2, or from a point mutation m.8561C > G or a single deletion in mtDNA. Interestingly, five patients were biallelic for the recently identified pathogenic repeat expansion in RFC1. All the five patients presented with the phenotype of cerebellar ataxia, neuropathy, and vestibular areflexia (CANVAS). Moreover, screening of 54 patients with Charcot-Marie-Tooth neuropathy revealed four additional patients with biallelic repeat expansion in RFC1, but none of them had cerebellar symptoms.Conclusions: Expansion in ATXN8/OS results in the majority of dominant ataxias in Finland, while mutations in RFC1 and POLG are the most common cause of recessive ataxias. Our results suggest that analysis of RFC1 should be included in the routine diagnostics of idiopathic ataxia and Charcot-Marie-Tooth polyneuropathy. [ABSTRACT FROM AUTHOR]

Analyses of mitochondrial DNA (mtDNA) sequences have revealed non-neutral patterns, suggesting that many amino acid mutations in animal mtDNA may be mildly deleterious, but this has not been verified in human clinical series. Since sensorineural hearing impairment (SNHI) is a common manifestation in many of the syndromes caused by mutations in mtDNA, this may be regarded as the phenotype of choice in attempts to detect mutations that may have a mildly deleterious effect on mitochondrial function. We selected 32 subjects from among 117 unrelated SNHI patients with SNHI in maternal relatives by means of family history, determined the entire coding region sequence of mtDNA and compared the sequence variation with that in 32 haplogroup-matched controls taken at random from 192 Finnish sequences. The 32 control sequences differed from the remaining 160 sequences by 36±9 substitutions (mean ± SD), while the difference for the 32 patients was 58±4 substitutions (P=0.005 for difference; Wilcoxon signed rank test). Differences were also found in the number of new haplotypes and new non-synonymous mutations or mutations in tRNA or rRNA genes. A total of 12 rare mtDNA variants were detected in the patients, and only 3 of these were considered to be neutral in effect. It is proposed that increased sequence variation in mtDNA may be a genetic risk factor for SNHI, and the increased frequency of rare haplotypes in these patients points to the presence of mildly deleterious mutations in mtDNA. [ABSTRACT FROM AUTHOR]

Presents a study which determined the nucleotide sequence in the coding region of mitochondrial DNA from a sample of people in Finland. Materials and methods; Results; Discussion.

Cardiomyopathy and cardiac conduction defects are common manifestations of mitochondrial disease. Previous studies suggest that clinically asymptomatic individuals harbouring pathogenic mitochondrial DNA (mtDNA) mutations in the cardiac muscle may have sudden cardiac death (SCD) as the first manifestation of mitochondrial disease. We investigated the contribution of pathogenic mtDNA point mutations and mtDNA haplogroups in cardiac muscle in a cohort of 280 Finnish subjects that had died from non-ischaemic SCD with the median age of death at 59 years and in 537 population controls. We did not find any common or novel pathogenic mutations, but the frequency of haplogroup H1 was higher in the SCD subjects than that in 537 population controls (odds ratio: 1.76, confidence interval 95%: 1.02–3.04). We conclude that, at the population level, pathogenic point mutations in mtDNA do not contribute to non-ischaemic SCD, but natural variation may modify the risk. [ABSTRACT FROM AUTHOR]

Variants associated with Parkinson's disease (PD) have generally a small effect size and, therefore, large sample sizes or targeted analyses are required to detect significant associations in a whole exome sequencing (WES) study. Here, we used protein-protein interaction (PPI) information on 36 genes with established or suggested associations with PD to target the analysis of the WES data. We performed an association analysis on WES data from 439 Finnish PD subjects and 855 controls, and included a Finnish population cohort as the replication dataset with 60 PD subjects and 8214 controls. Single variant association (SVA) test in the discovery dataset yielded 11 candidate variants in seven genes, but the associations were not significant in the replication cohort after correction for multiple testing. Polygenic risk score using variants rs2230288 and rs2291312, however, was associated to PD with odds ratio of 2.7 (95% confidence interval 1.4–5.2; p < 2.56e-03). Furthermore, an analysis of the PPI network revealed enriched clusters of biological processes among established and candidate genes, and these functional networks were visualized in the study. We identified novel candidate variants for PD using a gene prioritization based on PPI information, and described why these variants may be involved in the pathogenesis of PD. [ABSTRACT FROM AUTHOR]

Summary: Objective: Previous studies have suggested that heterozygous variants p.Q1236H and p.E1143G in mitochondrial DNA polymerase gamma (POLG1) increase the risk for liver injury for patients on valproate (VPA) therapy. We assessed the prevalence of these common variants and seven other pathogenic mutations in POLG1 and determined the occurrence of VPA‐induced hepatotoxicity (VHT) or pancreatic toxicity in a cohort of patients with epilepsy. Methods: Patients with epilepsy (N = 367) were retrospectively identified from medical record files and screened for mutations in POLG1. Patients who had received VPA monotherapy and carried either of the two variants, p.Q1236H or p.E1143G, without other pathogenic mutations in POLG1 (n = 33, variant group) and patients without these variants (n = 28, nonvariant group) were included in the study. Clinical data on epilepsy, characteristics of VPA treatment, risk factors for VHT, laboratory data on liver and pancreas functions, and adverse effects were collected. Results: A total of 122 patients had either the POLG1 p.Q1236H (n = 99) or p.E1143G (n = 24) variant in the heterozygous or homozygous state. Transient liver dysfunction was identified in three (n = 33, 9.1%) variant group patients and in one (n = 28, 3.6%) nonvariant group patient (P = 0.62). Mild to moderate elevations in liver enzymes were encountered in both groups. Furthermore, two patients on VPA polytherapy developed acute pancreatitis, and two pediatric patients with heterozygous p.Q1236H variants and mutations in IQSEC2 and GLDC, respectively, had elevated levels of VPA metabolites in urine, elevated plasma glycine, and/or increased acylglycine excretion. Significance: POLG1 p.Q1236H and p.E1143G variants could not be identified as statistically significant risk factors for VHT or pancreatic toxicity. We suggest that VPA treatment could be suitable for patients who harbor these common variants in the absence of other pathogenic mutations in POLG1. [ABSTRACT FROM AUTHOR]

The m.1555A>G mtDNA variant causes maternally inherited deafness, but the reasons for the highly variable clinical penetrance are not known. Exome sequencing identified a heterozygous start loss mutation in SSBP1, encoding the single stranded binding protein 1 (SSBP1), segregating with hearing loss in a multi-generational family transmitting m.1555A>G, associated with mtDNA depletion and multiple deletions in skeletal muscle. The SSBP1 mutation reduced steady state SSBP1 levels leading to a perturbation of mtDNA metabolism, likely compounding the intra-mitochondrial translation defect due to m.1555A>G in a tissue-specific manner. This family demonstrates the importance of rare trans-acting genetic nuclear modifiers in the clinical expression of mtDNA disease. [ABSTRACT FROM AUTHOR]

Introduction: Variation contributing to the risk of Parkinson's disease (PD) has been identified in several genes and at several loci including GBA, SMPD1, LRRK2, POLG1, CHCHD10 and MAPT, but the frequencies of risk variants seem to vary according to ethnic background. Our aim was to analyze how variation in these genes contributes to PD in the Finnish population.Methods: The subjects consisted of 527 Finnish patients with early-onset PD, 325 patients with late-onset PD and 403 population controls. We screened for known genetic risk variants in GBA, SMPD1, LRRK2, POLG1, CHCHD10 and MAPT. In addition, DNA from 225 patients with early-onset Parkinson's disease was subjected to whole exome sequencing (WES).Results: We detected a significant difference in the length variation of the CAG repeat in POLG1 between patients with early-onset PD compared to controls. The p.N370S and p.L444P variants in GBA contributed to a relative risk of 3.8 in early-onset PD and 2.5 in late-onset PD. WES revealed five variants in LRRK2 and SMPD1 that were found in the patients but not in the Finnish ExAC sequences. These are possible risk variants that require further confirmation. The p.G2019S variant in LRRK2, common in North African Arabs and Ashkenazi Jews, was not detected in any of the 849 PD patients.Conclusions: The POLG1 CAG repeat length variation and the GBA p.L444P variant are associated with PD in the Finnish population. [ABSTRACT FROM AUTHOR]

Wolfram syndrome (WS) is caused by recessive mutations in the Wolfram syndrome 1 ( WFS1 ) gene. Sensorineural hearing impairment (HI) is a frequent feature in WS and, furthermore, certain mutations in WFS1 cause nonsyndromic dominantly inherited low-frequency sensorineural HI. These two phenotypes are clinically distinct indicating that WFS1 is a reasonable candidate for genetic studies in patients with other phenotypes of HI. Here we have investigated, whether the variation in WFS1 has a pathogenic role in age-related hearing impairment (ARHI). WFS1 gene was investigated in a population sample of 518 Finnish adults born in 1938–1949 and representing variable hearing phenotypes. Identified variants were evaluated with respect to pathogenic potential. A rare mutation predicted to be pathogenic was found in a family with many members with impaired hearing. Twenty members were recruited to a segregation study and a detailed clinical examination. Heterozygous p.Tyr528His variant segregated completely with late-onset HI in which hearing deteriorated first at high frequencies and progressed to mid and low frequencies later in life. We report the first mutation in the WFS1 gene causing late-onset HI with audiogram configurations typical for ARHI. Monogenic forms of ARHI are rare and our results add WFS1 to the short list of such genes. [ABSTRACT FROM AUTHOR]

The phenotype of juvenile Huntington's disease (HD) differs clearly from that of adult-onset HD, but information about differences between mid-age-onset HD and late-onset HD (LOHD) is scarce. A national cohort of 206 patients with adult-onset HD was identified using national registries and patient records. LOHD was defined as age ≥60 years at HD diagnosis. Genetic disease burden was assessed using CAG age product (CAP) score. LOHD comprised 25% of the adult-onset HD cohort giving a point prevalence of 2.38/100,000 in the Finnish population at least 60 years of age. The proportion of LOHD out of new HD diagnoses increased from 21% in 1991-2000 to 33% in 2001-2010. At the time of diagnosis, patients with LOHD had 10.4 units (95% CI 4.8-15.9; p = 0.0003) higher CAP scores, more severe motor impairment and slightly more severe functional impairment than that in patients with mid-age-onset HD. There was no difference in the rate of disease progression or survival between LOHD and mid-age-onset patients. The lifespans of deceased patients were shorter in mid-age-onset HD ( p < 0.001) and LOHD ( p = 0.002) than their life expectancies. Causes of death differed between the two patient groups ( p = 0.025). LOHD comprises a quarter of Finnish HD patients and the proportion appears to be increasing. Our results did not reveal differences in the phenotype between mid-age-onset HD and LOHD, but prospective studies are needed. [ABSTRACT FROM AUTHOR]

Background: Mitochondrial cytochrome c oxidase 2, MT-CO2, encodes one of the three subunits, which form the catalytic core of cytochrome c oxidase (COX), complex IV. Mutations in MT-CO2 are rare and the associated phenotypes are variable including nonsyndromic and syndromic forms of mitochondrial diseases.Case Presentation: We describe a 30-year-old man with cognitive decline, epilepsy, psychosis, exercise intolerance, sensorineural hearing impairment, retinitis pigmentosa, cataract and lactic acidosis. COX-deficient fibers and ragged red fibers were abundant in the muscle. Sequencing of mitochondrial DNA (mtDNA) revealed a novel frameshift mutation m.8156delG that was predicted to cause altered C-terminal amino acid sequence and to lead to truncation of the COX subunit 2. The deletion was heteroplasmic being present in 26% of the mtDNA in blood, 33% in buccal mucosa and 95% in muscle. Deletion heteroplasmy correlated with COX-deficiency in muscle histochemistry. The mother and the siblings of the proband did not harbor the deletion.Conclusions: The clinical features and muscle histology of the proband suggested a mitochondrial disorder. The m.8156delG deletion is a new addition to the short list of pathogenic mutations in the mtDNA-encoded subunits of COX. This case illustrates the importance of mtDNA sequence analysis in patients with an evident mitochondrial disorder. [ABSTRACT FROM AUTHOR]

Background: Mitochondrial diseases present with variable multi-organ symptoms. Common disease-causing mutations in mitochondrial DNA (mtDNA) are regularly screened in diagnostic work-up, but novel mutations may remain unnoticed. Methods: Patients (N = 66) with a clinical suspicion of mitochondrial disease were screened for their mtDNA coding region using conformation sensitive gel electrophoresis and sequencing. Long-PCR was used to detect deletions followed by POLG1 sequencing in patients with multiple deletions. Results: We discovered three novel mtDNA variants that included m.8743G > C, m.11322A > G and m.15933G > A. The novel MTTT variant m.15933G > A is suggested to be pathogenic. Analysis revealed also multiple mtDNA deletions in two patients and five nonsynonymous variants that were putatively pathogenic according to in-silico prediction algorithms. In addition, a rare haplogroup H associated m.7585_7586insT variant was discovered. Conclusions: Among patients with a suspected mitochondrial disease, a novel MTTT variant m.15933G > A was discovered and is suggested to be pathogenic. In addition, several putatively pathogenic nonsynonymous variants and rare variants were found. These findings highlight the importance of coding region mtDNA screening among patients with clinical features suggesting a mitochondrial disease, but who lack the common mitochondrial disease mutations. [ABSTRACT FROM AUTHOR]

Defects in the respiratory chain or mitochondrial ATP synthase (complex V) result in mitochondrial dysfunction that is an important cause of inherited neurological disease. Two of the subunits of complex V are encoded by MT- ATP6 and MT- ATP8 in the mitochondrial genome. Pathogenic mutations in MT- ATP6 are associated with the Leigh syndrome, the syndrome of neuropathy, ataxia, and retinitis pigmentosa (NARP), as well as with non-classical phenotypes, while MT- ATP8 is less frequently mutated in patients with mitochondrial disease. We investigated two adult siblings presenting with features of cerebellar ataxia, peripheral neuropathy, diabetes mellitus, sensorineural hearing impairment, and hypergonadotropic hypogonadism. As the phenotype was suggestive of mitochondrial disease, mitochondrial DNA was sequenced and a novel heteroplasmic mutation m.8561C>G in the overlapping region of the MT- ATP6 and MT- ATP8 was found. The mutation changed amino acids in both subunits. Mutation heteroplasmy correlated with the disease phenotype in five family members. An additional assembly intermediate of complex V and increased amount of subcomplex F were observed in myoblasts of the two patients, but the total amount of complex V was unaffected. Furthermore, intracellular ATP concentration was lower in patient myoblasts indicating defective energy production. We suggest that the m.8561C>G mutation in MT- ATP6/8 is pathogenic, leads biochemically to impaired assembly and decreased ATP production of complex V, and results clinically in a phenotype with the core features of cerebellar ataxia, peripheral neuropathy, diabetes mellitus, and hypergonadotropic hypogonadism. [ABSTRACT FROM AUTHOR]

Purpose To investigate the association of mutations in the mitochondrial DNA (mt DNA) or nuclear candidate genes with mitochondrial disease-related ophthalmic manifestations (nystagmus, ptosis, ophthalmoplegia, optic neuropathy and retinopathy) in children. Methods A retrospective cohort of children ( n = 98) was identified from the medical record files of a tertiary care hospital. The entire mt DNA and nuclear genes POLG1, OPA1 and PEO1 were analysed from the available DNA samples ( n = 38). Furthermore, some nuclear candidate genes were investigated based on family history and phenotype. Rare mt DNA mutations were evaluated using in silico predictors and sequence alignment. Results Three patients had previously identified mutations in mt DNA that are associated with optic neuropathy (in MT- ND6 and MT- ND1) and nystagmus (in tRNA Arg). Nine rare mutations in MT- ATP6 were identified in seven patients, of whom four manifested with retinopathy and three had clusters of MT- ATP6 mutations. Nuclear PEO1 and OPA1 were unchanged in all samples, but a patient with nystagmus had a heterozygous POLG1 mutation. The analysis of nuclear candidate genes revealed mutations in NDUF8 (patient with nystagmus), TULP1 (patient with optic neuropathy, nystagmus and retinopathy) and RP2 (patient with retinopathy) genes. Conclusions Children with retinopathy, nystagmus or optic neuropathy, especially together with developmental delay or positive family history, should be considered for mitochondrial disease. MT- ATP6 should be taken into account for children with retinopathy of unknown aetiology. [ABSTRACT FROM AUTHOR]

Objective The contribution of genetic causes to Parkinson's disease (PD) is strongest in early-onset cases. We ascertained a nationwide cohort of patients in order to study the genetic epidemiology of early-onset PD (EOPD) in Finland. Methods By means of a search in a national database we ascertained all patients with EOPD. These patients had become eligible for reimbursement of PD drugs between the years 1995–2006 and were <55 years of age at the time of PD diagnosis. A total of 441 patients consented and provided clinical and genealogical information. Results The incidence of EOPD increased 1.7-fold between the years 1995–2006, the mean annual incidence being 3.3/100,000. Fifty-two patients (11.8%) reported an affected first-degree relative. The birthplaces of patients with PD among first-degree relatives were clustered in certain regions in the southwestern and western coastal provinces of Finland and in the eastern province of Savo. Furthermore, the distance between the birthplaces of the patients' parents was smaller for patients, who had first-degree relatives with PD than for patients with no family history of PD. Conclusions Our data suggest that the incidence of EOPD is increasing. The birthplaces of patients with PD among first-degree relatives were clustered in certain provinces of Finland suggesting that monogenic forms of PD or genetic susceptibility of PD are present in the population. [ABSTRACT FROM AUTHOR]

A computerized adaptive Finnish speech-in-noise test has recently been developed. The purpose of the present study was to measure speech recognition thresholds in noise (SRTN) in patients with sensorineural hearing impairment (SNHI) caused by mitochondrial mutation [mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS)] and in patients with SNHI from other causes and to compare them with those in normal hearing controls. SRTN differed significantly between controls and the patients with SNHI from other causes and between controls and the MELAS group, but not between SNHI patients and the MELAS group. Hearing in a noisy environment seems to be as impaired in MELAS patients as in patients with SNHI from other causes, in spite of the possible coexisting defects in the central nervous system. [ABSTRACT FROM AUTHOR]

Effects of Complex I mutations were studied by modeling in NuoH, NuoJ or NuoK subunits of Escherichia coli NDH-1 by simultaneous optical monitoring of deamino-NADH oxidation and proton translocation and fitting to the data a model equation of transmembrane proton transport. A homolog of the ND1-E24 LHON/MELAS mutation caused 95% inhibition of d-NADH oxidation and proton translocation. The NuoJ-Y59F replacement decreased proton translocation. The NuoK-E72Q mutation lowered the enzyme activity, but proton pumping could be rescued by the double mutation NuoK-E72Q/I39D. Moving the NuoK-E72/E36 pair one helix turn towards the periplasm did not affect redox activity but decreased proton pumping. [ABSTRACT FROM AUTHOR]

Background: Mutations in the two MT-RNR genes in mitochondrial DNA can cause hearing impairment that presents with variable severity and age of onset. In order to study the prevalence of mutations in MT-RNR1 and MT-RNR2 genes among Finnish children, we studied a ten-year cohort of hearing impaired children born in Northern Finland. Methods: We studied children, who had been born in Northern Finland in 1993-2002 and who had been ascertained to have hearing impairment by 31 December 2007. Samples from 103 children were sequenced in order to find mutations in the MT-RNR1 and MT-RNR2 genes. Results: One child harboured the pathogenic m.1555A > G mutation in MT-RNR1 suggesting a frequency of 4.4/ 100,000 in the Finnish paediatric population. In addition, eight rare variants and 13 polymorphisms were found in MT-RNR1 and MT-RNR2 genes. Five of the rare variants were deemed to be haplogroup-specific polymorphisms rather than putative pathogenic mutations, while the remaining three variants have been reported in various haplogroups. Among them m.990 T > C occurs at a conserved site. Conclusions: The presence of m.990 T > C variant in various haplogroups and the rather high degree of conservation at this site suggest that this transition is a pathogenic rather than homoplasic neutral variant. Identification of further patients with m.990 T > C and segregation analysis in their families should help in determining the pathogenic potential of this variant. [ABSTRACT FROM AUTHOR]

Object: To estimate the prevalence of Huntington's disease (HD) in Finland. Methods: Persons diagnosed with HD from 1987 to 2010 were identified in the national registers and hospital records of the identified patients, and death certificates of the deceased subjects were obtained. Results of genetic analyses were obtained from the two national laboratories. Results: Following the discovery of the Huntingtin gene (HTT), the rate of new diagnoses of HD has increased in Finland. We ascertained 207 patients with HD, 114 of whom were alive on 31 December, 2010 suggesting a minimum estimate of point prevalence of 2.12/100,000. The age at the time of diagnosis was 52.6 ± 12.1 years (mean ± standard deviation) and the duration of the disease was 8.5 ± 4.4 years among deceased patients. The length of the CAG repeats in the affected allele was 43.3 ± 3.5 repeats and the length was inversely correlated with the age at diagnosis (β = -0.73, p < 0.001). The number of diagnoses varied regionally, whereas the repeat length did not. The frequency of the high risk HTT haplogroup A was 39% in Finnish chromosomes abstracted from the 1000 Genomes database compared to 53% in other European samples (p = 0.024). Conclusions: The annual rate of HD diagnoses and the age at diagnosis have increased. The prevalence of HD in the Finnish population is lower than that of other Caucasian populations, partly explained by the low frequency of HTT haplogroup A among the Finns. [ABSTRACT FROM AUTHOR]

Object To estimate the prevalence of Huntington's disease (HD) in Finland. Methods Persons diagnosed with HD from 1987 to 2010 were identified in the national registers and hospital records of the identified patients, and death certificates of the deceased subjects were obtained. Results of genetic analyses were obtained from the two national laboratories. Results Following the discovery of the Huntingtin gene ( HTT ), the rate of new diagnoses of HD has increased in Finland. We ascertained 207 patients with HD, 114 of whom were alive on 31 December, 2010 suggesting a minimum estimate of point prevalence of 2.12/100,000. The age at the time of diagnosis was 52.6 ± 12.1 years (mean ± standard deviation) and the duration of the disease was 8.5 ± 4.4 years among deceased patients. The length of the CAG repeats in the affected allele was 43.3 ± 3.5 repeats and the length was inversely correlated with the age at diagnosis ( β = −0.73, p < 0.001). The number of diagnoses varied regionally, whereas the repeat length did not. The frequency of the high risk HTT haplogroup A was 39% in Finnish chromosomes abstracted from the 1000 Genomes database compared to 53% in other European samples ( p = 0.024). Conclusions The annual rate of HD diagnoses and the age at diagnosis have increased. The prevalence of HD in the Finnish population is lower than that of other Caucasian populations, partly explained by the low frequency of HTT haplogroup A among the Finns. [ABSTRACT FROM AUTHOR]

Objectives The purpose of this study was to determine the prevalence and etiology of hearing impairment (HI) in Finnish children and to evaluate the frequency and type of additional disabilities among children with HI. Methods Subjects consisted of 214 children with mild to profound HI ascertained until the age of 10 years. They belonged to the birth cohort spanning the years 1993–2002 in northern Finland. The clinical data were collected from the electronic patient records of the Oulu University Hospital. Age at ascertainment, degree and type of HI and audiogram configuration were determined. Risk factors and etiology of HI and co-existing disabilities were recorded. Results The prevalence of childhood HI was 2.3/1000 live births (95% CI; 2.0, 2.7). The etiology of HI was genetic in 47.2%, acquired in 16.4% and unknown in 36.4% children. Among the 214 children with HI, 101 (47.2%) had other minor or major disabilities. The frequency of additional disabilities did not differ between children with mild HI and those with moderate or severe HI ( p = 0.78). Additional disabilities were more common (65.7%) in children with acquired HI than in children with genetic or unknown HI (43.6%) ( p = 0.035). Conclusion The prevalence of childhood HI has remained unchanged in northern Finland as compared to previous studies. Genetic causes were the most common (47%) etiology of childhood HI. Among acquired causes of HI, perinatal risk factors were more common than previously. The frequency of additional disabilities was similar among children with different degrees of HI. Because almost 40% of children had one or more additional disabilities affecting development or learning, it is important to take them into consideration in rehabilitation. [ABSTRACT FROM AUTHOR]

Objective: Mutations in the WFS1 gene can cause Wolfram syndrome or nonsyndromic hearing impairment (HI). The objective of this study was to ascertain the presence of mutations in WFS1 among children with HI from unknown causes. Design: We screened 105 Finnish children with HI for mutations in exon 8 in WFS1. Study sample: Children were born in a defined area in Northern Finland and they had sensorineural, mild to profound, syndromic, or nonsyndromic HI. They were negative for GJB2 mutations and for the m.1555A> G and m.3243A> G mutations in mitochondrial DNA. Results: We found three rare variants and the novel p.Gly831Ser variant in WFS1. Segregation analysis suggested that the novel variant had arisen de novo. The p.Gly831Ser variant may be a new member to the group of heterozygous WFS1 mutations that lead to HI, while the pathogenicity of the rare variant p.Gly674Arg remained unclear. The other two rare variants, p.Glu385Lys and p.Glu776Val, did not segregate with HI in the families. Conclusions: WFS1 gene mutations are a rare cause of HI among Finnish children with HI. [ABSTRACT FROM AUTHOR]