Papers by Antonella Spinazzola
Pediatric Neurology, Jan 1, 1994
Inherited Neuromuscular Diseases, Jan 1, 2009
More than one billion years ago, mitochondria were free-living prokaryotic organisms with their o... more More than one billion years ago, mitochondria were free-living prokaryotic organisms with their own DNA. However, during the evolution, ancestral genes have been transferred from the mitochondrial to the nuclear genome so that mtDNA became dependent on numerous nucleus-encoded factors for its integrity, replication and expression. Mutations in any of these factors may alter the cross-talk between the two genomes and cause Mendelian diseases that affect mtDNA integrity or expression.
Mitochondrion, Jan 1, 2002
Neuromuscular Disorders, Jan 1, 2004
A 21-year-old woman described proximal muscle weakness since early childhood. At age 16, she deve... more A 21-year-old woman described proximal muscle weakness since early childhood. At age 16, she developed bilateral ptosis, progressive external ophthalmoplegia, and exercise intolerance. She harbored a heteroplasmic G12315A mutation in the mitochondrial DNA tRNA Leu(CUN) gene, which disrupts a highly conserved G-C base pair in the TCC stem of the molecule. Mutant mitochondrial DNA was 62% of total in muscle and 17% in blood. The mutation was undetectable in blood, urinary sediment, and hair follicles from the patient's mother. This second patient with G12315A and progressive external ophthalmoplegia confirms the pathogenicity of the mutation and helps to define the correlation between genotype and phenotype. q
Neuromuscular Disorders, Jan 1, 2008
Navajo neurohepatopathy is a hepato-cerebral variant of mitochondrial DNA depletion syndrome due ... more Navajo neurohepatopathy is a hepato-cerebral variant of mitochondrial DNA depletion syndrome due to a specific mutation in MPV17, a gene located on human chromosome 2p. The same mutation was reported in an Italian family. To understand whether the MPV17 mutation was transmitted by descent from a common ancestor to Navajos and Italians we constructed a dense haplotype of the MPV17 locus using suitable single nucleotide polymorphisms. Complete discordance between Italian and Navajo haplotypes rules out the former hypothesis, suggesting that the mutation occurred independently in the two populations.
Archives of …, Jan 1, 2008
Autosomal recessive mutations in MPV17 (OMIM *137960) have been identified in the hepatocerebral ... more Autosomal recessive mutations in MPV17 (OMIM *137960) have been identified in the hepatocerebral form of mitochondrial DNA depletion syndrome (MDS). To describe the clinical, morphologic, and genetic findings in 3 children with MPV17-related MDS from 2 unrelated families. Case report. Academic research. We identified 3 novel pathogenic mutations in 3 children. Two children were homozygous for nonsense mutation p.W120X. A third child was compound heterozygous for missense mutation p.G24W and for a macrodeletion spanning MPV17 exon 8. All patients demonstrated lactic acidosis, hypoglycemia, hepatomegaly, and progressive liver failure. Neurologic symptoms manifested at a later stage of the disease. Death occurred within the first year of life in all 3 patients. These data confirm that MPV17 mutations are associated with a 2-stage syndrome. The first symptoms are metabolic and rapidly progress to hepatic failure. This stage is followed by neurologic involvement affecting the central and peripheral systems.
Journal of …, Jan 1, 2009
… et Biophysica Acta (BBA …, Jan 1, 2009
Human Molecular …, Jan 1, 2009
In humans, MPV17 mutations are responsible for severe mitochondrial depletion syndrome, mainly af... more In humans, MPV17 mutations are responsible for severe mitochondrial depletion syndrome, mainly affecting the liver and the nervous system. To gain insight into physiopathology of MPV17-related disease, we investigated an available Mpv17 knockout animal model. We found severe mtDNA depletion in liver and, albeit to a lesser extent, in skeletal muscle, whereas hardly any depletion was detected in brain and kidney, up to 1 year after birth. Mouse embryonic fibroblasts did show mtDNA depletion, but only after several culturing passages, or in a serumless culturing medium. In spite of severe mtDNA depletion, only moderate decrease in respiratory chain enzymatic activities, and mild cytoarchitectural alterations, were observed in the Mpv17 2/2 livers, but neither cirrhosis nor failure ever occurred in this organ at any age. The mtDNA transcription rate was markedly increased in liver, which could contribute to compensate the severe mtDNA depletion. This phenomenon was associated with specific downregulation of Mterf1, a negative modulator of mtDNA transcription. The most relevant clinical features involved skin, inner ear and kidney. The coat of the Mpv17 2/2 mice turned gray early in adulthood, and 18-month or older mice developed focal segmental glomerulosclerosis (FSGS) with massive proteinuria. Concomitant degeneration of cochlear sensory epithelia was reported as well. These symptoms were associated with significantly shorter lifespan. Coincidental with the onset of FSGS, there was hardly any mtDNA left in the glomerular tufts. These results demonstrate that Mpv17 controls mtDNA copy number by a highly tissue-and possibly cytotype-specific mechanism.
Methods in Cell Biology, Jan 1, 2001
Bioscience reports, Jan 1, 2007
In the course of evolution, mitochondria lost their independence, and mtDNA became ''slave'' of n... more In the course of evolution, mitochondria lost their independence, and mtDNA became ''slave'' of nDNA, depending on numerous nucleus-encoded factors for its integrity, replication and expression. Mutations in any of these factors may alter the cross-talk between the two genomes and cause diseases that affect mtDNA integrity or expression, being inherited as mendelian traits.
Neuromuscular Disorders, Jan 1, 2001
Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a unique autosomal recessive dis... more Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a unique autosomal recessive disorder with mitochondrial DNA alterations. The disease is characterized clinically by ptosis, progressive external ophthalmoparesis, gastrointestinal dysmotility, cachexia, peripheral neuropathy, and leukoencephalopathy. Muscle biopsies typically reveal mitochondrial abnormalities including ragged-red ®bers and focal cytochrome c oxidase de®ciency. Analysis of mitochondrial DNA in skeletal muscle shows partial depletion, multiple deletions, or both. To identify the cause of MNGIE, we mapped the disease locus to chromosome 22q13.32±qter. Within this region, we identi®ed the gene encoding thymidine phosphorylase as the MNGIE gene. We have identi®ed homozygous or compound-heterozygous thymidine phosphorylase gene mutations in 35 MNGIE patients (21 families) from diverse ethnic groups, including: Ashkenazi Jewish, Western European, Jamaican, Hispanic, and Japanese. We con®rmed pathogenicity of the mutations by a spectrophotometric assay of thymidine phosphorylase activity with peripheral leukocytes of 15 MNGIE patients. Thymidine phosphorylase enzymatic activity was severely reduced, thus enabling us to conclude that the loss-of-function mutations in thymidine phosphorylase gene cause MNGIE. Thymidine phosphorylase catabolizes thymidine to thymine. In agreement with this notion, we noted that plasma thymidine level is increased more than 20-fold in MNGIE patients compared to controls. Therefore, we have hypothesized that increased thymidine causes mitochondrial nucleotide pool imbalance which, in turn, leads to motochondrial DNA alterations, via a mitochondria-speci®c thymidine salvage pathway. The identi®cation of the MNGIE gene has allowed us to classify MNGIE as a disease of nucleoside dysmetabolism. We may be entering a new era of research on mitochondrial nucleoside metabolism. q
Clinical …, Jan 1, 2004
Background: Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is caused by mutations ... more Background: Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is caused by mutations in the gene encoding thymidine phosphorylase (TP). The clinical manifestations of MNGIE are recognizable and homogeneous, but in the early stages, the disease is often misdiagnosed. This study assesses the reliability of biochemical assays to diagnose MNGIE. Methods: We studied 180 patients with clinical features suggestive of MNGIE, 14 asymptomatic TP mutation carriers, and 20 controls. TP enzyme activity in the buffy coat was determined by a fixed-time method, and the plasma nucleosides thymidine (dThd) and deoxyuridine (dUrd) were assessed by a gradient-elution reversed phase HPLC method. TP was sequenced through standard procedures in patients who met the clinical criteria for MNGIE. Results: Twenty-five of the 180 patients fulfilled the clinical criteria for MNGIE and had homozygous or compound heterozygous TP mutations. All had drastically decreased TP activity [mean (SD), 10 (15) nmol thymine formed ⅐ h ؊1 ⅐ (mg protein) ؊1 vs 634 (217) nmol thymine formed ⅐ h ؊1 ⅐ (mg protein) ؊1 for the controls]. Relative to the control mean, TP activities were reduced to 35% in mutation carriers and 65% in MNGIE-like patients. All 25 MNGIE patients had detectable plasma dThd [8.6 (3.4) mol/L] and dUrd [14.2 (4.4) mol/L].
Current neurology and neuroscience reports, Jan 1, 2003
Current opinion in genetics & …, Jan 1, 2003
Journal of Biological …, Jan 1, 1999
A T 3 G mutation at position 8993 in human mitochondrial DNA is associated with the syndrome neur... more A T 3 G mutation at position 8993 in human mitochondrial DNA is associated with the syndrome neuropathy, ataxia, and retinitis pigmentosa and with a maternally inherited form of Leigh's syndrome. The mutation substitutes an arginine for a leucine at amino acid position 156 in ATPase 6, a component of the F 0 portion of the mitochondrial ATP synthase complex. Fibroblasts harboring high levels of the T8993G mutation have decreased ATP synthesis activity, but do not display any growth defect under standard culture conditions. Combining the notions that cells with respiratory chain defects grow poorly in medium containing galactose as the major carbon source, and that resistance to oligomycin, a mitochondrial inhibitor, is associated with mutations in the ATPase 6 gene in the same transmembrane domain where the T8993G amino acid substitution is located, we created selective culture conditions using galactose and oligomycin that elicited a pathological phenotype in T8993G cells and that allowed for the rapid selection of wild-type over T8993G mutant cells. We then generated cytoplasmic hybrid clones containing heteroplasmic levels of the T8993G mutation, and showed that selection in galactose-oligomycin caused a significant increase in the fraction of wild-type molecules (from 16 to 28%) in these cells.
Journal of Biological …, Jan 1, 2002
Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive human dis... more Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive human disease due to mutations in the thymidine phosphorylase (TP) gene. TP enzyme catalyzes the reversible phosphorolysis of thymidine to thymine and 2-deoxy-D-ribose 1-phosphate. We present evidence that thymidine metabolism is altered in MNGIE. TP activities in buffy coats were reduced drastically in all 27 MNGIE patients compared with 19 controls. All MNGIE patients had much higher plasma levels of thymidine than normal individuals and asymptomatic TP mutation carriers. In two patients, the renal clearance of thymidine was ϳ20% that of creatinine, and because hemodialysis demonstrated that thymidine is ultrafiltratable, most of the filtered thymidine is likely to be reabsorbed by the kidney. In vitro, fibroblasts from controls catabolized thymidine in medium; by contrast, MNGIE fibroblasts released thymidine. In MNGIE, severe impairment of TP enzyme activity leads to increased plasma thymidine. In patients who are suspected of having MNGIE, determination of TP activity in buffy coats and thymidine levels in plasma are diagnostic. We hypothesize that excess thymidine alters mitochondrial nucleoside and nucleotide pools leading to impaired mitochondrial DNA replication, repair, or both. Therapies to reduce thymidine levels may be beneficial to MNGIE patients.
Nature genetics, Jan 1, 2006
Nature genetics, Jan 1, 2006
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Papers by Antonella Spinazzola