Sandra Mercier

Centre Hospitalier Universitaire de Nantes | CHU Nantes

Objective X-linked myopathy with excessive autophagy (XMEA) linked to the VMA21 gene leads to autophagy failure with progressive vacuolation and atrophy of skeletal muscles. Current knowledge of this rare disease is limited. Our objective was to define the clinical, radiological, and natural history of XMEA. Methods We conducted a retrospective st...

Duplications of the 3q29 cytoband are rare chromosomal copy number variations (CNVs) (overlapping or recurrent ~1.6 Mb 3q29 duplications). They have been associated with highly variable neurodevelopmental disorders (NDDs) with various associated features or reported as a susceptibility factor to the development of learning disabilities and neuropsy...

Central nervous system (CNS) dural arteriovenous fistulas (DAVF) have been reported in PTEN‐related hamartoma tumor syndrome (PHTS). However, PHTS‐associated DAVF remain an underexplored field of the PHTS clinical landscape. Here, we studied cases with a PTEN pathogenic variant identified between 2007 and 2020 in our laboratory (n = 58), and for wh...

The ubiquitin-proteasome system (UPS) is a conserved degradation pathway in eukaryotes, playing a central role in various cellular processes, including maintaining protein homeostasis, regulating the cell cycle and signaling pathways, as well as orchestrating cell survival and death. Proteins targeted for UPS-mediated degradation undergo ubiquitin...

AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs) mediate fast excitatory neurotransmission in the brain. AMPARs form by homo- or heteromeric assembly of subunits encoded by the GRIA1-GRIA4 genes, of which only GRIA3 is X-chromosomal. Increasing numbers of GRIA3 missense variants are reported in patients with neurodeve...

DYRK1A Syndrome (OMIM #614104) is caused by pathogenic variations in the DYRK1A gene located on 21q22. Haploinsufficiency of DYRK1A causes a syndrome with global psychomotor delay and intellectual disability. Low birth weight, growth restriction with feeding difficulties, stature insufficiency, and microcephaly are frequently reported. This study a...

Background Weill-Marchesani syndrome (WMS) belongs to the group of acromelic dysplasias, defined by short stature, brachydactyly and joint limitations. WMS is characterised by specific ophthalmological abnormalities, although cardiovascular defects have also been reported. Monoallelic variations in FBN1 are associated with a dominant form of WMS, w...

The recent advances in high throughput sequencing technology have drastically changed the practice of medical diagnosis, allowing for rapid identification of hundreds of genes causing human diseases. This unprecedented progress has made clear that most forms of intellectual disability that affect more than 3% of individuals worldwide are monogenic...

Heterozygous, pathogenic CUX1 variants are associated with global developmental delay or intellectual disability. This study delineates the clinical presentation in an extended cohort and investigates the molecular mechanism underlying the disorder in a Cux1+/- mouse model. Through international collaboration, we assembled the phenotypic and molecu...

Introduction: The MYH7 c.5135G > A p.(Arg1712Gln) variant has been identified in several patients worldwide and is classified as pathogenic in the ClinVar database. We aimed to delineate its associated phenotype and evaluate a potential founder effect. Methods: We retrospectively collected clinical and genetic data of 22 probands and 74 family m...

Becker muscular dystrophy (BMD) is one of the most frequent among neuromuscular diseases, affecting approximately 1 in 18,000 male births. It is linked to a genetic mutation on the X chromosome. In contrast to Duchenne muscular dystrophy, for which improved care and management have changed the prognosis and life expectancy of patients, few guidelin...

We examined more than 38,000 spouse pairs from four neurodevelopmental disease cohorts and the UK Biobank to identify phenotypic and genetic patterns in parents associated with neurodevelopmental disease risk in children. We identified correlations between six phenotypes in parents and children, including correlations of clinical diagnoses such as...

Background: Spinal muscular atrophy type 1 (SMA1) is the most severe and early form of SMA, a genetic disease with motor neuron degeneration. Onasemnogene abeparvovec gene therapy (GT) has changed SMA1’s natural history, but real-world data is scarce. Methods: A French national expert committee identified 95 newly diagnosed and treatment-naive SMA...

Introduction: Exome sequencing has a diagnostic yield ranging from 25% to 70% in rare diseases and regularly implicates genes in novel disorders. Retrospective data reanalysis has demonstrated strong efficacy in improving diagnosis, but poses organizational difficulties for clinical laboratories. Patients and methods: We applied a reanalysis strate...

Introduction: Prenatal ultrasound (US) anomalies are detected in around 5%–10% of pregnancies. In prenatal diagnosis, exome sequencing (ES) diagnostic yield ranges from 6% to 80% depending on the inclusion criteria. We describe the first French national multicenter pilot study aiming to implement ES in prenatal diagnosis following the detection of...

Heterozygous, pathogenic CUX1 variants are associated with global developmental delay or intellectual disability. This study delineates the clinical presentation in an extended cohort and investigates the molecular mechanism underlying the disorder in a Cux1 +/− mouse model. Through international collaboration, we assembled the phenotypic and molec...

Purpose: WNK3 kinase (PRKWNK3) has been implicated in the development and function of the brain via its regulation of the cation-chloride cotransporters, but the role of WNK3 in human development is unknown. Method: We ascertained exome or genome sequences of individuals with rare familial or sporadic forms of intellectual disability (ID). Resu...

Adeno-Associated Virus (AAV) gene therapies are highly promising, such as the onasemnogene abeparvovec (Zolgensma®) in Spinal Muscle Atrophy (SMA). We report the first case of fatal systemic Thrombotic MicroAngiopathy (TMA) following onasemnogene abeparvovec in a 6-month-old child with SMA type 1, carrying a potential genetic predisposition in the...

RNA-binding proteins (RBPs) are essential for post-transcriptional regulation and processing of RNAs. Pathogenic missense variants in RBPs underlie a spectrum of disease phenotypes, including amyotrophic lateral sclerosis, frontotemporal dementia, inclusion body myopathy, distal myopathy, and Paget’s disease of the bone. Here, we present ten indepe...

Purpose: Exome sequencing has a diagnostic yield ranging from 25% to 70% in rare diseases and regularly implicates genes in novel disorders. Prospective data reanalysis has demonstrated strong efficacy in improving diagnosis, but poses organizational difficulties for clinical laboratories. We applied a reanalysis strategy based on intensive prospec...

The ryanodine receptor RyR1 is the main sarcoplasmic reticulum Ca ²⁺ channel in skeletal muscle and acts as a connecting link between electrical stimulation and Ca ²⁺ -dependent muscle contraction. Abnormal RyR1 activity compromises normal muscle function and results in various human disorders including malignant hyperthermia, central core disease,...

Background: In France, the Ministry of Health has implemented a comprehensive program for rare diseases (RD) that includes an epidemiological program as well as the establishment of expert centers for the clinical care of patients with RD. Since 2007, most of these centers have entered the data for patients with developmental disorders into the CE...

Many copy number variants (CNVs) confer risk for the same range of neurodevelopmental symptoms and psychiatric conditions including autism and schizophrenia. Yet, to date neuroimaging studies have typically been carried out one mutation at a time, showing that CNVs have large effects on brain anatomy. Here, we aimed to characterize and quantify the...

RNA-binding proteins (RBPs) are essential for post-transcriptional regulation and processing of RNAs. Pathogenic missense variants in RBPs underlie a spectrum of disease phenotypes, including amyotrophic lateral sclerosis, frontotemporal dementia, inclusion body myopathy, distal myopathy, and Paget's disease of the bone. Here, we present ten indepe...

Muscular dystrophies due to heterozygous pathogenic variants in LMNA gene cover a broad spectrum of clinical presentations and severity with an age of onset ranging from the neonatal period to adulthood. The natural history of these conditions is not well defined, particularly in patients with congenital or early onset who arguably present with the...

Background Arthrogryposis multiplex congenita (AMC) is characterised by congenital joint contractures in two or more body areas. AMC exhibits wide phenotypic and genetic heterogeneity. Our goals were to improve the genetic diagnosis rates of AMC, to evaluate the added value of whole exome sequencing (WES) compared with targeted exome sequencing (TE...

Myotonic dystrophy type 1 (DM1) is the most complex and variable trinucleotide repeat disorder caused by an unstable CTG repeat expansion, reaching up to 4000 CTG in the most severe cases. The genetic and clinical variability of DM1 depend on the sex and age of the transmitting parent, but also on the CTG repeat number, presence of repeat interrupt...

Although somatic mutations in Histone 3.3 (H3.3) are well-studied drivers of oncogenesis, the role of germline mutations remains unreported. We analyze 46 patients bearing de novo germline mutations in histone 3 family 3A (H3F3A) or H3F3B with progressive neurologic dysfunction and congenital anomalies without malignancies. Molecular modeling of al...

Background Spastic paraparesis and biallelic variants functionally characterized as deleterious in the RNF170 gene have recently been reported by Wagner et al. 2019, strongly supporting the involvement of this gene in hereditary spastic paraplegia. Methods Exome sequencing was performed on 6 hereditary spastic paraplegia families previously tested...

De novo pathogenic variants in the GATAD2B gene have been associated with a syndromic neurodevelopmental disorder (GAND) characterized by severe intellectual disability (ID), impaired speech, childhood hypotonia, and dysmorphic features. Since its first description in 2013, nine patients have been reported in case reports and a series of 50 patient...

Background: An accurate estimation of the risk of life-threatening (LT) ventricular tachyarrhythmia (VTA) in patients with LMNA mutations is crucial to select candidates for implantable cardioverter defibrillator (ICD) implantation. Methods: We included 839 adult patients with LMNA mutations, including 660 from a French nationwide registry in th...

Background: The X-chromosome gene USP9X encodes a deubiquitylating enzyme that has been associated with neurodevelopmental disorders primarily in female subjects. USP9X escapes X inactivation, and in female subjects de novo heterozygous copy number loss or truncating mutations cause haploinsufficiency culminating in a recognizable syndrome with in...

Dear Editor, Hereditary Fibrosing Poikiloderma with Tendon Contractures, Myopathy and Pulmonary Fibrosis (POIKTMP [MIM 615704]) is a recently described autosomal dominant disorder due to missense mutations in the FAM111B gene. Key features are early‐onset poikiloderma, muscle contractures in particular of the triceps surae, diffuse progressive fatt...

Introduction La poïkilodermie héréditaire fibrosante, myopathie rétractile et fibrose pulmonaire (POIKTMP) est une génodermatose caractérisée par des anomalies cutanées (poïkilodermie, hypotrichose), musculaires (faiblesse et rétractions musculaires), respiratoires (syndrome restrictif, fibrose pulmonaire) et/ou digestives (insuffisance pancréatiqu...

Purpose: To assess the contribution of rare variants in the genetic background toward variability of neurodevelopmental phenotypes in individuals with rare copy-number variants (CNVs) and gene-disruptive variants. Methods: We analyzed quantitative clinical information, exome sequencing, and microarray data from 757 probands and 233 parents and s...

X-linked dominant chondrodysplasia punctata (CDPX2 or Conradi-Hünermann-Happle syndrome, MIM #302960) is caused by mutations in the EBP gene. Affected female patients present with Blaschkolinear ichthyosis, coarse hair or alopecia, short stature, and normal psychomotor development. The disease is usually lethal in boys. Nevertheless, few male patie...

ZIC2 mutation is known to cause holoprosencephaly (HPE). A subset of ZIC2 HPE probands harbour cardiovascular and visceral anomalies suggestive of laterality defects. 3D-imaging of novel mouse Zic2 mutants uncovers, in addition to HPE, laterality defects in lungs, heart, vasculature and viscera. A strong bias towards right isomerism indicates a fai...

Purpose To assess the contribution of rare variants in the genetic background towards variability of neurodevelopmental phenotypes in individuals with rare copy-number variants (CNVs) and gene-disruptive mutations. Methods We analyzed quantitative clinical information, exome-sequencing, and microarray data from 757 probands and 233 parents and sib...

La dystrophie musculaire de Becker (DMB) est une maladie neuromusculaire liée à une mutation sur le gène de la dystrophine avec un phénotype moins sévère que dans la dystrophie musculaire de Duchenne (DMD). Outre l’atteinte musculaire, il peut exister dans les dystrophinopathies des atteintes du système nerveux central. Ces dernières sont bien conn...

X-linked myotubular myopathy (XLMTM), a severe congenital myopathy, is caused by mutations in the MTM1 gene located on the X chromosome. A majority of affected males die in the early postnatal period, whereas female carriers are believed to be usually asymptomatic. Nevertheless, several affected females have been reported. To assess the phenotypic...

Hearing loss is the most common sensory disorder and because of its high genetic heterogeneity, implementation of Massively Parallel Sequencing (MPS) in diagnostic laboratories is greatly improving the possibilities of offering optimal care to patients. We present the results of a two-year period of molecular diagnosis that included 207 French fami...

CHARGE syndrome (CS) is a genetic disorder whose first description included Coloboma, Heart disease, Atresia of choanae, Retarded growth and development, Genital hypoplasia, and Ear anomalies and deafness, most often caused by a genetic mutation in the CHD7 gene. Two features were then added: semicircular canal anomalies and arhinencephaly/olfactor...

DHX30 is a member of the family of DExH-box helicases, which use ATP hydrolysis to unwind RNA secondary structures. Here we identified six different de novo missense mutations in DHX30 in twelve unrelated individuals affected by global developmental delay (GDD), intellectual disability (ID), severe speech impairment and gait abnormalities. While fo...

Calcium/calmodulin-dependent protein kinase II (CAMK2) is one of the first proteins shown to be essential for normal learning and synaptic plasticity in mice, but its requirement for human brain development has not yet been established. Through a multi-center collaborative study based on a whole-exome sequencing approach, we identified 19 exceeding...

Background: Inherited cardiac conduction disease is a rare bradyarrhythmia associated with mutations in various genes that affect action potential propagation. It is often characterized by isolated conduction disturbance of the His-Purkinje system, but it is rarely described as a syndromic form. Objectives: The authors sought to identify the gen...

Sex chromosome aneuploidies (SCA) is a group of conditions in which individuals have an abnormal number of sex chromosomes. SCA, such as Klinefelter's syndrome, XYY syndrome, and Triple X syndrome are associated with a large range of neurological outcome. Another genetic event such as another cytogenetic abnormality may explain a part of this varia...

Objective We aimed to generate a review and description of the phenotypic and genotypic spectra of ARHGEF9 mutations. Methods Patients with mutations or chromosomal disruptions affecting ARHGEF9 were identified through our clinics and review of the literature. Detailed medical history and examination findings were obtained via a standardized quest...

Background Given the rarity of most single-gene Mendelian disorders, concerted efforts of data exchange between clinical and scientific communities are critical to optimize molecular diagnosis and novel disease gene discovery. Methods We designed and implemented protocols for the study of cases for which a plausible molecular diagnosis was not achi...

Cet homme de 62 ans a ete vu en consultation en juin 2016 pour un deficit des 4 membres d’aggravation progressive. Dix ans auparavant, il avait ete victime d’un traumatisme du rachis cervical responsable d’une tetraparesie spastique ayant secondairement bien recupere. Le tableau s’est degrade plus recemment avec une reaggravation du deficit moteur,...

Degradation of proteins by the ubiquitin-proteasome system (UPS) is an essential biological process in the development of eukaryotic organisms. Dysregulation of this mechanism leads to numerous human neurodegenerative or neurodevelopmental disorders. Through a multi-center collaboration, we identified six de novo genomic deletions and four de novo...

Congenital myopathies are phenotypically and genetically heterogeneous.¹ While SCN4A mutations were previously described in hypokalemic or hyperkalemic periodic paralysis, paramyotonia, myotonia congenita, or myasthenic syndrome,2–6 loss-of-function recessive mutations in SCN4A were recently identified in 11 individuals with severe fetal hypokinesi...

Homozygous frameshift variants in CNTNAP1 have recently been reported in patients with arthrogryposis and abnormal axon myelination. In two brothers with severe congenital hypotonia and foot deformities, we identified compound heterozygous variants in CNTNAP1, reporting the first causative missense variant, p.(Cys323Arg). Motor nerve conductions we...

Whole-exome sequencing of 13 individuals with developmental delay commonly accompanied by abnormal muscle tone and seizures identified de novo missense mutations enriched within a sub-region of GNB1, a gene encoding the guanine nucleotide-binding protein subunit beta-1, Gβ. These 13 individuals were identified among a base of 5,855 individuals recr...

Introduction L’ataluren est le premier médicament utilisé pour le traitement de la cause sous-jacente de la nmDMD. Objectifs Fournir une vue d’ensemble des résultats des essais cliniques de l’ataluren chez les patients souffrant de la nmDMD. Patients et méthodes Les études de phases 2 et 3 d’ataluren dans la nmDMD ont été analysées et les résulta...

Intellectual Disability (ID) is characterized by deficits in intellectual functions such as reasoning, problem-solving, planning, abstract thinking, judgment, and learning. As new avenues are emerging for treatment of genetically determined ID (such as Down’s syndrome or Fragile X syndrome), it is necessary to identify objective reliable and sensit...

A rare syndromic form of intellectual disability with impaired speech was recently found associated with mutations in CHAMP1 (chromosome alignment-maintaining phosphoprotein 1), the protein product of which is directly involved in microtubule-kinetochore attachment. Through whole-exome sequencing in six unrelated non-consanguineous families having...

Dystrophin is a large cytoskeletal protein located at the plasma membrane in both muscle and non-muscle tissues, which mediates interactions between the cytoskeleton, cell membrane, and extracellular matrix. Dystrophin is a key component of multiprotein complexes (dystrophin- associated glycoprotein complex, or DGC). It is also involved in many int...

Becker muscular dystrophy (BMD) was first described in 1955 and linked to the DMD gene in 1987. Compared to Duchenne muscular dystrophy (DMD), clinical onset of BMD usually occurs after the age of 12 and wheelchair is required after the age of 16. BMD is characterized by generalized weakness first affecting limb girdle muscles, hypertrophy of the c...

Becker muscular dystrophy (BMD) was first described in 1955 and linked to the DMD gene in 1987. Compared to Duchenne muscular dystrophy (DMD), clinical onset of BMD usually occurs after the age of 12 and wheelchair is required after the age of 16. BMD is characterized by generalized weakness first affecting limb girdle muscles, hypertrophy of the c...

Microarray-based comparative genomic hybridization (aCGH) is commonly used in diagnosing patients with intellectual disability (ID) with or without congenital malformation. Since aCGH interrogates the whole genome, there is a risk of being confronted with incidental findings (IF). In order to anticipate the ethical issues of IF with the generalizat...

Background Hereditary Fibrosing Poikiloderma (HFP) with tendon contractures, myopathy and pulmonary fibrosis (POIKTMP [MIM 615704]) is a very recently described entity of syndromic inherited poikiloderma. Previously by using whole exome sequencing in five families, we identified the causative gene, FAM111B (NM_198947.3), the function of which is st...

The European Journal of Human Genetics is the official Journal of the European Society of Human Genetics, publishing high-quality, original research papers, short reports, News and Commentary articles and reviews in the rapidly expanding field of human genetics and genomics.

Introduction L’amyotrophie spinale infantile (SMA), maladie génétique définie par une dégénérescence des moto-neurones de la corne antérieure, serait aussi caractérisée par des anomalies de maturation de la jonction neuromusculaire. Objectifs Nous avons réalisé chez nos patients atteints de SMA de type II ou III ainsi que chez des témoins sains de...

X-linked myopathy with excessive autophagy (XMEA) is an X-linked recessive myopathy due to recently reported mutations in the VMA21 gene. Four men from 2 separate families were studied. The clinical presentation, genetic data, muscle biopsy, and muscle MRI were analyzed. A known VMA21 mutation c.163 + 4A>G and a new mutation c.163 + 3A>G, respectiv...

Treacher Collins/Franceschetti syndrome (TCS; OMIM 154500) is a disorder of craniofacial development belonging to the heterogeneous group of mandibulofacial dysostoses. TCS is classically characterized by bilateral mandibular and malar hypoplasia, downward-slanting palpebral fissures, and microtia. To date, three genes have been identified in TCS:,...

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Seipinopathies are a group of inherited diseases affecting upper and lower motor neurons due to mutations in the Berardinelli–Seip congenital lipodystrophy 2 gene (BSCL2). We report a French family carrying the N88S mutation in the BSCL2 gene. A 12-yr-old girl complained of bilateral asymmetrical pes cavus with right hand motor deficit and amyotrop...