Publications by authors named "Anne Rovelet-Lecrux"

41 Publications

Early-Onset Cerebral Amyloid Angiopathy and Alzheimer Disease Related to an APP Locus Triplication.

Neurol Genet 2021 Oct 8;7(5):e609. Epub 2021 Sep 8.

Department of Neurology and CNR-MAJ (L.G., D.W.), Normandie University, UNIROUEN, Inserm U1245, CHU Rouen, CIC-CRB1404, F 76000; Department of Genetics and CNR-MAJ (K.C., S.R., N.L.M., A.R.-L., D.C., G.N.), Normandie University, UNIROUEN, Inserm U1245 and CHU Rouen, F 76000; Department of Neurology (B.C., M.F.), Lyon University Hospital; Department of Neurology (O.M.), Grenoble University Hospital; Department of Histology (J.B.), Grenoble University Hospital; AP-HP (M.M., T.C., E.T.-L.), Groupe Hospitalier Saint-Louis Lariboisière-Fernand-Widal, Service de Génétique Moléculaire Neurovasculaire, INSERM UMR 1141, NeuroDiderot,Université de Paris; Department of Histology Embryology and Cytogenetics (E.P.), Jean Verdier Hospital; Paris 13 University (E.P.), Sorbonne Paris Cité, UFR SMBH Bobigny; and PROTECT (E.P.), INSERM, Paris Diderot University, Bondy, France.

Background And Objective: To report a triplication of the amyloid-β precursor protein () locus along with relative messenger RNA (mRNA) expression in a family with autosomal dominant early-onset cerebral amyloid angiopathy (CAA) and Alzheimer disease (AD).

Methods: Four copies of the gene were identified by quantitative multiplex PCR of short fluorescent fragments, fluorescent in situ hybridization (FISH), and array comparative genomic hybridization. mRNA levels were assessed using reverse-transcription-digital droplet PCR in the proband's whole blood and compared with 10 controls and 9 duplication carriers.

Results: Beginning at age 39 years, the proband developed severe episodic memory deficits with a CSF biomarker profile typical of AD and multiple lobar microbleeds in the posterior regions on brain MRI. His father had seizures and recurrent cerebral hemorrhage since the age of 37 years. His cerebral biopsy showed abundant perivascular amyloid deposits, leading to a diagnosis of CAA. In the proband, we identified 4 copies of a 506-kb region located on chromosome 21q21.3 and encompassing the whole gene without any other gene. FISH suggested that the genotype of the proband was 3 copies/1 copy corresponding to an locus triplication, which was consistent with the presence of 2 copies in the healthy mother and with the paternal medical history. Analysis of the mRNA level showed a 2-fold increase in the proband and a 1.8 fold increase in duplication carriers compared with controls.

Discussion: Increased copy number of is sufficient to cause AD and CAA, with likely earlier onset in case of triplication compared with duplication.
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http://dx.doi.org/10.1212/NXG.0000000000000609DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8439959PMC
October 2021

Clinical and neuropathological diversity of tauopathy in MAPT duplication carriers.

Acta Neuropathol 2021 08 6;142(2):259-278. Epub 2021 Jun 6.

Normandie Univ, UNIROUEN, Inserm U1245, CHU Rouen, Department of Genetics and CNR-MAJ, F-76000, Rouen, France.

Microduplications of the 17q21.31 chromosomal region encompassing the MAPT gene, which encodes the Tau protein, were identified in patients with a progressive disorder initially characterized by severe memory impairment with or without behavioral changes that can clinically mimic Alzheimer disease. The unique neuropathological report showed a primary tauopathy, which could not be unanimously classified in a given known subtype, showing both 4R- and 3R-tau inclusions, mainly within temporal cortical subregions and basal ganglia, without amyloid deposits. Recently, two subjects harboring the same duplication were reported with an atypical extrapyramidal syndrome and gait disorder. To decipher the phenotypic spectrum associated with MAPT duplications, we studied ten carriers from nine families, including two novel unrelated probands, gathering clinical (n = 10), cerebrospinal fluid (n = 6), MRI (n = 8), dopamine transporter scan (n = 4), functional (n = 5), amyloid (n = 3) and Tau-tracer (n = 2) PET imaging data as well as neuropathological examination (n = 4). Ages at onset ranged from 37 to 57 years, with prominent episodic memory impairment in 8/10 patients, associated with behavioral changes in four, while two patients showed atypical extrapyramidal syndrome with gait disorder at presentation, including one with associated cognitive deficits. Amyloid imaging was negative but Tau imaging showed significant deposits mainly in both mesiotemporal cortex. Dopaminergic denervation was found in 4/4 patients, including three without extrapyramidal symptoms. Neuropathological examination exclusively showed Tau-immunoreactive lesions. Distribution, aspect and 4R/3R tau aggregates composition suggested a spectrum from predominantly 3R, mainly cortical deposits well correlating with cognitive and behavioral changes, to predominantly 4R deposits, mainly in the basal ganglia and midbrain, in patients with prominent extrapyramidal syndrome. Finally, we performed in vitro seeding experiments in HEK-biosensor cells. Morphological features of aggregates induced by homogenates of three MAPT duplication carriers showed dense/granular ratios graduating between those induced by homogenates of a Pick disease and a progressive supranuclear palsy cases. These results suggest that MAPT duplication causes a primary tauopathy associated with diverse clinical and neuropathological features.
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http://dx.doi.org/10.1007/s00401-021-02320-4DOI Listing
August 2021

Atypical astroglial pTDP-43 pathology in astroglial predominant tauopathy.

Neuropathol Appl Neurobiol 2021 Mar 17. Epub 2021 Mar 17.

Department of Pathology and Experimental Therapeutics, University of Barcelona, Bellvitge University Hospital-IDIBELL, CIBERNED, Hospitalet de Llobregat, Spain.

We observed atypical astrocytic pTDP-43 pathology in astroglial predominant tauopathy.
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http://dx.doi.org/10.1111/nan.12707DOI Listing
March 2021

Patient-specific Alzheimer-like pathology in trisomy 21 cerebral organoids reveals BACE2 as a gene dose-sensitive AD suppressor in human brain.

Mol Psychiatry 2020 Jul 10. Epub 2020 Jul 10.

Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, 308232, Singapore.

A population of more than six million people worldwide at high risk of Alzheimer's disease (AD) are those with Down Syndrome (DS, caused by trisomy 21 (T21)), 70% of whom develop dementia during lifetime, caused by an extra copy of β-amyloid-(Aβ)-precursor-protein gene. We report AD-like pathology in cerebral organoids grown in vitro from non-invasively sampled strands of hair from 71% of DS donors. The pathology consisted of extracellular diffuse and fibrillar Aβ deposits, hyperphosphorylated/pathologically conformed Tau, and premature neuronal loss. Presence/absence of AD-like pathology was donor-specific (reproducible between individual organoids/iPSC lines/experiments). Pathology could be triggered in pathology-negative T21 organoids by CRISPR/Cas9-mediated elimination of the third copy of chromosome 21 gene BACE2, but prevented by combined chemical β and γ-secretase inhibition. We found that T21 organoids secrete increased proportions of Aβ-preventing (Aβ1-19) and Aβ-degradation products (Aβ1-20 and Aβ1-34). We show these profiles mirror in cerebrospinal fluid of people with DS. We demonstrate that this protective mechanism is mediated by BACE2-trisomy and cross-inhibited by clinically trialled BACE1 inhibitors. Combined, our data prove the physiological role of BACE2 as a dose-sensitive AD-suppressor gene, potentially explaining the dementia delay in ~30% of people with DS. We also show that DS cerebral organoids could be explored as pre-morbid AD-risk population detector and a system for hypothesis-free drug screens as well as identification of natural suppressor genes for neurodegenerative diseases.
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http://dx.doi.org/10.1038/s41380-020-0806-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8190957PMC
July 2020

Detection of copy-number variations from NGS data using read depth information: a diagnostic performance evaluation.

Eur J Hum Genet 2021 01 26;29(1):99-109. Epub 2020 Jun 26.

Normandie Univ, UNIROUEN, Inserm U1245 and Rouen University Hospital, Department of Genetics, Normandy Center for Genomic and Personalized Medicine, Rouen, France.

The detection of copy-number variations (CNVs) from NGS data is underexploited as chip-based or targeted techniques are still commonly used. We assessed the performances of a workflow centered on CANOES, a bioinformatics tool based on read depth information. We applied our workflow to gene panel (GP) and whole-exome sequencing (WES) data, and compared CNV calls to quantitative multiplex PCR of short fluorescent fragments (QMSPF) or array comparative genomic hybridization (aCGH) results. From GP data of 3776 samples, we reached an overall positive predictive value (PPV) of 87.8%. This dataset included a complete comprehensive QMPSF comparison of four genes (60 exons) on which we obtained 100% sensitivity and specificity. From WES data, we first compared 137 samples with aCGH and filtered comparable events (exonic CNVs encompassing enough aCGH probes) and obtained an 87.25% sensitivity. The overall PPV was 86.4% following the targeted confirmation of candidate CNVs from 1056 additional WES. In addition, our CANOES-centered workflow on WES data allowed the detection of CNVs with a resolution of single exons, allowing the detection of CNVs that were missed by aCGH. Overall, switching to an NGS-only approach should be cost-effective as it allows a reduction in overall costs together with likely stable diagnostic yields. Our bioinformatics pipeline is available at: https://gitlab.bioinfo-diag.fr/nc4gpm/canoes-centered-workflow .
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http://dx.doi.org/10.1038/s41431-020-0672-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7852510PMC
January 2021

Haploinsufficiency of the Primary Familial Brain Calcification Gene SLC20A2 Mediated by Disruption of a Regulatory Element.

Mov Disord 2020 08 7;35(8):1336-1345. Epub 2020 Jun 7.

Department of Genetics and CNR-MAJ, Normandy Center for Genomic and Personalized Medicine, Normandie Univ, UNIROUEN, Inserm U1245 and Rouen University Hospital, Rouen, France.

Objective: Primary familial brain calcification (PFBC) is a rare cerebral microvascular calcifying disorder with diverse neuropsychiatric expression. Five genes were reported as PFBC causative when carrying pathogenic variants. Haploinsufficiency of SLC20A2, which encodes an inorganic phosphate importer, is a major cause of autosomal-dominant PFBC. However, PFBC remains genetically unexplained in a proportion of patients, suggesting the existence of additional genes or cryptic mutations. We analyzed exome sequencing data of 71 unrelated, genetically unexplained PFBC patients with the aim to detect copy number variations that may disrupt the expression of core PFBC-causing genes.

Methods: After the identification of a deletion upstream of SLC20A2, we assessed its consequences on gene function by reverse transcriptase droplet digital polymerase chain reaction (RT-ddPCR), an ex vivo inorganic phosphate uptake assay, and introduced the deletion of a putative SLC20A2 enhancer mapping to this region in human embryonic kidney 293 (HEK293) cells by clustered regularly interspaced short palindromic repeats (CRISPR) - CRISPR-associated protein 9 (Cas9).

Results: The 8p11.21 deletion, segregating with PFBC in a family, mapped 35 kb upstream of SLC20A2. The deletion carriers/normal controls ratio of relative SLC20A2 mRNA levels was 60.2% (P < 0.001). This was comparable with that of patients carrying an SLC20A2 premature stop codon (63.4%; P < 0.001). The proband exhibited a 39.3% decrease of inorganic phosphate uptake in blood (P = 0.015). In HEK293 cells, we observed a 39.8% decrease in relative SLC20A2 mRNA levels after normalization on DNA copy number (P < 0.001).

Discussion: We identified a deletion of an enhancer of SLC20A2 expression, with carriers showing haploinsufficiency in similar ranges to loss-of-function alleles, and we observed reduced mRNA levels after deleting this element in a cellular model. We propose a 3-step strategy to identify and easily assess the effect of such events. © 2020 International Parkinson and Movement Disorder Society.
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http://dx.doi.org/10.1002/mds.28090DOI Listing
August 2020

Detection of all adult Tau isoforms in a 3D culture model of iPSC-derived neurons.

Stem Cell Res 2019 10 23;40:101541. Epub 2019 Aug 23.

Normandie Univ, UNIROUEN, Inserm U1245 and Rouen University Hospital, Department of Genetics and CNR-MAJ, F 76000, Normandy Center for Genomic and Personalized Medicine, Rouen, France. Electronic address:

Tauopathies are a class of neurodegenerative diseases characterized by the presence of pathological intracellular deposits of Tau proteins. Six isoforms of Tau are expressed in the adult human brain, resulting from alternative splicing of the MAPT gene. Tau splicing is developmentally regulated such that only the smallest Tau isoform is expressed in fetal brain, contrary to the adult brain showing the expression of all 6 isoforms. Induced Pluripotent Stem Cell (iPSC) technology has opened up new perspectives in human disease modeling, including tauopathies. However, a major challenge to in vitro recapitulation of Tau pathology in iPSC-derived neurons is their relative immaturity. In this study, we examined the switch in Tau splicing from fetal-only to all adult Tau isoforms during the differentiation of iPSC-derived neurons in a new 3D culture system. First, we showed that iPSC-induced neurons inside Matrigel-coated alginate capsules were able to differentiate into cortical neurons. Then, using a new assay that allowed both the qualitative and the quantitative analysis of all adult MAPT mRNA isoforms individually, we demonstrated that BrainPhys-maintained neurons expressed the 6 adult MAPT mRNA transcripts from 25 weeks of maturation, making this model highly suitable for modeling Tau pathology and therapeutic purposes.
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http://dx.doi.org/10.1016/j.scr.2019.101541DOI Listing
October 2019

Causative Mutations and Genetic Risk Factors in Sporadic Early Onset Alzheimer's Disease Before 51 Years.

J Alzheimers Dis 2019 ;71(1):227-243

CMRR Department of Neurology, Toulouse University Hospital, Toulouse, France.

Background: Pathogenic variants in the autosomal dominant genes PSEN1, PSEN2, or APP, APOE4 alleles, and rare variants within TREM2, SORL1, and ABCA7 contribute to early-onset Alzheimer's disease (EOAD). However, sporadic EOAD patients have been insufficiently studied to define the probability of being a carrier of one of these variants.

Objective: To describe the proportion of each genetic variation among patients with very young-onset sporadic AD.

Methods: We first screened PSEN1, PSEN2, and APP in 154 EOAD patients with an onset before 51 years and a negative family history. Among 99 patients with no mutation (NMC), whole exome sequencing (WES) was performed. We analyzed the APOE genotype and rare protein-truncating or missense predicted damaging variants of TREM2, SORL1, and ABCA7. Neurological examination and cerebrospinal fluid (CSF) biomarkers were systematically retrieved.

Results: Nineteen (12.3%) mutation carriers (MC) harbored an APP or PSEN1 pathogenic or likely pathogenic variant. Among the NMC, 54/99 carried at least one genetic risk factor, including 9 APOE4/E4 homozygous, 37 APOE4 heterozygous, and 14 with a rare variant in another risk factor gene: 3 SORL1, 4 TREM2, and 9 ABCA7. MC presented an earlier disease onset (p < 0.0001) and associated neurologic symptoms more frequently (p < 0.002). All but one patient had at least 2 CSF biomarkers in abnormal ranges.

Conclusion: The genetic component of very early sporadic EOAD gathers a substantial proportion of pathogenic variants in autosomal dominant genes and an even higher proportion of patients carrying genetic risk factors, suggesting an oligogenic determinism, even at this range of ages.
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http://dx.doi.org/10.3233/JAD-190193DOI Listing
October 2020

A Simple, Universal, and Cost-Efficient Digital PCR Method for the Targeted Analysis of Copy Number Variations.

Clin Chem 2019 09 10;65(9):1153-1160. Epub 2019 Jul 10.

Normandie Univ, UNIROUEN, Inserm U1245 and Rouen University Hospital, Department of Genetics, F76000, Normandy Center for Genomic and Personalized Medicine, Rouen, France;

Background: Rare copy number variations (CNVs) are a major cause of genetic diseases. Simple targeted methods are required for their confirmation and segregation analysis. We developed a simple and universal CNV assay based on digital PCR (dPCR) and universal locked nucleic acid (LNA) hydrolysis probes.

Methods: We analyzed the mapping of the 90 LNA hydrolysis probes from the Roche Universal ProbeLibrary (UPL). For each CNV, selection of the optimal primers and LNA probe was almost automated; probes were reused across assays and each dPCR assay included the CNV amplicon and a reference amplicon. We assessed the assay performance on 93 small and large CNVs and performed a comparative cost-efficiency analysis.

Results: UPL-LNA probes presented nearly 20000000 occurrences on the human genome and were homogeneously distributed with a mean interval of 156 bp. The assay accurately detected all the 93 CNVs, except one (<200 bp), with coefficient of variation <10%. The assay was more cost-efficient than all the other methods.

Conclusions: The universal dPCR CNV assay is simple, robust, and cost-efficient because it combines a straightforward design allowed by universal probes and end point PCR, the advantages of a relative quantification of the target to the reference within the same reaction, and the high flexibility of the LNA hydrolysis probes. This method should be a useful tool for genomic medicine, which requires simple methods for the interpretation and segregation analysis of genomic variations.
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http://dx.doi.org/10.1373/clinchem.2019.304246DOI Listing
September 2019

Biallelic MYORG mutation carriers exhibit primary brain calcification with a distinct phenotype.

Brain 2019 06;142(6):1573-1586

Normandie Univ, UNIROUEN, Inserm U1245 and Rouen University Hospital, Department of Genetics and CNR-MAJ, F, Normandy Center for Genomic and Personalized Medicine, Rouen, France.

Primary familial brain calcification (PFBC) is a rare neurogenetic disorder with diverse neuropsychiatric expression. Mutations in four genes cause autosomal dominant PFBC: SLC20A2, XPR1, PDGFB and PDGFRB. Recently, biallelic mutations in the MYORG gene have been reported to cause PFBC with an autosomal recessive pattern of inheritance. We screened MYORG in 29 unrelated probands negatively screened for the autosomal dominant PFBC genes and identified 11 families with a biallelic rare or novel predicted damaging variant. We studied the clinical and radiological features of 16 patients of these 11 families and compared them to that of 102 autosomal dominant PFBC patients carrying a mutation in one of the four known autosomal dominant PFBC genes. We found that MYORG patients exhibited a high clinical penetrance with a median age of onset of 52 years (range: 21-62) with motor impairment at the forefront. In particular, dysarthria was the presenting sign in 11/16 patients. In contrast to patients with autosomal dominant PFBC, 12/15 (80%) symptomatic patients eventually presented at least four of the following five symptoms: dysarthria, cerebellar syndrome, gait disorder of any origin, akinetic-hypertonic syndrome and pyramidal signs. In addition to the most severe clinical pattern, MYORG patients exhibited the most severe pattern of calcifications as compared to the patients from the four autosomal dominant PFBC gene categories. Strikingly, 12/15 presented with brainstem calcifications in addition to extensive calcifications in other brain areas (lenticular nuclei, thalamus, cerebellar hemispheres, vermis, ±cortex). Among them, eight patients exhibited pontine calcifications, which were observed in none of the autosomal dominant PFBC patients and hence appeared to be highly specific. Finally, all patients exhibited cerebellar atrophy with diverse degrees of severity on CT scans. We confirmed the existence of cerebellar atrophy by performing MRI voxel-based morphometry analyses of MYORG patients with autosomal dominant PFBC mutation carriers as a comparison group. Of note, in three families, the father carried small pallido-dentate calcifications while carrying the mutation at the heterozygous state, suggesting a putative phenotypic expression in some heterozygous carriers. In conclusion, we confirm that MYORG is a novel major PFBC causative gene and that the phenotype associated with such mutations may be recognized based on pedigree, clinical and radiological features.
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http://dx.doi.org/10.1093/brain/awz095DOI Listing
June 2019

Copy Number Variants in miR-138 as a Potential Risk Factor for Early-Onset Alzheimer's Disease.

J Alzheimers Dis 2019 ;68(3):1243-1255

Department of Genetics and CNR-MAJ, Normandie Univ, UNIROUEN, Rouen University Hospital, Normandy Center for Genomic and Personalized Medicine, Rouen, France.

Early-onset Alzheimer's disease (EOAD) accounts for 5-10% of all AD cases, with a heritability ranging between 92% to 100%. With the exception of rare mutations in APP, PSEN1, and PSEN2 genes causing autosomal dominant EOAD, little is known about the genetic factors underlying most of the EOAD cases. In this study, we hypothesized that copy number variations (CNVs) in microRNA (miR) genes could contribute to risk for EOAD. miRs are short non-coding RNAs previously implicated in the regulation of AD-related genes and phenotypes. Using whole exome sequencing, we screened a series of 546 EOAD patients negative for autosomal dominant EOAD mutations and 597 controls. We identified 86 CNVs in miR genes of which 31 were exclusive to EOAD cases, including a duplication of the MIR138-2 locus. In functional studies in human cultured cells, we could demonstrate that miR-138 overexpression leads to higher Aβ production as well as tau phosphorylation, both implicated in AD pathophysiology. These changes were mediated in part by GSK-3β and FERMT2, a potential risk factor for AD. Additional disease-related genes were also prone to miR-138 regulation including APP and BACE1. This study suggests that increased gene dosage of MIR138-2 could contribute to risk for EOAD by regulating different biological pathways implicated in amyloid and tau metabolism. Additional studies are now required to better understand the role of miR-CNVs in EOAD.
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http://dx.doi.org/10.3233/JAD-180940DOI Listing
August 2020

Deletion of exons 9 and 10 of the Presenilin 1 gene in a patient with Early-onset Alzheimer Disease generates longer amyloid seeds.

Neurobiol Dis 2017 Aug 28;104:97-103. Epub 2017 Apr 28.

Normandie Univ, UNIROUEN, Inserm U1245, Rouen University Hospital, Department of Genetics and CNR-MAJ, Normandy Center for Genomic and Personalized Medicine, F 76000 Rouen, France. Electronic address:

Presenilin 1 (PSEN1) mutations are the main cause of autosomal dominant Early-onset Alzheimer Disease (EOAD). Among them, deletions of exon 9 have been reported to be associated with a phenotype of spastic paraparesis. Using exome data from a large sample of 522 EOAD cases and 584 controls to search for genomic copy-number variations (CNVs), we report here a novel partial, in-frame deletion of PSEN1, removing both exons 9 and 10. The patient presented with memory impairment associated with spastic paraparesis, both starting from the age of 56years. He presented a positive family history of EOAD. We performed functional analysis to elucidate the impact of this novel deletion on PSEN1 activity as part of the γ-secretase complex. The deletion does not affect the assembly of a mature protease complex but has an extreme impact on its global endopeptidase activity. The mutant carboxypeptidase-like activity is also strongly impaired and the deleterious mutant effect leads to an incomplete digestion of long Aβ peptides and enhances the production of Aβ43, which has been shown to be potently amyloidogenic and neurotoxic in vivo.
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http://dx.doi.org/10.1016/j.nbd.2017.04.020DOI Listing
August 2017

APP, PSEN1, and PSEN2 mutations in early-onset Alzheimer disease: A genetic screening study of familial and sporadic cases.

PLoS Med 2017 Mar 28;14(3):e1002270. Epub 2017 Mar 28.

Department of Neurology, Montpellier University Hospital, Montpellier, France.

Background: Amyloid protein precursor (APP), presenilin-1 (PSEN1), and presenilin-2 (PSEN2) mutations cause autosomal dominant forms of early-onset Alzheimer disease (AD-EOAD). Although these genes were identified in the 1990s, variant classification remains a challenge, highlighting the need to colligate mutations from large series.

Methods And Findings: We report here a novel update (2012-2016) of the genetic screening of the large AD-EOAD series ascertained across 28 French hospitals from 1993 onwards, bringing the total number of families with identified mutations to n = 170. Families were included when at least two first-degree relatives suffered from early-onset Alzheimer disease (EOAD) with an age of onset (AOO) ≤65 y in two generations. Furthermore, we also screened 129 sporadic cases of Alzheimer disease with an AOO below age 51 (44% males, mean AOO = 45 ± 2 y). APP, PSEN1, or PSEN2 mutations were identified in 53 novel AD-EOAD families. Of the 129 sporadic cases screened, 17 carried a PSEN1 mutation and 1 carried an APP duplication (13%). Parental DNA was available for 10 sporadic mutation carriers, allowing us to show that the mutation had occurred de novo in each case. Thirteen mutations (12 in PSEN1 and 1 in PSEN2) identified either in familial or in sporadic cases were previously unreported. Of the 53 mutation carriers with available cerebrospinal fluid (CSF) biomarkers, 46 (87%) had all three CSF biomarkers-total tau protein (Tau), phospho-tau protein (P-Tau), and amyloid β (Aβ)42-in abnormal ranges. No mutation carrier had the three biomarkers in normal ranges. One limitation of this study is the absence of functional assessment of the possibly and probably pathogenic variants, which should help their classification.

Conclusions: Our findings suggest that a nonnegligible fraction of PSEN1 mutations occurs de novo, which is of high importance for genetic counseling, as PSEN1 mutational screening is currently performed in familial cases only. Among the 90 distinct mutations found in the whole sample of families and isolated cases, definite pathogenicity is currently established for only 77%, emphasizing the need to pursue the effort to classify variants.
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http://dx.doi.org/10.1371/journal.pmed.1002270DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5370101PMC
March 2017

APP Mutations in Cerebral Amyloid Angiopathy with or without Cortical Calcifications: Report of Three Families and a Literature Review.

J Alzheimers Dis 2017 ;56(1):37-46

CNR-MAJ, Rouen University Hospital, Rouen, France.

Background: Specific APP mutations cause cerebral amyloid angiopathy (CAA) with or without Alzheimer's disease (AD).

Objective: We aimed at reporting APP mutations associated with CAA, describe the clinical, cerebrospinal fluid AD biomarkers, and neuroimaging features, and compare them with the data from the literature.

Methods: We performed a retrospective study in two French genetics laboratories by gathering all clinical and neuroimaging data from patients referred for a genetic diagnosis of CAA with an age of onset before 66 years and fulfilling the other Boston revised criteria. We studied the segregation of mutations in families and performed a comprehensive literature review of all cases reported with the same APP mutation.

Results: We screened APP in 61 unrelated French patients. Three mutations, located in the Aβ coding region, were detected in five patients from three families: p.Ala692Gly (Flemish), p.Glu693Lys (Italian), and p.Asp694Asn (Iowa). Patients exhibited CAA and progressive cognitive impairment associated with cortical calcifications in the Iowa and Italian mutation carriers, but not the patient carrying the Flemish mutation.

Conclusions: This is the first evidence of cortical calcification in patients with an APP mutation other than the Iowa mutation. We discuss the radiological, cerebrospinal fluid, and clinical phenotype of patients carrying these mutations in the literature.
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http://dx.doi.org/10.3233/JAD-160709DOI Listing
February 2018

Seizures in dominantly inherited Alzheimer disease.

Neurology 2016 Aug 27;87(9):912-9. Epub 2016 Jul 27.

From the Departments of Neurology (A.Z., A.B., O.M., D.H., D.W.) and Genetics (G.N., D.H.), and CNR-MAJ (A.Z., G.N., S.R., O.M., D.C., D.H.), Rouen University Hospital; Inserm U1079 (C.C., A.R.-L., G.N., S.R., D.C., D.H., D.W.), Normandy Centre for Genomic Medicine and Personalized Medicine, Rouen University, IRIB, Normandy University, Rouen; Department of Neurology (J.P.), CMRR and INSERM U825, Purpan University Hospital, Toulouse; CNR-MAJ (I.L.B.), Pitié-Salpêtrière Paris and CRCICM, IM2A, UMR-S975 AP-HP, University Hospital Pitié-Salpêtrière, Paris; Université Lille (F.P., A.R.-S.), Inserm U1171, Memory Centre and CNR-MAJ, CHU, Lille; Department of Neuropsychology (M.F., B.C.), CMRR, University Hospital, Groupe Hospitalier Est, Bron; Department of Neurology (M.S.), AP-HP, University Hospital Saint-Anne, Paris; Department of Neurology (C.B.-B.), CMRR, Nantes University Hospital; Department of Neurology and Neuropsychology (M.C.), Aix-Marseille University, CMRR, Timone Hospital and INSERM UMR1106, Marseille; CMRR Montpellier (A.G.), Department of Neurology, University Hospital of Montpellier and INSERM U1163, Montpellier; Department of Neurology (L.C.), CMRR, Besançon University Hospital; CMRR (F.B.), Department of Geriatrics, University Hospital of Strasbourg and ICube Laboratory, CNRS, University of Strasbourg; and CMRR Paris Nord AP-HP (C.P.), Hopital Lariboisière, INSERM, U942, Université Paris Diderot, Sorbonne Paris Cité, UMRS 942, Paris, France.

Objective: To assess seizure frequency in a large French cohort of autosomal dominant early-onset Alzheimer disease (ADEOAD) and to determine possible correlations with causative mutations.

Methods: A national multicentric study was performed in patients with ADEOAD harboring a pathogenic mutation within PSEN1, PSEN2, APP, or a duplication of APP, and a minimal follow-up of 5 years. Clinical, EEG, and imaging data were systematically recorded.

Results: We included 132 patients from 77 families: 94 PSEN1 mutation carriers (MCs), 16 APP duplication carriers, 15 APP MCs, and 7 PSEN2 MCs. Seizure frequency was 47.7% after a mean follow-up of 8.4 years (range 5-25). After 5-year follow-up and using a Cox model analysis, the percentages of patients with seizures were respectively 19.1% (10.8%-26.7%) for PSEN1, 28.6% (0%-55.3%) for PSEN2, 31.2% (4.3%-50.6%) for APP duplications, and no patient for APP mutation. APP duplication carriers showed a significantly increased seizure risk compared to both APP MCs (hazard ratio [HR] = 5.55 [95% confidence interval 1.87-16.44]) and PSEN1 MCs (HR = 4.46 [2.11-9.44]). Among all PSEN1 mutations, those within the domains of protein hydrophilic I, transmembrane II (TM-II), TM-III, TM-IV, and TM-VII were associated with a significant increase in seizure frequency compared to other domains (HR = 4.53 [1.93-10.65], p = 0.0005).

Conclusions: Seizures are a common feature of ADEOAD. In this population, risk was significantly higher in the APP duplication group than in all other groups. Within PSEN1, 5 specific domains were associated with a higher seizure risk indicating specific correlations between causative mutation and seizures.
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http://dx.doi.org/10.1212/WNL.0000000000003048DOI Listing
August 2016

Identification of partial SLC20A2 deletions in primary brain calcification using whole-exome sequencing.

Eur J Hum Genet 2016 11 1;24(11):1630-1634. Epub 2016 Jun 1.

Inserm U1079, Rouen University, IRIB, Normandy University, Rouen, France.

Primary brain calcification (PBC) is a dominantly inherited calcifying disorder of the brain. SLC20A2 loss-of-function variants account for the majority of families. Only one genomic deletion encompassing SLC20A2 and six other genes has been reported. We performed whole-exome sequencing (WES) in 24 unrelated French patients with PBC, negatively screened for sequence variant in the known genes SLC20A2, PDGFB, PDGFRB and XPR1. We used the CANOES tool to detect copy number variations (CNVs). We detected two deletions of exon 2 of SLC20A2 in two unrelated patients, which segregated with PBC in one family. We then reanalyzed the same series using a QMPSF assay including one amplicon in each exon of SLC20A2 and detected two supplemental partial deletions in two patients: one deletion of exon 4 and one deletion of exons 4 and 5. These deletions were missed by the first screening step of CANOES but could finally be detected after readjustment of bioinformatic parameters and use of a genotyping step of CANOES. This study reports the first partial deletions of SLC20A2 and strengthens its position as the major PBC-causative gene. It is possible to detect short CNVs from WES data, although the sensitivity of such tools should be evaluated in comparison with other methods.
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http://dx.doi.org/10.1038/ejhg.2016.50DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5110050PMC
November 2016

ABCA7 rare variants and Alzheimer disease risk.

Neurology 2016 Jun 1;86(23):2134-7. Epub 2016 Apr 1.

From INSERM (K.L.G., G.N., O.Q., C.C., D.W., S.R., A.C.R., A.R.-L., T.F., D.H., D.C.), U1079, IRIB, University of Rouen, Normandy University; Normandy Centre for Genomic Medicine and Personalized Medicine (K.L.G., G.N., O.Q., C.C., D.W., S.R., A.-C.R., A.R.-L., T.F., D.H., D.C.), Rouen; Department of Genetics (G.N., T.F., D.H.), CNR-MAJ (G.N., O.Q., C.C., D.W., S.R., A.-C.R., F.P., A.R.-S., D.H., D.C.), and Department of Neurology (D.W., D.H.), Rouen University Hospital; INSERM (C.B., B.G.-B., P.A., J.-C.L.), U1167, Lille; Institut Pasteur de Lille (C.B., B.G.-B., P.A., J.-C.L.); Université Lille-Nord de France (C.B., B.G.-B., P.A., J.-C.L.); Centre National de Génotypage (D.B., J.-G.G., R.O., A.B., V.M., J.-F.Deleuze.), Institut de Génomique, CEA, Evry; Fondation Jean Dausset (J.-F.Deleuze.), Centre d'Etudes du Polymorphisme Humain, Paris, France; McGill University and Génome Québec Innovation Centre (H.M.M., G.B., M.L.), Montréal, Canada; INSERM (R.R.), UMR 1087, l'Institut du Thorax, CHU Nantes; CNRS (R.R.), UMR 6291, Université de Nantes; INSERM (L.L., J.-F.Dartigues.), U897, Bordeaux; University of Bordeaux (L.L., J.-F.Dartigues.); Department of Neurology (F.P., A.R.S.), Lille University Hospital; INSERM (E.G.), UMR1078, CHU Brest, Université Bretagne Occidentale, Brest; and Department of Research (D.C.), Rouvray Psychiatric Hospital, Sotteville-lès-Rouen, France.

Objective: To study the association between ABCA7 rare coding variants and Alzheimer disease (AD) in a case-control setting.

Methods: We conducted a whole exome analysis among 484 French patients with early-onset AD and 590 ethnically matched controls.

Results: After collapsing rare variants (minor allele frequency ≤1%), we detected an enrichment of ABCA7 loss of function (LOF) and predicted damaging missense variants in cases (odds ratio [OR] 3.40, 95% confidence interval [CI] 1.68-7.35, p = 0.0002). Performing a meta-analysis with previously published data, we found that in a combined sample of 1,256 patients and 1,347 controls from France and Belgium, the OR was 2.81 (95% CI 1.89-4.20, p = 3.60 × 10(-7)).

Conclusions: These results confirm that ABCA7 LOF variants are enriched in patients with AD and extend this finding to predicted damaging missense variants.
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http://dx.doi.org/10.1212/WNL.0000000000002627DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4898320PMC
June 2016

The 22q11 PRODH/DGCR6 deletion is frequent in hyperprolinemic subjects but is not a strong risk factor for ASD.

Am J Med Genet B Neuropsychiatr Genet 2016 04 14;171B(3):377-82. Epub 2016 Jan 14.

Inserm U1079, Institute for Research and Innovation in Biomedicine, University of Rouen, France.

The proline dehydrogenase (PRODH) gene maps to 22q11.2 in the region deleted in the velo-cardio-facial syndrome (VCFS). A moderate to severe reduction (>50%) in PRODH activity resulting from recessive deletions and/or missense mutations has been shown to cause type 1 hyperprolinemia (HPI). Autistic features have been reported as a common clinical manifestation of HPI. Here we studied the frequency of a recurrent small 22q11.2 deletion encompassing PRODH and the neighboring DGCR6 gene in three case-control studies, one comprising HPI patients (n = 83), and the other two comprising autism spectrum disorder (ASD) patients (total of n = 2800), analyzed with high-resolution microarrays. We found that the PRODH deletion is a strong risk factor for HPI (OR = 50.7; 95%CI = 7.5-2147) but not for ASD (P = 0.4, OR = 0.6-3.3). This result indicates either that the suggested association between ASD and HPI is spurious and results from a bias leading to the preferential inclusion of patients with autistic features in HPI series, or that HPI is present in only a very small subset of ASD patients. In this latter case, a very large sample size would be required to detect an association between the PRODH deletion and ASD in a case-control study.
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http://dx.doi.org/10.1002/ajmg.b.32416DOI Listing
April 2016

Screening of dementia genes by whole-exome sequencing in early-onset Alzheimer disease: input and lessons.

Eur J Hum Genet 2016 May 5;24(5):710-6. Epub 2015 Aug 5.

Department of Neurology, CMRR, University Hospital Nord, Saint Etienne, France.

Causative variants in APP, PSEN1 or PSEN2 account for a majority of cases of autosomal dominant early-onset Alzheimer disease (ADEOAD, onset before 65 years). Variant detection rates in other EOAD patients, that is, with family history of late-onset AD (LOAD) (and no incidence of EOAD) and sporadic cases might be much lower. We analyzed the genomes from 264 patients using whole-exome sequencing (WES) with high depth of coverage: 90 EOAD patients with family history of LOAD and no incidence of EOAD in the family and 174 patients with sporadic AD starting between 51 and 65 years. We found three PSEN1 and one PSEN2 causative, probably or possibly causative variants in four patients (1.5%). Given the absence of PSEN1, PSEN2 and APP causative variants, we investigated whether these 260 patients might be burdened with protein-modifying variants in 20 genes that were previously shown to cause other types of dementia when mutated. For this analysis, we included an additional set of 160 patients who were previously shown to be free of causative variants in PSEN1, PSEN2 and APP: 107 ADEOAD patients and 53 sporadic EOAD patients with an age of onset before 51 years. In these 420 patients, we detected no variant that might modify the function of the 20 dementia-causing genes. We conclude that EOAD patients with family history of LOAD and no incidence of EOAD in the family or patients with sporadic AD starting between 51 and 65 years have a low variant-detection rate in AD genes.
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http://dx.doi.org/10.1038/ejhg.2015.173DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4930083PMC
May 2016

Mutation in the 3'untranslated region of APP as a genetic determinant of cerebral amyloid angiopathy.

Eur J Hum Genet 2016 Jan 1;24(1):92-8. Epub 2015 Apr 1.

INSERM U1079, University of Rouen, Normandy Univ, Institute for Research and Innovation in Biomedicine, Rouen, France.

Aβ-related cerebral amyloid angiopathy (CAA) is a major cause of primary non-traumatic brain hemorrhage. In families with an early onset of the disease, CAA can be due to amyloid precursor protein (APP) pathogenic variants or duplications. APP duplications lead to a ~1.5-fold increased APP expression, resulting in Aβ overproduction and deposition in the walls of leptomeningeal vessels. We hypothesized that rare variants in the 3'untranslated region (UTR) of APP might lead to APP overexpression in patients with CAA and no APP pathogenic variant or duplication. We performed direct sequencing of the whole APP 3'UTR in 90 patients with CAA and explored the functional consequences of one previously unreported variant. We identified three sequence variants in four patients, of which a two-base pair deletion (c.*331_*332del) was previously unannotated and absent from 175 controls of same ethnicity. This latter variant was associated with increased APP expression in vivo and in vitro. Bioinformatics and functional assays showed that the APP c.*331_*332del variant affected APP messenger RNA (mRNA) structure and binding of two microRNAs (miR-582-3p and miR-892b), providing a mechanism for the observed effects on APP expression. These results identify APP 3'UTR sequence variants as genetic determinants of Aβ-CAA.
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http://dx.doi.org/10.1038/ejhg.2015.61DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4795229PMC
January 2016

Regional distribution of synaptic markers and APP correlate with distinct clinicopathological features in sporadic and familial Alzheimer's disease.

Brain 2014 May 12;137(Pt 5):1533-49. Epub 2014 Mar 12.

1 Department of Neuroscience, Mayo Clinic, Jacksonville, FL, USA.

Recent studies suggest that subcortical structures, including striatum, are vulnerable to amyloid-β accumulation and other neuropathological features in familial Alzheimer's disease due to autosomal dominant mutations. We explored differences between familial and sporadic Alzheimer's disease that might shed light on their respective pathogenic mechanisms. To this end, we analysed 12 brain regions, including neocortical, limbic and subcortical areas, from post-mortem brains of familial Alzheimer's disease (n = 10; age at death: 50.0 ± 8.6 years) with mutations in amyloid precursor protein (APP) or presenilin 1 (PSEN1), sporadic Alzheimer's disease (n = 19; age at death: 84.7 ± 7.8 years), neurologically normal elderly without amyloid-β accumulation (normal ageing; n = 13, age at death: 82.9 ± 10.8 years) and neurologically normal elderly with extensive cortical amyloid-β deposits (pathological ageing; n = 15; age at death: 92.7 ± 5.9 years). The levels of amyloid-β₄₀, amyloid-β₄₂, APP, apolipoprotein E, the synaptic marker PSD95 (now known as DLG4), the astrocyte marker GFAP, other molecules related to amyloid-β metabolism, and tau were determined by enzyme-linked immunosorbent assays. We observed that familial Alzheimer's disease had disproportionate amyloid-β₄₂ accumulation in subcortical areas compared with sporadic Alzheimer's disease, whereas sporadic Alzheimer's disease had disproportionate amyloid-β₄₂ accumulation in cortical areas compared to familial Alzheimer's disease. Compared with normal ageing, the levels of several proteins involved in amyloid-β metabolism were significantly altered in both sporadic and familial Alzheimer's disease; however, such changes were not present in pathological ageing. Among molecules related to amyloid-β metabolism, the regional distribution of PSD95 strongly correlated with the regional pattern of amyloid-β₄₂ accumulation in sporadic Alzheimer's disease and pathological ageing, whereas the regional distribution of APP as well as β-C-terminal fragment of APP were strongly associated with the regional pattern of amyloid-β₄₂ accumulation in familial Alzheimer's disease. Apolipoprotein E and GFAP showed negative regional association with amyloid-β (especially amyloid-β₄₀) accumulation in both sporadic and familial Alzheimer's disease. Familial Alzheimer's disease had greater striatal tau pathology than sporadic Alzheimer's disease. In a retrospective medical record review, atypical signs and symptoms were more frequent in familial Alzheimer's disease compared with sporadic Alzheimer's disease. These results suggest that disproportionate amyloid-β₄₂ accumulation in cortical areas in sporadic Alzheimer's disease may be mediated by synaptic processes, whereas disproportionate amyloid-β₄₂ accumulation in subcortical areas in familial Alzheimer's disease may be driven by APP and its processing. Region-specific amyloid-β₄₂ accumulation might account for differences in the relative amounts of tau pathology and clinical symptoms in familial and sporadic Alzheimer's disease.
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http://dx.doi.org/10.1093/brain/awu046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3999719PMC
May 2014

PDGFB partial deletion: a new, rare mechanism causing brain calcification with leukoencephalopathy.

J Mol Neurosci 2014 Jun 7;53(2):171-5. Epub 2014 Mar 7.

Inserm U1079, Rouen, France.

Idiopathic basal ganglia calcification (IBGC) is a progressive cerebral disorder with diverse motor, cognitive, and psychiatric expression. It is inherited as an autosomal dominant trait. Three IBGC-causing genes have been identified in the past 2 years: SLC20A2, PDGFRB, and PDGFB. Biological and genetic evidence showed that loss of function of either SLC20A2 or the PDGFB/PDGFRB pathway was the mechanism underlying calcification in patients with a mutation. Recently, in a study focusing on SLC20A2, a large deletion at this locus was reported. No study has systematically searched for copy number variants (CNV) involving these three genes. We designed a quantitative PCR assay of multiple short fluorescent fragments (QMPSF) to detect CNVs involving one of these three genes in a single assay. Among the 27 unrelated patients from our IBGC case series with no mutation in SLC20A2, PDGFRB, and PDGFB, we identified in one patient a heterozygous partial deletion involving exons 2 to 5 of PDGFB. This patient exhibited both strio-pallido-dentate calcification and white matter hyperintensity of presumed vascular origin, associated with mood disorder, subtle cognitive decline, and gait disorder. We confirmed by RT-PCR experiments that the allele carrying the deletion was transcribed. The resulting cDNA lacks sequence for several critical functional domains of the protein. Intragenic deletion of PDGFB is a new and rare mechanism causing IBGC. CNVs involving the three IBGC-causing genes should be investigated in patients with no point mutation.
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http://dx.doi.org/10.1007/s12031-014-0265-zDOI Listing
June 2014

A de novo nonsense PDGFB mutation causing idiopathic basal ganglia calcification with laryngeal dystonia.

Eur J Hum Genet 2014 Oct 12;22(10):1236-8. Epub 2014 Feb 12.

1] Inserm U1079, Rouen, France [2] IRIB, Normandie University, Rouen, France [3] Department of Genetics, Rouen University Hospital, Rouen, France [4] CNR-MAJ, Lille, Paris-Salpêtrière and Rouen University Hospitals, Paris, France [5] Department of Neurology, Rouen University Hospital, Rouen, France.

Idiopathic basal ganglia calcification (IBGC) is characterized by brain calcification and a wide variety of neurologic and psychiatric symptoms. In families with autosomal dominant inheritance, three causative genes have been identified: SLC20A2, PDGFRB, and, very recently, PDGFB. Whereas in clinical practice sporadic presentation of IBGC is frequent, well-documented reports of true sporadic occurrence are rare. We report the case of a 20-year-old woman who presented laryngeal dystonia revealing IBGC. Her healthy parents' CT scans were both normal. We identified in the proband a new nonsense mutation in exon 4 of PDGFB, c.439C>T (p.Gln147*), which was absent from the parents' DNA. This mutation may result in a loss-of-function of PDGF-B, which has been shown to cause IBGC in humans and to disrupt the blood-brain barrier in mice, resulting in brain calcification. The c.439C>T mutation is located between two previously reported nonsense mutations, c.433C>T (p.Gln145*) and c.445C>T (p.Arg149*), on a region that could be a hot spot for de novo mutations. We present the first full demonstration of the de novo occurrence of an IBGC-causative mutation in a sporadic case.
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http://dx.doi.org/10.1038/ejhg.2014.9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4169546PMC
October 2014

Partial deletions of the GRN gene are a cause of frontotemporal lobar degeneration.

Neurogenetics 2014 May 28;15(2):95-100. Epub 2014 Jan 28.

Département de Génétique, Cytogénétique et Embryologie, Hôpitaux Universitaires La Pitié Salpêtrière-Charles Foix, Assistance Publique-Hôpitaux de Paris, Paris, France,

Mutations in the progranulin gene (GRN) are an important cause of frontotemporal lobar degeneration (FTLD). Most known GRN mutations are null mutations, such as nonsense and frameshift mutations, which create a premature stop codon resulting in loss of function of the progranulin protein. Complete or near-complete genomic GRN deletions have also been found in three families, but heterozygous partial deletions that remove only one or two exons have not been reported to date. In this study, we analysed three unrelated FTLD patients with low plasma progranulin levels but no point GRN mutations by multiplex ligation-dependent probe amplification (MLPA) and quantitative multiplex polymerase chain reaction of short fluorescent fragments (QMPSF). We detected two heterozygous partial GRN deletions in two patients. One deletion removed exon 1 and part of intron 1. The second deletion was complex: it removed 1,410 bp extending from the part of intron 1 to the part of exon 3, with a small 5-bp insertion at the breakpoint junction (c.-7-1121_159delinsGATCA). Our findings illustrate the usefulness of a quantitative analysis in addition to GRN gene sequencing for a comprehensive genetic diagnosis of FTLD, particularly in patients with low plasma progranulin levels.
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http://dx.doi.org/10.1007/s10048-014-0389-xDOI Listing
May 2014

Phenotypic spectrum of probable and genetically-confirmed idiopathic basal ganglia calcification.

Brain 2013 Nov 24;136(Pt 11):3395-407. Epub 2013 Sep 24.

1 Inserm U1079, Rouen, France.

Idiopathic basal ganglia calcification is characterized by mineral deposits in the brain, an autosomal dominant pattern of inheritance in most cases and genetic heterogeneity. The first causal genes, SLC20A2 and PDGFRB, have recently been reported. Diagnosing idiopathic basal ganglia calcification necessitates the exclusion of other causes, including calcification related to normal ageing, for which no normative data exist. Our objectives were to diagnose accurately and then describe the clinical and radiological characteristics of idiopathic basal ganglia calcification. First, calcifications were evaluated using a visual rating scale on the computerized tomography scans of 600 consecutively hospitalized unselected controls. We determined an age-specific threshold in these control computerized tomography scans as the value of the 99th percentile of the total calcification score within three age categories: <40, 40-60, and >60 years. To study the phenotype of the disease, patients with basal ganglia calcification were recruited from several medical centres. Calcifications that rated below the age-specific threshold using the same scale were excluded, as were patients with differential diagnoses of idiopathic basal ganglia calcification, after an extensive aetiological assessment. Sanger sequencing of SLC20A2 and PDGFRB was performed. In total, 72 patients were diagnosed with idiopathic basal ganglia calcification, 25 of whom bore a mutation in either SLC20A2 (two families, four sporadic cases) or PDGFRB (one family, two sporadic cases). Five mutations were novel. Seventy-one per cent of the patients with idiopathic basal ganglia calcification were symptomatic (mean age of clinical onset: 39 ± 20 years; mean age at last evaluation: 55 ± 19 years). Among them, the most frequent signs were: cognitive impairment (58.8%), psychiatric symptoms (56.9%) and movement disorders (54.9%). Few clinical differences appeared between SLC20A2 and PDGFRB mutation carriers. Radiological analysis revealed that the total calcification scores correlated positively with age in controls and patients, but increased more rapidly with age in patients. The expected total calcification score was greater in SLC20A2 than PDGFRB mutation carriers, beyond the effect of the age alone. No patient with a PDGFRB mutation exhibited a cortical or a vermis calcification. The total calcification score was more severe in symptomatic versus asymptomatic individuals. We provide the first phenotypical description of a case series of patients with idiopathic basal ganglia calcification since the identification of the first causative genes. Clinical and radiological diversity is confirmed, whatever the genetic status. Quantification of calcification is correlated with the symptomatic status, but the location and the severity of the calcifications don't reflect the whole clinical diversity. Other biomarkers may be helpful in better predicting clinical expression.
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http://dx.doi.org/10.1093/brain/awt255DOI Listing
November 2013

TREM2 R47H variant as a risk factor for early-onset Alzheimer's disease.

J Alzheimers Dis 2013 ;35(1):45-9

INSERM U1079, Faculté de Médecine, IRIB, Rouen, France.

The rs75932628-T variant of the gene encoding the triggering receptor expressed on myeloid cells 2 (TREM2) has recently been identified as a rare risk factor for late-onset Alzheimer's disease (AD). In this study we examined the association between TREM2 exon 2 variants and early-onset AD in a sample of Caucasian subjects of French origin including 726 patients with age of onset ≤65 years and 783 controls. Only the rs75932628-T variant (predicted to cause an R47H substitution) conferred a significant risk for early-onset AD (OR, 4.07; 95% CI, 1.3 to 16.9; p = 0.009). These results confirm the association between this variant and AD and underline its involvement in early-onset cases.
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http://dx.doi.org/10.3233/JAD-122311DOI Listing
December 2013

Mutation of the PDGFRB gene as a cause of idiopathic basal ganglia calcification.

Neurology 2013 Jan 19;80(2):181-7. Epub 2012 Dec 19.

Inserm U1079, University Hospital and Faculty of Medicine, Rouen.

Objectives: To identify a new idiopathic basal ganglia calcification (IBGC)-causing gene.

Methods: In a 3-generation family with no SLC20A2 mutation, we performed whole exome sequencing in 2 affected first cousins, once removed. Nonsynonymous coding variants, splice acceptor and donor site variants, and frameshift coding indels (NS/SS/I) were filtered against dbSNP131, the HapMap Project, 1000 Genomes Project, and our in-house database including 72 exomes.

Results: Seventeen genes were affected by identical unknown NS/SS/I variations in the 2 patients. After screening the relatives, the p.Leu658Pro substitution within the PDGFRB gene remained the sole unknown mutation segregating with the disease in the family. This variation, which is predicted to be highly damaging, was present in 13 of 13 affected subjects and absent in 8 relatives without calcifications. Sequencing PDGFRB of 19 other unrelated IBGC cases allowed us to detect another potentially pathogenic substitution within PDGFRB, p.Arg987Trp, also predicted to be highly damaging. PDGFRB encodes a protein involved in angiogenesis and in the regulation of inorganic phosphate (Pi) transport in vascular smooth muscle cells via Pit-1, a Pi transporter encoded by SLC20A1.

Conclusion: Mutations of PDGFRB further support the involvement of this biological pathway in IBGC pathophysiology.
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http://dx.doi.org/10.1212/WNL.0b013e31827ccf34DOI Listing
January 2013

Copy number variations involving the microtubule-associated protein tau in human diseases.

Biochem Soc Trans 2012 Aug;40(4):672-6

Inserm, U1079, Rouen, France.

Mutations of the MAPT (microtubule-associated protein tau) gene are associated with FTLD (frontotemporal lobar degeneration) with tau pathology. These mutations result in a decreased ability of tau to bind MTs (microtubules), an increased production of tau with four MT-binding repeats or enhanced tau aggregation. In two FTLD patients, we recently described CNVs (copy number variations) affecting the MAPT gene, consisting of a partial deletion and a complete duplication of the gene. The partial deletion resulted in a truncated protein lacking the first MT-binding domain, which had a dramatic decrease in the binding to MTs but acquired the ability to bind MAP (microtubule-associated protein) 1-B. In this case, tauopathy probably resulted from both a loss of normal function and a gain of function by which truncated tau would sequester another MAP. In the other FTLD patient, the complete duplication might result in the overexpression of tau, which in the mouse model induces axonopathy and tau aggregates reminiscent of FTLD-tau pathology. Interestingly, the same rearrangement was also described in several children with mental retardation, autism spectrum disorders and dysmorphic features, as well as in a schizophrenic patient. Finally, complete deletions of the MAPT gene have been associated with mental retardation, hypotonia and facial dysmorphism.
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http://dx.doi.org/10.1042/BST20120045DOI Listing
August 2012

Definite behavioral variant of frontotemporal dementia with C9ORF72 expansions despite positive Alzheimer's disease cerebrospinal fluid biomarkers.

J Alzheimers Dis 2012 ;32(1):19-22

Inserm UMR1079 and University of Rouen, Institute for Research and Innovation in Biomedicine, Rouen, France.

Hexanucleotide expansion repeats in the C9ORF72 gene are a major cause of familial and, to a lesser extent, sporadic frontotemporal lobar degeneration (FTLD), amyotrophic lateral sclerosis (ALS), and FTLD-ALS. To examine whether C9ORF72 expansions could be involved in early-onset Alzheimer's disease (EOAD), we genotyped the hexanucleotide repeat region in a large cohort of 114 EOAD patients who all had positive AD cerebrospinal fluid (CSF) biomarkers. We found hexanucleotide expansion repeats of the C9ORF72 gene in 3 out of 114 patients (2.6%). We raise several hypotheses to explain our results and discuss the current status of AD CSF biomarkers in the dementia diagnostic algorithm.
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http://dx.doi.org/10.3233/JAD-2012-120877DOI Listing
February 2013
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