NARP-MILS syndrome caused by 8993 T > G mitochondrial DNA mutation: a clinical, genetic and neuropathological study

The 8993 T > G mutation in mitochondrial DNA has been associated with variable syndromes of differing severity ranging from maternally inherited Leigh’s syndrome (MILS) to neuropathy, ataxia, retinitis pigmentosa (NARP), depending on the mutation loads in affected patients. We report a kindred with several members in the same generation suffering NARP or Leigh’s syndrome due to a 8993 T > G mutation. Post-mortem studies of the brain in one affected member clinically presenting with a neurological disorder intermediate between adult Leigh’s syndrome and NARP showed symmetrical lesions of the basal ganglia and brainstem closely resembling those usually described in typical Leigh’s syndrome. Analysis of mtDNA in different tissues showed a high proportion of mutant genome in brainstem, cerebral cortex, putamen, cerebellum and thalamus. These observations illustrate the continuum of clinical and neuropathological manifestations associated with the 8993 T > G mutation of the mtDNA.A. Rojo and Y. Campos contributed equally and should be considered first authors     

Functional analysis of a novel POLγA mutation associated with a severe perinatal mitochondrial encephalomyopathy

Mutations in the mitochondrial DNA polymerase gamma catalytic subunit (POLγA) compromise the stability of mitochondrial DNA (mtDNA) by leading to mutations, deletions and depletions in mtDNA. Patients with mutations in POLγA often differ remarkably in disease severity and age of onset. In this work we have studied the functional consequence of POLγA mutations in a patient with an uncommon and a very severe disease phenotype characterized by prenatal onset with intrauterine growth restriction, lactic acidosis from birth, encephalopathy, hepatopathy, myopathy, and early death. Muscle biopsy identified scattered COX-deficient muscle fibers, respiratory chain dysfunction and mtDNA depletion. We identified a novel POLγA mutation (p.His1134Tyr) in trans with the previously identified p.Thr251Ile/Pro587Leu double mutant. Biochemical characterization of the purified recombinant POLγA variants showed that the p.His1134Tyr mutation caused severe polymerase dysfunction. The p.Thr251Ile/Pro587Leu mutation caused reduced polymerase function in conditions of low dNTP concentration that mimic postmitotic tissues. Critically, when p.His1134Tyr and p.Thr251Ile/Pro587Leu were combined under these conditions, mtDNA replication was severely diminished and featured prominent stalling. Our data provide a molecular explanation for the patient´s mtDNA depletion and clinical features, particularly in tissues such as brain and muscle that have low dNTP concentration.     

MELAS syndrome with m.4450 G > A mutation in mitochondrial tRNAMet gene

Mutations in the mitochondrial tRNA^Met gene have been reported in only five patients to date, all of whom presented with muscle weakness and exercise intolerance as signs of myopathy. We herein report the case of a 12-year-old girl with focal epilepsy since the age of eight years. At age 11, the patient developed sudden visual disturbances and headaches accompanied by recurrent, stroke-like episodes with lactic acidosis (pH 7.279, lactic acid 11.6?mmol/L). The patient frequently developed a delirious state, exhibited regression of intellectual ability. Brain magnetic resonance imaging revealed high-intensity signals on T2-weighted images of the left occipital lobe. Mitochondrial gene analysis revealed a heteroplasmic m.4450G?>?A mutation in the mitochondrial tRNA^Met. The heteroplasmic rate of the m.4450G?>?A mutation in blood, skin, urinary sediment, hair, saliva, and nail samples were 20, 38, 59, 41, 27, and 35%, respectively. The patient’s fibroblast showed an approximately 53% reduction in the oxygen consumption rate, compared to a control, and decreased complex I and IV activities. Stroke-like episodes, lactic acidosis, encephalopathy with brain magnetic resonance imaging findings, and declined mitochondrial function were consistent with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome. To our knowledge, the findings associated with this first patient with MELAS syndrome harboring the m.4450G?>?A mutation in mitochondrial tRNA^Met expand the phenotypic spectrum of tRNA^Met gene.     

Cerebral vasculopathy in a Chinese family with neurofibromatosis type Ⅰ mutation

Neurofibromatosis type I（NF1） is a hereditary,autosomal dominant,neurocutaneous syndrome that is attributed to NF1 gene mutation.NF1 has been associated with scoliosis,macrocephaly,pseudoarthrosis,short stature,mental retardation,and malignancies.NF1-associated vasculopathy is an uncommon and easily-overlooked presentation.Examination of a Chinese family affected by NF1 combined with cerebral vessel stenosis and/ or abnormality suggested a possible relationship between NF1 and vessel stenosis.To determine which NF1 gene mutation is associated with vascular lesions,particularly cerebral vessel stenosis,we examined one rare family with combined cerebral vessel lesions or maldevelopment.Vascular lesions were detected using transcranial Doppler sonography and digital subtraction angiography in family members.Next,denaturing high-performance liquid chromatography and sequencing were used to screen for NF1 gene mutations.The results revealed a nonsense mutation,c.541C＆gt;T,in the NF1 gene.This mutation truncated the NF1 protein by 2659 aminoacid residues at the C-terminus and co-segregated with all of the patients,but was not present in unaffected individuals in the family.Exceptionally,three novel mutations were identified in unaffected family members,but these did not affect the product of the NF1 gene.Thus the nonsense mutation,c.541C＆gt;T,located in the NF1 gene could constitute one genetic factor for cerebral vessel lesions.     

The m.3243A>G mitochondrial DNA mutation and related phenotypes. A matter of gender?

The m.3243A>G “MELAS” (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes) mutation is one of the most common point mutations of the mitochondrial DNA, but its phenotypic variability is incompletely understood. The aim of this study was to revise the phenotypic spectrum associated with the mitochondrial m.3243A>G mutation in 126 Italian carriers of the mutation, by a retrospective, database-based study (“Nation-wide Italian Collaborative Network of Mitochondrial Diseases”). Our results confirmed the high clinical heterogeneity of the m.3243A>G mutation. Hearing loss and diabetes were the most frequent clinical features, followed by stroke-like episodes. “MIDD” (maternally-inherited diabetes and deafness) and “PEO” (progressive external ophthalmoplegia) are nosographic terms without any real prognostic value, because these patients may be even more prone to the development of multisystem complications such as stroke-like episodes and heart involvement. The “MELAS” acronym is convincing and useful to denote patients with histological, biochemical and/or molecular evidence of mitochondrial disease who experience stroke-like episodes. Of note, we observed for the first time that male gender could represent a risk factor for the development of stroke-like episodes in Italian m.3243A>G carriers. Gender effect is not a new concept in mitochondrial medicine, but it has never been observed in MELAS. A better elucidation of the complex network linking mitochondrial dysfunction, apoptosis, estrogen effects and stroke-like episodes may hold therapeutic promises.     

Quantification of dysarthrοphonia in a Cypriot family with autosomal recessive hereditary spastic paraplegia associated with a homozygous SPG11 mutation

Background

Dysarthrophonia is often reported by hereditary spastic paraplegia (HSP) patients with SPG11 mutations but it has been poorly investigated.

Objective

The goal of this study was to investigate dysarthrophonia in SPG11 patients using quantitative measures. The voice/speech of two patients and a non-affected mutation carrier was recorded and analyzed using electroglottography (EGG) and speech acoustics.

Results

Dysarthrophonia showed a higher standard deviation of the average fundamental frequency, a three to eight times higher jitter, a 80–110 Hz higher mean fundamental frequency, and a two times higher fundamental frequency range. Diadochokinesis showed a pattern of a two to three times increase in the mean duration of the release burst of the phonemes /p/, /t/, /k/ as well as a 1.5 time increase in the mean vowel duration of the syllables /pa/, /ta/, /ka/.

Conclusion

Non-invasive physiological methods (EGG and speech acoustics) offer essential tools for the assessment of dysarthrophonia in SPG11 patients.

     

Lewy body and Alzheimer pathology in a family with the amyloid-β precursor protein APP717 gene mutation

Mutations in the amyloid precursor protein (APP) gene cause one form of early onset familial Alzheimer’s disease (AD). One such family has been studied genetically and neuropathologically and represents the basis of the present report. Four siblings with the APP717 Val to Ile mutation, aged 59, 65, 61 and 64 years, apolipoprotein E (APOE) genotyped 2,4 (first three) and 2,3 respectively, had severe AD, Braak stage VI with frequent neurofibrillary tangles in the primary visual cortex, Brodmann area 17. The first one also met McKeith criteria for the limbic stage of dementia with Lewy bodies but did not have substantia nigra Lewy bodies. The second two met McKeith criteria for the neocortical stage of dementia with Lewy bodies and both had substantia nigra Lewy bodies. The fourth had AD but no Lewy bodies. A cousin without the APP717 mutation who was APOE 3, 4, developed dementia at age 60 and died at age 75. She had severe cerebrovascular atherosclerosis, less severe AD, Braak stage V, with sparing of area 17. She also had Lewy bodies in the substantia nigra and in the cortex and met McKeith criteria for neocortical stage of dementia with Lewy bodies. Extrapyramidal features were present in all five. Lewy bodies have been described in 53% of reported autopsies on individuals with the APP717 Val to Ile mutation coincident with dementia and AD neuropathologic changes. These observations suggest an association between the chromosome 21 APP mutation and Lewy body formation, possibly mediated by other environmental or genetic factors. Received: 6 July 1999 / Revised, accepted: 19 October 1999     

Phenocopies in a large GCH1 mutation positive family with dopa responsive dystonia: confusing the picture?

BACKGROUND: Dopa responsive dystonia (DRD) is a disorder characterised by childhood onset dystonia but a wide range of clinical presentations has now been described. OBJECTIVE: To study a large Canadian family with presumed DRD. METHODS: The clinical features of the family were collected before molecular genetic mutational analysis. RESULTS: All nine individuals in whom a clinical diagnosis of DRD was definite or probable were heterozygous for a GCH1 gene deletion. However, eight of nine possibly clinically affected members did not carry the GCH1 mutation. CONCLUSIONS: Great care must be taken in diagnosing DRD even in families with the classic phenotype, because of potential phenocopies of the disease.     

A novel AIFM1 mutation in a Chinese family with X-linked Charcot–Marie–Tooth disease type 4

X-linked Charcot–Marie–Tooth disease type 4 (CMTX4), caused by AIFM1 (Apoptosis-Inducing Factor, Mitochondrion associated 1) mutations and associated with deafness and cognitive impairment, is a rare subtype of Charcot–Marie–Tooth disease. Here, we report a novel missense variant of AIFM1 in a X-linked recessive Chinese family with childhood-onset, slowly progressive, isolated axonal motor and sensory neuropathy. Calf magnetic resonance imaging revealed fatty infiltration and atrophy severely involving the muscles of peroneal compartment. Pathologies exhibited abnormal mitochondrial morphology and accumulation in axoplasm of nerve fiber and subsarcolemmal area of muscle. A hemizygous variant (c.513G>A, p.Met171Ile) in the family was identified and was classified as likely pathogenic according to the standards and guidelines of the American College of Medical Genetics and Genomics. Our report expands the genetic spectrum of diseases related to AIFM1 mutations and indicates that fatty infiltration and atrophy of muscles in the peroneal compartment may be a feature of CMTX4 in early stage.     

Heterozygous mutation in 5’-untranslated region of sepiapterin reductase gene<Emphasis Type="Italic"> (SPR)</Emphasis> in a patient with dopa-responsive dystonia

The search for mutations in genes coding for components of the biopterin pathway other than GTPCH1 revealed a mutation in the gene coding for sepiapterin reductase ( SPR) in 1 of 95 patients with GCH1-negative dopa-responsive dystonia (DRD). The mutation detected in SPR is a GA transition at position –13 of the untranslated region of the gene. This resulted in drastically reduced activity of sepiapterin reductase in the patients fibroblasts. The findings indicate that haploinsufficiency of SPR can be a rare cause of DRD.     

BAG3 p.Pro209Ser mutation identified in a Chinese family with Charcot–Marie–Tooth disease

Journal of Neurology - Bcl2-associated athanogene 3 (BAG3) gene mutations cause dilated cardiomyopathy and myofibrillar myopathy. Recently, a novel c.625C&gt;T (p.Pro209Ser) mutation in BAG3...     

The 894G > T (Glu298Asp) Variant in the Endothelial NOS Gene and MTHFR Polymorphisms Influence Homocysteine Levels in Patients with Cognitive Decline

The presence and severity of cerebrovascular pathological findings have been shown to increase the risk and stage of cognitive decline observed in Alzheimer’s disease and vascular dementia. Thus, the modification of vascular risk factors seems useful to reduce the risk of dementia regardless of type. Hyperhomocysteinemia has long been known as a major independent risk factor for vascular dysfunction. In this study, we evaluated the relationships between plasma homocysteine levels and genetic risk factors for hyperhomocysteinemia, i.e., the presence of gene variants for methylenetetrahydrofolate reductase (MTHFR) and endothelial nitric oxide synthase (eNOS) in patients with cognitive impairment. Genotyping for MTHFR C677T and eNOS 894G > T polymorphisms was carried out in 69 patients with probable diagnosis of AD and anamnestic mild cognitive impairment, matched for age and gender with 69 healthy volunteers. Patients with MTHFR TT677 genotype showed higher plasma Hcy levels than controls, even after adjustment for folate levels (P < 0.05). Moreover, Hcy plasma levels were higher in cases than controls for any given eNOS genotype. In particular, the presence of eNOS TT894 genotype in patients with cognitive decline resulted significantly associated with increased plasma Hcy levels when compared with controls having the same genotype or patients having other eNOS genotypes (P = 0.02). These data suggest that both MTHFR C677T and eNOS G894T variants should be regarded as genetic risk factors for hyperhomocysteinemia in patients with cognitive decline.     

Variations of mitochondrial DNA polymerase γ in patients with Parkinson’s disease

Parkinson’s disease is associated with mitochondrial dysfunction. The POLG1 gene encodes DNA-polymerase γ, which is responsible for the replication of mitochondrial DNA. Mutations in POLG1 cause neurodegenerative diseases such as progressive external ophthalmoplegia and Alpers syndrome. In this study, we investigated if mutations in POLG1 had any correlation with Parkinson’s disease. Subjects consisted of Finnish patients with early-onset Parkinson’s disease (EOPD, N = 441) or late-onset Parkinson’s disease (LOPD, N = 263). The POLG1 gene was screened for nine previously known mutations. Two patients were compound heterozygotes with respect to putatively pathogenic alleles. Twenty-eight patients harbored a heterozygous missense mutation, but the allele frequencies did not differ from those of the controls. Interestingly, the frequency of affected siblings was 4.6-fold higher (95 % confidence interval; 1.09, 19.5) among the patients with EOPD and with heterozygous POLG1 mutations than among patients without mutations. Clinically the patients with or without POLG1 mutations did not differ from each other. Our findings provide two lines of evidence suggesting a role for POLG1 mutations in Parkinson’s disease: (1) identification of patients with compound heterozygous mutations in POLG1, and (2) higher frequency of affected siblings among the EOPD patients with heterozygous POLG1 mutations than among EOPD patients without mutations.     

A novel deletion–insertion mutation identified in exon 3 of <Emphasis Type="Italic">FXN</Emphasis> in two siblings with a severe Friedreich ataxia phenotype

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disease most commonly caused by a GAA trinucleotide repeat expansion in the first intron of FXN, which reduces expression of the mitochondrial protein frataxin. Approximately 98% of individuals with FRDA are homozygous for GAA expansions, with the remaining 2% compound heterozygotes for a GAA expansion and a point mutation within FXN. Two siblings with early onset of symptoms experienced rapid loss of ambulation by 8 and 10 years. Diagnostic testing for FRDA demonstrated one GAA repeat expansion of 1010 repeats and one non-expanded allele. Sequencing all five exons of FXN identified a novel deletion-insertion mutation in exon 3 (c.371_376del6ins15), which results in a modified frataxin protein sequence at amino acid positions 124–127. Specifically, the amino acid sequence changes from DVSF to VHLEDT, increasing frataxin from 211 residues to 214. Using the known structure of human frataxin, a theoretical 3D model of the mutant protein was developed. In the event that the modified protein is expressed and stable, it is predicted that the acidic interface of frataxin, known to be involved in iron binding and interactions with the iron–sulphur cluster assembly factor IscU, would be impaired.     

Charcot–Marie–Tooth disease type 2J with <Emphasis Type="Italic">MPZ</Emphasis> Thr124Met mutation: clinico-electrophysiological and MRI study of a family

The purpose of the present study was to describe clinico-electrophysiological features and lower limb muscle MRI findings in a CMT2J pedigree due to MPZ Thr124Met mutation. We examined the proband, aged 56 years, and her affected daughter and son, aged 30 and 29 years. Disease severity in terms of ability to walk and run was established using a nine-point functional disability scale (FDS). We administered the CMT neuropathy score (CMTNS) based on patient’s symptoms, neurologic examination and neurophysiologic testing. All three patients had non-symptomatic Adie’s pupil. The proband and her son presented with late-onset lower limb sensorimotor neuropathy and pes cavus; the proband’s daughter had no signs of polyneuropathy. FDS score was 4 in the proband, 2 in her son, and 0 (normal) in her daughter. In both symptomatic patients, electrophysiological study showed a pattern of length-dependent axonal neuropathy mainly involving lower limb nerves; this was normal in the other patient. CMTNS was 18 in the proband, 12 in her son, and 0 (normal) in her daughter. MRI of foot and leg musculature was normal in the proband’s daughter, whereas the other two patients showed massive fatty atrophy of intrinsic foot musculature, extensive and diffuse fatty atrophy of leg muscles in the proband, and mild distally accentuated fatty infiltration of calf muscles in her son. Muscle edema, detected only in the proband’s son, was present in 7 out of 22 (33%) of visualized leg muscles, whereas contrast enhancement occurred in 6 of them. The reported mutation may manifest with either isolated Adie’s pupil or pupil abnormalities with late-onset sensorimotor length-dependent axonal polyneuropathy, though the presence of pes cavus might indicate an earlier onset. MRI examination helps to delineate an accurate extent of muscle involvement in the disease.     

Investigation of TNFA 308G > A and TNFB 252G > A polymorphisms in genetic susceptibility to migraine

We aimed to look for the association of tumor necrosis factor (TNF) gene polymorphisms (TNFA 308G > A, and TNFB 252G > A) in genetic susceptibility to migraine. The pathogenesis of migraine involves many immune-mediated mechanisms in the vascular endothelium. TNF, being a potent immunomodulator and pro-inflammatory cytokine, is suggested to be involved in inflammatory reactions leading to migraine attacks. A total of 216 normotensive migraine patients, 160 tension type headache (TTH) patients and 216 healthy controls (HC) were recruited in the study. The genetic polymorphisms were investigated through SNP association analysis using a matched case control migraine population. Genotyping of TNFA 308G > A polymorphism and TNFB 252G > A was done using ARMS PCR and PCR–RFLP, respectively. A borderline association was observed in TNFA 308GA genotype in migraine patients versus HC (p = 0.043; OR = 1.763; 95% CI = 1.019–3.051). After sub-grouping migraine into migraine with aura (MA) or without aura, significant difference at genotypic (p = 0.015; OR = 2.293; 95% CI = 1.172–4.487) as well as allelic (p = 0.035; OR = 1.955; 95% CI = 1.047–3.651) level was evident. The difference was even more significant in female MA at genotypic (p = 0.006; OR = 2.901; 95% CI = 1.361–6.181) and allelic level (p = 0.017; OR = 2.318; 95% CI = 1.159–4.635) as well as for A allele carriers in MA [p value = 0.020; OR = 2.205 (1.132–4.295)] and female MA (p value = 0.008; OR = 2.741; CI = 1.297–5.792). No association of TNFB252G > A was observed in migraine patients or any subgroups. We did not find any association of TNFA or TNFB gene polymorphisms with TTH. In conclusion, the TNFA 308G > A polymorphism was found to be associated with MA, particularly in females, whereas we could not find any association of TNFB 252G > A polymorphism in genetic susceptibility to migraine on comparing the migraine patients with HC or TTH patients.