Publications by authors named "Agnes Rastetter"

22 Publications

  • Page 1 of 1

Variants in the SK2 channel gene (KCNN2) lead to dominant neurodevelopmental movement disorders.

Brain 2020 12;143(12):3564-3573

Institute of Human Genetics, University Hospital Magdeburg, Magdeburg, Germany.

KCNN2 encodes the small conductance calcium-activated potassium channel 2 (SK2). Rodent models with spontaneous Kcnn2 mutations show abnormal gait and locomotor activity, tremor and memory deficits, but human disorders related to KCNN2 variants are largely unknown. Using exome sequencing, we identified a de novo KCNN2 frameshift deletion in a patient with learning disabilities, cerebellar ataxia and white matter abnormalities on brain MRI. This discovery prompted us to collect data from nine additional patients with de novo KCNN2 variants (one nonsense, one splice site, six missense variants and one in-frame deletion) and one family with a missense variant inherited from the affected mother. We investigated the functional impact of six selected variants on SK2 channel function using the patch-clamp technique. All variants tested but one, which was reclassified to uncertain significance, led to a loss-of-function of SK2 channels. Patients with KCNN2 variants had motor and language developmental delay, intellectual disability often associated with early-onset movement disorders comprising cerebellar ataxia and/or extrapyramidal symptoms. Altogether, our findings provide evidence that heterozygous variants, likely causing a haploinsufficiency of the KCNN2 gene, lead to novel autosomal dominant neurodevelopmental movement disorders mirroring phenotypes previously described in rodents.
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http://dx.doi.org/10.1093/brain/awaa346DOI Listing
December 2020

Exome Sequencing Reveals Signal Transduction Genes Involved in Impulse Control Disorders in Parkinson's Disease.

Front Neurol 2020 21;11:641. Epub 2020 Jul 21.

Sorbonne Université, INSERM UMRS 1127, CNRS UMR 7225, Institut du Cerveau et de la Moelle, ICM, Paris, France.

Impulse control disorders (ICDs) frequently complicate dopamine agonist (DA) therapy in Parkinson's disease (PD). There is growing evidence of a high heritability for ICDs in the general population and in PD. Variants on genes belonging to the reward pathway have been shown to account for part of this heritability. We aimed to identify new pathways associated with ICDs in PD. Thirty-six Parkinsonian patients on DA therapy with ( = 18) and without ICDs ( = 18) matched on age at PD's onset, and gender was selected to represent the most extreme phenotypes of their category. Exome sequencing was performed, and variants with a strong functional impact in brain-expressed genes were selected. Allele frequencies and their distribution in genes and pathways were analyzed with single variant and SKAT-O tests. The 10 most associated variants, genes, and pathways were retained for replication in the Parkinson's progression markers initiative (PPMI) cohort. None of markers tested passed the significance threshold adjusted for multiple comparisons. However, the "Adenylate cyclase activating" pathway, one of the top associated pathways in the discovery data set ( = 1.6 × 10) was replicated in the PPMI cohort and was significantly associated with ICDs in a pooled analysis (combined value 3.3 × 10). Two of the 10 most associated variants belonged to genes implicated in cAMP and ERK signaling (rs34193571 in = 5 × 10; rs1877652 in = 8 × 10) although non-significant after Bonferroni correction. Our results suggest that genes implicated in the signaling pathways linked to G protein-coupled receptors participate to genetic susceptibility to ICDs in PD.
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http://dx.doi.org/10.3389/fneur.2020.00641DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7385236PMC
July 2020

Mutations in the KIF21B kinesin gene cause neurodevelopmental disorders through imbalanced canonical motor activity.

Nat Commun 2020 05 15;11(1):2441. Epub 2020 May 15.

Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.

KIF21B is a kinesin protein that promotes intracellular transport and controls microtubule dynamics. We report three missense variants and one duplication in KIF21B in individuals with neurodevelopmental disorders associated with brain malformations, including corpus callosum agenesis (ACC) and microcephaly. We demonstrate, in vivo, that the expression of KIF21B missense variants specifically recapitulates patients' neurodevelopmental abnormalities, including microcephaly and reduced intra- and inter-hemispheric connectivity. We establish that missense KIF21B variants impede neuronal migration through attenuation of kinesin autoinhibition leading to aberrant KIF21B motility activity. We also show that the ACC-related KIF21B variant independently perturbs axonal growth and ipsilateral axon branching through two distinct mechanisms, both leading to deregulation of canonical kinesin motor activity. The duplication introduces a premature termination codon leading to nonsense-mediated mRNA decay. Although we demonstrate that Kif21b haploinsufficiency leads to an impaired neuronal positioning, the duplication variant might not be pathogenic. Altogether, our data indicate that impaired KIF21B autoregulation and function play a critical role in the pathogenicity of human neurodevelopmental disorder.
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http://dx.doi.org/10.1038/s41467-020-16294-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7229210PMC
May 2020

PAK3 mutations responsible for severe intellectual disability and callosal agenesis inhibit cell migration.

Neurobiol Dis 2020 03 14;136:104709. Epub 2019 Dec 14.

Department of Cognition and Behavior, Paris-Saclay Institute of Neuroscience (Neuro-PSI CNRS, UMR 9197), Paris-Sud and Paris-Saclay Universities, Orsay, France. Electronic address:

Corpus callosum agenesis (CCA) is a brain malformation associated with a wide clinical spectrum including intellectual disability (ID) and an etiopathological complexity. We identified a novel missense G424R mutation in the X-linked p21-activated kinase 3 (PAK3) gene in a boy presenting with severe ID, microcephaly and CCA and his fetal sibling with CCA and severe hydrocephaly. PAK3 kinase is known to control synaptic plasticity and dendritic spine dynamics but its implication is less characterized in brain ontogenesis. In order to identify developmental functions of PAK3 impacted by mutations responsible for CCA, we compared the biochemical and biological effects of three PAK3 mutations localized in the catalytic domain. These mutations include two "severe" G424R and K389N variants (responsible for severe ID and CCA) and the "mild" A365E variant (responsible for nonsyndromic mild ID). Whereas they suppressed kinase activity, only the two severe variants displayed normal protein stability. Furthermore, they increased interactions between PAK3 and the guanine exchange factor αPIX/ARHGEF6, disturbed adhesion point dynamics and cell spreading, and severely impacted cell migration. Our findings highlight new molecular defects associated with mutations responsible for severe clinical phenotypes with developmental brain defects.
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http://dx.doi.org/10.1016/j.nbd.2019.104709DOI Listing
March 2020

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

Targeted versus untargeted omics - the CAFSA story.

J Inherit Metab Dis 2018 05 8;41(3):447-456. Epub 2018 Feb 8.

Université Pierre et Marie Curie, Groupe de Recherche Clinique Neurométabolique et Centre de Référence Neurométabolique Adulte, Paris, France.

Background: In 2009, untargeted metabolomics led to the delineation of a new clinico-biological entity called cerebellar ataxia with elevated cerebrospinal free sialic acid, or CAFSA. In order to elucidate CAFSA, we applied sequentially targeted and untargeted omic approaches.

Methods And Results: First, we studied five of the six CAFSA patients initially described. Besides increased CSF free sialic acid concentrations, three patients presented with markedly decreased 5-methyltetrahydrofolate (5-MTHF) CSF concentrations. Exome sequencing identified a homozygous POLG mutation in two affected sisters, but failed to identify a causative gene in the three sporadic patients with high sialic acid but low 5-MTHF. Using targeted mass spectrometry, we confirmed that free sialic acid was increased in the CSF of a third known POLG-mutated patient. We then pursued pathophysiological analyses of CAFSA using mass spectrometry-based metabolomics on CSF from two sporadic CAFSA patients as well as 95 patients with an unexplained encephalopathy and 39 controls. This led to the identification of a common metabotype between the two initial CAFSA patients and three additional patients, including one patient with Kearns-Sayre syndrome. Metabolites of the CSF metabotype were positioned in a reconstruction of the human metabolic network, which highlighted the proximity of the metabotype with acetyl-CoA and carnitine, two key metabolites regulating mitochondrial energy homeostasis.

Conclusion: Our genetic and metabolomics analyses suggest that CAFSA is a heterogeneous entity related to mitochondrial DNA alterations either through POLG mutations or a mechanism similar to what is observed in Kearns-Sayre syndrome.
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http://dx.doi.org/10.1007/s10545-017-0134-3DOI Listing
May 2018

DCC mutation update: Congenital mirror movements, isolated agenesis of the corpus callosum, and developmental split brain syndrome.

Hum Mutat 2018 01 11;39(1):23-39. Epub 2017 Nov 11.

Bruce Lefroy Centre for Genetic Health Research, Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia.

The deleted in colorectal cancer (DCC) gene encodes the netrin-1 (NTN1) receptor DCC, a transmembrane protein required for the guidance of commissural axons. Germline DCC mutations disrupt the development of predominantly commissural tracts in the central nervous system (CNS) and cause a spectrum of neurological disorders. Monoallelic, missense, and predicted loss-of-function DCC mutations cause congenital mirror movements, isolated agenesis of the corpus callosum (ACC), or both. Biallelic, predicted loss-of-function DCC mutations cause developmental split brain syndrome (DSBS). Although the underlying molecular mechanisms leading to disease remain poorly understood, they are thought to stem from reduced or perturbed NTN1 signaling. Here, we review the 26 reported DCC mutations associated with abnormal CNS development in humans, including 14 missense and 12 predicted loss-of-function mutations, and discuss their associated clinical characteristics and diagnostic features. We provide an update on the observed genotype-phenotype relationships of congenital mirror movements, isolated ACC and DSBS, and correlate this to our current understanding of the biological function of DCC in the development of the CNS. All mutations and their associated phenotypes were deposited into a locus-specific LOVD (https://databases.lovd.nl/shared/genes/DCC).
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http://dx.doi.org/10.1002/humu.23361DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5722687PMC
January 2018

Genetic and phenotypic dissection of 1q43q44 microdeletion syndrome and neurodevelopmental phenotypes associated with mutations in ZBTB18 and HNRNPU.

Hum Genet 2017 04 10;136(4):463-479. Epub 2017 Mar 10.

Institut de Génétique Médicale, CHRU de Lille, Lille, France.

Subtelomeric 1q43q44 microdeletions cause a syndrome associating intellectual disability, microcephaly, seizures and anomalies of the corpus callosum. Despite several previous studies assessing genotype-phenotype correlations, the contribution of genes located in this region to the specific features of this syndrome remains uncertain. Among those, three genes, AKT3, HNRNPU and ZBTB18 are highly expressed in the brain and point mutations in these genes have been recently identified in children with neurodevelopmental phenotypes. In this study, we report the clinical and molecular data from 17 patients with 1q43q44 microdeletions, four with ZBTB18 mutations and seven with HNRNPU mutations, and review additional data from 37 previously published patients with 1q43q44 microdeletions. We compare clinical data of patients with 1q43q44 microdeletions with those of patients with point mutations in HNRNPU and ZBTB18 to assess the contribution of each gene as well as the possibility of epistasis between genes. Our study demonstrates that AKT3 haploinsufficiency is the main driver for microcephaly, whereas HNRNPU alteration mostly drives epilepsy and determines the degree of intellectual disability. ZBTB18 deletions or mutations are associated with variable corpus callosum anomalies with an incomplete penetrance. ZBTB18 may also contribute to microcephaly and HNRNPU to thin corpus callosum, but with a lower penetrance. Co-deletion of contiguous genes has additive effects. Our results confirm and refine the complex genotype-phenotype correlations existing in the 1qter microdeletion syndrome and define more precisely the neurodevelopmental phenotypes associated with genetic alterations of AKT3, ZBTB18 and HNRNPU in humans.
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http://dx.doi.org/10.1007/s00439-017-1772-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5360844PMC
April 2017

Mutations in DCC cause isolated agenesis of the corpus callosum with incomplete penetrance.

Nat Genet 2017 Apr 27;49(4):511-514. Epub 2017 Feb 27.

AP-HP, Groupe Hospitalier Saint-Louis -La Riboisière -Fernand Vidal, Laboratoire de Génétique, Paris, France.

Brain malformations involving the corpus callosum are common in children with developmental disabilities. We identified DCC mutations in four families and five sporadic individuals with isolated agenesis of the corpus callosum (ACC) without intellectual disability. DCC mutations result in variable dominant phenotypes with decreased penetrance, including mirror movements and ACC associated with a favorable developmental prognosis. Possible phenotypic modifiers include the type and location of mutation and the sex of the individual.
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http://dx.doi.org/10.1038/ng.3794DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5894478PMC
April 2017

ARID1B mutations are the major genetic cause of corpus callosum anomalies in patients with intellectual disability.

Brain 2016 11;139(11):e64

Assistance Publique-Hôpitaux de Paris, Département de Génétique and Centre de Référence Déficiences Intellectuelles de Causes Rares and GRC UPMC "Déficiences Intellectuelles et Autisme", Groupe Hospitalier Pitié-Salpêtrière, Paris, France.

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http://dx.doi.org/10.1093/brain/aww181DOI Listing
November 2016

Genetic and neurodevelopmental spectrum of SYNGAP1-associated intellectual disability and epilepsy.

J Med Genet 2016 08 17;53(8):511-22. Epub 2016 Mar 17.

Svt. Luka's Institute of Child Neurology and Epilepsy, Moscow, Russia.

Objective: We aimed to delineate the neurodevelopmental spectrum associated with SYNGAP1 mutations and to investigate genotype-phenotype correlations.

Methods: We sequenced the exome or screened the exons of SYNGAP1 in a total of 251 patients with neurodevelopmental disorders. Molecular and clinical data from patients with SYNGAP1 mutations from other centres were also collected, focusing on developmental aspects and the associated epilepsy phenotype. A review of SYNGAP1 mutations published in the literature was also performed.

Results: We describe 17 unrelated affected individuals carrying 13 different novel loss-of-function SYNGAP1 mutations. Developmental delay was the first manifestation of SYNGAP1-related encephalopathy; intellectual disability became progressively obvious and was associated with autistic behaviours in eight patients. Hypotonia and unstable gait were frequent associated neurological features. With the exception of one patient who experienced a single seizure, all patients had epilepsy, characterised by falls or head drops due to atonic or myoclonic seizures, (myoclonic) absences and/or eyelid myoclonia. Triggers of seizures were frequent (n=7). Seizures were pharmacoresistant in half of the patients. The severity of the epilepsy did not correlate with the presence of autistic features or with the severity of cognitive impairment. Mutations were distributed throughout the gene, but spared spliced 3' and 5' exons. Seizures in patients with mutations in exons 4-5 were more pharmacoresponsive than in patients with mutations in exons 8-15.

Conclusions: SYNGAP1 encephalopathy is characterised by early neurodevelopmental delay typically preceding the onset of a relatively recognisable epilepsy comprising generalised seizures (absences, myoclonic jerks) and frequent triggers.
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http://dx.doi.org/10.1136/jmedgenet-2015-103451DOI Listing
August 2016

Hypomorphic variants of cationic amino acid transporter 3 in males with autism spectrum disorders.

Amino Acids 2015 Dec 28;47(12):2647-58. Epub 2015 Jul 28.

Sorbonne Universités, UPMC Univ Paris 06, UMR S 1127, ICM, 75013, Paris, France.

Cationic amino acid transporters (CATs) mediate the entry of L-type cationic amino acids (arginine, ornithine and lysine) into the cells including neurons. CAT-3, encoded by the SLC7A3 gene on chromosome X, is one of the three CATs present in the human genome, with selective expression in brain. SLC7A3 is highly intolerant to variation in humans, as attested by the low frequency of deleterious variants in available databases, but the impact on variants in this gene in humans remains undefined. In this study, we identified a missense variant in SLC7A3, encoding the CAT-3 cationic amino acid transporter, on chromosome X by exome sequencing in two brothers with autism spectrum disorder (ASD). We then sequenced the SLC7A3 coding sequence in 148 male patients with ASD and identified three additional rare missense variants in unrelated patients. Functional analyses of the mutant transporters showed that two of the four identified variants cause severe or moderate loss of CAT-3 function due to altered protein stability or abnormal trafficking to the plasma membrane. The patient with the most deleterious SLC7A3 variant had high-functioning autism and epilepsy, and also carries a de novo 16p11.2 duplication possibly contributing to his phenotype. This study shows that rare hypomorphic variants of SLC7A3 exist in male individuals and suggest that SLC7A3 variants possibly contribute to the etiology of ASD in male subjects in association with other genetic factors.
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http://dx.doi.org/10.1007/s00726-015-2057-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4633447PMC
December 2015

Meta-analysis of SHANK Mutations in Autism Spectrum Disorders: a gradient of severity in cognitive impairments.

PLoS Genet 2014 Sep 4;10(9):e1004580. Epub 2014 Sep 4.

Assistance Publique-Hôpitaux de Paris, Hôpital Pitié-Salpêtrière, Département de Génétique et de Cytogénétique, Unité fonctionnelle de génétique clinique, Paris, France; Centre de Référence "Déficiences intellectuelles de causes rares", Paris, France and Groupe de Recherche Clinique "Déficience intellectuelle et autisme", UPMC, Paris, France; Assistance Publique-Hôpitaux de Paris, Hôpital Armand Trousseau, Service de Neuropédiatrie, Paris, France.

SHANK genes code for scaffold proteins located at the post-synaptic density of glutamatergic synapses. In neurons, SHANK2 and SHANK3 have a positive effect on the induction and maturation of dendritic spines, whereas SHANK1 induces the enlargement of spine heads. Mutations in SHANK genes have been associated with autism spectrum disorders (ASD), but their prevalence and clinical relevance remain to be determined. Here, we performed a new screen and a meta-analysis of SHANK copy-number and coding-sequence variants in ASD. Copy-number variants were analyzed in 5,657 patients and 19,163 controls, coding-sequence variants were ascertained in 760 to 2,147 patients and 492 to 1,090 controls (depending on the gene), and, individuals carrying de novo or truncating SHANK mutations underwent an extensive clinical investigation. Copy-number variants and truncating mutations in SHANK genes were present in ∼1% of patients with ASD: mutations in SHANK1 were rare (0.04%) and present in males with normal IQ and autism; mutations in SHANK2 were present in 0.17% of patients with ASD and mild intellectual disability; mutations in SHANK3 were present in 0.69% of patients with ASD and up to 2.12% of the cases with moderate to profound intellectual disability. In summary, mutations of the SHANK genes were detected in the whole spectrum of autism with a gradient of severity in cognitive impairment. Given the rare frequency of SHANK1 and SHANK2 deleterious mutations, the clinical relevance of these genes remains to be ascertained. In contrast, the frequency and the penetrance of SHANK3 mutations in individuals with ASD and intellectual disability-more than 1 in 50-warrant its consideration for mutation screening in clinical practice.
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http://dx.doi.org/10.1371/journal.pgen.1004580DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4154644PMC
September 2014

De novo mutations in HCN1 cause early infantile epileptic encephalopathy.

Nat Genet 2014 Jun 20;46(6):640-5. Epub 2014 Apr 20.

1] Neurogenetics Group, Department of Molecular Genetics, VIB, Antwerp, Belgium. [2] Laboratory of Neurogenetics, Institute Born-Bunge, University of Antwerp, Antwerp, Belgium.

Hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels contribute to cationic Ih current in neurons and regulate the excitability of neuronal networks. Studies in rat models have shown that the Hcn1 gene has a key role in epilepsy, but clinical evidence implicating HCN1 mutations in human epilepsy is lacking. We carried out exome sequencing for parent-offspring trios with fever-sensitive, intractable epileptic encephalopathy, leading to the discovery of two de novo missense HCN1 mutations. Screening of follow-up cohorts comprising 157 cases in total identified 4 additional amino acid substitutions. Patch-clamp recordings of Ih currents in cells expressing wild-type or mutant human HCN1 channels showed that the mutations had striking but divergent effects on homomeric channels. Individuals with mutations had clinical features resembling those of Dravet syndrome with progression toward atypical absences, intellectual disability and autistic traits. These findings provide clear evidence that de novo HCN1 point mutations cause a recognizable early-onset epileptic encephalopathy in humans.
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http://dx.doi.org/10.1038/ng.2952DOI Listing
June 2014

Annonacin, a natural lipophilic mitochondrial complex I inhibitor, increases phosphorylation of tau in the brain of FTDP-17 transgenic mice.

Exp Neurol 2014 Mar 3;253:113-25. Epub 2014 Jan 3.

Experimental Neurology, Philipps University, D-35037 Marburg, Germany; German Center for Neurodegenerative Diseases (DZNE), D-81677 Munich, Germany; Department of Neurology, Technical University Munich, D-81377 Munich, Germany. Electronic address:

Both genetic and environmental factors likely contribute to the neuropathology of tauopathies, but it remains unclear how specific genetic backgrounds affect the susceptibility towards environmental toxins. Mutations in the tau gene have been associated with familial tauopathies, while annonacin, a plant-derived mitochondrial inhibitor, has been implicated in an environmental form of tauopathy. We therefore determined whether there was a pathogenic synergy between annonacin exposure and the expression of the R406W-tau mutation in transgenic mice. We found that annonacin exposure caused an increase in the number of neurons with phosphorylated tau in the somatodendritic compartment in several brain areas in R406W(+/+) mice as opposed to mice that had only the endogenous mouse tau (R406W(-/-)). Western blot analysis demonstrated a concomitant increase in total tau protein without increase in tau mRNA, but reduced proteasomal proteolytic activity in R406W(+/+), but not R406W(-/-) mice, upon annonacin-treatment. Phosphorylated tau levels exceeded the increase in total tau protein, along with increased levels of different tau kinases, foremost a striking increase in the p25/p35 ratio, known to activate the tau kinase Cdk5. In summary, we observed a synergistic interaction between annonacin exposure and the presence of the R406W-tau mutation, which resulted in reduced degradation, increased phosphorylation and redistribution of neuronal tau.
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http://dx.doi.org/10.1016/j.expneurol.2013.12.017DOI Listing
March 2014

Prospective diagnostic analysis of copy number variants using SNP microarrays in individuals with autism spectrum disorders.

Eur J Hum Genet 2014 Jan 1;22(1):71-8. Epub 2013 May 1.

1] INSERM, U975 (CRICM), Institut du cerveau et de la moelle épinière (ICM), Hôpital Pitié-Salpêtrière, Paris, France [2] CNRS 7225 (CRICM), Hôpital Pitié-Salpêtrière, Paris, France [3] Université Pierre et Marie Curie-Paris-6 (UPMC), UMR_S 975, Paris, France [4] AP-HP, Hôpital Pitié-Salpêtrière, Département de Génétique et de Cytogénétique, Unité fonctionnelle de génétique clinique, Paris, France [5] AP-HP, Hôpital Pitié-Salpêtrière, Département de Génétique et de Cytogénétique, Unité fonctionnelle de neurogénétique moléculaire et cellulaire, Paris, France.

Copy number variants (CNVs) have repeatedly been found to cause or predispose to autism spectrum disorders (ASDs). For diagnostic purposes, we screened 194 individuals with ASDs for CNVs using Illumina SNP arrays. In several probands, we also analyzed candidate genes located in inherited deletions to unmask autosomal recessive variants. Three CNVs, a de novo triplication of chromosome 15q11-q12 of paternal origin, a deletion on chromosome 9p24 and a de novo 3q29 deletion, were identified as the cause of the disorder in one individual each. An autosomal recessive cause was considered possible in two patients: a homozygous 1p31.1 deletion encompassing PTGER3 and a deletion of the entire DOCK10 gene associated with a rare hemizygous missense variant. We also identified multiple private or recurrent CNVs, the majority of which were inherited from asymptomatic parents. Although highly penetrant CNVs or variants inherited in an autosomal recessive manner were detected in rare cases, our results mainly support the hypothesis that most CNVs contribute to ASDs in association with other CNVs or point variants located elsewhere in the genome. Identification of these genetic interactions in individuals with ASDs constitutes a formidable challenge.
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http://dx.doi.org/10.1038/ejhg.2013.88DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3865413PMC
January 2014

Loss of function of glucocerebrosidase GBA2 is responsible for motor neuron defects in hereditary spastic paraplegia.

Am J Hum Genet 2013 Feb 17;92(2):238-44. Epub 2013 Jan 17.

Unité Mixte de Recherche S975, Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière, Pitie-Salpêtrière Hospital, Université Pierre et Marie Curie (Paris 6), Paris, France.

Spastic paraplegia 46 refers to a locus mapped to chromosome 9 that accounts for a complicated autosomal-recessive form of hereditary spastic paraplegia (HSP). With next-generation sequencing in three independent families, we identified four different mutations in GBA2 (three truncating variants and one missense variant), which were found to cosegregate with the disease and were absent in controls. GBA2 encodes a microsomal nonlysosomal glucosylceramidase that catalyzes the conversion of glucosylceramide to free glucose and ceramide and the hydrolysis of bile acid 3-O-glucosides. The missense variant was also found at the homozygous state in a simplex subject in whom no residual glucocerebrosidase activity of GBA2 could be evidenced in blood cells, opening the way to a possible measurement of this enzyme activity in clinical practice. The overall phenotype was a complex HSP with mental impairment, cataract, and hypogonadism in males associated with various degrees of corpus callosum and cerebellar atrophy on brain imaging. Antisense morpholino oligonucleotides targeting the zebrafish GBA2 orthologous gene led to abnormal motor behavior and axonal shortening/branching of motoneurons that were rescued by the human wild-type mRNA but not by applying the same mRNA containing the missense mutation. This study highlights the role of ceramide metabolism in HSP pathology.
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http://dx.doi.org/10.1016/j.ajhg.2012.11.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3567271PMC
February 2013

Spatacsin and spastizin act in the same pathway required for proper spinal motor neuron axon outgrowth in zebrafish.

Neurobiol Dis 2012 Dec 16;48(3):299-308. Epub 2012 Jul 16.

INSERM, U975, 75013 Paris, France.

Hereditary spastic paraplegias (HSPs) are rare neurological conditions caused by degeneration of the long axons of the cerebrospinal tracts, leading to locomotor impairment and additional neurological symptoms. There are more than 40 different causative genes, 24 of which have been identified, including SPG11 and SPG15 mutated in complex clinical forms. Since the vast majority of the causative mutations lead to loss of function of the corresponding proteins, we made use of morpholino-oligonucleotide (MO)-mediated gene knock-down to generate zebrafish models of both SPG11 and SPG15 and determine how invalidation of the causative genes (zspg11 and zspg15) during development might contribute to the disease. Micro-injection of MOs targeting each gene caused locomotor impairment and abnormal branching of spinal cord motor neurons at the neuromuscular junction. More severe phenotypes with abnormal tail developments were also seen. Moreover, partial depletion of both proteins at sub-phenotypic levels resulted in the same phenotypes, suggesting for the first time, in vivo, a genetic interaction between these genes. In conclusion, the zebrafish orthologues of the SPG11 and SPG15 genes are important for proper development of the axons of spinal motor neurons and likely act in a common pathway to promote their proper path finding towards the neuromuscular junction.
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http://dx.doi.org/10.1016/j.nbd.2012.07.003DOI Listing
December 2012

Reversible generalized dystonia and encephalopathy from thiamine transporter 2 deficiency.

Mov Disord 2012 Sep 6;27(10):1295-8. Epub 2012 Jul 6.

Child Neurology and Radiology Departments, Hospital Sant Joan de Déu, Barcelona, Spain.

Background: Thiamine transporter-2 deficiency, a condition resulting from mutations in the SLC19A3 gene, has been described in patients with subacute dystonia and striatal necrosis. The condition responds extremely well to treatment with biotin and has thus been named biotin-responsive basal ganglia disease. Recently, this deficiency has also been related to Wernicke's-like encephalopathy and atypical infantile spasms, showing heterogeneous responses to biotin and/or thiamine.

Methods: Two Spanish siblings with a biotin-responsive basal ganglia disease phenotype and mutations in SLC19A3 presented with acute episodes of generalized dystonia, rigidity, and symmetrical lesions involving the striatum, midline nuclei of the thalami, and the cortex of cerebral hemispheres as shown by magnetic resonance imaging.

Results: The clinical features resolved rapidly after thiamine administration.

Conclusions: Despite the rarity of thiamine transporter-2 deficiency, it should be suspected in patients with acute dystonia and basal ganglia injury, as thiamine can halt disease evolution and prevent further episodes. © 2012 Movement Disorder Society.
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http://dx.doi.org/10.1002/mds.25008DOI Listing
September 2012

KIF1A missense mutations in SPG30, an autosomal recessive spastic paraplegia: distinct phenotypes according to the nature of the mutations.

Eur J Hum Genet 2012 Jun 18;20(6):645-9. Epub 2012 Jan 18.

INSERM, U975, Paris, France.

The hereditary spastic paraplegias (HSPs) are a clinically and genetically heterogeneous group of neurodegenerative diseases characterised by progressive spasticity in the lower limbs. The nosology of autosomal recessive forms is complex as most mapped loci have been identified in only one or a few families and account for only a small percentage of patients. We used next-generation sequencing focused on the SPG30 chromosomal region on chromosome 2q37.3 in two patients from the original linked family. In addition, wide genome scan and candidate gene analysis were performed in a second family of Palestinian origin. We identified a single homozygous mutation, p.R350G, that was found to cosegregate with the disease in the SPG30 kindred and was absent in 970 control chromosomes while affecting a strongly conserved amino acid at the end of the motor domain of KIF1A. Homozygosity and linkage mapping followed by mutation screening of KIF1A allowed us to identify a second mutation, p.A255V, in the second family. Comparison of the clinical features with the nature of the mutations of all reported KIF1A families, including those reported recently with hereditary sensory and autonomic neuropathy, suggests phenotype-genotype correlations that may help to understand the mechanisms involved in motor neuron degeneration. We have shown that mutations in the KIF1A gene are responsible for SPG30 in two autosomal recessive HSP families. In published families, the nature of the KIF1A mutations seems to be of good predictor of the underlying phenotype and vice versa.
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http://dx.doi.org/10.1038/ejhg.2011.261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3355258PMC
June 2012

Cellular distribution and subcellular localization of spatacsin and spastizin, two proteins involved in hereditary spastic paraplegia.

Mol Cell Neurosci 2011 Jul 27;47(3):191-202. Epub 2011 Apr 27.

INSERM, U975, Université Pierre et Marie Curie-Paris 6, UMR_S975, Centre de Recherche de l'Institut du Cerveau et de la Moelle épinière (CR-icm), GHU Pitié-Salpêtrière, CNRS, Paris, France.

Truncating mutations in the SPG11 and SPG15 genes cause complicated spastic paraplegia, severe neurological conditions due to loss of the functions of spatacsin and spastizin, respectively. We developed specific polyclonal anti-spatacsin (SPG11) and anti-spastizin (SPG15) antisera, which we then used to explore the intracellular and tissue localizations of these proteins. We observed expression of both proteins in human and rat central nervous system, which was particularly strong in cortical and spinal motor neurons as well as in retina. Both proteins were also expressed ubiquitously and strongly in embryos. In cultured cells, these two proteins had similar diffuse punctate, cytoplasmic and sometimes nuclear (spastizin) distributions. They partially co-localized with multiple organelles, particularly with protein-trafficking vesicles, endoplasmic reticulum and microtubules. Spastizin was also found at the mitochondria surface. This first study of the endogenous expression of spatacsin and spastizin shows similarities in their expression patterns that could account for their overlapping clinical phenotypes and involvement in a common protein complex.
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http://dx.doi.org/10.1016/j.mcn.2011.04.004DOI Listing
July 2011

Biotin-responsive basal ganglia disease in ethnic Europeans with novel SLC19A3 mutations.

Arch Neurol 2010 Jan;67(1):126-30

Federation of Nervous System Diseases, Assistance Publique-Hôpitaux de Paris, Hôpital de la Salpêtrière, Université Pierre et Marie Curie, Paris CEDEX 13, France.

Objective: To report the first 2 European cases of biotin-responsive basal ganglia disease and novel SLC19A3 mutations.

Design: Case reports.

Setting: University hospital. Patients A 33-year-old man and his 29-year-old sister, both of Portuguese ancestry, presented with recurrent episodes of encephalopathy. Between episodes patients exhibited generalized dystonia, epilepsy, and bilateral hyperintensities of the caudate and putamen.

Main Outcome Measures: Clinical and radiologic findings.

Results: Administration of high doses of biotin or of a combination of biotin and thiamine during encephalopathies resulted in spectacular clinical and radiologic improvement in both patients. Sequencing of the SLC19A3 disclosed 2 novel mutations, both of which created premature stop codons in the protein sequence of hTHTR2.

Conclusion: This study demonstrates that biotin-responsive basal ganglia disease is a panethnic condition. A therapeutic trial with high doses of biotin and thiamine seems mandatory in every unexplained encephalopathy with bilateral lesions of putamen and caudate nuclei.
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http://dx.doi.org/10.1001/archneurol.2009.293DOI Listing
January 2010