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Mastrangelo M, Greco C, Tolve M, Bartolini E, Russo A, Nicita F, Pruna D, Galli J, Favaro J, Terrone G, De Felice C, Pisani F. Epilepsy phenotypes across the different age-ranges in IQSEC2-related encephalopathy: An Italian multicentre retrospective cohort study. Seizure 2024; 119:119-127. [PMID: 38851096 DOI: 10.1016/j.seizure.2024.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2024] [Revised: 05/29/2024] [Accepted: 06/03/2024] [Indexed: 06/10/2024] Open
Abstract
BACKGROUND Epilepsy is a hallmark of IQSEC2-related encephalopathy within a phenotypic variability ranging between early onset epileptic and developmental encephalopathy and X-linked intellectual disability with epilepsy. PATIENTS AND METHODS Data including demographic aspects, gene variants, seizure semiology and timing, EEG features, neuroimaging and response to therapy were retrospectively collected in patients with IQSEC2-related epilepsy referring to 8 Italian tertiary centres. RESULTS The reported cohort included 11 patients (8 males and 3 females). Mean age at the onset of epilepsy was 3.90±2.80 years. No cases were reported in the first year of life. No specific epileptic syndromes were recognized. Predominant seizure-types in the age range 12-36 months included focal onset tonic seizures with impaired awareness, myoclonic seizures, and late onset spasms. Generalized motor seizures were predominant in patients between 3 and 6 years and between 12 and 18 years while focal motor seizures with impaired awareness were the most represented types between 6 and 12 years. No patients experienced status epilepticus. EEG patterns included a delayed maturation of EEG organization, irregular focal or diffuse slow activity, multifocal or diffuse epileptiform abnormalities. No structural epileptogenic lesions were detected at MRI. Valproate, lamotrigine, clobazam, topiramate and levetiracetam were the most used antiseizure medication. Complete seizure freedom was achieved only in 2 patients. CONCLUSIONS Onset of epilepsy after the first year of age, predominance of focal seizures with impaired awareness and generalized motor seizures, no pathognomonic underlying epileptic syndrome and infrequent occurrence of status epilepticus emerged as the main features of IQSEC2-related epilepsy phenotype.
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Affiliation(s)
- Mario Mastrangelo
- Woman/Child Health and Urological Sciences Department, Sapienza University of Rome, Rome, Italy; Unit of Child Neurology and Psychiatry, Department of Neuroscience/Mental Health-Azienda Ospedaliero Universitaria Policlinico Umberto, Rome, Italy.
| | - Carlo Greco
- Department of Human Neuroscience-Sapienza, University of Rome, Rome, Italy
| | - Manuela Tolve
- Unit of Clinical Pathology, Azienda Ospedalieo Universitaria Policilinico Umberto I, Rome, Italy
| | - Emanuele Bartolini
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, Pisa, Italy
| | - Angelo Russo
- Istituto delle Scienze Neurologiche di Bologna, UOC Neuropsichiatria dell'età Pediatrica, IRCCS, Bologna, Italy
| | - Francesco Nicita
- Unit of Neuromuscolar and Neurodegenerative Disorders, IRCCS Bambino Gesù Children Hospital, Rome, Italy
| | - Dario Pruna
- Child Neurology and Epilepsy Unit Pediatric Department ARNAS Brotzu Cagliari, Italy
| | - Jessica Galli
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, Italy; Unit of Child Neurology and Psychiatry, ASST Spedali Civili of Brescia, Brescia, Italy
| | - Jacopo Favaro
- Pediatric Neurology and Neurophysiology Unit, Department of Women's and Children Health, University of Padua, Padua 35128, Italy
| | - Gaetano Terrone
- Child Neuropsychiatry Unit, Department of Translational Medical Sciences, University of Naples Federico II, Naples, Italy
| | - Claudio De Felice
- Pediatrics Unit, University Hospital Azienda Ospedaliera Universitaria Senese, Siena, Italy
| | - Francesco Pisani
- Unit of Child Neurology and Psychiatry, Department of Neuroscience/Mental Health-Azienda Ospedaliero Universitaria Policlinico Umberto, Rome, Italy; Department of Human Neuroscience-Sapienza, University of Rome, Rome, Italy
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Nakashima M, Shiroshima T, Fukaya M, Sugawara T, Sakagami H, Yamazawa K. C-terminal truncations in IQSEC2: implications for synaptic localization, guanine nucleotide exchange factor activity, and neurological manifestations. J Hum Genet 2024; 69:119-123. [PMID: 38200111 DOI: 10.1038/s10038-023-01210-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 11/29/2023] [Accepted: 11/30/2023] [Indexed: 01/12/2024]
Abstract
IQSEC2 gene on chromosome Xq11.22 encodes a member of guanine nucleotide exchange factor (GEF) protein that is implicated in the activation of ADP-ribosylation factors (Arfs) at the postsynaptic density (PSD), and plays a crucial role in synaptic transmission and dendritic spine formation. Alterations in IQSEC2 have been linked to X-linked intellectual developmental disorders including epilepsy and behavioral abnormalities. Of interest, truncating variants at the C-terminus of IQSEC2 can cause severe phenotypes, akin to truncating variants located in other regions. Here, we present a 5-year-old boy with severe intellectual disability and progressive epilepsy. The individual carried a nonsense variant p.Q1227* in the last exon of the IQSEC2 gene that was supposed to escape nonsense-mediated mRNA decay, thereby leading to a translation of C-terminus truncated IQSEC2 protein with residual activity. The functional analyses showed that the GEF activity of IQSEC2 Q1227* was compromised, and that the IQSEC2 Q1227* lacked preferential synaptic localization due to the absence of functional domains for binding to scaffolding proteins in the PSD. The impaired GEF activity and disrupted synaptic localization of the mutant IQSEC2 protein could impact dendritic and spine development in neurons, potentially explaining the patient's severe neurological manifestations. Our findings indicate that C-terminal truncations in IQSEC2, previously not well-characterized, may have significant pathogenic implications.
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Affiliation(s)
- Moeko Nakashima
- Department of Medical Genetics, NHO Tokyo Medical Center, Tokyo, 152-8902, Japan
| | - Tomoko Shiroshima
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, 252-0374, Japan
| | - Masahiro Fukaya
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, 252-0374, Japan
| | - Takeyuki Sugawara
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, 252-0374, Japan
| | - Hiroyuki Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, 252-0374, Japan.
| | - Kazuki Yamazawa
- Department of Medical Genetics, NHO Tokyo Medical Center, Tokyo, 152-8902, Japan.
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3
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Zhao X, He Z, Li Y, Yang X, Li B. Atypical absence seizures and gene variants: A gene-based review of etiology, electro-clinical features, and associated epilepsy syndrome. Epilepsy Behav 2024; 151:109636. [PMID: 38232560 DOI: 10.1016/j.yebeh.2024.109636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Revised: 01/01/2024] [Accepted: 01/05/2024] [Indexed: 01/19/2024]
Abstract
Atypical absence seizures are generalized non-convulsive seizures that often occur in children with cognitive impairment. They are common in refractory epilepsy and have been recognized as one of the hallmarks of developmental epileptic encephalopathies. Notably, pathogenic variants associated with AAS, such as GABRG2, GABRG3, SLC6A1, CACNB4, SCN8A, and SYNGAP1, are also linked to developmental epileptic encephalopathies. Atypical absences differ from typical absences in that they are frequently drug-resistant and the prognosis is dependent on the etiology or related epileptic syndromes. To improve clinicians' understanding of atypical absences and provide novel perspectives for clinical treatment, we have reviewed the electro-clinical characteristics, etiologies, treatment, and prognosis of atypical absences, with a focus on the etiology of advancements in gene variants, shedding light on potential avenues for improved clinical management.
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Affiliation(s)
| | - Zimeng He
- Shandong University, Jinan, Shandong, China
| | - Yumei Li
- Shandong University, Jinan, Shandong, China
| | - Xiaofan Yang
- Shandong University, Jinan, Shandong, China; Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, Shandong, China.
| | - Baomin Li
- Shandong University, Jinan, Shandong, China; Department of Pediatrics, Qilu Hospital of Shandong University, Jinan, Shandong, China.
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4
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Bai G, Li H, Qin P, Guo Y, Yang W, Lian Y, Ye F, Chen J, Wu M, Huang R, Li J, Lu Y, Zhang M. Ca2+-induced release of IQSEC2/BRAG1 autoinhibition under physiological and pathological conditions. J Cell Biol 2023; 222:e202307117. [PMID: 37787765 PMCID: PMC10548395 DOI: 10.1083/jcb.202307117] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 08/31/2023] [Accepted: 09/14/2023] [Indexed: 10/04/2023] Open
Abstract
IQSEC2 (aka BRAG1) is a guanine nucleotide exchange factor (GEF) highly enriched in synapses. As a top neurodevelopmental disorder risk gene, numerous mutations are identified in Iqsec2 in patients with intellectual disabilities accompanied by other developmental, neurological, and psychiatric symptoms, though with poorly understood underlying molecular mechanisms. The atomic structures of IQSECs, together with biochemical analysis, presented in this study reveal an autoinhibition and Ca2+-dependent allosteric activation mechanism for all IQSECs and rationalize how each identified Iqsec2 mutation can alter the structure and function of the enzyme. Transgenic mice modeling two pathogenic variants of Iqsec2 (R359C and Q801P), with one activating and the other inhibiting the GEF activity of the enzyme, recapitulate distinct clinical phenotypes in patients. Our study demonstrates that different mutations on one gene such as Iqsec2 can have distinct neurological phenotypes and accordingly will require different therapeutic strategies.
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Affiliation(s)
- Guanhua Bai
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Hao Li
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Pengwei Qin
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Yiqing Guo
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Wanfa Yang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Yinmiao Lian
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Fei Ye
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Jianxin Chen
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | - Meiling Wu
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Ruifeng Huang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Jinsong Li
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | - Youming Lu
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Mingjie Zhang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
- Greater Bay Biomedical Innocenter, Shenzhen Bay Laboratory, Shenzhen, China
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5
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Brown JC, Hell JW, Gerges NZ. BRAG about (s)lots. J Cell Biol 2023; 222:e202310023. [PMID: 37938213 PMCID: PMC10631466 DOI: 10.1083/jcb.202310023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2023] Open
Abstract
Mutations in IQSEC2/BRAG1 cause intellectual dysfunction by impairing ARF-GEF activity and long-term depression. In this issue, Bai et al. (https://doi.org/10.1083/jcb.202307117) discover how constitutive ARF-GEF activity is regulated by a closed conformation which opens in the presence of Ca2+. Two known pathogenic mutations cause "leaky" autoinhibition with reduced synaptic dynamic range and impaired cognitive performance.
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Affiliation(s)
- Joshua C. Brown
- Division of Depression and Anxiety Disorders, Brain Stimulation Mechanisms Laboratory, McLean Hospital, Belmont, MA, USA
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Johannes W. Hell
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, USA
| | - Nashaat Z. Gerges
- Biopharmaceutical Sciences Department, School of Pharmacy, Medical College of Wisconsin, Milwaukee, WI, USA
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Zaravinos A. Special Issue "Latest Review Papers in Molecular Genetics and Genomics 2023". Int J Mol Sci 2023; 24:14171. [PMID: 37762474 PMCID: PMC10532209 DOI: 10.3390/ijms241814171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Accepted: 09/13/2023] [Indexed: 09/29/2023] Open
Abstract
In the rapidly evolving landscape of molecular genetics and genomics, this Special Issue brings together a collection of insightful review articles that delve into the forefront of scientific exploration [...].
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Affiliation(s)
- Apostolos Zaravinos
- Department of Life Sciences, School of Sciences, European University Cyprus, 2404 Nicosia, Cyprus;
- Cancer Genetics, Genomics and Systems Biology Laboratory, Basic and Translational Cancer Research Center (BTCRC), 2404 Nicosia, Cyprus
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7
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Leoncini S, Boasiako L, Lopergolo D, Altamura M, Fazzi C, Canitano R, Grosso S, Meloni I, Baldassarri M, Croci S, Renieri A, Mastrangelo M, De Felice C. Natural Course of IQSEC2-Related Encephalopathy: An Italian National Structured Survey. CHILDREN (BASEL, SWITZERLAND) 2023; 10:1442. [PMID: 37761403 PMCID: PMC10528631 DOI: 10.3390/children10091442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 08/16/2023] [Accepted: 08/22/2023] [Indexed: 09/29/2023]
Abstract
Pathogenic loss-of-function variants in the IQ motif and SEC7 domain containing protein 2 (IQSEC2) gene cause intellectual disability with Rett syndrome (RTT)-like features. The aim of this study was to obtain systematic information on the natural history and extra-central nervous system (CNS) manifestations for the Italian IQSEC2 population (>90%) by using structured family interviews and semi-quantitative questionnaires. IQSEC2 encephalopathy prevalence estimate was 7.0 to 7.9 × 10-7. Criteria for typical RTT were met in 42.1% of the cases, although psychomotor regression was occasionally evidenced. Genetic diagnosis was occasionally achieved in infancy despite a clinical onset before the first 24 months of life. High severity in both the CNS and extra-CNS manifestations for the IQSEC2 patients was documented and related to a consistently adverse quality of life. Neurodevelopmental delay was diagnosed before the onset of epilepsy by 1.8 to 2.4 years. An earlier age at menarche in IQSEC2 female patients was reported. Sleep disturbance was highly prevalent (60 to 77.8%), with mandatory co-sleeping behavior (50% of the female patients) being related to de novo variant origin, younger age, taller height with underweight, better social interaction, and lower life quality impact for the family and friends area. In conclusion, the IQSEC2 encephalopathy is a rare and likely underdiagnosed developmental encephalopathy leading to an adverse life quality impact.
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Affiliation(s)
- Silvia Leoncini
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Lidia Boasiako
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Diego Lopergolo
- Department of Medicine, Surgery and Neurosciences, University of Siena, 53100 Siena, Italy;
- UOC Neurologia e Malattie Neurometaboliche, Azienda Ospedaliero Universitaria Senese, Policlinico Le Scotte, 53100 Siena, Italy
- IRCCS Stella Maris Foundation, Molecular Medicine for Neurodegenerative and Neuromuscular Diseases Unit, 56018 Pisa, Italy
| | - Maria Altamura
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Caterina Fazzi
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Roberto Canitano
- Child Neuropsychiatry Unit, Department of Mental Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy;
| | - Salvatore Grosso
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy;
- Pediatric Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Ilaria Meloni
- Medical Genetics, University of Siena, 53100 Siena, Italy; (I.M.); (M.B.); (S.C.); (A.R.)
- Med Biotech Hub and Competence Center, Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy
| | - Margherita Baldassarri
- Medical Genetics, University of Siena, 53100 Siena, Italy; (I.M.); (M.B.); (S.C.); (A.R.)
- Med Biotech Hub and Competence Center, Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy
- Genetica Medica, Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Susanna Croci
- Medical Genetics, University of Siena, 53100 Siena, Italy; (I.M.); (M.B.); (S.C.); (A.R.)
- Med Biotech Hub and Competence Center, Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy
| | - Alessandra Renieri
- Medical Genetics, University of Siena, 53100 Siena, Italy; (I.M.); (M.B.); (S.C.); (A.R.)
- Med Biotech Hub and Competence Center, Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy
- Genetica Medica, Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Mario Mastrangelo
- Maternal Infantile and Urological Sciences Department, Sapienza University of Rome, 00185 Rome, Italy;
- Child Neurology and Psychiatry Unit, Department of Neurosciences and Mental Health, Azienda Ospedaliero-Universitaria Policlinico Umberto I, 00161 Rome, Italy
| | - Claudio De Felice
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
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