Publications by authors named "Davide Mei"

82 Publications

Clinical and molecular delineation of PUS3-associated neurodevelopmental disorders.

Clin Genet 2021 Nov 31;100(5):628-633. Epub 2021 Aug 31.

Kennedy Center, Department of Clinical Genetics, Copenhagen University Hospital, Copenhagen, Denmark.

Biallelic variants in PUS3 have recently been recognized as a rare cause of neurodevelopmental disorders. Pseudouridine synthase-3 encoded by PUS3 is an enzyme important for modification of various RNAs, including transfer RNA (tRNA). Here we present the clinical and genetic features of 21 individuals with biallelic PUS3 variants: seven new and 14 previously reported individuals, where clinical features of two were updated. The clinical and genetic information were collected through collaborations or by literature search. All individuals were characterized by the local clinicians and the gene variants were identified by next generation sequencing (NGS) based methodologies. The clinical picture was dominated by global developmental delay, epilepsy, hypotonia and microcephaly. Gray sclera, which has previously been suggested to be a characteristic feature of PUS3-associated phenotypes, was reported in only seven individuals. The patients had some dysmorphic facial features, but a recognizable gestalt was not observed. In conclusion, homozygous and compound heterozygous PUS3 variants lead to a rare neurodevelopmental disorder. Further functional studies are necessary to understand involvement of PUS3 and tRNA biogenesis in normal and abnormal brain development.
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http://dx.doi.org/10.1111/cge.14051DOI Listing
November 2021

CDKL5 deficiency disorder in males: Five new variants and review of the literature.

Eur J Paediatr Neurol 2021 Jul 30;33:9-20. Epub 2021 Apr 30.

Paediatric Neurology Unit V. Buzzi Children's Hospital Milan, Italy.

The X-linked Cyclin-Dependent Kinase-Like 5 (CDKL5) gene encodes a serine-threonine kinase highly expressed in the developing brain. Loss of function of CDKL5 is pointed out to underlie the CDKL5 Deficiency Disorder (CDD), an X-linked dominant disease characterized by early-onset epileptic encephalopathy and developmental delay, usually affecting females more than males. To the best to our knowledge, only 45 males with CDD have been reported so far. Type and position of CDKL5 variants with different impact on the protein are reported to influence the clinical presentation. X-chromosome inactivation occurring in females and post-zygotic mosaicism in males are also believed to contribute to this variability. Based on these issues, genotype-phenotype correlations are still challenging. Here, we describe clinical features of five additional affected males with unreported CDKL5 variants, expanding the molecular spectrum of the disorder. We also reviewed the clinical profile of the previously reported 45 males with molecularly confirmed CDD. Severe developmental delay, cortical visual impairment, and early-onset refractory epilepsy characterize the CDD picture in males. By assessing the molecular spectrum, we confirm that germ-line truncating CDKL5 variants, equally distributed across the coding sequence, are the most recurrent mutations in CDD, and cause the worsen phenotype. While recurrence and relevance of missense substitutions within C-terminal remain still debated, disease-causing missense changes affecting the N-terminal catalytic domain correlate to a severe clinical phenotype. Finally, our data provide evidence that post-zygotic CDKL5 mosaicism may result in milder phenotypes and, at least in a subset of subjects, in variable response to antiepileptic treatments.
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http://dx.doi.org/10.1016/j.ejpn.2021.04.007DOI Listing
July 2021

Remote monitoring and telemedicine in heart failure: implementation and benefits.

Curr Cardiol Rep 2021 05 7;23(6):55. Epub 2021 May 7.

Cardiology Division, Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Policlinico di Modena, Modena, Italy.

Purpose Of Review: Remote monitoring (RM) of cardiac implantable electronic devices (CIEDs) is recommended as part of the individualized multidisciplinary follow-up of heart failure (HF) patients. Aim of this article is to critically review recent findings on RM, highlighting potential benefits and barriers to its implementation.

Recent Findings: Device-based RM is useful in the early detection of CIEDs technical issues and cardiac arrhythmias. Moreover, RM allows the continuous monitoring of several patients' clinical parameters associated with impending HF decompensation, but there is still uncertainty regarding its effectiveness in reducing mortality and hospitalizations. Implementation of RM strategies, together with a proactive physicians' attitude towards clinical actions in response to RM data reception, will make RM a more valuable tool, potentially leading to better outcomes.
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http://dx.doi.org/10.1007/s11886-021-01487-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8102149PMC
May 2021

Real-life survey of pitfalls and successes of precision medicine in genetic epilepsies.

J Neurol Neurosurg Psychiatry 2021 Oct 26;92(10):1044-1052. Epub 2021 Apr 26.

Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, and Chalfont Centre for Epilepsy, Gerrard Cross, UK

Objective: The term 'precision medicine' describes a rational treatment strategy tailored to one person that reverses or modifies the disease pathophysiology. In epilepsy, single case and small cohort reports document nascent precision medicine strategies in specific genetic epilepsies. The aim of this multicentre observational study was to investigate the deeper complexity of precision medicine in epilepsy.

Methods: A systematic survey of patients with epilepsy with a molecular genetic diagnosis was conducted in six tertiary epilepsy centres including children and adults. A standardised questionnaire was used for data collection, including genetic findings and impact on clinical and therapeutic management.

Results: We included 293 patients with genetic epilepsies, 137 children and 156 adults, 162 females and 131 males. Treatment changes were undertaken because of the genetic findings in 94 patients (32%), including rational precision medicine treatment and/or a treatment change prompted by the genetic diagnosis, but not directly related to known pathophysiological mechanisms. There was a rational precision medicine treatment for 56 patients (19%), and this was tried in 33/56 (59%) and was successful (ie, >50% seizure reduction) in 10/33 (30%) patients. In 73/293 (25%) patients there was a treatment change prompted by the genetic diagnosis, but not directly related to known pathophysiological mechanisms, and this was successful in 24/73 (33%).

Significance: Our survey of clinical practice in specialised epilepsy centres shows high variability of clinical outcomes following the identification of a genetic cause for an epilepsy. Meaningful change in the treatment paradigm after genetic testing is not yet possible for many people with epilepsy. This systematic survey provides an overview of the current application of precision medicine in the epilepsies, and suggests the adoption of a more considered approach.
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http://dx.doi.org/10.1136/jnnp-2020-325932DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8458055PMC
October 2021

ATP1A2- and ATP1A3-associated early profound epileptic encephalopathy and polymicrogyria.

Brain 2021 06;144(5):1435-1450

Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children's Hospital, University of Florence, Florence, Italy.

Constitutional heterozygous mutations of ATP1A2 and ATP1A3, encoding for two distinct isoforms of the Na+/K+-ATPase (NKA) alpha-subunit, have been associated with familial hemiplegic migraine (ATP1A2), alternating hemiplegia of childhood (ATP1A2/A3), rapid-onset dystonia-parkinsonism, cerebellar ataxia-areflexia-progressive optic atrophy, and relapsing encephalopathy with cerebellar ataxia (all ATP1A3). A few reports have described single individuals with heterozygous mutations of ATP1A2/A3 associated with severe childhood epilepsies. Early lethal hydrops fetalis, arthrogryposis, microcephaly, and polymicrogyria have been associated with homozygous truncating mutations in ATP1A2. We investigated the genetic causes of developmental and epileptic encephalopathies variably associated with malformations of cortical development in a large cohort and identified 22 patients with de novo or inherited heterozygous ATP1A2/A3 mutations. We characterized clinical, neuroimaging and neuropathological findings, performed in silico and in vitro assays of the mutations' effects on the NKA-pump function, and studied genotype-phenotype correlations. Twenty-two patients harboured 19 distinct heterozygous mutations of ATP1A2 (six patients, five mutations) and ATP1A3 (16 patients, 14 mutations, including a mosaic individual). Polymicrogyria occurred in 10 (45%) patients, showing a mainly bilateral perisylvian pattern. Most patients manifested early, often neonatal, onset seizures with a multifocal or migrating pattern. A distinctive, 'profound' phenotype, featuring polymicrogyria or progressive brain atrophy and epilepsy, resulted in early lethality in seven patients (32%). In silico evaluation predicted all mutations to be detrimental. We tested 14 mutations in transfected COS-1 cells and demonstrated impaired NKA-pump activity, consistent with severe loss of function. Genotype-phenotype analysis suggested a link between the most severe phenotypes and lack of COS-1 cell survival, and also revealed a wide continuum of severity distributed across mutations that variably impair NKA-pump activity. We performed neuropathological analysis of the whole brain in two individuals with polymicrogyria respectively related to a heterozygous ATP1A3 mutation and a homozygous ATP1A2 mutation and found close similarities with findings suggesting a mainly neural pathogenesis, compounded by vascular and leptomeningeal abnormalities. Combining our report with other studies, we estimate that ∼5% of mutations in ATP1A2 and 12% in ATP1A3 can be associated with the severe and novel phenotypes that we describe here. Notably, a few of these mutations were associated with more than one phenotype. These findings assign novel, 'profound' and early lethal phenotypes of developmental and epileptic encephalopathies and polymicrogyria to the phenotypic spectrum associated with heterozygous ATP1A2/A3 mutations and indicate that severely impaired NKA pump function can disrupt brain morphogenesis.
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http://dx.doi.org/10.1093/brain/awab052DOI Listing
June 2021

Morquio B disease: From pathophysiology towards diagnosis.

Mol Genet Metab 2021 03 1;132(3):180-188. Epub 2021 Feb 1.

Molecular and Cell Biology Laboratory, Paediatric Neurology Unit and Laboratories, Neuroscience Department, A. Meyer Children's Hospital, Florence, Italy; Department of Neurosciences, Psychology, Pharmacology and Child Health, University of Florence, Italy. Electronic address:

Morquio B disease is an attenuated phenotype within the spectrum of beta galactosidase (GLB1) deficiencies. It is characterised by dysostosis multiplex, ligament laxity, mildly coarse facies and heart valve defects due to keratan sulphate accumulation, predominantly in the cartilage. Morquio B patients have normal neurological development, setting them apart from those with the more severe GM1 gangliosidosis. Morquio B disease, with an incidence of 1:250.000 to 1:1.000.000 live births, is very rare. Here we report the clinical-biochemical data of nine patients. High amounts of keratan sulfate were detected using LC-MS/MS in the patients' urinary samples, while electrophoresis, the standard procedure of qualitative glycosaminoglycans analysis, failed to identify this metabolite in any of the patients' samples. We performed molecular analyses at gene, gene expression and protein expression levels, for both isoforms of the GLB1 gene, lysosomal GLB1, and the cell-surface expressed Elastin Binding Protein. We characterised three novel GLB1 mutations [c.75 + 2 T > G, c.575A > G (p.Tyr192Cys) and c.2030 T > G (p.Val677Gly)] identified in three heterozygous patients. We also set up a copy number variation assay by quantitative PCR to evaluate the presence of deletions/ insertions in the GLB1 gene. We propose a diagnostic plan, setting out the specific clinical- biochemical and molecular features of Morquio B, in order to avoid misdiagnoses and improve patients' management.
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http://dx.doi.org/10.1016/j.ymgme.2021.01.008DOI Listing
March 2021

Multicenter prospective longitudinal study in 34 patients with Dravet syndrome: Neuropsychological development in the first six years of life.

Brain Dev 2021 Mar 18;43(3):419-430. Epub 2021 Jan 18.

Università Cattolica del Sacro Cuore, Rome, Italy.

The objective of this study was to identify developmental trajectories of developmental/behavioral phenotypes and possibly their relationship to epilepsy and genotype by analyzing developmental and behavioral features collected prospectively and longitudinally in a cohort of patients with Dravet syndrome (DS). Thirty-four patients from seven Italian tertiary pediatric neurology centers were enrolled in the study. All patients were examined for the SCN1A gene mutation and prospectively assessed from the first years of life with repeated full clinical observations including neurological and developmental examinations. Subjects were found to follow three neurodevelopmental trajectories. In the first group (16 patients), an initial and usually mild decline was observed between the second and the third year of life, specifically concerning visuomotor abilities, later progressing towards global involvement of all abilities. The second group (12 patients) showed an earlier onset of global developmental impairment, progressing towards a generally worse outcome. The third group of only two patients ended up with a normal neurodevelopmental quotient, but with behavioral and linguistic problems. The remaining four patients were not classifiable due to a lack of critical assessments just before developmental decline. The neurodevelopmental trajectories described in this study suggest a differential contribution of neurobiological and genetic factors. The profile of the first group, which included the largest fraction of patients, suggests that in the initial phase of the disease, visuomotor defects might play a major role in determining developmental decline. Early diagnosis of milder cases with initial visuomotor impairment may therefore provide new tools for a more accurate habilitation strategy.
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http://dx.doi.org/10.1016/j.braindev.2020.10.004DOI Listing
March 2021

Efficacy and safety of Fenfluramine hydrochloride for the treatment of seizures in Dravet syndrome: A real-world study.

Epilepsia 2020 11 18;61(11):2405-2414. Epub 2020 Sep 18.

Child Neuropsychiatry, Department of Surgical Sciences, Dentistry, Gynecology, and Pediatrics, University of Verona, Verona, Italy.

Objective: Dravet syndrome (DS) is a drug-resistant, infantile onset epilepsy syndrome with multiple seizure types and developmental delay. In recently published randomized controlled trials, fenfluramine (FFA) proved to be safe and effective in DS.

Methods: DS patients were treated with FFA in the Zogenix Early Access Program at four Italian pediatric epilepsy centers. FFA was administered as add-on, twice daily at an initial dose of 0.2 mg/kg/d up to 0.7 mg/kg/d. Seizures were recorded in a diary. Adverse events and cardiac safety (with Doppler echocardiography) were investigated every 3 to 6 months.

Results: Fifty-two patients were enrolled, with a median age of 8.6 years (interquartile range [IQR] = 4.1-13.9). Forty-five (86.5%) patients completed the efficacy analysis. The median follow-up was 9.0 months (IQR = 3.2-9.5). At last follow-up visit, there was a 77.4% median reduction in convulsive seizures. Thirty-two patients (71.1%) had a ≥50% reduction of convulsive seizures, 24 (53.3%) had a ≥75% reduction, and five (11.1%) were seizure-free. The most common adverse event was decreased appetite (n = 7, 13.4%). No echocardiographic signs of cardiac valvulopathy or pulmonary hypertension were observed. There was no correlation between type of genetic variants and response to FFA.

Significance: In this real-world study, FFA provided a clinically meaningful reduction in convulsive seizure frequency in the majority of patients with DS and was well tolerated.
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http://dx.doi.org/10.1111/epi.16690DOI Listing
November 2020

Dravet Syndrome: A Case Series.

Indian J Pediatr 2021 01 26;88(1):82. Epub 2020 Jun 26.

Department of Pediatrics, The Royal Hospital, Ministry of Health, Muscat, Oman.

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http://dx.doi.org/10.1007/s12098-020-03383-zDOI Listing
January 2021

Quantitative MRI-Based Analysis Identifies Developmental Limbic Abnormalities in PCDH19 Encephalopathy.

Cereb Cortex 2020 10;30(11):6039-6050

Child Neurology Unit and Laboratories, Neuroscience Department, Children's Hospital A. Meyer - University of Florence, 50139 Florence, Italy.

Protocadherin-19 (PCDH19) is a calcium dependent cell-adhesion molecule involved in neuronal circuit formation with prevalent expression in the limbic structures. PCDH19-gene mutations cause a developmental encephalopathy with prominent infantile onset focal seizures, variably associated with intellectual disability and autistic features. Diagnostic neuroimaging is usually unrevealing. We used quantitative MRI to investigate the cortex and white matter in a group of 20 PCDH19-mutated patients. By a statistical comparison between quantitative features in PCDH19 brains and in a group of age and sex matched controls, we found that patients exhibited bilateral reductions of local gyrification index (lGI) in limbic cortical areas, including the parahippocampal and entorhinal cortex and the fusiform and lingual gyri, and altered diffusivity features in the underlying white matter. In patients with an earlier onset of seizures, worse psychiatric manifestations and cognitive impairment, reductions of lGI and diffusivity abnormalities in the limbic areas were more pronounced. Developmental abnormalities involving the limbic structures likely represent a measurable anatomic counterpart of the reduced contribution of the PCDH19 protein to local cortical folding and white matter organization and are functionally reflected in the phenotypic features involving cognitive and communicative skills as well as local epileptogenesis.
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http://dx.doi.org/10.1093/cercor/bhaa177DOI Listing
October 2020

Shedding light on dark genes: enhanced targeted resequencing by optimizing the combination of enrichment technology and DNA fragment length.

Sci Rep 2020 06 10;10(1):9424. Epub 2020 Jun 10.

Department of Biotechnology, University of Verona, Strada Le Grazie 15, 37134, Verona, Italy.

The exome contains many obscure regions difficult to explore with current short-read sequencing methods. Repetitious genomic regions prevent the unique alignment of reads, which is essential for the identification of clinically-relevant genetic variants. Long-read technologies attempt to resolve multiple-mapping regions, but they still produce many sequencing errors. Thus, a new approach is required to enlighten the obscure regions of the genome and rescue variants that would be otherwise neglected. This work aims to improve the alignment of multiple-mapping reads through the extension of the standard DNA fragment size. As Illumina can sequence fragments up to 550 bp, we tested different DNA fragment lengths using four major commercial WES platforms and found that longer DNA fragments achieved a higher genotypability. This metric, which indicates base calling calculated by combining depth of coverage with the confidence of read alignment, increased from hundreds to thousands of genes, including several associated with clinical phenotypes. While depth of coverage has been considered crucial for the assessment of WES performance, we demonstrated that genotypability has a greater impact in revealing obscure regions, with ~1% increase in variant calling in respect to shorter DNA fragments. Results confirmed that this approach enlightened many regions previously not explored.
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http://dx.doi.org/10.1038/s41598-020-66331-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7287100PMC
June 2020

Phenotypic and genetic spectrum of epilepsy with myoclonic atonic seizures.

Epilepsia 2020 05 29;61(5):995-1007. Epub 2020 May 29.

Meyer Children's Hospital, University of Florence, Florence, Italy.

Objective: We aimed to describe the extent of neurodevelopmental impairments and identify the genetic etiologies in a large cohort of patients with epilepsy with myoclonic atonic seizures (MAE).

Methods: We deeply phenotyped MAE patients for epilepsy features, intellectual disability, autism spectrum disorder, and attention-deficit/hyperactivity disorder using standardized neuropsychological instruments. We performed exome analysis (whole exome sequencing) filtered on epilepsy and neuropsychiatric gene sets to identify genetic etiologies.

Results: We analyzed 101 patients with MAE (70% male). The median age of seizure onset was 34 months (range = 6-72 months). The main seizure types were myoclonic atonic or atonic in 100%, generalized tonic-clonic in 72%, myoclonic in 69%, absence in 60%, and tonic seizures in 19% of patients. We observed intellectual disability in 62% of patients, with extremely low adaptive behavioral scores in 69%. In addition, 24% exhibited symptoms of autism and 37% exhibited attention-deficit/hyperactivity symptoms. We discovered pathogenic variants in 12 (14%) of 85 patients, including five previously published patients. These were pathogenic genetic variants in SYNGAP1 (n = 3), KIAA2022 (n = 2), and SLC6A1 (n = 2), as well as KCNA2, SCN2A, STX1B, KCNB1, and MECP2 (n = 1 each). We also identified three new candidate genes, ASH1L, CHD4, and SMARCA2 in one patient each.

Significance: MAE is associated with significant neurodevelopmental impairment. MAE is genetically heterogeneous, and we identified a pathogenic genetic etiology in 14% of this cohort by exome analysis. These findings suggest that MAE is a manifestation of several etiologies rather than a discrete syndromic entity.
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http://dx.doi.org/10.1111/epi.16508DOI Listing
May 2020

Early infantile epileptic-dyskinetic encephalopathy due to biallelic mutations.

Neurol Genet 2020 Feb 2;6(1):e387. Epub 2020 Jan 2.

Pediatric Neurology (A.V., T.P., S.C., E. Parrini, D.M., S.V., R.G.), Neurogenetics and Neurobiology Unit and Laboratories, Meyer Children's Hospital, University of Florence; Metabolic and Muscular Unit (E. Procopio), Meyer Children's Hospital, University of Florence; Department of Medical and Surgical Science (A.G.), University of Modena and Reggio Emilia; Pediatric Immunology (G.M., C.A.), Department of Health Sciences, Meyer Children's Hospital, University of Florence; and IRCCS Stella Maris (R.G.), Pisa, Italy.

Objective: To describe clinical, biochemical, and molecular genetic findings in a large inbred family in which 4 children with a severe early-onset epileptic-dyskinetic encephalopathy, with suppression burst EEG, harbored homozygous mutations of phosphatidylinositol glycan anchor biosynthesis, class P (), a member of the large glycosylphosphatidylinositol (GPI) anchor biosynthesis gene family.

Methods: We studied clinical features, EEG, brain MRI scans, whole-exome sequencing (WES), and measured the expression of a subset of GPI-anchored proteins (GPI-APs) in circulating granulocytes using flow cytometry.

Results: The 4 affected children exhibited a severe neurodevelopmental disorder featuring severe hypotonia with early dyskinesia progressing to quadriplegia, associated with infantile spasms, focal, tonic, and tonic-clonic seizures and a burst suppression EEG pattern. Two of the children died prematurely between age 2 and 12 years; the remaining 2 children are aged 2 years 7 months and 7 years 4 months. The homozygous c.384del variant of , present in the 4 patients, introduces a frame shift 6 codons before the expected stop signal and is predicted to result in the synthesis of a protein longer than the wild type, with impaired functionality. We demonstrated a reduced expression of the GPI-AP CD16 in the granulocytic membrane in affected individuals.

Conclusions: mutations are consistently associated with an epileptic-dyskinetic encephalopathy with the features of early infantile epileptic encephalopathy with profound disability and premature death. CD16 is a valuable marker to support a genetic diagnosis of inherited GPI deficiencies.
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http://dx.doi.org/10.1212/NXG.0000000000000387DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6984131PMC
February 2020

Dravet syndrome as part of the clinical and genetic spectrum of sodium channel epilepsies and encephalopathies.

Epilepsia 2019 12;60 Suppl 3:S2-S7

Pediatric Neurology, Neurogenetics, and Neurobiology Unit and Laboratories, Meyer Children's Hospital-University of Florence, Florence, Italy.

Dravet syndrome is the most studied form of genetic epilepsy. It has now been clarified that the clinical spectrum of the syndrome does not have firmly established boundaries. The core phenotype is characterized by intractable, mainly clonic, seizures precipitated by increased body temperature with onset in the first year of life and subsequent appearance of multiple seizures types still precipitated by, but not confined to, hyperthermia. Cognitive impairment is invariably present when the full syndrome is manifested. This complex of symptoms is related to mutations in the SCN1A gene, which are often de novo and constitutional but can also be inherited from a parent with less severe clinical manifestations or be present as somatic mosaicism. Inheritance from less severely affected individuals, at times only having experienced a few febrile seizures, and differences in severity, even within the same family, with a subset of patients only showing fragments of the syndrome, testify to a remarkable phenotypic heterogeneity as far as severity, but less so clinical phenomenology, are concerned. This characteristic, together with underascertainment of SCN1A mutations due to human errors or technical limitations in uncovering alternative pathogenic molecular mechanisms, such as genomic rearrangements or poison exons, has contributed to making clinicians and geneticists suspicious that Dravet syndrome may be caused by more than one gene. This opinion has been further amplified by the description of other genetic disorders, such as PCDH19- or CHD2-related epilepsy, whose phenotypes have included fragments of the Dravet phenotypic spectrum, and by the suboptimal characterization of phenotypes associated with mutations in SCN1B, HCN1, KCN2A, GABRA1, GABRG2, and STXBP1. The SCN1A gene-Dravet syndrome association is in our opinion highly specific. However, because the syndrome spectrum is wide, fragments of it can at times also be manifested in other genetic epilepsy syndromes, thereby leading to overdiagnosis of Dravet syndrome beyond SCN1A. Dravet syndrome is in turn a severe SCN1A phenotype within a continuum of SCN1A-related clinical phenomenology.
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http://dx.doi.org/10.1111/epi.16054DOI Listing
December 2019

Infantile-Onset Syndromic Cerebellar Ataxia and CACNA1G Mutations.

Pediatr Neurol 2020 03 19;104:40-45. Epub 2019 Oct 19.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy.

Background: Congenital ataxias associated with cerebellar atrophy are clinically heterogeneous conditions with a variable age of onset and a diverse molecular basis. The hypothesis-free approach of genomic sequencing has led to the discovery of new genes implicated in these disorders and the identification of unexpected genotype-phenotype correlations. Although a recurrent heterozygous mutation (p.Arg1715His) in CACNA1G is known to cause adult-onset spinocerebellar ataxia 42 (SCA42*616795), gain-of-function mutations in this gene have recently been identified by whole exome sequencing (WES) in four children with cerebellar atrophy and ataxia, psychomotor delay, and other variable features.

Methods: We describe four children from unrelated families with cerebellar anomalies on magnetic resonance imaging (atrophy or hypoplasia of the cerebellar vermis), hypertonia, psychomotor and speech delay, severe intellectual disability, ophthalmologic features and peculiar dysmorphic traits. All patients underwent a trio-based WES analysis. Clinical records were used to characterize the clinical profile of this newly recognized disorder.

Results: Two previously reported de novo disease-causing mutations in CACNA1G (c.2881G>A, p.Ala961Thr and c.4591A>G, p.Met1531Val) were identified in these patients, providing further evidence of the specific impact of these variants. All four patients exhibit distinctive dysmorphic and ectodermal features which overlap those of the previously reported patients, allowing us to define the major features characterizing this homogeneous neurodevelopmental syndromic disorder associated with upregulated CACNA1G function.

Conclusion: Our findings confirm the specific association between a narrow spectrum of missense mutations in CACNA1G and a novel syndrome with infantile-onset cerebellar ataxiaand provide a dysmorphologic delineation of this novel neurodevelopmental trait.
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http://dx.doi.org/10.1016/j.pediatrneurol.2019.09.005DOI Listing
March 2020

Biallelic DMXL2 mutations impair autophagy and cause Ohtahara syndrome with progressive course.

Brain 2019 12;142(12):3876-3891

Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Children's Hospital A. Meyer-University of Florence, Florence, Italy.

Ohtahara syndrome, early infantile epileptic encephalopathy with a suppression burst EEG pattern, is an aetiologically heterogeneous condition starting in the first weeks or months of life with intractable seizures and profound developmental disability. Using whole exome sequencing, we identified biallelic DMXL2 mutations in three sibling pairs with Ohtahara syndrome, belonging to three unrelated families. Siblings in Family 1 were compound heterozygous for the c.5135C>T (p.Ala1712Val) missense substitution and the c.4478C>G (p.Ser1493*) nonsense substitution; in Family 2 were homozygous for the c.4478C>A (p.Ser1493*) nonsense substitution and in Family 3 were homozygous for the c.7518-1G>A (p.Trp2507Argfs*4) substitution. The severe developmental and epileptic encephalopathy manifested from the first day of life and was associated with deafness, mild peripheral polyneuropathy and dysmorphic features. Early brain MRI investigations in the first months of life revealed thin corpus callosum with brain hypomyelination in all. Follow-up MRI scans in three patients revealed progressive moderate brain shrinkage with leukoencephalopathy. Five patients died within the first 9 years of life and none achieved developmental, communicative or motor skills following birth. These clinical findings are consistent with a developmental brain disorder that begins in the prenatal brain, prevents neural connections from reaching the expected stages at birth, and follows a progressive course. DMXL2 is highly expressed in the brain and at synaptic terminals, regulates v-ATPase assembly and activity and participates in intracellular signalling pathways; however, its functional role is far from complete elucidation. Expression analysis in patient-derived skin fibroblasts demonstrated absence of the DMXL2 protein, revealing a loss of function phenotype. Patients' fibroblasts also exhibited an increased LysoTracker® signal associated with decreased endolysosomal markers and degradative processes. Defective endolysosomal homeostasis was accompanied by impaired autophagy, revealed by lower LC3II signal, accumulation of polyubiquitinated proteins, and autophagy receptor p62, with morphological alterations of the autolysosomal structures on electron microscopy. Altered lysosomal homeostasis and defective autophagy were recapitulated in Dmxl2-silenced mouse hippocampal neurons, which exhibited impaired neurite elongation and synaptic loss. Impaired lysosomal function and autophagy caused by biallelic DMXL2 mutations affect neuronal development and synapse formation and result in Ohtahara syndrome with profound developmental impairment and reduced life expectancy.
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http://dx.doi.org/10.1093/brain/awz326DOI Listing
December 2019

Intronic ATTTC repeat expansions in STARD7 in familial adult myoclonic epilepsy linked to chromosome 2.

Nat Commun 2019 10 29;10(1):4920. Epub 2019 Oct 29.

Department of Human Neurosciences, Sapienza University of Rome, Viale dell'Università, 30, 00185, Rome, Italy.

Familial Adult Myoclonic Epilepsy (FAME) is characterised by cortical myoclonic tremor usually from the second decade of life and overt myoclonic or generalised tonic-clonic seizures. Four independent loci have been implicated in FAME on chromosomes (chr) 2, 3, 5 and 8. Using whole genome sequencing and repeat primed PCR, we provide evidence that chr2-linked FAME (FAME2) is caused by an expansion of an ATTTC pentamer within the first intron of STARD7. The ATTTC expansions segregate in 158/158 individuals typically affected by FAME from 22 pedigrees including 16 previously reported families recruited worldwide. RNA sequencing from patient derived fibroblasts shows no accumulation of the AUUUU or AUUUC repeat sequences and STARD7 gene expression is not affected. These data, in combination with other genes bearing similar mutations that have been implicated in FAME, suggest ATTTC expansions may cause this disorder, irrespective of the genomic locus involved.
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http://dx.doi.org/10.1038/s41467-019-12671-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6820779PMC
October 2019

A novel developmental encephalopathy with epilepsy and hyperkinetic movement disorders associated with a deletion of the sodium channel gene cluster on chromosome 2q24.3.

Parkinsonism Relat Disord 2019 11 18;68:1-3. Epub 2019 Sep 18.

Division of Child Neurology and Infantile Psychiatry, Department of Neuroscience, Sapienza University of Rome, Italy. Electronic address:

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http://dx.doi.org/10.1016/j.parkreldis.2019.09.016DOI Listing
November 2019

Broadening phenotype of adenylosuccinate lyase deficiency: A novel clinical pattern resembling neuronal ceroid lipofuscinosis.

Mol Genet Metab Rep 2019 Dec 21;21:100502. Epub 2019 Aug 21.

Division of Child Neurology and Infantile Psychiatry, Department of Human Neurosciences, Sapienza University of Rome, Rome, Italy.

We describe a 7-year-old boy presenting with a developmental encephalopathy, severe epilepsy, retinopathy with salt and pepper fundus, and ultrastructural skin alterations resembling a neuronal ceroid lipofuscinosis. Whole exome-sequencing detected biallelic variants in the gene (c.65C > T [p.(Ala22Val)] and c.340 T > C [p.(Tyr114His)]). The increase of SAICAR and S-Ado in blood and urine was consistent with the pattern of adenylosuccinate lyase deficiency (OMIM 103050). An unusual increase of AICAR, that was due to a residual ADSL enzyme activity of about 28%, was also detected. Neither salt and pepper retinopathy nor ultrastructural skin alterations had been reported in ADSL deficiency before. Impaired purinergic signaling inside the retina is probably involved in visual failure. Ultrastructural alterations in fibroblasts suggest a possible damage of autophagic processes, whose role in the pathogenesis of neurological dysfunction deserves further study.
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http://dx.doi.org/10.1016/j.ymgmr.2019.100502DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6713842PMC
December 2019

Somatic double-hit in MTOR and RPS6 in hemimegalencephaly with intractable epilepsy.

Hum Mol Genet 2019 11;28(22):3755-3765

INMED, Aix-Marseille University, INSERM UMR1249, Marseille 13009, France.

Single germline or somatic activating mutations of mammalian target of rapamycin (mTOR) pathway genes are emerging as a major cause of type II focal cortical dysplasia (FCD), hemimegalencephaly (HME) and tuberous sclerosis complex (TSC). A double-hit mechanism, based on a primary germline mutation in one allele and a secondary somatic hit affecting the other allele of the same gene in a small number of cells, has been documented in some patients with TSC or FCD. In a patient with HME, severe intellectual disability, intractable seizures and hypochromic skin patches, we identified the ribosomal protein S6 (RPS6) p.R232H variant, present as somatic mosaicism at ~15.1% in dysplastic brain tissue and ~11% in blood, and the MTOR p.S2215F variant, detected as ~8.8% mosaicism in brain tissue, but not in blood. Overexpressing the two variants independently in animal models, we demonstrated that MTOR p.S2215F caused neuronal migration delay and cytomegaly, while RPS6 p.R232H prompted increased cell proliferation. Double mutants exhibited a more severe phenotype, with increased proliferation and migration defects at embryonic stage and, at postnatal stage, cytomegalic cells exhibiting eccentric nuclei and binucleation, which are typical features of balloon cells. These findings suggest a synergistic effect of the two variants. This study indicates that, in addition to single activating mutations and double-hit inactivating mutations in mTOR pathway genes, severe forms of cortical dysplasia can also result from activating mutations affecting different genes in this pathway. RPS6 is a potential novel disease-related gene.
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http://dx.doi.org/10.1093/hmg/ddz194DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6935386PMC
November 2019

What is the role of next generation sequencing in status epilepticus?

Epilepsy Behav 2019 12 9;101(Pt B):106373. Epub 2019 Jul 9.

Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Department of Neuroscience, A. Meyer Children's Hospital, University of Florence, viale Pieraccini 24, 50139 Florence, Italy.

Status epilepticus is a life-threatening medical condition which requires immediate diagnosis and treatment. In children, it may be a recurrent manifestation in the context of heterogeneous severe developmental genetic encephalopathies, as well as the first neurological manifestation. Mutations in several genes have been consistently associated with status epilepticus despite none of them can be considered as 'pure' Mendelian status epilepticus gene. Most genetic conditions featuring status epilepticus can be assigned to specific phenotypic subgroups, including cortical dysplasias, inborn errors of metabolism, mitochondrial diseases, or epileptic encephalopathies and childhood syndromes. Next generation sequencing (NGS) has increased the number of genes associated with, and improved the turnaround time for molecular diagnosis of, status epilepticus, allowing more timely and rationale management choices for specific conditions. Next generation sequencing might become part of the standard of care in the near future for a large subset of patients with status epilepticus, especially in early life. At present, trios whole exome sequencing, with a first analysis of point and copy number variants of an in silico panel containing 'status epilepticus' genes might represent best choice as it would allow a rapid screening. This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures".
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http://dx.doi.org/10.1016/j.yebeh.2019.06.017DOI Listing
December 2019

TBC1D24-TLDc-related epilepsy exercise-induced dystonia: rescue by antioxidants in a disease model.

Brain 2019 08;142(8):2319-2335

Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Children's Hospital A. Meyer-University of Florence, Florence, Italy.

Genetic mutations in TBC1D24 have been associated with multiple phenotypes, with epilepsy being the main clinical manifestation. The TBC1D24 protein consists of the unique association of a Tre2/Bub2/Cdc16 (TBC) domain and a TBC/lysin motif domain/catalytic (TLDc) domain. More than 50 missense and loss-of-function mutations have been described and are spread over the entire protein. Through whole genome/exome sequencing we identified compound heterozygous mutations, R360H and G501R, within the TLDc domain, in an index family with a Rolandic epilepsy exercise-induced dystonia phenotype (http://omim.org/entry/608105). A 20-year long clinical follow-up revealed that epilepsy was self-limited in all three affected patients, but exercise-induced dystonia persisted into adulthood in two. Furthermore, we identified three additional sporadic paediatric patients with a remarkably similar phenotype, two of whom had compound heterozygous mutations consisting of an in-frame deletion I81_K84 and an A500V mutation, and the third carried T182M and G511R missense mutations, overall revealing that all six patients harbour a missense mutation in the subdomain of TLDc between residues 500 and 511. We solved the crystal structure of the conserved Drosophila TLDc domain. This allowed us to predict destabilizing effects of the G501R and G511R mutations and, to a lesser degree, of R360H and potentially A500V. Next, we characterized the functional consequences of a strong and a weak TLDc mutation (TBC1D24G501R and TBC1D24R360H) using Drosophila, where TBC1D24/Skywalker regulates synaptic vesicle trafficking. In a Drosophila model neuronally expressing human TBC1D24, we demonstrated that the TBC1D24G501R TLDc mutation causes activity-induced locomotion and synaptic vesicle trafficking defects, while TBC1D24R360H is benign. The neuronal phenotypes of the TBC1D24G501R mutation are consistent with exacerbated oxidative stress sensitivity, which is rescued by treating TBC1D24G501R mutant animals with antioxidants N-acetylcysteine amide or α-tocopherol as indicated by restored synaptic vesicle trafficking levels and sustained behavioural activity. Our data thus show that mutations in the TLDc domain of TBC1D24 cause Rolandic-type focal motor epilepsy and exercise-induced dystonia. The humanized TBC1D24G501R fly model exhibits sustained activity and vesicle transport defects. We propose that the TBC1D24/Sky TLDc domain is a reactive oxygen species sensor mediating synaptic vesicle trafficking rates that, when dysfunctional, causes a movement disorder in patients and flies. The TLDc and TBC domain mutations' response to antioxidant treatment we observed in the animal model suggests a potential for combining antioxidant-based therapeutic approaches to TBC1D24-associated disorders with previously described lipid-altering strategies for TBC domain mutations.
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http://dx.doi.org/10.1093/brain/awz175DOI Listing
August 2019

Clinical spectrum of -related epileptic disorders.

Neurology 2019 03 8;92(11):e1238-e1249. Epub 2019 Feb 8.

From the University of Tübingen (S. Wolking, J.M., Y.G.W., H.L., J.S.), Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, Tübingen, Germany; Luxembourg Centre for Systems Biomedicine (P.M.), University of Luxembourg, Esch-sur-Alzette; Pediatric Neurology and Neurogenetics Unit and Laboratories (D.M., R.G., C.M.), Children's Hospital Anna Meyer, University of Florence, Italy; Danish Epilepsy Centre (R.S.M.), Dianalund; Institute for Regional Health Services (R.S.M.), University of Southern Denmark, Odense; Department of Clinical and Experimental Epilepsy (S.B.), UCL Institute of Neurology and Epilepsy Society, UK, London; Division of Neurology (K.L.H., I.H.), Children's Hospital of Philadelphia, PA; Department of Pediatric Neurology (C.D.A.), Centre de Compétences Maladies Rares, CHU Besançon; Service de Génétique (N.C.), Hospices Civils des Lyon, Bron; GENDEV Team (N.C.), Neurosciences Research Center of Lyon, Bron, France; Neuropediatric Clinic and Clinic for Neurorehabilitation (K.S.), Epilepsy Center for Children and Adolescents, Schoen Klinik Vogtareuth, Germany; Beaumont Hospital (P.W.-W.), Dublin, Ireland; Department of Pediatrics, Division of Medical Genetics, Institute of Human Genetics (B.A.M.), Departments of Neurology and Pediatrics (A.N.), and Departments of Neurology and Pediatrics, and Institute of Human Genetics (M.R.C.), University of California, San Francisco; Department of Neurology (W.V.P.), University Hospitals Leuven, Belgium; Department of Pediatrics (L.L.S.), Hvidovre Hospital, Denmark; King's College Hospital (S.O., E.H., S.G., D.K.P.), London; Evelina London Children's Hospital (S.O., E.H., S.G.), London, UK; Section of Genetics (K.B., M.S.S.), Department of Pediatrics, University of Colorado and Children's Hospital Colorado, Aurora; Clinique Bernoise Montana (T.D.), Crans-Montana, Switzerland; Department of Neuropediatrics (H.M.), University Medical Center Schleswig-Holstein, Christian-Albrechts University, Kiel, Germany; National Institute for Health Research Oxford Biomedical Research Centre, Wellcome Centre for Human Genetics (A.T.P., S.J.L.K., J.C.T.) and Department of Oncology (D.V.V.), University of Oxford, UK; Epilepsy Center (M.P.C.), Health Sciences Department, San Paolo Hospital, University of Milan; Child Neuropsychiatry (F.D.), Department of Surgical Sciences, Dentistry, Gynecology and Pediatrics, University of Verona, Italy; Departments of Neurology and Clinical Genomics (R.H.G.) and Health Sciences Research and Clinical Genomics (E.W.K., C.K.), Mayo Clinic, Rochester, MN; Ambry Genetics (Z.P.), Aliso Viejo, CA; Department of Clinical Neuroscience (S.T.), King's College London; New Medicines (M.A., D.M.), UCB Pharma, Slough, UK; Neuropediatric Clinic and Clinic for Neurorehabilitation (G.J.K.), Epilepsy Center for Children and Adolescents, Schoen Klinik Vogtareuth, Germany; Research Institute for Rehabilitation, Transition and Palliation (G.J.K.), PMU Salzburg, Austria; Department of Neurology (D.H.L.), University of California, San Francisco; Neurogenetics Group (S. Weckhuysen), Center for Molecular Neurology, VIB, Antwerp; Laboratory of Neurogenetics (S. Weckhuysen), Institute Born-Bunge, University of Antwerp; Department of Neurology (S. Weckhuysen), Antwerp University Hospital, Antwerp, Belgium; Department of Basic & Clinical Neuroscience, Institute of Psychiatry, Psychology & Neuroscience (D.K.P.), MRC Centre for Neurodevelopmental Disorders (D.K.P.), King's College London, UK; Evelina London Children's Hospital (D.K.P.), London, UK; Department of Neuropediatrics (I.H.), University Medical Center Schleswig-Holstein, Christian-Albrechts University, Kiel, Germany; Institute of Neuroscience (R.H.T.), Henry Wellcome Building, Newcastle University; Neurology Research Group (M.I.R.), Institute of Life Science, Swansea University Medical School, Swansea, UK; Service de Génétique (G.L.), Hospices Civils des Lyon, Bron; GENDEV Team (G.L.), Neurosciences Research Center of Lyon, Bron, France; NIHR University College London Hospitals Biomedical Research Centre (S.M.S.), UCL Institute of Neurology, London, UK; Cologne Center for Genomics (D.L.), University of Cologne, Germany; Stanley Center for Psychiatric Research (D.L.) and Program in Medical and Population Genetics (D.L.), Broad Institute of MIT and Harvard, Cambridge; Psychiatric and Neurodevelopmental Genetics Unit (D.L.), Massachusetts General Hospital and Harvard Medical School, Boston.

Objective: The aim of this study was to expand the spectrum of epilepsy syndromes related to , encoding the presynaptic protein syntaxin-1B, and establish genotype-phenotype correlations by identifying further disease-related variants.

Methods: We used next-generation sequencing in the framework of research projects and diagnostic testing. Clinical data and EEGs were reviewed, including already published cases. To estimate the pathogenicity of the variants, we used established and newly developed in silico prediction tools.

Results: We describe 17 new variants in , which are distributed across the whole gene. We discerned 4 different phenotypic groups across the newly identified and previously published patients (49 patients in 23 families): (1) 6 sporadic patients or families (31 affected individuals) with febrile and afebrile seizures with a benign course, generally good drug response, normal development, and without permanent neurologic deficits; (2) 2 patients with genetic generalized epilepsy without febrile seizures and cognitive deficits; (3) 13 patients or families with intractable seizures, developmental regression after seizure onset and additional neuropsychiatric symptoms; (4) 2 patients with focal epilepsy. More often, we found loss-of-function mutations in benign syndromes, whereas missense variants in the SNARE motif of syntaxin-1B were associated with more severe phenotypes.

Conclusion: These data expand the genetic and phenotypic spectrum of -related epilepsies to a diverse range of epilepsies that span the International League Against Epilepsy classification. Variants in are protean and contribute to many different epilepsy phenotypes, similar to , the most important gene associated with fever-associated epilepsies.
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http://dx.doi.org/10.1212/WNL.0000000000007089DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6511102PMC
March 2019

encephalopathy: A distinctive generalized developmental and epileptic encephalopathy.

Neurology 2019 01 12;92(2):e96-e107. Epub 2018 Dec 12.

From the Epilepsy Research Centre (D.R.M.V., B.J.S., R.B., M.F.B., S.F.B., M.S.H., I.E.S.), Department of Medicine, University of Melbourne, Austin Health, Australia; Departments of Genetics (D.R.M.V., C.M.A.v.R.-A.) and Neurology (D.R.M.V.), University Medical Center Groningen, University of Groningen, the Netherlands; Pediatric Neurology Unit and Laboratories (D.M., M.M.) and Pediatric Neurology (R.G.), Neurogenetics and Neurobiology Unit and Laboratories, A. Meyer Children's Hospital, University of Florence, Italy; Department of Pediatrics and Pediatric Epilepsy Centre (H.X., W.X.W., Y.J.), Peking University First Hospital, Beijing, China; Department of Pediatrics (C.T.M., H.C.M.), Division of Genetic Medicine, University of Washington, Seattle; Population Health and Immunity Division (M.F.B.), Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia; Department of Medical Biology (M.F.B.), University of Melbourne, Australia; Caulfield (D.W.), Melbourne, Australia; Department of Clinical Genetics (S.M.M.), Academic Medical Centre, Amsterdam, the Netherlands; Department of Clinical Genetics (A.S.B., G.M.S.M., I.M.B.H.v.d.L.), Erasmus University Medical Centre, Rotterdam, the Netherlands; Department of Clinical Genetics (J.M.v.H.), VU University Medical Center, Amsterdam, the Netherlands; Tasmanian Health Service (T.L.W.), Women's and Children's Services, Launceston General Hospital, Tasmania, Australia; TY Nelson Department of Neurology and Neurosurgery (R.I.W.) and Institute of Neuroscience and Muscle Research (R.I.W.), Children's Hospital at Westmead, Sydney, Australia; Department of Neurosciences (S.M.), Lady Cilento Children's Hospital, Brisbane, Australia; Department of Anatomical Pathology (R.M.K.), Austin Hospital, Melbourne, Australia; IRCCS Stella Maris Foundation (F.S., R.G.), Pisa, Italy; Klinikum Oldenburg (G.C.K.), Zentrum für Kinder-und Jugendmedizin, Klinik für Neuropädiatrie u. angeborene Stoffwechselerkrankungen, Oldenburg, Germany; Centre of Epilepsy (Y.J.), Beijing Institute for Brain Disorders, China; Department of Paediatrics (I.E.S.), University of Melbourne, Royal Children's Hospital, Australia; and Florey Institute of Neurosciences and Mental Health (I.E.S.), Parkville, Australia.

Objective: To delineate the epileptology, a key part of the phenotypic spectrum, in a large patient cohort.

Methods: Patients were recruited via investigators' practices or social media. We included patients with (likely) pathogenic variants or chromosome 6p21.32 microdeletions incorporating . We analyzed patients' phenotypes using a standardized epilepsy questionnaire, medical records, EEG, MRI, and seizure videos.

Results: We included 57 patients (53% male, median age 8 years) with mutations (n = 53) or microdeletions (n = 4). Of the 57 patients, 56 had epilepsy: generalized in 55, with focal seizures in 7 and infantile spasms in 1. Median seizure onset age was 2 years. A novel type of drop attack was identified comprising eyelid myoclonia evolving to a myoclonic-atonic (n = 5) or atonic (n = 8) seizure. Seizure types included eyelid myoclonia with absences (65%), myoclonic seizures (34%), atypical (20%) and typical (18%) absences, and atonic seizures (14%), triggered by eating in 25%. Developmental delay preceded seizure onset in 54 of 56 (96%) patients for whom early developmental history was available. Developmental plateauing or regression occurred with seizures in 56 in the context of a developmental and epileptic encephalopathy (DEE). Fifty-five of 57 patients had intellectual disability, which was moderate to severe in 50. Other common features included behavioral problems (73%); high pain threshold (72%); eating problems, including oral aversion (68%); hypotonia (67%); sleeping problems (62%); autism spectrum disorder (54%); and ataxia or gait abnormalities (51%).

Conclusions: mutations cause a generalized DEE with a distinctive syndrome combining epilepsy with eyelid myoclonia with absences and myoclonic-atonic seizures, as well as a predilection to seizures triggered by eating.
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http://dx.doi.org/10.1212/WNL.0000000000006729DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6340340PMC
January 2019

Defining the electroclinical phenotype and outcome of PCDH19-related epilepsy: A multicenter study.

Epilepsia 2018 12 19;59(12):2260-2271. Epub 2018 Nov 19.

Epilepsy Center, San Paolo Hospital, Milan, Italy.

Objective: PCDH19-related epilepsy is an epileptic syndrome with infantile onset, characterized by clustered and fever-induced seizures, often associated with intellectual disability (ID) and autistic features. The aim of this study was to analyze a large cohort of patients with PCDH19-related epilepsy and better define the epileptic phenotype, genotype-phenotype correlations, and related outcome-predicting factors.

Methods: We retrospectively collected genetic, clinical, and electroencephalogram (EEG) data of 61 patients with PCDH19-related epilepsy followed at 15 epilepsy centers. All consecutively performed EEGs were analyzed, totaling 551. We considered as outcome measures the development of ID, autistic spectrum disorder (ASD), and seizure persistence. The analyzed variables were the following: gender, age at onset, age at study, genetic variant, fever sensitivity, seizure type, cluster occurrence, status epilepticus, EEG abnormalities, and cognitive and behavioral disorders. Receiver operating characteristic curve analysis was performed to evaluate the age at which seizures might decrease in frequency.

Results: At last follow-up (median = 12 years, range = 1.9-42.1 years), 48 patients (78.7%) had annual seizures/clusters, 13 patients (21.3%) had monthly to weekly seizures, and 12 patients (19.7%) were seizure-free for ≥2 years. Receiver operating characteristic analysis showed a significant decrease of seizure frequency after the age of 10.5 years (sensitivity = 81.0%, specificity = 70.0%). Thirty-six patients (59.0%) had ID and behavioral disturbances. ASD was present in 31 patients. An earlier age at epilepsy onset emerged as the only predictive factor for ID (P = 0.047) and ASD (P = 0.014). Conversely, age at onset was not a predictive factor for seizure outcome (P = 0.124).

Significance: We found that earlier age at epilepsy onset is related to a significant risk for ID and ASD. Furthermore, long-term follow-up showed that after the age of 10 years, seizures decrease in frequency and cognitive and behavioral disturbances remain the primary clinical problems.
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http://dx.doi.org/10.1111/epi.14600DOI Listing
December 2018

Neurologic phenotypes associated with / mutations: Expanding the spectrum of disease.

Neurology 2018 11 9;91(22):e2078-e2088. Epub 2018 Nov 9.

From the Department of Clinical and Experimental Epilepsy (S.Z., Z.M., L.H.-H., S.K., S. Balestrini, S.M.S.) and Division of Neuropathology (Z.M., M.T.), UCL Institute of Neurology, London, UK; Clinic of Neurology (S.Z.), Department of Experimental and Clinical Medicine, Marche Polytechnic University, Ancona, Italy; Department of Pediatric Neurology and Neurological Rehabilitation (C.S., T.H., P.W., G.J.K.) and Neurosurgery Clinic and Clinic for Epilepsy Surgery (M.K.), Schön Klinik Vogtareuth; Department of Pediatrics (C.S., M.S.), Children's Hospital Augsburg, Germany; UCL Great Ormond Street Institute of Child Health (J.R.N., K.V., S.M.V., J.H.C.), London, UK; Paediatric Neurology and Neurogenetics Unit and Laboratories (D.M., R.G.), A. Meyer Children's Hospital, University of Florence, Italy; Chalfont Centre for Epilepsy (Z.M., L.H.-H., S.K., S. Balestrini, S.M.S.), Chalfont-St-Peter, Buckinghamshire, UK; CeGaT-Center for Genomics and Transcriptomics (A.P., S. Biskup), Tübingen, Germany; Neurogenetics Unit (M.L.), Department of Medical Genetics, Hospital de São João, Porto, Portugal; Department of Pediatrics and Adolescent Medicine (J.G.), University Medical Center Göttingen; Hospital for Children and Adolescents (A.M.), University Clinic Leipzig, Germany; Freiburg Medical Laboratory (M.J.), Dubai; The Danish Epilepsy Centre (R.S.M., E.G.), Dianalund; Institute for Regional Health Services (R.S.M., E.G.), University of Southern Denmark, Odense; Department of Clinical Genetics (B.S.K.), Odense University Hospital; Hans Christian Andersen Children's Hospital (L.K.H.), Odense, Denmark; Pediatric Neurology and Muscular Diseases Unit (M.S.V., P.S.), Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, and Maternal and Child Health, University of Genoa "G. Gaslini" Institute, Italy; Division of Neurology (K.L.H.), Children's Hospital of Philadelphia, PA; Department of Neurology (S.D., C.L.S.-H.), Division of Neurogenetics, Kennedy Krieger Institute, Baltimore, MD; Center for Genomic Medicine (N.H.-F.), Tohoku University; Department of Pediatrics (N.H.-F.), Tohoku University School of Medicine, Sendai, Japan; Department of Pediatrics (T.T., R.L.) and Institute of Clinical Medicine (K.O.), University of Tartu; Children's Clinic (T.T., R.L.), Department of Radiology (P.I.), and Department of Clinical Genetics, United Laboratories (K.O.), Tartu University Hospital, Estonia; Ludwig-Maximilians-University Munich (I.K.); Department of Pediatric Neurology (A.H.), Clinic Traunstein; Children's Hospital (M.K.), Dr. Horst Schmidt Klinik, Wiesbaden; Altona Children's Hospital (J.H.), Hamburg; Department of Pediatrics (C. Makowski), Technische Universität München, Germany; Department of Clinical Genetics (S.G.), Royal North Shore Hospital, St Leonards; John Hunter Children's Hospital (G.M.S.), New Lambton Heights, New South Wales, Australia; Department of Neurology (R.T.), University Hospital of Wales; Institute of Psychological Medicine and Clinical Neurosciences (R.H.T.), Cardiff University; Division of Neuroradiology (C. Micallef), National Hospital for Neurology and Neurosurgery, London; Department of Brain Repair & Rehabilitation (D.J.W.), Stroke Research Centre, UCL Institute of Neurology, London, UK; Paracelsus Medical University (G.J.K.), Salzburg, Austria; and IRCCS Stella Maris Foundation (R.G.), Pisa, Italy.

Objective: To characterize the neurologic phenotypes associated with mutations and to seek genotype-phenotype correlation.

Methods: We analyzed clinical, EEG, and neuroimaging data of 44 new and 55 previously reported patients with mutations.

Results: Childhood-onset focal seizures, frequently complicated by status epilepticus and resistance to antiepileptic drugs, was the most common phenotype. EEG typically showed focal epileptiform discharges in the context of other abnormalities, including generalized sharp waves or slowing. In 46.4% of new patients with focal seizures, porencephalic cysts on brain MRI colocalized with the area of the focal epileptiform discharges. In patients with porencephalic cysts, brain MRI frequently also showed extensive white matter abnormalities, consistent with the finding of diffuse cerebral disturbance on EEG. Notably, we also identified a subgroup of patients with epilepsy as their main clinical feature, in which brain MRI showed nonspecific findings, in particular periventricular leukoencephalopathy and ventricular asymmetry. Analysis of 15 pedigrees suggested a worsening of the severity of clinical phenotype in succeeding generations, particularly when maternally inherited. Mutations associated with epilepsy were spread across and a clear genotype-phenotype correlation did not emerge.

Conclusion: mutations typically cause a severe neurologic condition and a broader spectrum of milder phenotypes, in which epilepsy is the predominant feature. Early identification of patients carrying mutations may have important clinical consequences, while for research efforts, omission from large-scale epilepsy sequencing studies of individuals with abnormalities on brain MRI may generate misleading estimates of the genetic contribution to the epilepsies overall.
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http://dx.doi.org/10.1212/WNL.0000000000006567DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6282239PMC
November 2018

HCN1 mutation spectrum: from neonatal epileptic encephalopathy to benign generalized epilepsy and beyond.

Brain 2018 11;141(11):3160-3178

Neuropediatric Department, Centro Hospitalar do Porto, Porto, Portugal.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels control neuronal excitability and their dysfunction has been linked to epileptogenesis but few individuals with neurological disorders related to variants altering HCN channels have been reported so far. In 2014, we described five individuals with epileptic encephalopathy due to de novo HCN1 variants. To delineate HCN1-related disorders and investigate genotype-phenotype correlations further, we assembled a cohort of 33 unpublished patients with novel pathogenic or likely pathogenic variants: 19 probands carrying 14 different de novo mutations and four families with dominantly inherited variants segregating with epilepsy in 14 individuals, but not penetrant in six additional individuals. Sporadic patients had epilepsy with median onset at age 7 months and in 36% the first seizure occurred during a febrile illness. Overall, considering familial and sporadic patients, the predominant phenotypes were mild, including genetic generalized epilepsies and genetic epilepsy with febrile seizures plus (GEFS+) spectrum. About 20% manifested neonatal/infantile onset otherwise unclassified epileptic encephalopathy. The study also included eight patients with variants of unknown significance: one adopted patient had two HCN1 variants, four probands had intellectual disability without seizures, and three individuals had missense variants inherited from an asymptomatic parent. Of the 18 novel pathogenic missense variants identified, 12 were associated with severe phenotypes and clustered within or close to transmembrane domains, while variants segregating with milder phenotypes were located outside transmembrane domains, in the intracellular N- and C-terminal parts of the channel. Five recurrent variants were associated with similar phenotypes. Using whole-cell patch-clamp, we showed that the impact of 12 selected variants ranged from complete loss-of-function to significant shifts in activation kinetics and/or voltage dependence. Functional analysis of three different substitutions altering Gly391 revealed that these variants had different consequences on channel biophysical properties. The Gly391Asp variant, associated with the most severe, neonatal phenotype, also had the most severe impact on channel function. Molecular dynamics simulation on channel structure showed that homotetramers were not conducting ions because the permeation path was blocked by cation(s) strongly complexed to the Asp residue, whereas heterotetramers showed an instantaneous current component possibly linked to deformation of the channel pore. In conclusion, our results considerably expand the clinical spectrum related to HCN1 variants to include common generalized epilepsy phenotypes and further illustrate how HCN1 has a pivotal function in brain development and control of neuronal excitability.
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http://dx.doi.org/10.1093/brain/awy263DOI Listing
November 2018

Familial dominant epilepsy and mild pachygyria associated with a constitutional LIS1 mutation.

Am J Med Genet A 2018 12 25;176(12):2808-2812. Epub 2018 Aug 25.

Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Neuroscience Department, A. Meyer Children's Hospital, University of Florence, Italy.

We describe a mother and son with focal epilepsy, mild cognitive impairment, and pachygyria, which was parieto-occipital in the mother and with remarkable posterior greater than anterior severity in the son. Overall clinical manifestations, although overlapping in type, were likewise slightly more severe in the son. Using targeted resequencing through a gene panel for malformations of cortical development, we identified the c.655 T > A [p.(Trp219Arg)] novel missense variant in the LIS1 gene, segregating in the proband and in his mother. Western Blot analysis, qPCR gene expression and RT-PCR disclosed no significant differences between proband, his parents, and controls. Epilepsy and mild cognitive impairment can be the only clinical presentation of constitutional LIS1 mutations, which can therefore be inherited if the associated phenotype implies limited or no reproductive disadvantage. Parents of patients harboring LIS1 mutations should be assessed for their mutation carrier status.
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http://dx.doi.org/10.1002/ajmg.a.40503DOI Listing
December 2018

Unstable non-coding pentanucleotide repeats destabilize cortical excitability.

Brain 2018 08;141(8):2232-2235

Pediatric Neurology, Neurogenetics and Neurobiology Unit and Laboratories, Children's Hospital A. Meyer-University of Florence, Florence, Italy.

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http://dx.doi.org/10.1093/brain/awy196DOI Listing
August 2018

Analysis of 17 genes detects mutations in 81% of 811 patients with lissencephaly.

Genet Med 2018 11 19;20(11):1354-1364. Epub 2018 Apr 19.

Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, Washington, USA.

Purpose: To estimate diagnostic yield and genotype-phenotype correlations in a cohort of 811 patients with lissencephaly or subcortical band heterotopia.

Methods: We collected DNA from 756 children with lissencephaly over 30 years. Many were tested for deletion 17p13.3 and mutations of LIS1, DCX, and ARX, but few other genes. Among those tested, 216 remained unsolved and were tested by a targeted panel of 17 genes (ACTB, ACTG1, ARX, CRADD, DCX, LIS1, TUBA1A, TUBA8, TUBB2B, TUBB, TUBB3, TUBG1, KIF2A, KIF5C, DYNC1H1, RELN, and VLDLR) or by whole-exome sequencing. Fifty-five patients studied at another institution were added as a validation cohort.

Results: The overall mutation frequency in the entire cohort was 81%. LIS1 accounted for 40% of patients, followed by DCX (23%), TUBA1A (5%), and DYNC1H1 (3%). Other genes accounted for 1% or less of patients. Nineteen percent remained unsolved, which suggests that several additional genes remain to be discovered. The majority of unsolved patients had posterior pachygyria, subcortical band heterotopia, or mild frontal pachygyria.

Conclusion: The brain-imaging pattern correlates with mutations in single lissencephaly-associated genes, as well as in biological pathways. We propose the first LIS classification system based on the underlying molecular mechanisms.
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http://dx.doi.org/10.1038/gim.2018.8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6195491PMC
November 2018
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