Publications by authors named "Jacques L Michaud"

105 Publications

Sensory processing dysregulations as reliable translational biomarkers in SYNGAP1 haploinsufficiency.

Brain 2021 Nov 13. Epub 2021 Nov 13.

Centre de Recherche, CHU Sainte-Justine (CHUSJ), Montreal, Quebec, Canada.

Amongst the numerous genes associated with intellectual disability, SYNGAP1 stands out for its frequency and penetrance of loss-of-function variants found in patients, as well as the wide range of co-morbid disorders associated with its mutation. Most studies exploring the pathophysiological alterations caused by Syngap1 haploinsufficiency in mouse models have focused on cognitive problems and epilepsy, however whether and to what extent sensory perception and processing are altered by Syngap1 haploinsufficiency is less clear. By performing EEG recordings in awake mice, we identified specific alterations in multiple aspects of auditory and visual processing, including increased baseline gamma oscillation power, increased theta/gamma phase amplitude coupling following stimulus presentation and abnormal neural entrainment in response to different sensory modality-specific frequencies. We also report lack of habituation to repetitive auditory stimuli and abnormal deviant sound detection. Interestingly, we found that most of these alterations are present in human patients as well, thus making them strong candidates as translational biomarkers of sensory-processing alterations associated with SYNGAP1/Syngap1 haploinsufficiency.
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http://dx.doi.org/10.1093/brain/awab329DOI Listing
November 2021

Ectopic expression of and in the paraventricular nucleus of the hypothalamus contributes to defects in haploinsufficiency.

Sci Adv 2021 Oct 27;7(44):eabh4503. Epub 2021 Oct 27.

Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.

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http://dx.doi.org/10.1126/sciadv.abh4503DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8550250PMC
October 2021

Differential auditory brain response abnormalities in two intellectual disability conditions: SYNGAP1 mutations and Down syndrome.

Clin Neurophysiol 2021 08 13;132(8):1802-1812. Epub 2021 May 13.

Department of Psychology, University of Montreal, Montreal, Québec, Canada; CHU Sainte-Justine Research Center, Montreal, Quebec, Canada. Electronic address:

Objective: Altered sensory processing is common in intellectual disability (ID). Here, we study electroencephalographic responses to auditory stimulation in human subjects presenting a rare condition (mutations in SYNGAP1) which causes ID, epilepsy and autism.

Methods: Auditory evoked potentials, time-frequency and inter-trial coherence analyses were used to compare subjects with SYNGAP1 mutations with Down syndrome (DS) and neurotypical (NT) participants (N = 61 ranging from three to 19 years of age).

Results: Altered synchronization in the brain responses to sound were found in both ID groups. The SYNGAP1 mutations group showed less phase-locking in early time windows and lower frequency bands compared to NT, and in later time windows compared to NT and DS. Time-frequency analysis showed more power in beta-gamma in the SYNGAP1 group compared to NT participants.

Conclusions: This study indicated reduced synchronization as well as more high frequencies power in SYNGAP1 mutations, while maintained synchronization was found in the DS group. These results might reflect dysfunctional sensory information processing caused by excitation/inhibition imbalance, or an imperfect compensatory mechanism in SYNGAP1 mutations individuals.

Significance: Our study is the first to reveal brain response abnormalities in auditory sensory processing in SYNGAP1 mutations individuals, that are distinct from DS, another ID condition.
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http://dx.doi.org/10.1016/j.clinph.2021.03.054DOI Listing
August 2021

FBXO28 causes developmental and epileptic encephalopathy with profound intellectual disability.

Epilepsia 2021 01 6;62(1):e13-e21. Epub 2020 Dec 6.

Epilepsy Research Centre, Department of Medicine, Austin Health, The University of Melbourne, Heidelberg, Victoria, Australia.

Chromosome 1q41-q42 deletion syndrome is a rare cause of intellectual disability, seizures, dysmorphology, and multiple anomalies. Two genes in the 1q41-q42 microdeletion, WDR26 and FBXO28, have been implicated in monogenic disease. Patients with WDR26 encephalopathy overlap clinically with those with 1q41-q42 deletion syndrome, whereas only one patient with FBXO28 encephalopathy has been described. Seizures are a prominent feature of 1q41-q42 deletion syndrome; therefore, we hypothesized that pathogenic FBXO28 variants cause developmental and epileptic encephalopathies (DEEs). We describe nine new patients with FBXO28 pathogenic variants (four missense, including one recurrent, three nonsense, and one frameshift) and analyze all 10 known cases to delineate the phenotypic spectrum. All patients had epilepsy and 9 of 10 had DEE, including infantile spasms (3) and a progressive myoclonic epilepsy (1). Median age at seizure onset was 22.5 months (range 8 months to 5 years). Nine of 10 patients had intellectual disability, which was profound in six of nine and severe in three of nine. Movement disorders occurred in eight of 10 patients, six of 10 had hypotonia, four of 10 had acquired microcephaly, and five of 10 had dysmorphic features, albeit different to those typically seen in 1q41-q42 deletion syndrome and WDR26 encephalopathy. We distinguish FBXO28 encephalopathy from both of these disorders with more severe intellectual impairment, drug-resistant epilepsy, and hyperkinetic movement disorders.
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http://dx.doi.org/10.1111/epi.16784DOI Listing
January 2021

A framework for an evidence-based gene list relevant to autism spectrum disorder.

Nat Rev Genet 2020 06 21;21(6):367-376. Epub 2020 Apr 21.

The Centre for Applied Genomics, Program in Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON, Canada.

Autism spectrum disorder (ASD) is often grouped with other brain-related phenotypes into a broader category of neurodevelopmental disorders (NDDs). In clinical practice, providers need to decide which genes to test in individuals with ASD phenotypes, which requires an understanding of the level of evidence for individual NDD genes that supports an association with ASD. Consensus is currently lacking about which NDD genes have sufficient evidence to support a relationship to ASD. Estimates of the number of genes relevant to ASD differ greatly among research groups and clinical sequencing panels, varying from a few to several hundred. This Roadmap discusses important considerations necessary to provide an evidence-based framework for the curation of NDD genes based on the level of information supporting a clinically relevant relationship between a given gene and ASD.
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http://dx.doi.org/10.1038/s41576-020-0231-2DOI Listing
June 2020

A variant of neonatal progeroid syndrome, or Wiedemann-Rautenstrauch syndrome, is associated with a nonsense variant in POLR3GL.

Eur J Hum Genet 2020 04 6;28(4):461-468. Epub 2019 Nov 6.

Medical Genetics Division, Department of Pediatrics, Sainte-Justine University Hospital Center, Montreal, QC, Canada.

Neonatal progeroid syndrome, also known as Wiedemann-Rautenstrauch syndrome, is a rare condition characterized by severe growth retardation, apparent macrocephaly with prominent scalp veins, and lipodystrophy. It is caused by biallelic variants in POLR3A, a gene encoding for a subunit of RNA polymerase III. All variants reported in the literature lead to at least a partial loss-of-function (when considering both alleles together). Here, we describe an individual with several clinical features of neonatal progeroid syndrome in whom exome sequencing revealed a homozygous nonsense variant in POLR3GL (NM_032305.2:c.358C>T; p.(Arg120Ter)). POLR3GL also encodes a subunit of RNA polymerase III and has recently been associated with endosteal hyperostosis and oligodontia in three patients with a phenotype distinct from the patient described here. Given the important role of POLR3GL in the same complex as the protein implicated in neonatal progeroid syndrome, the nature of the variant identified, our RNA studies suggesting nonsense-mediated decay, and the clinical overlap, we propose POLR3GL as a gene causing a variant of neonatal progeroid syndrome and therefore expand the phenotype associated with POLR3GL variants.
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http://dx.doi.org/10.1038/s41431-019-0539-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7080780PMC
April 2020

Association of rare non-coding SNVs in the lung-specific FOXF1 enhancer with a mitigation of the lethal ACDMPV phenotype.

Hum Genet 2019 Dec 4;138(11-12):1301-1311. Epub 2019 Nov 4.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

Haploinsufficiency of FOXF1 causes alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV), a lethal neonatal lung developmental disorder. We describe two similar heterozygous CNV deletions involving the FOXF1 enhancer and re-analyze FOXF1 missense mutation, all associated with an unexpectedly mitigated disease phenotype. In one case, the deletion of the maternal allele of the FOXF1 enhancer caused pulmonary hypertension and histopathologically diagnosed MPV without the typical ACD features. In the second case, the deletion of the paternal enhancer resulted in ACDMPV rather than the expected neonatal lethality. In both cases, FOXF1 expression in lung tissue was higher than usually seen or expected in patients with similar deletions, suggesting an increased activity of the remaining allele of the enhancer. Sequencing of these alleles revealed two rare SNVs, rs150502618-A and rs79301423-T, mapping to the partially overlapping binding sites for TFAP2s and CTCF in the core region of the enhancer. Moreover, in a family with three histopathologically-diagnosed ACDMPV siblings whose missense FOXF1 mutation was inherited from the healthy non-mosaic carrier mother, we have identified a rare SNV rs28571077-A within 2-kb of the above-mentioned non-coding SNVs in the FOXF1 enhancer in the mother, that was absent in the affected newborns and 13 unrelated ACDMPV patients with CNV deletions of this genomic region. Based on the low population frequencies of these three variants, their absence in ACDMPV patients, the results of reporter assay, RNAi and EMSA experiments, and in silico predictions, we propose that the described SNVs might have acted on FOXF1 enhancer as hypermorphs.
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http://dx.doi.org/10.1007/s00439-019-02073-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6874894PMC
December 2019

Biallelic variants in the transcription factor PAX7 are a new genetic cause of myopathy.

Genet Med 2019 11 16;21(11):2521-2531. Epub 2019 May 16.

Department of Pathology, CHU Sainte-Justine, Université de Montréal, Montreal, QC, Canada.

Purpose: Skeletal muscle growth and regeneration rely on muscle stem cells, called satellite cells. Specific transcription factors, particularly PAX7, are key regulators of the function of these cells. Knockout of this factor in mice leads to poor postnatal survival; however, the consequences of a lack of PAX7 in humans have not been established.

Methods: Here, we study five individuals with myopathy of variable severity from four unrelated consanguineous couples. Exome sequencing identified pathogenic variants in the PAX7 gene. Clinical examination, laboratory tests, and muscle biopsies were performed to characterize the disease.

Results: The disease was characterized by hypotonia, ptosis, muscular atrophy, scoliosis, and mildly dysmorphic facial features. The disease spectrum ranged from mild to severe and appears to be progressive. Muscle biopsies showed the presence of atrophic fibers and fibroadipose tissue replacement, with the absence of myofiber necrosis. A lack of PAX7 expression was associated with satellite cell pool exhaustion; however, the presence of residual myoblasts together with regenerating myofibers suggest that a population of PAX7-independent myogenic cells partially contributes to muscle regeneration.

Conclusion: These findings show that biallelic variants in the master transcription factor PAX7 cause a new type of myopathy that specifically affects satellite cell survival.
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http://dx.doi.org/10.1038/s41436-019-0532-zDOI Listing
November 2019

Mutations in ACTL6B Cause Neurodevelopmental Deficits and Epilepsy and Lead to Loss of Dendrites in Human Neurons.

Am J Hum Genet 2019 05 25;104(5):815-834. Epub 2019 Apr 25.

Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, WC1N 3BG London, UK.

We identified individuals with variations in ACTL6B, a component of the chromatin remodeling machinery including the BAF complex. Ten individuals harbored bi-allelic mutations and presented with global developmental delay, epileptic encephalopathy, and spasticity, and ten individuals with de novo heterozygous mutations displayed intellectual disability, ambulation deficits, severe language impairment, hypotonia, Rett-like stereotypies, and minor facial dysmorphisms (wide mouth, diastema, bulbous nose). Nine of these ten unrelated individuals had the identical de novo c.1027G>A (p.Gly343Arg) mutation. Human-derived neurons were generated that recaptured ACTL6B expression patterns in development from progenitor cell to post-mitotic neuron, validating the use of this model. Engineered knock-out of ACTL6B in wild-type human neurons resulted in profound deficits in dendrite development, a result recapitulated in two individuals with different bi-allelic mutations, and reversed on clonal genetic repair or exogenous expression of ACTL6B. Whole-transcriptome analyses and whole-genomic profiling of the BAF complex in wild-type and bi-allelic mutant ACTL6B neural progenitor cells and neurons revealed increased genomic binding of the BAF complex in ACTL6B mutants, with corresponding transcriptional changes in several genes including TPPP and FSCN1, suggesting that altered regulation of some cytoskeletal genes contribute to altered dendrite development. Assessment of bi-alleic and heterozygous ACTL6B mutations on an ACTL6B knock-out human background demonstrated that bi-allelic mutations mimic engineered deletion deficits while heterozygous mutations do not, suggesting that the former are loss of function and the latter are gain of function. These results reveal a role for ACTL6B in neurodevelopment and implicate another component of chromatin remodeling machinery in brain disease.
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http://dx.doi.org/10.1016/j.ajhg.2019.03.022DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6507050PMC
May 2019

Whole exome sequencing identifies novel predisposing genes in neural tube defects.

Mol Genet Genomic Med 2019 01 10;7(1):e00467. Epub 2018 Nov 10.

IRCCS Istituto Giannina Gaslini, Genoa, Italy.

Background: Neural tube defects (NTD) are among the most common defects affecting 1:1000 births. They are caused by a failure of neural tube closure during development. Their clinical presentation is diverse and dependent on the site and severity of the original defect on the embryonic axis. The etiology of NTD is multifactorial involving environmental factors and genetic variants that remain largely unknown.

Methods: We have conducted a whole exome sequencing (WES) study in five new NTD families and pooled the results with WES data from three NTD families and 43 trios that were previously investigated by our group. We analyzed the data using biased candidate gene and unbiased gene burden approaches.

Results: We identified four novel loss-of-function variants in three genes, MTHFR, DLC1, and ITGB1, previously associated with NTD. Notably, DLC1 carried two protein truncating variants in two independent cases. We also demonstrated an enrichment of variants in MYO1E involved in cytoskeletal remodeling. This enrichment reached borderline significance in a replication cohort supporting the association of this new candidate gene to NTD.

Conclusion: These data provide some key insights into the pathogenic mechanisms of human NTD and demonstrate the power of next-generation sequencing in deciphering the genetics of this complex trait.
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http://dx.doi.org/10.1002/mgg3.467DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6382446PMC
January 2019

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

LINE- and Alu-containing genomic instability hotspot at 16q24.1 associated with recurrent and nonrecurrent CNV deletions causative for ACDMPV.

Hum Mutat 2018 12 22;39(12):1916-1925. Epub 2018 Aug 22.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas.

Transposable elements modify human genome by inserting into new loci or by mediating homology-, microhomology-, or homeology-driven DNA recombination or repair, resulting in genomic structural variation. Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare lethal neonatal developmental lung disorder caused by point mutations or copy-number variant (CNV) deletions of FOXF1 or its distant tissue-specific enhancer. Eighty-five percent of 45 ACDMPV-causative CNV deletions, of which junctions have been sequenced, had at least one of their two breakpoints located in a retrotransposon, with more than half of them being Alu elements. We describe a novel ∼35 kb-large genomic instability hotspot at 16q24.1, involving two evolutionarily young LINE-1 (L1) elements, L1PA2 and L1PA3, flanking AluY, two AluSx, AluSx1, and AluJr elements. The occurrence of L1s at this location coincided with the branching out of the Homo-Pan-Gorilla clade, and was preceded by the insertion of AluSx, AluSx1, and AluJr. Our data show that, in addition to mediating recurrent CNVs, L1 and Alu retrotransposons can predispose the human genome to formation of variably sized CNVs, both of clinical and evolutionary relevance. Nonetheless, epigenetic or other genomic features of this locus might also contribute to its increased instability.
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http://dx.doi.org/10.1002/humu.23608DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6240370PMC
December 2018

Global characterization of copy number variants in epilepsy patients from whole genome sequencing.

PLoS Genet 2018 04 12;14(4):e1007285. Epub 2018 Apr 12.

Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Canada.

Epilepsy will affect nearly 3% of people at some point during their lifetime. Previous copy number variants (CNVs) studies of epilepsy have used array-based technology and were restricted to the detection of large or exonic events. In contrast, whole-genome sequencing (WGS) has the potential to more comprehensively profile CNVs but existing analytic methods suffer from limited accuracy. We show that this is in part due to the non-uniformity of read coverage, even after intra-sample normalization. To improve on this, we developed PopSV, an algorithm that uses multiple samples to control for technical variation and enables the robust detection of CNVs. Using WGS and PopSV, we performed a comprehensive characterization of CNVs in 198 individuals affected with epilepsy and 301 controls. For both large and small variants, we found an enrichment of rare exonic events in epilepsy patients, especially in genes with predicted loss-of-function intolerance. Notably, this genome-wide survey also revealed an enrichment of rare non-coding CNVs near previously known epilepsy genes. This enrichment was strongest for non-coding CNVs located within 100 Kbp of an epilepsy gene and in regions associated with changes in the gene expression, such as expression QTLs or DNase I hypersensitive sites. Finally, we report on 21 potentially damaging events that could be associated with known or new candidate epilepsy genes. Our results suggest that comprehensive sequence-based profiling of CNVs could help explain a larger fraction of epilepsy cases.
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http://dx.doi.org/10.1371/journal.pgen.1007285DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5978987PMC
April 2018

Chitayat-Hall and Schaaf-Yang syndromes:a common aetiology: expanding the phenotype of -related disorders.

J Med Genet 2018 05 29;55(5):316-321. Epub 2018 Mar 29.

Division of Clinical Genetics and Metabolism, Department of Pediatrics, The Hospital for Sick Children, Toronto, Ontario, Canada.

Background: Chitayat-Hall syndrome, initially described in 1990, is a rare condition characterised by distal arthrogryposis, intellectual disability, dysmorphic features and hypopituitarism, in particular growth hormone deficiency. The genetic aetiology has not been identified.

Methods And Results: We identified three unrelated families with a total of six affected patients with the clinical manifestations of Chitayat-Hall syndrome. Through whole exome or whole genome sequencing, pathogenic variants in the gene were identified in all affected patients. All disease-causing sequence variants detected are predicted to result in a truncated protein, including one complex variant that comprised a deletion and inversion.

Conclusions: Chitayat-Hall syndrome is caused by pathogenic variants in and shares a common aetiology with the recently described Schaaf-Yang syndrome. The phenotype of -related disorders is expanded to include growth hormone deficiency as an important and treatable complication.
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http://dx.doi.org/10.1136/jmedgenet-2017-105222DOI Listing
May 2018

Recessive mutations in VPS13D cause childhood onset movement disorders.

Ann Neurol 2018 06 10;83(6):1089-1095. Epub 2018 Apr 10.

Department of Pediatrics, Saint Justine University Hospital Center and University of Montreal, Montreal, Canada.

VPS13 protein family members VPS13A through VPS13C have been associated with various recessive movement disorders. We describe the first disease association of rare recessive VPS13D variants including frameshift, missense, and partial duplication mutations with a novel complex, hyperkinetic neurological disorder. The clinical features include developmental delay, a childhood onset movement disorder (chorea, dystonia, or tremor), and progressive spastic ataxia or paraparesis. Characteristic brain magnetic resonance imaging shows basal ganglia or diffuse white matter T2 hyperintensities as seen in Leigh syndrome and choreoacanthocytosis. Muscle biopsy in 1 case showed mitochondrial aggregates and lipidosis, suggesting mitochondrial dysfunction. These findings underline the importance of the VPS13 complex in neurological diseases and a possible role in mitochondrial function. Ann Neurol 2018;83:1089-1095.
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http://dx.doi.org/10.1002/ana.25204DOI Listing
June 2018

A novel homozygous AP4B1 mutation in two brothers with AP-4 deficiency syndrome and ocular anomalies.

Am J Med Genet A 2018 04 12;176(4):985-991. Epub 2018 Feb 12.

Department of Pediatrics, McGill University, Montreal, Canada.

Adaptor protein complex-4 (AP-4) is a heterotetrameric protein complex which plays a key role in vesicle trafficking in neurons. Mutations in genes affecting different subunits of AP-4, including AP4B1, AP4E1, AP4S1, and AP4M1, have been recently associated with an autosomal recessive phenotype, consisting of spastic tetraplegia, and intellectual disability (ID). The overlapping clinical picture among individuals carrying mutations in any of these genes has prompted the terms "AP-4 deficiency syndrome" for this clinically recognizable phenotype. Using whole-exome sequencing, we identified a novel homozygous mutation (c.991C>T, p.Q331*, NM_006594.4) in AP4B1 in two siblings from a consanguineous Pakistani couple, who presented with severe ID, progressive spastic tetraplegia, epilepsy, and microcephaly. Sanger sequencing confirmed the mutation was homozygous in the siblings and heterozygous in the parents. Similar to previously reported individuals with AP4B1 mutations, brain MRI revealed ventriculomegaly and white matter loss. Interestingly, in addition to the typical facial gestalt reported in other AP-4 deficiency cases, the older brother presented with congenital left Horner syndrome, bilateral optic nerve atrophy and cataract, which have not been previously reported in this condition. In summary, we report a novel AP4B1 homozygous mutation in two siblings and review the phenotype of AP-4 deficiency, speculating on a possible role of AP-4 complex in eye development.
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http://dx.doi.org/10.1002/ajmg.a.38628DOI Listing
April 2018

Auditory repetition suppression alterations in relation to cognitive functioning in fragile X syndrome: a combined EEG and machine learning approach.

J Neurodev Disord 2018 01 29;10(1). Epub 2018 Jan 29.

Neuroscience of Early Development (NED), 90 Avenue Vincent-D'indy, Montreal, QC, H2V 2S9, Canada.

Background: Fragile X syndrome (FXS) is a neurodevelopmental genetic disorder causing cognitive and behavioural deficits. Repetition suppression (RS), a learning phenomenon in which stimulus repetitions result in diminished brain activity, has been found to be impaired in FXS. Alterations in RS have been associated with behavioural problems in FXS; however, relations between RS and intellectual functioning have not yet been elucidated.

Methods: EEG was recorded in 14 FXS participants and 25 neurotypical controls during an auditory habituation paradigm using repeatedly presented pseudowords. Non-phased locked signal energy was compared across presentations and between groups using linear mixed models (LMMs) in order to investigate RS effects across repetitions and brain areas and a possible relation to non-verbal IQ (NVIQ) in FXS. In addition, we explored group differences according to NVIQ and we probed the feasibility of training a support vector machine to predict cognitive functioning levels across FXS participants based on single-trial RS features.

Results: LMM analyses showed that repetition effects differ between groups (FXS vs. controls) as well as with respect to NVIQ in FXS. When exploring group differences in RS patterns, we found that neurotypical controls revealed the expected pattern of RS between the first and second presentations of a pseudoword. More importantly, while FXS participants in the ≤ 42 NVIQ group showed no RS, the > 42 NVIQ group showed a delayed RS response after several presentations. Concordantly, single-trial estimates of repetition effects over the first four repetitions provided the highest decoding accuracies in the classification between the FXS participant groups.

Conclusion: Electrophysiological measures of repetition effects provide a non-invasive and unbiased measure of brain responses sensitive to cognitive functioning levels, which may be useful for clinical trials in FXS.
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http://dx.doi.org/10.1186/s11689-018-9223-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5789548PMC
January 2018

Genomic study of severe fetal anomalies and discovery of GREB1L mutations in renal agenesis.

Genet Med 2018 07 26;20(7):745-753. Epub 2017 Oct 26.

CHU Sainte-Justine, Montreal, Quebec, Canada.

Purpose: Fetal anomalies represent a poorly studied group of developmental disorders. Our objective was to assess the impact of whole-exome sequencing (WES) on the investigation of these anomalies.

Methods: We performed WES in 101 fetuses or stillborns who presented prenatally with severe anomalies, including renal a/dysgenesis, VACTERL association (vertebral defects, anal atresia, cardiac defects, tracheoesophageal fistula, renal anomalies, and limb abnormalities), brain anomalies, suspected ciliopathies, multiple major malformations, and akinesia.

Results: A molecular diagnosis was obtained in 19 cases (19%). In 13 of these cases, the diagnosis was not initially suspected by the clinicians because the phenotype was nonspecific or atypical, corresponding in some cases to the severe end of the spectrum of a known disease (e.g., MNX1-, RYR1-, or TUBB-related disorders). In addition, we identified likely pathogenic variants in genes (DSTYK, ACTB, and HIVEP2) previously associated with phenotypes that were substantially different from those found in our cases. Finally, we identified variants in novel candidate genes that were associated with perinatal lethality, including de novo mutations in GREB1L in two cases with bilateral renal agenesis, which represents a significant enrichment of such mutations in our cohort.

Conclusion: Our study opens a window on the distinctive genetic landscape associated with fetal anomalies and highlights the power-but also the challenges-of WES in prenatal diagnosis.
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http://dx.doi.org/10.1038/gim.2017.173DOI Listing
July 2018

High Rate of Recurrent De Novo Mutations in Developmental and Epileptic Encephalopathies.

Am J Hum Genet 2017 Nov;101(5):664-685

Manchester Centre for Genomic Medicine, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester M13 9WL, UK.

Developmental and epileptic encephalopathy (DEE) is a group of conditions characterized by the co-occurrence of epilepsy and intellectual disability (ID), typically with developmental plateauing or regression associated with frequent epileptiform activity. The cause of DEE remains unknown in the majority of cases. We performed whole-genome sequencing (WGS) in 197 individuals with unexplained DEE and pharmaco-resistant seizures and in their unaffected parents. We focused our attention on de novo mutations (DNMs) and identified candidate genes containing such variants. We sought to identify additional subjects with DNMs in these genes by performing targeted sequencing in another series of individuals with DEE and by mining various sequencing datasets. We also performed meta-analyses to document enrichment of DNMs in candidate genes by leveraging our WGS dataset with those of several DEE and ID series. By combining these strategies, we were able to provide a causal link between DEE and the following genes: NTRK2, GABRB2, CLTC, DHDDS, NUS1, RAB11A, GABBR2, and SNAP25. Overall, we established a molecular diagnosis in 63/197 (32%) individuals in our WGS series. The main cause of DEE in these individuals was de novo point mutations (53/63 solved cases), followed by inherited mutations (6/63 solved cases) and de novo CNVs (4/63 solved cases). De novo missense variants explained a larger proportion of individuals in our series than in other series that were primarily ascertained because of ID. Moreover, these DNMs were more frequently recurrent than those identified in ID series. These observations indicate that the genetic landscape of DEE might be different from that of ID without epilepsy.
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http://dx.doi.org/10.1016/j.ajhg.2017.09.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5673604PMC
November 2017

-related intellectual disability syndrome: a recognisable entity.

J Med Genet 2017 09 22;54(9):613-623. Epub 2017 Jul 22.

Laboratory of Medical Genetics, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.

Background: Mutations in forkhead box protein P1 () cause intellectual disability (ID) and specific language impairment (SLI), with or without autistic features (MIM: 613670). Despite multiple case reports no specific phenotype emerged so far.

Methods: We correlate clinical and molecular data of 25 novel and 23 previously reported patients with defects. We evaluated FOXP1 activity by an in vitro luciferase model and assessed protein stability in vitro by western blotting.

Results: Patients show ID, SLI, neuromotor delay (NMD) and recurrent facial features including a high broad forehead, bent downslanting palpebral fissures, ptosis and/or blepharophimosis and a bulbous nasal tip. Behavioural problems and autistic features are common. Brain, cardiac and urogenital malformations can be associated. More severe ID and NMD, sensorineural hearing loss and feeding difficulties are more common in patients with interstitial 3p deletions (14 patients) versus patients with monogenic defects (34 patients). Mutations result in impaired transcriptional repression and/or reduced protein stability.

Conclusions: -related ID syndrome is a recognisable entity with a wide clinical spectrum and frequent systemic involvement. Our data will be helpful to evaluate genotype-phenotype correlations when interpreting next-generation sequencing data obtained in patients with ID and/or SLI and will guide clinical management.
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http://dx.doi.org/10.1136/jmedgenet-2017-104579DOI Listing
September 2017

Functionally Null Missense Mutation Associates Strongly with Ovarian Carcinoma.

Cancer Res 2017 08 23;77(16):4517-4529. Epub 2017 Jun 23.

Department of Human Genetics, McGill University, Montreal, Canada.

RAD51D is a key player in DNA repair by homologous recombination (HR), and truncating variant carriers have an increased risk for ovarian cancer. However, the contribution of nontruncating variants to cancer predisposition remains uncertain. Using deep sequencing and case-control genotyping studies, we show that in French Canadians, the missense variant c.620C>T;p.S207L is highly prevalent and is associated with a significantly increased risk for ovarian high-grade serous carcinoma (HGSC; 3.8% cases vs. 0.2% controls). The frequency of the p.S207L variant did not significantly differ from that of controls in breast, endometrial, pancreas, or colorectal adenocarcinomas. Functionally, we show that this mutation impairs HR by disrupting the RAD51D-XRCC2 interaction and confers PARP inhibitor sensitivity. These results highlight the importance of a functional RAD51D-XRCC2 interaction to promote HR and prevent the development of HGSC. This study identifies c.620C>T;p.S207L as the first bona fide pathogenic missense cancer susceptibility allele and supports the use of targeted PARP-inhibitor therapies in ovarian cancer patients carrying deleterious missense variants. .
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http://dx.doi.org/10.1158/0008-5472.CAN-17-0190DOI Listing
August 2017

Dysfunction of the Cerebral Glucose Transporter SLC45A1 in Individuals with Intellectual Disability and Epilepsy.

Am J Hum Genet 2017 May 20;100(5):824-830. Epub 2017 Apr 20.

Centre Hospitalier Universitaire Sainte-Justine Research Center, Montreal, QC H3T 1C5, Canada; Departments of Pediatrics and Neurosciences, Université de Montréal, Montreal, QC H3T 1J4, Canada.

Glucose transport across the blood brain barrier and into neural cells is critical for normal cerebral physiologic function. Dysfunction of the cerebral glucose transporter GLUT1 (encoded by SLC2A1) is known to result in epilepsy, intellectual disability (ID), and movement disorder. Using whole-exome sequencing, we identified rare homozygous missense variants (c.526C>T [p.Arg176Trp] and c.629C>T [p.Ala210Val]) in SLC45A1, encoding another cerebral glucose transporter, in two consanguineous multiplex families with moderate to severe ID, epilepsy, and variable neuropsychiatric features. The variants segregate with the phenotype in these families, affect well-conserved amino acids, and are predicted to be damaging by in silico programs. Intracellular glucose transport activity of the p.Arg176Trp and p.Ala210Val SLC45A1 variants, measured in transfected COS-7 cells, was approximately 50% (p = 0.013) and 33% (p = 0.008) lower, respectively, than that of intact SLC45A1. These results indicate that residues at positions 176 and 210 are critical for the glucose transport activity of SLC45A1. All together, our data strongly suggest that recessive mutations in SLC45A1 cause ID and epilepsy. SLC45A1 thus represents the second cerebral glucose transporter, in addition to GLUT1, to be involved in neurodevelopmental disability. Identification of additional individuals with mutations in SLC45A1 will allow better definition of the associated phenotypic spectrum and the exploration of potential targeted treatment options.
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http://dx.doi.org/10.1016/j.ajhg.2017.03.009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5420346PMC
May 2017

Expansion of the clinical phenotype of the distal 10q26.3 deletion syndrome to include ataxia and hyperemia of the hands and feet.

Am J Med Genet A 2017 Jun 21;173(6):1611-1619. Epub 2017 Apr 21.

Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Ontario.

Distal deletion of the long arm of chromosome 10 is associated with a dysmorphic craniofacial appearance, microcephaly, behavioral issues, developmental delay, intellectual disability, and ocular, urogenital, and limb abnormalities. Herein, we present clinical, molecular, and cytogenetic investigations of four patients, including two siblings, with nearly identical terminal deletions of 10q26.3, all of whom have an atypical presentation of this syndrome. Their prominent features include ataxia, mild-to-moderate intellectual disability, and hyperemia of the hands and feet, and they do not display many of the other features commonly associated with deletions of this region. These results point to a novel gene locus associated with ataxia and highlight the variability of the clinical presentation of patients with deletions of this region.
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http://dx.doi.org/10.1002/ajmg.a.38231DOI Listing
June 2017

Heterozygous HNRNPU variants cause early onset epilepsy and severe intellectual disability.

Hum Genet 2017 07 9;136(7):821-834. Epub 2017 Apr 9.

Institut für Humangenetik, Universitätsklinikum Essen, Universität Duisburg-Essen, Hufelandstr. 55, 45122, Essen, Germany.

Pathogenic variants in genes encoding subunits of the spliceosome are the cause of several human diseases, such as neurodegenerative diseases. The RNA splicing process is facilitated by the spliceosome, a large RNA-protein complex consisting of small nuclear ribonucleoproteins (snRNPs), and many other proteins, such as heterogeneous nuclear ribonucleoproteins (hnRNPs). The HNRNPU gene (OMIM *602869) encodes the heterogeneous nuclear ribonucleoprotein U, which plays a crucial role in mammalian development. HNRNPU is expressed in the fetal brain and adult heart, kidney, liver, brain, and cerebellum. Microdeletions in the 1q44 region encompassing HNRNPU have been described in patients with intellectual disability (ID) and other clinical features, such as seizures, corpus callosum abnormalities (CCA), and microcephaly. Recently, pathogenic HNRNPU variants were identified in large ID and epileptic encephalopathy cohorts. In this study, we provide detailed clinical information of five novels and review two of the previously published individuals with (likely) pathogenic de novo variants in the HNRNPU gene including three non-sense and two missense variants, one small intragenic deletion, and one duplication. The phenotype in individuals with variants in HNRNPU is characterized by early onset seizures (6/7), severe ID (6/6), severe speech impairment (6/6), hypotonia (6/7), and central nervous system (CNS) (5/6), cardiac (4/6), and renal abnormalities (3/4). In this study, we broaden the clinical and mutational HNRNPU-associated spectrum, and demonstrate that heterozygous HNRNPU variants cause epilepsy, severe ID with striking speech impairment and variable CNS, cardiac, and renal anomalies.
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http://dx.doi.org/10.1007/s00439-017-1795-6DOI Listing
July 2017

Altered visual repetition suppression in Fragile X Syndrome: New evidence from ERPs and oscillatory activity.

Int J Dev Neurosci 2017 Jun 19;59:52-59. Epub 2017 Mar 19.

Departement de Psychologie, Université de Montréal, Montreal, Canada; Neuroscience of Early Development (NED), Montreal, Canada; Centre de Recherche en Neuropsychologie et Cognition (CERNEC), Montreal, Canada; Research Center of the CHU Ste-Justine Mother and Child University Hospital Center, Université de Montreal, Quebec, Canada; International Laboratory for Brain, Music and Sound Research (BRAMS), Montreal, Quebec, Canada.

Fragile X Syndrome (FXS) is a neurodevelopmental genetic disorder associated with cognitive and behavioural deficits. In particular, neuronal habituation processes have been shown to be altered in FXS patients. Yet, while such deficits have been primarily explored using auditory stimuli, less is known in the visual modality. Here, we investigated the putative alteration of repetition suppression using faces in FXS patients compared to controls that had the same age distribution. Electroencephalographic (EEG) signals were acquired while participants were presented with 18 different faces, each repeated ten times successively. The repetition suppression effect was probed by comparing the brain responses to the first and second presentation, based on task-evoked event-related potentials (ERP) as well as on task-induced oscillatory activity. We found different patterns of habituation for controls and patients both in ERP and oscillatory power. While the N170 was not affected by face repetition in controls, it was altered in FXS patients. Conversely, while a repetition suppression effect was observed in the theta band (4-8Hz) over frontal and parieto-occipital areas in controls, it was not seen in FXS patients. These results provide the first evidence for diminished ERP and oscillatory habituation effects in response to face repetitions in FXS. These findings extend previous observations of impairments in learning mechanisms and may be linked to deficits in the maturation processes of synapses caused by the mutation. The present study contributes to bridging the gap between animal models of synaptic plasticity dysfunctions and human research in FXS.
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http://dx.doi.org/10.1016/j.ijdevneu.2017.03.008DOI Listing
June 2017

Overstressed response to EIF2S3 variants in MEHMO syndrome.

Hum Mutat 2017 04;38(4):337

CHU Sainte-Justine and Université de Montréal, Canada.

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http://dx.doi.org/10.1002/humu.23195DOI Listing
April 2017
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