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Biomedical subjects

Massimo Zeviani

Publications and source records attributed to Massimo Zeviani.

12 recordsLinked to original sources
PubMed2003

A missense mutation in the mitochondrial ND5 gene associated with a Leigh-MELAS overlap syndrome.

A 13084 A->T missense mutation in the mitochondrial ND5 gene was identified in a 16-year-old boy affected with a progressive neurodegenerative disorder combining features of Leigh and MELAS (mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes) syndromes. Muscle biopsy analysis revealed partial complex I deficiency. The mutation presented a variable degree of heteroplasmy in the patient's tissues. This finding underlines the contribution of mtDNA-encoded complex I subunits in the etiology of complex I deficiency associated with encephalopathy.

Adolescent↗
PubMed2003

Constitutive knockout of Surf1 is associated with high embryonic lethality, mitochondrial disease and cytochrome c oxidase deficiency in mice.

We report here the creation of a constitutive knockout mouse for SURF1, a gene encoding one of the assembly proteins involved in the formation of cytochrome c oxidase (COX). Loss-of-function mutations of SURF1 cause Leigh syndrome associated with an isolated and generalized COX deficiency in humans. The murine phenotype is characterized by the following hallmarks: (1) high post-implantation embryonic lethality, affecting approximately 90% of the Surf1(-/-) individuals; (2) early-onset mortality of post-natal individuals; (3) highly significant deficit in muscle strength and motor performance; (4) profound and isolated defect of COX activity in skeletal muscle and liver, and, to a lesser extent, heart and brain; (5) morphological abnormalities of skeletal muscle, characterized by reduced histochemical reaction to COX and mitochondrial proliferation; (6) no obvious abnormalities in brain morphology, reflecting the virtual absence of overt neurological symptoms. These results indicate a function for murine Surf1 protein (Surf1p) specifically related to COX and recapitulate, at least in part, the human phenotype. This is the first mammalian model for a nuclear disease gene of a human mitochondrial disorder. Our model constitutes a useful tool to investigate the function of Surf1p, help understand the pathogenesis of Surf1p deficiency in vivo, and evaluate the efficacy of treatment.

Alleles↗
PubMed2003

Mitochondrial disorders.

We present here a discussion on the most relevant recent publications on mitochondrial disease. In addition to many papers concerning the description of the genotype-to-phenotype correlations in mitochondrial DNA-related disorders, this very broad area of neurogenetics includes a number of novel observations on the basic aspects of mitochondrial biogenesis that can be relevant in explaining the molecular mechanisms of mitochondrial abnormalities. The completion of the human genome project and the wealth of knowledge gained on the genetics of oxidative phosphorylation in yeast have promoted a substantial acceleration in the discovery of a remarkable number of nuclear genes associated with specific mitochondrial disorders. A further development of these contributions has been the generation of several cellular and animal models of disease that can now be exploited for testing both pathogenetic hypotheses and therapeutic strategies. Most of the latter are based on the use of chemical compounds aimed at reducing the negative impact of mitochondrial defects on both energy production and generation of reactive oxygen species. The first successful attempts for gene therapy of some mitochondrial diseases have recently been achieved and will hopefully increase in the near future.

Animals↗
PubMed2003

Nuclear genes in mitochondrial disorders.

Nuclear genes encode hundreds of proteins involved in mitochondrial biogenesis and oxidative phosphorylation (OXPHOS). Nevertheless, the identification of nuclear genes responsible for OXPHOS-related disorders has proceeded at a much slower pace, compared with the discovery and characterization of mtDNA mutations. Reasons for such a gap include rarity of syndromes, genetic heterogeneity, and ignorance on this nuclear gene repertoire in humans. This scenario is changing rapidly, thanks to the discovery of several OXPHOS-related human genes, and to the identification in some of them of disease-associated mutations. In addition, new strategies - based on transcriptome and proteome analysis, and functional complementation assays - have been applied successfully to mitochondrial medicine.

Cell Nucleus↗
PubMed2002

Biochemical-clinical correlation in patients with different loads of the mitochondrial DNA T8993G mutation.

OBJECTIVE: To investigate the correlation between biochemical and clinical phenotype in 6 patients from 3 unrelated families with different mutation loads (heteroplasmy) of the T8993G mitochondrial DNA mutation associated with neuropathy, ataxia, and retinitis pigmentosa-Leigh syndrome. METHODS: We studied adenosine triphosphate (ATP) synthase activity (synthesis and hydrolysis) in platelet-derived submitochondrial particles and assessed mutant loads both in platelets used for biochemical analysis and in other available tissues. Biochemical and molecular results were correlated with clinical features. RESULTS: The rate of ATP hydrolysis was normal, but ATP synthesis was severely impaired (30% to 4% of residual activity) in patients harboring 34% to 90% mutant mitochondrial DNA, without any evidence of a threshold for the expression of this defect. There was little variation in heteroplasmy among tissues from each patient, but wider variability was detected in 2 mothers. Correlation of heteroplasmy and clinical and biochemical features suggested that ATP synthesis is defective at mutant loads as low as 34% and is extremely reduced at mutant loads above 80% when the phenotype is neuropathy, ataxia, and retinitis pigmentosa-Leigh syndrome. CONCLUSIONS: This study indicates a close relationship between tissue heteroplasmy, expression of the biochemical defect in platelets, and clinical involvement. The biochemical defect was greater than previously reported, and we found no evidence of a biochemical threshold. The uniform distribution of high mutant loads among our patients' tissues suggests a differential tissue-specific reliance on mitochondrial ATP synthesis.

Adenosine Triphosphate↗
PubMed2002

Mutations of mitochondrial DNA polymerase gammaA are a frequent cause of autosomal dominant or recessive progressive external ophthalmoplegia.

One form of familial progressive external ophthalmoplegia with multiple mitochondrial DNA deletions recently has been associated with mutations in POLG1, the gene encoding pol gammaA, the catalytic subunit of mitochondrial DNA polymerase. We screened the POLG1 gene in several PEO families and identified five different heterozygous missense mutations of POLG1 in 10 autosomal dominant families. Recessive mutations were found in three families. Our data show that mutations of POLG1 are the most frequent cause of familial progressive external ophthalmoplegia associated with accumulation of multiple mitochondrial DNA deletions, accounting for approximately 45% of our family cohort.

Amino Acid Sequence↗
PubMed2002

Frequency of DYT1 mutation in early onset primary dystonia in Italian patients.

Thirty Italian patients with sporadic, early-onset, primary dystonia were screened for the DYT1 mutation. Five patients were positive (mean age at onset, 8 years); two had the typical phenotype, two a generalised dystonia also involving the cranial muscles, and one a segmental dystonia. In the other 25 patients (mean age at onset, 7.7 years), dystonia was generalised in 22 patients and remained segmental in three. Our results indicate the role of DYT1 mutation in Italian patients and confirm clinical and genetic heterogeneity of early-onset primary dystonia.

Adolescent↗
PubMed2002

A novel nonsense mutation (Q352X) in the mitochondrial cytochrome b gene associated with a combined deficiency of complexes I and III.

We identified a novel mitochondrial cytochrome b mutation in a patient with progressive exercise intolerance, muscle cramps and lactic acidosis. A marked reduction of the enzymatic activities of respiratory chain complexes I and III was found in muscle biopsy. The mutation was a heteroplasmic C15800T transition, determining a stop-codon at amino acid position 352 (Q352X). Mutant mtDNA was approximately 45% of total genomes in muscle, while it was absent in all of the other examined tissues of the patient and in lymphocytes of the patient's mother. Clinical presentation and laboratory findings strongly support the hypothesis that this mutation is the primary cause of the disease in our patient.

Adult↗
PubMed2002

A novel mutation in the SURF1 gene in a child with Leigh disease, peripheral neuropathy, and cytochrome-c oxidase deficiency.

We report a 16-month-old boy with psychomotor regression, muscle hypotonia, peripheral neuropathy, and lactic acidosis. Brain magnetic resonance imaging showed a bilateral abnormal signal in the substantia nigra and in the subthalamic nucleus, suggestive of Leigh disease. Histochemical analysis of skeletal muscle showed decreased cytochrome-c oxidase activity. Biochemical analysis of respiratory chain enzymes in muscle homogenate and in cultured fibroblasts showed isolated cytochrome-c oxidase deficiency. Western blot analysis in fibroblasts showed the absence of Surf1 protein. Genetic analysis of the SURF1 gene revealed that the patient was compound heterozygous for a previously reported mutation at the splice-junction site of intron 3 (240 + 1G > T), and for a novel 4-bp deletion in exon 6 (531_534delAAAT). Our data further enlarge the spectrum of mutations in SURF1 gene in patients with Leigh disease and cytochrome-c oxidase deficiency, contributing to better characterization of the clinical and neuroradiologic features of this group of patients for genotype-phenotype correlations.

Biopsy↗
PubMed2002

MR findings in Leigh syndrome with COX deficiency and SURF-1 mutations.

BACKGROUND AND PURPOSE: In a large number of patients with Leigh syndrome (LS) and cytochrome c oxidase (COX) deficiency, mutations of the SURF-1 gene were recently identified. The aim of the present study was to review the MR findings in patients with LS to verify if the genetically homogeneous patients with LS and SURF-1 mutations (LS SURF-1 patients) had a homogeneous MR pattern that could be used to differentiate them from other patients with LS (LS non-SURF-1 patients). METHODS: T1-, proton density-, and T2-weighted MR images of eight LS SURF-1 patients and 14 LS non-SURF-1 patients were reviewed. Enzymatic activity was determined according to standard methods. Genetic analysis was mostly performed by using stored DNA samples. RESULTS: All LS SURF-1 patients had lesions in the brain stem and subthalamic nuclei. Six had lesions in the cerebellum. Only two had basal ganglial abnormalities. Ten LS non-SURF-1 patients had lesions in the brain stem, but in six they were mild. Ten patients had basal ganglial abnormalities (nine of 10 in the putamina). LS-SURF-1 patients had a more severe clinical course. CONCLUSION: The MR pattern in LS SURF-1 patients is characteristic. Brain stem and subthalamic nuclei lesions may suggest the specific diagnosis. These patients die soon, probably because of lower brain stem involvement. Basal ganglial abnormalities are common only in LS non-SURF-1 patients. The absence of putaminal lesions, therefore, does not exclude the diagnosis of LS.

Brain↗