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Dive into the research topics where Laura Melchionda is active.

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Featured researches published by Laura Melchionda.


American Journal of Human Genetics | 2012

Mutations of the Mitochondrial-tRNA Modifier MTO1 Cause Hypertrophic Cardiomyopathy and Lactic Acidosis

Daniele Ghezzi; Enrico Baruffini; Tobias B. Haack; Federica Invernizzi; Laura Melchionda; Cristina Dallabona; Tim M. Strom; Rossella Parini; Alberto Burlina; Thomas Meitinger; Holger Prokisch; Ileana Ferrero; Massimo Zeviani

Dysfunction of mitochondrial respiration is an increasingly recognized cause of isolated hypertrophic cardiomyopathy. To gain insight into the genetic origin of this condition, we used next-generation exome sequencing to identify mutations in MTO1, which encodes mitochondrial translation optimization 1. Two affected siblings carried a maternal c.1858dup (p.Arg620Lysfs(∗)8) frameshift and a paternal c.1282G>A (p.Ala428Thr) missense mutation. A third unrelated individual was homozygous for the latter change. In both humans and yeast, MTO1 increases the accuracy and efficiency of mtDNA translation by catalyzing the 5-carboxymethylaminomethylation of the wobble uridine base in three mitochondrial tRNAs (mt-tRNAs). Accordingly, mutant muscle and fibroblasts showed variably combined reduction in mtDNA-dependent respiratory chain activities. Reduced respiration in mutant cells was corrected by expressing a wild-type MTO1 cDNA. Conversely, defective respiration of a yeast mto1Δ strain failed to be corrected by an Mto1(Pro622∗) variant, equivalent to human MTO1(Arg620Lysfs∗8), whereas incomplete correction was achieved by an Mto1(Ala431Thr) variant, corresponding to human MTO1(Ala428Thr). The respiratory yeast phenotype was dramatically worsened in stress conditions and in the presence of a paromomycin-resistant (P(R)) mitochondrial rRNA mutation. Lastly, in vivo mtDNA translation was impaired in the mutant yeast strains.


Neurology | 2014

Novel (ovario) leukodystrophy related to AARS2 mutations

Cristina Dallabona; Daria Diodato; Sietske H. Kevelam; Tobias B. Haack; Lee-Jun C. Wong; Gajja S. Salomons; Enrico Baruffini; Laura Melchionda; Caterina Mariotti; Tim M. Strom; Thomas Meitinger; Holger Prokisch; Kim Chapman; Alison Colley; Helena Rocha; Katrin Őunap; Raphael Schiffmann; Ettore Salsano; Mario Savoiardo; Eline M. Hamilton; Truus E. M. Abbink; Nicole I. Wolf; Ileana Ferrero; Costanza Lamperti; Massimo Zeviani; Adeline Vanderver; Daniele Ghezzi; Marjo S. van der Knaap

Objectives: The study was focused on leukoencephalopathies of unknown cause in order to define a novel, homogeneous phenotype suggestive of a common genetic defect, based on clinical and MRI findings, and to identify the causal genetic defect shared by patients with this phenotype. Methods: Independent next-generation exome-sequencing studies were performed in 2 unrelated patients with a leukoencephalopathy. MRI findings in these patients were compared with available MRIs in a database of unclassified leukoencephalopathies; 11 patients with similar MRI abnormalities were selected. Clinical and MRI findings were investigated. Results: Next-generation sequencing revealed compound heterozygous mutations in AARS2 encoding mitochondrial alanyl-tRNA synthetase in both patients. Functional studies in yeast confirmed the pathogenicity of the mutations in one patient. Sanger sequencing revealed AARS2 mutations in 4 of the 11 selected patients. The 6 patients with AARS2 mutations had childhood- to adulthood-onset signs of neurologic deterioration consisting of ataxia, spasticity, and cognitive decline with features of frontal lobe dysfunction. MRIs showed a leukoencephalopathy with striking involvement of left-right connections, descending tracts, and cerebellar atrophy. All female patients had ovarian failure. None of the patients had signs of a cardiomyopathy. Conclusions: Mutations in AARS2 have been found in a severe form of infantile cardiomyopathy in 2 families. We present 6 patients with a new phenotype caused by AARS2 mutations, characterized by leukoencephalopathy and, in female patients, ovarian failure, indicating that the phenotypic spectrum associated with AARS2 variants is much wider than previously reported.


Human Mutation | 2013

MTO1 Mutations are Associated with Hypertrophic Cardiomyopathy and Lactic Acidosis and Cause Respiratory Chain Deficiency in Humans and Yeast

Enrico Baruffini; Cristina Dallabona; Federica Invernizzi; John W. Yarham; Laura Melchionda; Emma L. Blakely; Eleonora Lamantea; Claudia Donnini; Saikat Santra; Suresh Vijayaraghavan; Helen Roper; Alberto Burlina; Robert Kopajtich; Anett Walther; Tim M. Strom; Tobias B. Haack; Holger Prokisch; Robert W. Taylor; Ileana Ferrero; Massimo Zeviani; Daniele Ghezzi

We report three families presenting with hypertrophic cardiomyopathy, lactic acidosis, and multiple defects of mitochondrial respiratory chain (MRC) activities. By direct sequencing of the candidate gene MTO1, encoding the mitochondrial‐tRNA modifier 1, or whole exome sequencing analysis, we identified novel missense mutations. All MTO1 mutations were predicted to be deleterious on MTO1 function. Their pathogenic role was experimentally validated in a recombinant yeast model, by assessing oxidative growth, respiratory activity, mitochondrial protein synthesis, and complex IV activity. In one case, we also demonstrated that expression of wt MTO1 could rescue the respiratory defect in mutant fibroblasts. The severity of the yeast respiratory phenotypes partly correlated with the different clinical presentations observed in MTO1 mutant patients, although the clinical outcome was highly variable in patients with the same mutation and seemed also to depend on timely start of pharmacological treatment, centered on the control of lactic acidosis by dichloroacetate. Our results indicate that MTO1 mutations are commonly associated with a presentation of hypertrophic cardiomyopathy, lactic acidosis, and MRC deficiency, and that ad hoc recombinant yeast models represent a useful system to test the pathogenic potential of uncommon variants, and provide insight into their effects on the expression of a biochemical phenotype.


Human Mutation | 2014

VARS2 and TARS2 Mutations in Patients with Mitochondrial Encephalomyopathies

Daria Diodato; Laura Melchionda; Tobias B. Haack; Cristina Dallabona; Enrico Baruffini; Claudia Donnini; Tiziana Granata; Francesca Ragona; Paolo Balestri; Maria Margollicci; Eleonora Lamantea; Alessia Nasca; Christopher A. Powell; Michal Minczuk; Tim M. Strom; Thomas Meitinger; Holger Prokisch; Costanza Lamperti; Massimo Zeviani; Daniele Ghezzi

By way of whole‐exome sequencing, we identified a homozygous missense mutation in VARS2 in one subject with microcephaly and epilepsy associated with isolated deficiency of the mitochondrial respiratory chain (MRC) complex I and compound heterozygous mutations in TARS2 in two siblings presenting with axial hypotonia and severe psychomotor delay associated with multiple MRC defects. The nucleotide variants segregated within the families, were absent in Single Nucleotide Polymorphism (SNP) databases and are predicted to be deleterious. The amount of VARS2 and TARS2 proteins and valyl‐tRNA and threonyl‐tRNA levels were decreased in samples of afflicted patients according to the genetic defect. Expression of the corresponding wild‐type transcripts in immortalized mutant fibroblasts rescued the biochemical impairment of mitochondrial respiration and yeast modeling of the VARS2 mutation confirmed its pathogenic role. Taken together, these data demonstrate the role of the identified mutations for these mitochondriopathies. Our study reports the first mutations in the VARS2 and TARS2 genes, which encode two mitochondrial aminoacyl‐tRNA synthetases, as causes of clinically distinct, early‐onset mitochondrial encephalopathies.


American Journal of Human Genetics | 2015

RNASEH1 Mutations Impair mtDNA Replication and Cause Adult-Onset Mitochondrial Encephalomyopathy

Aurelio Reyes; Laura Melchionda; Alessia Nasca; Franco Carrara; Eleonora Lamantea; Alice Zanolini; Costanza Lamperti; Mingyan Fang; Jianguo Zhang; Dario Ronchi; S. Bonato; Gigliola Fagiolari; Maurizio Moggio; Daniele Ghezzi; Massimo Zeviani

Chronic progressive external ophthalmoplegia (CPEO) is common in mitochondrial disorders and is frequently associated with multiple mtDNA deletions. The onset is typically in adulthood, and affected subjects can also present with general muscle weakness. The underlying genetic defects comprise autosomal-dominant or recessive mutations in several nuclear genes, most of which play a role in mtDNA replication. Next-generation sequencing led to the identification of compound-heterozygous RNASEH1 mutations in two singleton subjects and a homozygous mutation in four siblings. RNASEH1, encoding ribonuclease H1 (RNase H1), is an endonuclease that is present in both the nucleus and mitochondria and digests the RNA component of RNA-DNA hybrids. Unlike mitochondria, the nucleus harbors a second ribonuclease (RNase H2). All affected individuals first presented with CPEO and exercise intolerance in their twenties, and these were followed by muscle weakness, dysphagia, and spino-cerebellar signs with impaired gait coordination, dysmetria, and dysarthria. Ragged-red and cytochrome c oxidase (COX)-negative fibers, together with impaired activity of various mitochondrial respiratory chain complexes, were observed in muscle biopsies of affected subjects. Western blot analysis showed the virtual absence of RNase H1 in total lysate from mutant fibroblasts. By an in vitro assay, we demonstrated that altered RNase H1 has a reduced capability to remove the RNA from RNA-DNA hybrids, confirming their pathogenic role. Given that an increasing amount of evidence indicates the presence of RNA primers during mtDNA replication, this result might also explain the accumulation of mtDNA deletions and underscores the importance of RNase H1 for mtDNA maintenance.


Neurology | 2013

SURF1 deficiency causes demyelinating Charcot-Marie-Tooth disease

Andoni Echaniz-Laguna; Daniele Ghezzi; Maïté Chassagne; Martine Mayençon; Sylvie Padet; Laura Melchionda; Isabelle Rouvet; Béatrice Lannes; Dominique Bozon; Philippe Latour; Massimo Zeviani; Bénédicte Mousson de Camaret

Objective: To investigate whether mutations in the SURF1 gene are a cause of Charcot-Marie-Tooth (CMT) disease. Methods: We describe 2 patients from a consanguineous family with demyelinating autosomal recessive CMT disease (CMT4) associated with the homozygous splice site mutation c.107-2A>G in the SURF1 gene, encoding an assembly factor of the mitochondrial respiratory chain complex IV. This observation led us to hypothesize that mutations in SURF1 might be an unrecognized cause of CMT4, and we investigated SURF1 in a total of 40 unrelated patients with CMT4 after exclusion of mutations in known CMT4 genes. The functional impact of c.107-2A>G on splicing, amount of SURF1 protein, and on complex IV activity and assembly was analyzed. Results: Another patient with CMT4 was found to harbor 2 additional SURF1 mutations. All 3 patients with SURF1-associated CMT4 presented with severe childhood-onset neuropathy, motor nerve conduction velocities <25 m/s, and lactic acidosis. Two patients had brain MRI abnormalities, including putaminal and periaqueductal lesions, and developed cerebellar ataxia years after polyneuropathy. The c.107-2A>G mutation produced no normally spliced transcript, leading to SURF1 absence. However, complex IV remained partially functional in muscle and fibroblasts. Conclusions: We found SURF1 mutations in 5% of families (2/41) presenting with CMT4. SURF1 should be systematically screened in patients with childhood-onset severe demyelinating neuropathy and additional features such as lactic acidosis, brain MRI abnormalities, and cerebellar ataxia developing years after polyneuropathy.


American Journal of Human Genetics | 2014

Mutations in APOPT1, encoding a mitochondrial protein, cause cavitating leukoencephalopathy with cytochrome c oxidase deficiency

Laura Melchionda; Tobias B. Haack; Steven A. Hardy; Truus E. M. Abbink; Erika Fernandez-Vizarra; Eleonora Lamantea; Silvia Marchet; Lucia Morandi; Maurizio Moggio; Rosalba Carrozzo; Alessandra Torraco; Daria Diodato; Tim M. Strom; Thomas Meitinger; Pinar Tekturk; Zuhal Yapici; Fathiya Al-Murshedi; René Stevens; Richard J. Rodenburg; Costanza Lamperti; Anna Ardissone; Isabella Moroni; Graziella Uziel; Holger Prokisch; Robert W. Taylor; Enrico Bertini; Marjo S. van der Knaap; Daniele Ghezzi; Massimo Zeviani

Cytochrome c oxidase (COX) deficiency is a frequent biochemical abnormality in mitochondrial disorders, but a large fraction of cases remains genetically undetermined. Whole-exome sequencing led to the identification of APOPT1 mutations in two Italian sisters and in a third Turkish individual presenting severe COX deficiency. All three subjects presented a distinctive brain MRI pattern characterized by cavitating leukodystrophy, predominantly in the posterior region of the cerebral hemispheres. We then found APOPT1 mutations in three additional unrelated children, selected on the basis of these particular MRI features. All identified mutations predicted the synthesis of severely damaged protein variants. The clinical features of the six subjects varied widely from acute neurometabolic decompensation in late infancy to subtle neurological signs, which appeared in adolescence; all presented a chronic, long-surviving clinical course. We showed that APOPT1 is targeted to and localized within mitochondria by an N-terminal mitochondrial targeting sequence that is eventually cleaved off from the mature protein. We then showed that APOPT1 is virtually absent in fibroblasts cultured in standard conditions, but its levels increase by inhibiting the proteasome or after oxidative challenge. Mutant fibroblasts showed reduced amount of COX holocomplex and higher levels of reactive oxygen species, which both shifted toward control values by expressing a recombinant, wild-type APOPT1 cDNA. The shRNA-mediated knockdown of APOPT1 in myoblasts and fibroblasts caused dramatic decrease in cell viability. APOPT1 mutations are responsible for infantile or childhood-onset mitochondrial disease, hallmarked by the combination of profound COX deficiency with a distinctive neuroimaging presentation.


Orphanet Journal of Rare Diseases | 2013

Adult-onset Alexander disease, associated with a mutation in an alternative GFAP transcript, may be phenotypically modulated by a non-neutral HDAC6 variant

Laura Melchionda; Mingyan Fang; Hairong Wang; Valeria Fugnanesi; Michela Morbin; Xuanzhu Liu; Wenyan Li; Isabella Ceccherini; Laura Farina; Mario Savoiardo; Pio D’Adamo; Jianguo Zhang; Alfredo Costa; Sabrina Ravaglia; Daniele Ghezzi; Massimo Zeviani

BackgroundWe studied a family including two half-siblings, sharing the same mother, affected by slowly progressive, adult-onset neurological syndromes. In spite of the diversity of the clinical features, characterized by a mild movement disorder with cognitive impairment in the elder patient, and severe motor-neuron disease (MND) in her half-brother, the brain Magnetic Resonance Imaging (MRI) features were compatible with adult-onset Alexander’s disease (AOAD), suggesting different expression of the same, genetically determined, condition.MethodsSince mutations in the alpha isoform of glial fibrillary acidic protein, GFAP-α, the only cause so far known of AOAD, were excluded, we applied exome Next Generation Sequencing (NGS) to identify gene variants, which were then functionally validated by molecular characterization of recombinant and patient-derived cells.ResultsExome-NGS revealed a mutation in a previously neglected GFAP isoform, GFAP-ϵ, which disrupts the GFAP-associated filamentous cytoskeletal meshwork of astrocytoma cells. To shed light on the different clinical features in the two patients, we sought for variants in other genes. The male patient had a mutation, absent in his half-sister, in X-linked histone deacetylase 6, a candidate MND susceptibility gene.ConclusionsExome-NGS is an unbiased approach that not only helps identify new disease genes, but may also contribute to elucidate phenotypic expression.


JIMD Reports | 2015

Mitochondrial Complex III Deficiency Caused by TTC19 Defects: Report of a Novel Mutation and Review of Literature

Anna Ardissone; Tiziana Granata; Andrea Legati; Daria Diodato; Laura Melchionda; Eleonora Lamantea; Barbara Garavaglia; Daniele Ghezzi; Isabella Moroni

We report about a patient with infantile-onset neurodegenerative disease associated with isolated mitochondrial respiratory chain complex III (cIII) deficiency. The boy, now 13 years old, presented with language regression and ataxia at 4 years of age and then showed a progressive course resulting in the loss of autonomous gait and speaking during the following 2 years. Brain MRI disclosed bilateral striatal necrosis. Sequencing of a panel containing nuclear genes associated with cIII deficiency revealed a previously undescribed homozygous rearrangement (c.782_786delinsGAAAAG) in TTC19 gene, which results in a frameshift with premature termination (p.Glu261Glyfs(*)8). TTC19 protein was absent in patients fibroblasts. TTC19 encodes tetratricopeptide 19, a putative assembly factor for cIII. To date TTC19 mutations have been reported only in few cases, invariably associated with cIII deficiency, but presenting heterogeneous clinical phenotypes. We reviewed the genetic, biochemical, clinical and neuroradiological features of TTC19 mutant patients described to date.


Frontiers in Genetics | 2014

A novel mutation in TTC19 associated with isolated complex III deficiency, cerebellar hypoplasia, and bilateral basal ganglia lesions

Laura Melchionda; Nadirah Damseh; Bassam Y. Abu Libdeh; Alessia Nasca; Orly Elpeleg; Alice Zanolini; Daniele Ghezzi

Isolated complex III (cIII) deficiency is a rare biochemical finding in mitochondrial disorders, mainly associated with mutations in mitochondrial DNA MTCYB gene, encoding cytochrome b, or in assembly factor genes (BCS1L, TTC19, UQCC2, and LYRM7), whereas mutations in nuclear genes encoding cIII structural subunits are extremely infrequent. We report here a patient, a 9 year old female born from first cousin related parents, with normal development till 18 months when she showed unsteady gait with frequent falling down, cognitive, and speech worsening. Her course deteriorated progressively. Brain MRI showed cerebellar vermis hypoplasia and bilateral lentiform nucleus high signal lesions. Now she is bed ridden with tetraparesis and severely impaired cognitive and language functions. Biochemical analysis revealed isolated cIII deficiency in muscle, and impaired respiration in fibroblasts. We identified a novel homozygous rearrangement in TTC19 (c.213_229dup), resulting in frameshift with creation of a premature termination codon (p.Gln77Argfs*30). Western blot analysis demonstrated the absence of TTC19 protein in patient’s fibroblasts, while Blue-Native Gel Electrophoresis analysis revealed the presence of cIII-specific assembly intermediates. Mutations in TTC19 have been rarely associated with mitochondrial disease to date, being described in about ten patients with heterogeneous clinical presentations, ranging from early onset encephalomyopathy to adult forms with cerebellar ataxia. Contrariwise, the biochemical defect was a common hallmark in TTC19 mutant patients, confirming the importance of TTC19 in cIII assembly/stability. Therefore, we suggest extending the TTC19 mutational screening to all patients with cIII deficiency, independently from their phenotypes.

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Daniele Ghezzi

Carlo Besta Neurological Institute

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Massimo Zeviani

MRC Mitochondrial Biology Unit

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Eleonora Lamantea

Carlo Besta Neurological Institute

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Daria Diodato

Boston Children's Hospital

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Alessia Nasca

Carlo Besta Neurological Institute

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