Mitochondrial dysfunction and autism: comprehensive genetic analyses of children with autism and mtDNA deletion.

BACKGROUND: The etiology of autism spectrum disorders (ASD) is very heterogeneous. Mitochondrial dysfunction has been described in ASD; however, primary mitochondrial disease has been genetically proven in a small subset of patients. The main goal of the present study was to investigate correlations between mitochondrial DNA (mtDNA) changes and alterations of genes associated with mtDNA maintenance or ASD. METHODS: Sixty patients with ASD and sixty healthy individuals were screened for common mtDNA mutations. Next generation sequencing was performed on patients with major mtDNA deletions (mtdel-ASD) using two gene panels to investigate nuclear genes that are associated with ASD or are responsible for mtDNA maintenance. Cohorts of healthy controls, ASD patients without mtDNA alterations, and patients with mitochondrial disorders (non-ASD) harbouring mtDNA deletions served as comparison groups. RESULTS: MtDNA deletions were confirmed in 16.6% (10/60) of patients with ASD (mtdel-ASD). In 90% of this mtdel-ASD children we found rare SNVs in ASD-associated genes (one of those was pathogenic). In the intergenomic panel of this cohort one likely pathogenic variant was present. In patients with mitochondrial disease in genes responsible for mtDNA maintenance pathogenic mutations and variants of uncertain significance (VUS) were detected more frequently than those found in patients from the mtdel-ASD or other comparison groups. In healthy controls and in patients without a mtDNA deletion, only VUS were detected in both panel. CONCLUSIONS: MtDNA alterations are more common in patients with ASD than in control individuals. MtDNA deletions are not isolated genetic alterations found in ASD; they coexist either with other ASD-associated genetic risk factors or with alterations in genes responsible for intergenomic communication. These findings indicate that mitochondrial dysfunction is not rare in ASD. The occurring mtDNA deletions in ASD may be mostly a consequence of the alterations of the causative culprit genes for autism or genes responsible for mtDNA maintenance, or because of the harmful effect of environmental factors.

The coexistence of dynamin 2 mutation and multiple mitochondrial DNA (mtDNA) deletions in the background of severe cardiomyopathy and centronuclear myopathy.

Dynamin2 (DNM2) gene mutations may result in Charcot-Marie-Tooth disease and centronuclear myopathy. Here, we present a patient suffering from cardiomyopathy and centronuclear myopathy with repetitive discharges and mild axonal neuropathy due to DNM2 mutation. Detailed cardiological and neurological examinations, electrophysiological tests, muscle biopsy, and molecular genetic analysis were performed. The patient developed left bundle branch block at age 40 and was fitted with a pacemaker at the age of 43. The patient has severe heart failure, ptosis, strabism, facial and proximal muscle weakness. Electrophysiological investigations found myopathy, complex repetitive discharges, and axonal neuropathy. Skeletal muscle biopsy detected centronuclear myopathy and cytochrome C oxidase (COX) negative fibers. Genetic analysis detected a pathogenic c.1105C>T (p.R369W) DNM2 gene mutation and heteroplasmic multiple mitochondrial DNA (mtDNA) deletion. Our data broadens the phenotypic spectrum of DNM2 mutations. The presence of the multiple mtDNA deletions may provide new aspects to understanding the pathogenesis of multisystemic symptoms in patients with DNM2 mutations.

The modifying effect a PMP22 deletion in a family with Charcot-Marie-Tooth type 1 neuropathy due to an EGR2 mutation.

BACKGROUND: Mutations of both the PMP22 and EGR2 genes cause Charcot-Marie-Tooth (CMT) disease type 1. Deletion of the PMP22 gene, results in hereditary neuropathy with liability to pressure palsies. More publications exist about the interaction of PMP22 duplication and other CMT-causing gene mutations. In these cases the intrafamiliar discordant phenotypes draw the attention to the possible role of modifying genes. The gene-gene interactions between the PMP22 and EGR2 genes are not well understood. CASE REPORT: We report two brothers with late onset CMT1 due to a c. 1142 G>A (Arg381His) heterozygous substitution in the EGR2 gene. Additionally, the older brother with the less severe symptoms harbored the PMP22 gene deletion also. CONCLUSION: The coexistence of the two genetic alterations did not aggravate the clinical symptoms. Moreover, the PMP22 deletion appeared to have a beneficial modifying effect, thus implying potential gene-gene interaction of PMP22 and EGR2. PMP22 deletion may increase Schwann cells proliferation and compensate the dominant-negative effect of the Arg381 His substitution in the EGR2 gene.

Psychiatric symptoms of patients with primary mitochondrial DNA disorders.

BACKGROUND: The aim of our study was to assess psychiatric symptoms in patients with genetically proven primary mutation of the mitochondrial DNA. METHODS: 19 adults with known mitochondrial mutation (MT) have been assessed with the Stanford Health Assessment Questionnaire 20-item Disability Index (HAQ-DI), the Symptom Check List-90-Revised (SCL-90-R), the Beck Depression Inventory-Short Form (BDI-SF), the Hamilton Depression Rating Scale (HDRS) and the clinical version of the Structured Clinical Interview for the the DSM-IV (SCID-I and SCID-II) As control, 10 patients with hereditary sensorimotor neuropathy (HN), harboring the peripheral myelin protein-22 (PMP22) mutation were examined with the same tools. RESULTS: The two groups did not differ significantly in gender, age or education. Mean HAQ-DI score was 0.82 in the MT (range: 0-1.625) and 0.71 in the HN group (range: 0-1.625). Level of disability between the two groups did not differ significantly (p = 0.6076). MT patients scored significantly higher on the BDI-SF and HDRS than HN patients (12.85 versus 4.40, p = 0.031, and 15.62 vs 7.30, p = 0.043, respectively). The Global Severity Index (GSI) of SCL-90-R also showed significant difference (1.44 vs 0.46, p = 0.013) as well as the subscales except for somatization. SCID-I interview yielded a variety of mood disorders in both groups. Eight MT patient (42%) had past, 6 (31%) had current, 5 (26%) had both past and current psychiatric diagnosis, yielding a lifetime prevalence of 9/19 (47%) in the MT group. In the HN group, 3 patients had both past and current diagnosis showing a lifetime prevalence of 3/10 (30%) in this group. SCID-II detected personality disorder in 8 MT cases (42%), yielding 3 avoidant, 2 obsessive-compulsive and 3 personality disorder not otherwise specified (NOS) diagnosis. No personality disorder was identified in the HN group. CONCLUSIONS: Clinicians should be aware of the high prevalence of psychiatric symptoms in patients with mitochondrial mutation which has both etiologic and therapeutic relevance.

A8344G mutation of the mitochondrial DNA with typical mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes syndrome.

We report an unusual case of juvenile ischaemic stroke syndrome associated with the A8344G mutation in tRNA(Lys) gene of mitochondrial DNA. The clinical phenotype of patient was typical for MELAS (mitochondrial ecephalomyapathy with lactate acidosis and stroke like episodes). The MELAS has been related to mutation A3243G in most cases, but some other mitochondrial DNA mutations were described in the background of this syndrome as well. A 22-years-old man and his family were investigated. Throughout clinical investigation as well as Doppler sonography, neuroradiological, and immunserological examinations were performed. Molecular studies included the analysis of the Leiden, prothrombin G20210A and the most common mitochondrial DNA mutations. The DNA analysis of the proband revealed a heteroplasmic A8344G substitution in the T-loop of the tRNALYS gene. The mutation could not been detected in her mother blood. We can conclude that A8344G mutation of the mitochondrial DNA resulted in juvenile ischemic stroke, which is associated only rarely to this genetic alteration. In young age onset of a stroke-like episode with undetermined etiology the mtDNA alterations always have to be excluded.

Asian-specific mitochondrial genome polymorphism (9-bp deletion) in Hungarian patients with mitochondrial disease.

A 9-bp deletion of the mtDNA is known as an anthropological marker of people with East-Asian origin. This 9-bp mtDNA deletion was analyzed in 1073 Hungarians with suspected mitochondrial disease and in 468 healthy control individuals. Fourteen cases with the 9-bp deletion were found in the cohort of mitochondrial patients, and one individual from 468 controls. In six cases the 9-bp deletion was present together with pathogenic major deletions in the mitochondrial genome. In one patient we found a frame shift mutation in the D-loop region, and in another family a pathogenic m.8322 A > G mutation in the tRNA(Lys) gene. Although the 9-bp deletion is common in the populations of the Pacific region and Asia, it is present in the Hungarian population as well. This 9-bp deletion may induce instability of the mtDNA and may provoke the introduction of other pathogenic mutations.

Retrospective assessment of the most common mitochondrial DNA mutations in a large Hungarian cohort of suspect mitochondrial cases.

Prevalence estimations for mitochondrial disorders still vary widely and only few epidemiologic studies have been carried out so far. With the present work we aim to give a comprehensive overview about frequencies of the most common mitochondrial mutations in Hungarian patients. A total of 1328 patients were tested between 1999 and 2012. Among them, 882 were screened for the m.3243A > G, m.8344A > G, m.8993T > C/G mutations and deletions, 446 for LHON primary mutations. The mutation frequency in our cohort was 2.61% for the m.3243A > G, 1.47% for the m.8344A > G, 17.94% for Leber's Hereditary Optic Neuropathy (m.3460G > A, m.11778G > A, m.14484T > C) and 0.45% for the m.8993T > C/G substitutions. Single mtDNA deletions were detected in 14.97%, while multiple deletions in 6.01% of the cases. The mutation frequency in Hungarian patients suggestive of mitochondrial disease was similar to other Caucasian populations. Further retrospective studies of different populations are needed in order to accurately assess the importance of mitochondrial diseases and manage these patients.

Mitochondrial DNA mutations and cognition: a case-series report.

Mutations in the mitochondrial genome can impair normal metabolic function in the central nervous system (CNS) where cellular energy demand is high. Primary mitochondrial DNA (mtDNA) mutations have been linked to several mitochondrial disorders that have comorbid psychiatric, neurologic, and cognitive sequelae. Here, we present a series of cases with primary mtDNA mutations who were genotyped and evaluated across a common neuropsychological battery. Nineteen patients with mtDNA mutations were genotyped and clinically and cognitively evaluated. Pronounced deficits in nonverbal/visuoperceptual reasoning, verbal recall, semantic word generativity, and processing speed were evident and consistent with a "mitochondrial dementia" that has been posited. However, variation in cognitive performance was noteworthy, suggesting that the phenotypic landscape of cognition linked to primary mtDNA mutations is heterogeneous. Our patients with mtDNA mutations evidenced cognitive deficits quite similar to those commonly seen in Alzheimer's disease and could have clinical relevance to the evaluation of dementia.

Interleukin-4 receptor alpha polymorphisms in autoimmune myasthenia gravis in a Caucasian population.

Autoimmune myasthenia gravis is a T-cell-dependent, antibody-mediated, rare neuromuscular disorder. Interleukin-4, acting via interleukin-4 receptor alpha, plays a pivotal role in B-cell differentiation and antibody production and has been implicated to influence disease progression in experimental autoimmune myasthenia gravis. Polymorphisms of the interleukin-4 receptor alpha gene have been shown to be associated with various autoimmune diseases. We compared the distribution of three polymorphisms of the interleukin-4 receptor alpha gene (S503P, rs1805015, Q576R, rs1801275, I75V, rs1805010), all affecting interleukin-4 signaling, in two cohorts of myasthenia gravis patients with ethnically matched controls. Although the distribution of the S503P and Q576R polymorphisms did not differ significantly between the groups, the frequency of the GG rare homozygote genotype of the I75V polymorphism was significantly higher in patients with myasthenia gravis. Our data suggest that the reduced responsiveness to interleukin-4 because the I75V polymorphism may contribute to the pathogenesis of myasthenia gravis.

Oestrogen receptor alpha gene intronic polymorphisms and autoimmune myasthenia gravis in Caucasian women.

Autoimmune myasthenia gravis is a disorder with a complex pathomechanism in which sex hormones, in particular oestrogen, have long been considered to play a role. Here we report the result of a case-control study which evaluated the association of two oestrogen receptor alpha gene polymorphisms with myasthenia gravis in Caucasian patients. PvuII (rs2234693) and XbaI (rs9340799) restriction fragment polymorphisms of the oestrogen receptor alpha gene were analyzed in 113 female myasthenia patients and 184 female controls. Distribution of these polymorphisms was compared with PCR-RFLP. Patients were divided into groups according to their oestrogen receptoralpha genotypes, and acetylcholine receptor antibody status and age of onset were compared between the groups. We found no significant difference between any of the groups implying that these two polymorphisms probably do not play a role in the pathomechanism of myasthenia gravis in Caucasian women.

Bcl-2 or bcl-XL gene therapy increases neural plasticity proteins nestin and c-fos expression in PC12 cells.

The anti-apoptotic gene replacements could be an option in preventing hypoxia-induced neuronal loss. In this paper we tested the effect of anti-apoptosis (bcl-2 and bcl-XL) gene transfer on cell plasticity. Nestin, synapsin-1 and c-fos genes and proteins expression were measured in PC12 cells in normal condition, and after hypoxia/re-oxygenation. Gene delivery results a significant increase in both bcl-2 and bcl-XL gene expression. Hypoxia (1h)/re-oxygenation (24h) have a detrimental effect upon cultured cells by increasing the pro-apoptotic, bax gene and protein expression. Bcl-2 or bcl-XL gene delivery resulted in a significant increase in and the cellular levels of the corresponding mRNAs and proteins. Bcl-2 gene augmented the nestin gene and protein expression which has been compromised previously by the hypoxic event. Similarly c-fos mRNA and protein expression decreased significantly after hypoxia, while the anti-apoptotic gene treatment normalized c-fos expression. Synapsin-1 gene or protein expression remained about on the same level under normoxic conditions or following hypoxia after gene treatment. We can conclude that anti-apoptotic gene transfers activate neuronal plasticity proteins nestin and c-fos. This link on anti-apoptotic proteins and cell plasticity is a new finding.