Publications by authors named "Julien Buratti"

36 Publications

Phenotype associated with TAF2 biallelic mutations: A clinical description of four individuals and review of the literature.

Eur J Med Genet 2021 Nov 30;64(11):104323. Epub 2021 Aug 30.

APHP, Département de Génétique, Centre de Référence Déficiences Intellectuelles de Causes Rares, Groupe Hospitalier Pitié Salpêtrière et GHUEP Hôpital Trousseau, Sorbonne Université, GRC "Déficience Intellectuelle et Autisme", Paris, France. Electronic address:

Transcription factor IID is a multimeric protein complex that is essential for the initiation of transcription by RNA polymerase II. One of its critical components, the TATA-binding protein-associated factor 2, is encoded by the gene TAF2. Pathogenic variants of this gene have been shown to be responsible for the Mental retardation, autosomal recessive 40 syndrome. This syndrome is characterized by severe intellectual disability, postnatal microcephaly, pyramidal signs and thin corpus callosum. Until now, only three families have been reported separately. Here we report four individuals, from two unrelated families, who present with severe intellectual disability and global developmental delay, postnatal microcephaly, feet deformities and thin corpus callosum and who carry homozygous TAF2 missense variants detected by Exome Sequencing. Taken together, our findings and those of previously reported subjects allow us to further delineate the clinical phenotype associated with TAF2 biallelic mutations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ejmg.2021.104323DOI Listing
November 2021

SCN1A-related epilepsy with recessive inheritance: Two further families.

Eur J Paediatr Neurol 2021 Jul 5;33:121-124. Epub 2021 Jun 5.

APHP.Sorbonne Université, Département de Génétique, Groupe Hospitalier Pitié Salpêtrière, Paris, France; Sorbonne Université, Institut du Cerveau, ICM, Inserm U1127, CNRS UMR 7225, Paris, France. Electronic address:

Background: Variants in SCN1A gene, encoding the voltage-gated sodium channel Na1.1, are associated with distinct epilepsy syndromes ranging from the relatively benign genetic epilepsy with febrile seizures plus (GEFS+) to Dravet syndrome, a severe developmental and epileptic encephalopathy (DEE). Most SCN1A pathogenic variants are heterozygous changes inherited in a dominant or de novo inheritance and many cause a loss-of-function of one allele. To date, recessive inheritance has been suggested in only two families with affected children harboring homozygous SCN1A missense variants while their heterozygous parents were asymptomatic. The aim of this report is to describe two additional families in which affected individuals have biallelic SCN1A variants possibly explaining their phenotype.

Methods And Results: We report two novel homozygous SCN1A missense variants in two patients from related parents. Both patients had fever-sensitive epilepsy beginning in the first months of life, followed by afebrile seizures, without severe cognitive impairment. Parents were asymptomatic. Next generation sequencing excluded a pathogenic variant in other genes involved in DEE. Estimation of pathogenicity scores by in-silico tools suggests that the impact of these SCN1A variants is less damaging than that of dominant pathogenic variants.

Conclusion: This study provides additional evidence that homozygous variants in SCN1A can cause GEFS+. This recessive inheritance would imply that hypomorphic variants may not necessarily cause epilepsy at the heterozygous state but may decrease the seizure threshold when combined.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ejpn.2021.05.018DOI Listing
July 2021

Biallelic and monoallelic variants in PLXNA1 are implicated in a novel neurodevelopmental disorder with variable cerebral and eye anomalies.

Genet Med 2021 09 30;23(9):1715-1725. Epub 2021 May 30.

Department of Medical Genetics, Centre for Applied Neurogenetics, University of British Columbia, Vancouver, BC, Canada.

Purpose: To investigate the effect of PLXNA1 variants on the phenotype of patients with autosomal dominant and recessive inheritance patterns and to functionally characterize the zebrafish homologs plxna1a and plxna1b during development.

Methods: We assembled ten patients from seven families with biallelic or de novo PLXNA1 variants. We describe genotype-phenotype correlations, investigated the variants by structural modeling, and used Morpholino knockdown experiments in zebrafish to characterize the embryonic role of plxna1a and plxna1b.

Results: Shared phenotypic features among patients include global developmental delay (9/10), brain anomalies (6/10), and eye anomalies (7/10). Notably, seizures were predominantly reported in patients with monoallelic variants. Structural modeling of missense variants in PLXNA1 suggests distortion in the native protein. Our zebrafish studies enforce an embryonic role of plxna1a and plxna1b in the development of the central nervous system and the eye.

Conclusion: We propose that different biallelic and monoallelic variants in PLXNA1 result in a novel neurodevelopmental syndrome mainly comprising developmental delay, brain, and eye anomalies. We hypothesize that biallelic variants in the extracellular Plexin-A1 domains lead to impaired dimerization or lack of receptor molecules, whereas monoallelic variants in the intracellular Plexin-A1 domains might impair downstream signaling through a dominant-negative effect.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41436-021-01196-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8460429PMC
September 2021

Patients with -related intellectual disability without distinctive features of Zimmermann-Laband/Temple-Baraitser syndrome.

J Med Genet 2021 Apr 2. Epub 2021 Apr 2.

APHP.Sorbonne Université, Département de Génétique, Groupe Hospitalier Pitié Salpêtrière et Hôpital Trousseau, Paris, Île-de-France, France.

De novo missense variants in encoding Kv10.1 are responsible for two clinically recognisable phenotypes: Temple-Baraitser syndrome (TBS) and Zimmermann-Laband syndrome (ZLS). The clinical overlap between these two syndromes suggests that they belong to a spectrum of -related encephalopathies. Affected patients have severe intellectual disability (ID) with or without epilepsy, hypertrichosis and distinctive features such as gingival hyperplasia and nail hypoplasia/aplasia (present in 20/23 reported cases).We report a series of seven patients with ID and de novo pathogenic variants identified by whole-exome sequencing or an epilepsy gene panel in whom the diagnosis of TBS/ZLS had not been first considered. Four of these variants, p.(Thr294Met), p.(Ala492Asp), p.(Thr493Asn) and p.(Gly496Arg), were located in the transmembrane domains S3 and S6 of Kv10.1 and one, p.(Arg693Gln), in its C-terminal cyclic nucleotide-binding homology domain (CNBHD). Clinical reappraisal by the referring clinical geneticists confirmed the absence of the distinctive gingival and nail features of TBS/ZLS.Our study expands the phenotypical spectrum of -related encephalopathies to individuals with an attenuated extraneurological phenotype preventing a clinical diagnosis of TBS or ZLS. This subtype may be related to recurrent substitutions of the Gly496, suggesting a genotype-phenotype correlation and, possibly, to variants in the CNBHD domain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/jmedgenet-2020-107511DOI Listing
April 2021

Functional characterization of ABCC8 variants of unknown significance based on bioinformatics predictions, splicing assays, and protein analyses: Benefits for the accurate diagnosis of congenital hyperinsulinism.

Hum Mutat 2021 Apr 28;42(4):408-420. Epub 2021 Jan 28.

Inserm U1245, UFR de Médecine et Pharmacie, UNIROUEN, Normandie University, Normandy Centre for Genomic and Personalized Medicine, Rouen, France.

ABCC8 encodes the SUR1 subunit of the β-cell ATP-sensitive potassium channel whose loss of function causes congenital hyperinsulinism (CHI). Molecular diagnosis is critical for optimal management of CHI patients. Unfortunately, assessing the impact of ABCC8 variants on RNA splicing remains very challenging as this gene is poorly expressed in leukocytes. Here, we performed bioinformatics analysis and cell-based minigene assays to assess the impact on splicing of 13 ABCC8 variants identified in 20 CHI patients. Next, channel properties of SUR1 proteins expected to originate from minigene-detected in-frame splicing defects were analyzed after ectopic expression in COSm6 cells. Out of the analyzed variants, seven induced out-of-frame splicing defects and were therefore classified as recessive pathogenic, whereas two led to skipping of in-frame exons. Channel functional analysis of the latter demonstrated their pathogenicity. Interestingly, the common rs757110 SNP increased exon skipping in our system suggesting that it may act as a disease modifier factor. Our strategy allowed determining the pathogenicity of all selected ABCC8 variants, and CHI-inheritance pattern for 16 out of the 20 patients. This study highlights the value of combining RNA and protein functional approaches in variant interpretation and reveals the minigene splicing assay as a new tool for CHI molecular diagnostics.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/humu.24164DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8049974PMC
April 2021

RNF170-Related Hereditary Spastic Paraplegia: Confirmation by a Novel Mutation.

Mov Disord 2021 03 9;36(3):771-774. Epub 2020 Nov 9.

Institut du Cerveau, Sorbonne Université (INSERM 1127, CNRS 7225), Paris, France.

Background: Spastic paraparesis and biallelic variants functionally characterized as deleterious in the RNF170 gene have recently been reported by Wagner et al. 2019, strongly supporting the involvement of this gene in hereditary spastic paraplegia.

Methods: Exome sequencing was performed on 6 hereditary spastic paraplegia families previously tested on an hereditary spastic paraplegia-specific panel.

Results: We describe here a novel hereditary spastic paraplegia family with 4 affected members carrying a homozygous p.(Tyr114*) stop gain variant in RNF170.

Conclusions: We confirm the involvement of biallelic truncating variants in RNF170 in a novel form of hereditary spastic paraplegia. © 2020 International Parkinson and Movement Disorder Society.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/mds.28371DOI Listing
March 2021

Congenital immobility and stiffness related to biallelic variants.

Neurol Genet 2020 Dec 24;6(6):e520. Epub 2020 Sep 24.

Département de Génétique (R.B., S.W., B.K., S.C.-B., M.-C.V., L.B., D.H., J.B., A.A., C.M.), Hôpital Armand Trousseau & Groupe Hospitalier Pitié-Salpêtrière, and Unité de Neuropédiatrie et Pathologie du Développement (D.D., M.M., D.R., A.I., T.B.V.), Hôpital Armand Trousseau, AP-HP Sorbonne Université, Paris; Centre de Référence des Maladies Neurogénétiques (D.D., D.R.); Centre de Référence Anomalies du Développement et Syndromes Malformatifs (S.W., C.M.); Hôpital de Pédiatrie et de Rééducation (K.M.), Bullion; INSERM UMR 1141 (D.R.), Paris; Réanimation Néonatale et Pédiatrique (P.-L.L.), and Service de Néonatologie (F.K., I.M.), Hôpital Armand Trousseau, AP-HP Sorbonne Université, Paris; Centre de Référence Déficience Intellectuelles de Causes Rares (D.H., A.A., T.B.V., C.M.); and INSERM (C.M.), U 1127, CNRS UMR 7225, Sorbonne Universités, UPMC Université Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle Epinière, Paris, France.

Objective: To delineate the phenotype associated with biallelic variants.

Methods: We describe 2 new patients with -related disorder diagnosed by whole-exome sequencing and compare their phenotype to 6 previous patients.

Results: Patients 1 and 2 had a similar distinctive phenotype comprising congenital stiffness of limbs, absent spontaneous movements, weak sucking, and hypoventilation. Both had absent brainstem evoked auditory responses (BEARs). Patient 1 carried the homozygous p.(His357Argfs*15) variant in . In the light of the finding in patient 1, a second reading of exome data for patient 2 revealed the novel homozygous p.(Gly128Val) variant.

Conclusions: Analysis of the phenotypes of these 2 patients and of the 6 previous cases showed that biallelic mutations are responsible for a unique congenital encephalopathy likely comprising absent BEAR, different from hyperekplexia and other conditions with neonatal hypertonia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1212/NXG.0000000000000520DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7577533PMC
December 2020

Mutations disrupting neuritogenesis genes confer risk for cerebral palsy.

Nat Genet 2020 10 28;52(10):1046-1056. Epub 2020 Sep 28.

Henan Key Laboratory of Child Brain Injury, Third Affiliated Hospital of Zhengzhou University, Zhengzhou, China.

In addition to commonly associated environmental factors, genomic factors may cause cerebral palsy. We performed whole-exome sequencing of 250 parent-offspring trios, and observed enrichment of damaging de novo mutations in cerebral palsy cases. Eight genes had multiple damaging de novo mutations; of these, two (TUBA1A and CTNNB1) met genome-wide significance. We identified two novel monogenic etiologies, FBXO31 and RHOB, and showed that the RHOB mutation enhances active-state Rho effector binding while the FBXO31 mutation diminishes cyclin D levels. Candidate cerebral palsy risk genes overlapped with neurodevelopmental disorder genes. Network analyses identified enrichment of Rho GTPase, extracellular matrix, focal adhesion and cytoskeleton pathways. Cerebral palsy risk genes in enriched pathways were shown to regulate neuromotor function in a Drosophila reverse genetics screen. We estimate that 14% of cases could be attributed to an excess of damaging de novo or recessive variants. These findings provide evidence for genetically mediated dysregulation of early neuronal connectivity in cerebral palsy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41588-020-0695-1DOI Listing
October 2020

Prenatal exome sequencing in 65 fetuses with abnormality of the corpus callosum: contribution to further diagnostic delineation.

Genet Med 2020 11 22;22(11):1887-1891. Epub 2020 Jun 22.

Service de Génétique Clinique, CHU de Dijon, Dijon, France.

Purpose: Abnormality of the corpus callosum (AbnCC) is etiologically a heterogeneous condition and the prognosis in prenatally diagnosed cases is difficult to predict. The purpose of our research was to establish the diagnostic yield using chromosomal microarray (CMA) and exome sequencing (ES) in cases with prenatally diagnosed isolated (iAbnCC) and nonisolated AbnCC (niAbnCC).

Methods: CMA and prenatal trio ES (pES) were done on 65 fetuses with iAbnCC and niAbnCC. Only pathogenic gene variants known to be associated with AbnCC and/or intellectual disability were considered.

Results: pES results were available within a median of 21.5 days (9-53 days). A pathogenic single-nucleotide variant (SNV) was identified in 12 cases (18%) and a pathogenic CNV was identified in 3 cases (4.5%). Thus, the genetic etiology was determined in 23% of cases. In all diagnosed cases, the results provided sufficient information regarding the neurodevelopmental prognosis and helped the parents to make an informed decision regarding the outcome of the pregnancy.

Conclusion: Our results show the significant diagnostic and prognostic contribution of CMA and pES in cases with prenatally diagnosed AbnCC. Further prospective cohort studies with long-term follow-up of the born children will be needed to provide accurate prenatal counseling after a negative pES result.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41436-020-0872-8DOI Listing
November 2020

De novo variants in encoding an E3 ubiquitin ligase, are associated with developmental delay, hypotonia and dysmorphic features.

J Med Genet 2021 03 19;58(3):205-212. Epub 2020 May 19.

Department of Genetics, Hadassah-Hebrew University Medical Center, Jerusalem, Israel

Background: Ubiquitination has a central role in numerous biological processes, including cell development, stress responses and ageing. Perturbed ubiquitination has been implicated in human diseases ranging from cancer to neurodegenerative diseases. encodes a RING-type E3 ubiquitin ligase involved in protein ubiquitination. Among numerous other roles, SIAH1 regulates metabotropic glutamate receptor signalling and affects neural cell fate. Moreover, SIAH1 positively regulates Wnt signalling through ubiquitin-mediated degradation of Axin and accumulation of β-catenin.

Methods: Trio exome sequencing followed by Sanger validation was undertaken in five individuals with syndromic developmental delay. Three-dimensional structural modelling was used to predict pathogenicity of affected residues. Wnt stimulatory activity was measured by luciferase reporter assays and Axin degradation assays in HEK293 cells transfected with wild-type and mutant SIAH1 expression plasmids.

Results: We report five unrelated individuals with shared features of developmental delay, infantile hypotonia, dysmorphic features and laryngomalacia, in whom exome sequencing identified de novo monoallelic variants in . In silico protein modelling suggested alteration of conserved functional sites. In vitro experiments demonstrated loss of Wnt stimulatory activity with the SIAH1 mutants, suggesting variant pathogenicity.

Conclusion: Our results lend support to as a candidate Mendelian disease gene for a recognisable syndrome, further strengthening the connection between and neurodevelopmental disorders. Furthermore, the results suggest that dysregulation of the Wnt/β-catenin pathway may be involved in the pathogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1136/jmedgenet-2019-106335DOI Listing
March 2021

Delineation of a Human Mendelian Disorder of the DNA Demethylation Machinery: TET3 Deficiency.

Am J Hum Genet 2020 02 9;106(2):234-245. Epub 2020 Jan 9.

Division of Evolution & Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PL, UK; Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University NHS Foundation Trust, Health Innovation Manchester, Manchester M13 9WL, UK.

Germline pathogenic variants in chromatin-modifying enzymes are a common cause of pediatric developmental disorders. These enzymes catalyze reactions that regulate epigenetic inheritance via histone post-translational modifications and DNA methylation. Cytosine methylation (5-methylcytosine [5mC]) of DNA is the quintessential epigenetic mark, yet no human Mendelian disorder of DNA demethylation has yet been delineated. Here, we describe in detail a Mendelian disorder caused by the disruption of DNA demethylation. TET3 is a methylcytosine dioxygenase that initiates DNA demethylation during early zygote formation, embryogenesis, and neuronal differentiation and is intolerant to haploinsufficiency in mice and humans. We identify and characterize 11 cases of human TET3 deficiency in eight families with the common phenotypic features of intellectual disability and/or global developmental delay; hypotonia; autistic traits; movement disorders; growth abnormalities; and facial dysmorphism. Mono-allelic frameshift and nonsense variants in TET3 occur throughout the coding region. Mono-allelic and bi-allelic missense variants localize to conserved residues; all but one such variant occur within the catalytic domain, and most display hypomorphic function in an assay of catalytic activity. TET3 deficiency and other Mendelian disorders of the epigenetic machinery show substantial phenotypic overlap, including features of intellectual disability and abnormal growth, underscoring shared disease mechanisms.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ajhg.2019.12.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7010978PMC
February 2020

New evidence that biallelic loss of function in EEF1B2 gene leads to intellectual disability.

Clin Genet 2020 04 7;97(4):639-643. Epub 2020 Jan 7.

APHP, Département d'Histologie, Embryologie et Cytogénétique, Hôpital Jean Verdier, Bondy, France.

The guanine exchange factor subunit eEF1Bα encoded by the EEF1B2 gene belongs to the eukaryotic elongation translational machinery. Pathogen variants in genes of the translational machinery have been associated with several neurodevelopmental disorders. However, only one family of three siblings with intellectual disability (ID) has been reported so far with a homozygous variant in EEF1B2. Here, we report a second family with a novel homozygous loss of function (LoF) variant p.(Ser128*), carried by two siblings with moderate ID and seizures. Our findings confirm the role of EEF1B2 variants in the pathogenesis of autosomal-recessive ID, expand the variant spectrum and precisely describe the clinical consequences of the LoF of EEF1B2.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/cge.13688DOI Listing
April 2020

Unstable TTTTA/TTTCA expansions in MARCH6 are associated with Familial Adult Myoclonic Epilepsy type 3.

Nat Commun 2019 10 29;10(1):4919. Epub 2019 Oct 29.

Department of Neurology-centre de référence des epilepsies rares, University Hospital of Strasbourg, 1 Avenue Molière, 67200, Strasbourg, France.

Familial Adult Myoclonic Epilepsy (FAME) is a genetically heterogeneous disorder characterized by cortical tremor and seizures. Intronic TTTTA/TTTCA repeat expansions in SAMD12 (FAME1) are the main cause of FAME in Asia. Using genome sequencing and repeat-primed PCR, we identify another site of this repeat expansion, in MARCH6 (FAME3) in four European families. Analysis of single DNA molecules with nanopore sequencing and molecular combing show that expansions range from 3.3 to 14 kb on average. However, we observe considerable variability in expansion length and structure, supporting the existence of multiple expansion configurations in blood cells and fibroblasts of the same individual. Moreover, the largest expansions are associated with micro-rearrangements occurring near the expansion in 20% of cells. This study provides further evidence that FAME is caused by intronic TTTTA/TTTCA expansions in distinct genes and reveals that expansions exhibit an unexpectedly high somatic instability that can ultimately result in genomic rearrangements.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-019-12763-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6820781PMC
October 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-019-12671-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6820779PMC
October 2019

The complete loss of function of the SMS gene results in a severe form of Snyder-Robinson syndrome.

Eur J Med Genet 2020 Apr 30;63(4):103777. Epub 2019 Sep 30.

APHP, UF de Génétique clinique, Centre de Référence Maladies Rares « Anomalies du développement et syndromes malformatifs », Hôpital Armand Trousseau, Paris, France.

Snyder-Robinson syndrome (SRS) is an X-linked syndromic intellectual disability condition caused by variants in the spermine synthase gene (SMS). The syndrome is characterized by facial dysmorphism, thin body build, kyphoscoliosis, osteoporosis, hypotonia, developmental delay and associated neurological features (seizures, unsteady gait, abnormal speech). Until now, only missense variants with a functionally characterized partial loss of function (LoF) have been described. Here we describe the first complete LoF variant, Met303Lysfs*, in a male patient with a severe form of Snyder-Robinson syndrome. He presented with multiple malformations and severly delayed development, and died at 4 months of age. Functional in vitro assays showed a complete absence of functional SMS protein. Taken together, our findings and those of previously reported patients confirm that pathogenic variants of SMS are indeed LoF and that there might exist a genotype-phenotype correlation between the type of variant and the severity of the syndrome.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ejmg.2019.103777DOI Listing
April 2020

Variants in TCF20 in neurodevelopmental disability: description of 27 new patients and review of literature.

Genet Med 2019 09 11;21(9):2036-2042. Epub 2019 Feb 11.

Spectrum Health Medical Genetics, Grand Rapids, MI, USA.

Purpose: To define the clinical characteristics of patients with variants in TCF20, we describe 27 patients, 26 of whom were identified via exome sequencing. We compare detailed clinical data with 17 previously reported patients.

Methods: Patients were ascertained through molecular testing laboratories performing exome sequencing (and other testing) with orthogonal confirmation; collaborating referring clinicians provided detailed clinical information.

Results: The cohort of 27 patients all had novel variants, and ranged in age from 2 to 68 years. All had developmental delay/intellectual disability. Autism spectrum disorders/autistic features were reported in 69%, attention disorders or hyperactivity in 67%, craniofacial features (no recognizable facial gestalt) in 67%, structural brain anomalies in 24%, and seizures in 12%. Additional features affecting various organ systems were described in 93%. In a majority of patients, we did not observe previously reported findings of postnatal overgrowth or craniosynostosis, in comparison with earlier reports.

Conclusion: We provide valuable data regarding the prognosis and clinical manifestations of patients with variants in TCF20.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41436-019-0454-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7171701PMC
September 2019

Both rare and common genetic variants contribute to autism in the Faroe Islands.

NPJ Genom Med 2019 21;4. Epub 2019 Jan 21.

1Human Genetics and Cognitive Functions Unit, Institut Pasteur, Paris, France.

The number of genes associated with autism is increasing, but few studies have been performed on epidemiological cohorts and in isolated populations. Here, we investigated 357 individuals from the Faroe Islands including 36 individuals with autism, 136 of their relatives and 185 non-autism controls. Data from SNP array and whole exome sequencing revealed that individuals with autism had a higher burden of rare exonic copy-number variants altering autism associated genes (deletions (  0.0352) or duplications (  0.0352)), higher inbreeding status (  0.023) and a higher load of rare homozygous deleterious variants (  0.011) compared to controls. Our analysis supports the role of several genes/loci associated with autism (e.g., , , 22q11 deletion) and identified new truncating (e.g., , and ) or recessive deleterious variants (e.g. and ) affecting autism-associated genes. It also revealed three genes involved in synaptic plasticity, , , and , carrying de novo deleterious variants in individuals with autism without intellectual disability. In summary, our analysis provides a better understanding of the genetic architecture of autism in isolated populations by highlighting the role of both common and rare gene variants and pointing at new autism-risk genes. It also indicates that more knowledge about how multiple genetic hits affect neuronal function will be necessary to fully understand the genetic architecture of autism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41525-018-0075-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6341098PMC
January 2019

CHD3 helicase domain mutations cause a neurodevelopmental syndrome with macrocephaly and impaired speech and language.

Nat Commun 2018 11 5;9(1):4619. Epub 2018 Nov 5.

AP-HP, Hôpital de la Pitié-Salpêtrière, Département de Génétique, Paris, 75013, France.

Chromatin remodeling is of crucial importance during brain development. Pathogenic alterations of several chromatin remodeling ATPases have been implicated in neurodevelopmental disorders. We describe an index case with a de novo missense mutation in CHD3, identified during whole genome sequencing of a cohort of children with rare speech disorders. To gain a comprehensive view of features associated with disruption of this gene, we use a genotype-driven approach, collecting and characterizing 35 individuals with de novo CHD3 mutations and overlapping phenotypes. Most mutations cluster within the ATPase/helicase domain of the encoded protein. Modeling their impact on the three-dimensional structure demonstrates disturbance of critical binding and interaction motifs. Experimental assays with six of the identified mutations show that a subset directly affects ATPase activity, and all but one yield alterations in chromatin remodeling. We implicate de novo CHD3 mutations in a syndrome characterized by intellectual disability, macrocephaly, and impaired speech and language.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-018-06014-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6218476PMC
November 2018

De Novo Pathogenic Variants in CACNA1E Cause Developmental and Epileptic Encephalopathy with Contractures, Macrocephaly, and Dyskinesias.

Am J Hum Genet 2018 11 18;103(5):666-678. Epub 2018 Oct 18.

Division of Genetics and Metabolism, Phoenix Children's Hospital, Phoenix, AZ 85016, USA.

Developmental and epileptic encephalopathies (DEEs) are severe neurodevelopmental disorders often beginning in infancy or early childhood that are characterized by intractable seizures, abundant epileptiform activity on EEG, and developmental impairment or regression. CACNA1E is highly expressed in the central nervous system and encodes the α-subunit of the voltage-gated Ca2.3 channel, which conducts high voltage-activated R-type calcium currents that initiate synaptic transmission. Using next-generation sequencing techniques, we identified de novo CACNA1E variants in 30 individuals with DEE, characterized by refractory infantile-onset seizures, severe hypotonia, and profound developmental impairment, often with congenital contractures, macrocephaly, hyperkinetic movement disorders, and early death. Most of the 14, partially recurring, variants cluster within the cytoplasmic ends of all four S6 segments, which form the presumed Ca2.3 channel activation gate. Functional analysis of several S6 variants revealed consistent gain-of-function effects comprising facilitated voltage-dependent activation and slowed inactivation. Another variant located in the domain II S4-S5 linker results in facilitated activation and increased current density. Five participants achieved seizure freedom on the anti-epileptic drug topiramate, which blocks R-type calcium channels. We establish pathogenic variants in CACNA1E as a cause of DEEs and suggest facilitated R-type calcium currents as a disease mechanism for human epilepsy and developmental disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ajhg.2018.09.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6216110PMC
November 2018

Correction: IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 Aug;21(8):1897-1898

APHP, Service de genetique medicale, Necker- Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.

This Article was originally published under Nature Research's License to Publish, but has now been made available under a CC BY 4.0 license. The PDF and HTML versions of the Article have been modified accordingly.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41436-018-0327-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608434PMC
August 2019

IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 04 12;21(4):837-849. Epub 2018 Sep 12.

APHP, Service de genetique medicale, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.

Purpose: Variants in IQSEC2, escaping X inactivation, cause X-linked intellectual disability with frequent epilepsy in males and females. We aimed to investigate sex-specific differences.

Methods: We collected the data of 37 unpublished patients (18 males and 19 females) with IQSEC2 pathogenic variants and 5 individuals with variants of unknown significance and reviewed published variants. We compared variant types and phenotypes in males and females and performed an analysis of IQSEC2 isoforms.

Results: IQSEC2 pathogenic variants mainly led to premature truncation and were scattered throughout the longest brain-specific isoform, encoding the synaptic IQSEC2/BRAG1 protein. Variants occurred de novo in females but were either de novo (2/3) or inherited (1/3) in males, with missense variants being predominantly inherited. Developmental delay and intellectual disability were overall more severe in males than in females. Likewise, seizures were more frequently observed and intractable, and started earlier in males than in females. No correlation was observed between the age at seizure onset and severity of intellectual disability or resistance to antiepileptic treatments.

Conclusion: This study provides a comprehensive overview of IQSEC2-related encephalopathy in males and females, and suggests that an accurate dosage of IQSEC2 at the synapse is crucial during normal brain development.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41436-018-0268-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752297PMC
April 2019

Association of modifiers and other genetic factors explain Marfan syndrome clinical variability.

Eur J Hum Genet 2018 12 7;26(12):1759-1772. Epub 2018 Aug 7.

Laboratory for Vascular Translational Science, INSERM U1148, DHU FIRE, Centre Hospitalo-Universitaire Xavier Bichat (APHP), 46 rue Henri Huchard, Paris, 75018, France.

Marfan syndrome (MFS) is a rare autosomal dominant connective tissue disorder related to variants in the FBN1 gene. Prognosis is related to aortic risk of dissection following aneurysm. MFS clinical variability is notable, for age of onset as well as severity and number of clinical manifestations. To identify genetic modifiers, we combined genome-wide approaches in 1070 clinically well-characterized FBN1 disease-causing variant carriers: (1) an FBN1 eQTL analysis in 80 fibroblasts of FBN1 stop variant carriers, (2) a linkage analysis, (3) a kinship matrix association study in 14 clinically concordant and discordant sib-pairs, (4) a genome-wide association study and (5) a whole exome sequencing in 98 extreme phenotype samples.Three genetic mechanisms of variability were found. A new genotype/phenotype correlation with an excess of loss-of-cysteine variants (P = 0.004) in severely affected subjects. A second pathogenic event in another thoracic aortic aneurysm gene or the COL4A1 gene (known to be involved in cerebral aneurysm) was found in nine individuals. A polygenic model involving at least nine modifier loci (named gMod-M1-9) was observed through cross-mapping of results. Notably, gMod-M2 which co-localizes with PRKG1, in which activating variants have already been described in thoracic aortic aneurysm, and gMod-M3 co-localized with a metalloprotease (proteins of extra-cellular matrix regulation) cluster. Our results represent a major advance in understanding the complex genetic architecture of MFS and provide the first steps toward prediction of clinical evolution.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41431-018-0164-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6244213PMC
December 2018

BCL11B mutations in patients affected by a neurodevelopmental disorder with reduced type 2 innate lymphoid cells.

Brain 2018 08;141(8):2299-2311

Département de Génétique, Hôpital La Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France.

The transcription factor BCL11B is essential for development of the nervous and the immune system, and Bcl11b deficiency results in structural brain defects, reduced learning capacity, and impaired immune cell development in mice. However, the precise role of BCL11B in humans is largely unexplored, except for a single patient with a BCL11B missense mutation, affected by multisystem anomalies and profound immune deficiency. Using massively parallel sequencing we identified 13 patients bearing heterozygous germline alterations in BCL11B. Notably, all of them are affected by global developmental delay with speech impairment and intellectual disability; however, none displayed overt clinical signs of immune deficiency. Six frameshift mutations, two nonsense mutations, one missense mutation, and two chromosomal rearrangements resulting in diminished BCL11B expression, arose de novo. A further frameshift mutation was transmitted from a similarly affected mother. Interestingly, the most severely affected patient harbours a missense mutation within a zinc-finger domain of BCL11B, probably affecting the DNA-binding structural interface, similar to the recently published patient. Furthermore, the most C-terminally located premature termination codon mutation fails to rescue the progenitor cell proliferation defect in hippocampal slice cultures from Bcl11b-deficient mice. Concerning the role of BCL11B in the immune system, extensive immune phenotyping of our patients revealed alterations in the T cell compartment and lack of peripheral type 2 innate lymphoid cells (ILC2s), consistent with the findings described in Bcl11b-deficient mice. Unsupervised analysis of 102 T lymphocyte subpopulations showed that the patients clearly cluster apart from healthy children, further supporting the common aetiology of the disorder. Taken together, we show here that mutations leading either to BCL11B haploinsufficiency or to a truncated BCL11B protein clinically cause a non-syndromic neurodevelopmental delay. In addition, we suggest that missense mutations affecting specific sites within zinc-finger domains might result in distinct and more severe clinical outcomes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/brain/awy173DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6061686PMC
August 2018
-->