Publications by authors named "Christelle Moufawad El Achkar"

12 Publications

  • Page 1 of 1

De novo TRIM8 variants impair its protein localization to nuclear bodies and cause developmental delay, epilepsy, and focal segmental glomerulosclerosis.

Am J Hum Genet 2021 02 27;108(2):357-367. Epub 2021 Jan 27.

Division of Pediatric Neurology and Developmental Medicine, Duke University Medical Center, Durham, NC 27710, USA.

Focal segmental glomerulosclerosis (FSGS) is the main pathology underlying steroid-resistant nephrotic syndrome (SRNS) and a leading cause of chronic kidney disease. Monogenic forms of pediatric SRNS are predominantly caused by recessive mutations, while the contribution of de novo variants (DNVs) to this trait is poorly understood. Using exome sequencing (ES) in a proband with FSGS/SRNS, developmental delay, and epilepsy, we discovered a nonsense DNV in TRIM8, which encodes the E3 ubiquitin ligase tripartite motif containing 8. To establish whether TRIM8 variants represent a cause of FSGS, we aggregated exome/genome-sequencing data for 2,501 pediatric FSGS/SRNS-affected individuals and 48,556 control subjects, detecting eight heterozygous TRIM8 truncating variants in affected subjects but none in control subjects (p = 3.28 × 10). In all six cases with available parental DNA, we demonstrated de novo inheritance (p = 2.21 × 10). Reverse phenotyping revealed neurodevelopmental disease in all eight families. We next analyzed ES from 9,067 individuals with epilepsy, yielding three additional families with truncating TRIM8 variants. Clinical review revealed FSGS in all. All TRIM8 variants cause protein truncation clustering within the last exon between residues 390 and 487 of the 551 amino acid protein, indicating a correlation between this syndrome and loss of the TRIM8 C-terminal region. Wild-type TRIM8 overexpressed in immortalized human podocytes and neuronal cells localized to nuclear bodies, while constructs harboring patient-specific variants mislocalized diffusely to the nucleoplasm. Co-localization studies demonstrated that Gemini and Cajal bodies frequently abut a TRIM8 nuclear body. Truncating TRIM8 DNVs cause a neuro-renal syndrome via aberrant TRIM8 localization, implicating nuclear bodies in FSGS and developmental brain disease.
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http://dx.doi.org/10.1016/j.ajhg.2021.01.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7895901PMC
February 2021

Clinical Reasoning: A 6-week-old infant with migrating focal seizures.

Neurology 2020 01 13;94(4):178-183. Epub 2020 Jan 13.

From the Epilepsy Genetics Program (L.S., C.M.E.A.) and Clinical Neurophysiology Fellowship Program (J.M.P.), Division of Epilepsy (I.B.), Department of Neurology, Boston Children's Hospital, MA.

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http://dx.doi.org/10.1212/WNL.0000000000008842DOI Listing
January 2020

Patient-Customized Oligonucleotide Therapy for a Rare Genetic Disease.

N Engl J Med 2019 10 9;381(17):1644-1652. Epub 2019 Oct 9.

From the Divisions of Genetics and Genomics (J.K., C.H., E.A.L., A.S., J.V., R.L.D., J.C., P.B.A., A.H.B., S.E.W., O.B., T.W.Y.), Newborn Medicine (P.B.A., P.E.G.), and Neuroradiology (P.E.G.), the Departments of Neurology (C.M.E.A., D.K.U., A. Poduri), Anesthesiology, Critical Care and Pain Medicine (L.C., C.B.B.), Physical and Occupational Therapy (A. Pasternak, E.R.B., K.A.P.), and Pharmacy (S.C., A. Patterson), the Institutional Centers for Clinical and Translational Research (A.K., B.B., L.W.), and the Manton Center for Orphan Disease Research (C.A.G., P.B.A., A.H.B.), Boston Children's Hospital (A.K., A.T., M.A., L.M.P., K.D., B.B., L.W., B.D.G., B.L.R., A.B.), the Department of Biomedical Informatics (J.K., P.J.P.), Harvard Medical School (J.K., C.M.E.A., E.A.L., L.C., B.D.G., B.L.R., P.B.A., A.H.B., P.E.G., D.K.U., S.E.W., P.J.P., A. Patterson, A.B., O.B., C.B.B., T.W.Y.), and the Gene Therapy Program (A.B.), Boston Children's and Dana-Farber Cancer and Blood Disorders Center (A.K., B.B., L.W.), Boston, Charles River Laboratories, Wilmington (L.E.B.), and Broad Institute of MIT and Harvard (E.A.L., O.B., T.W.Y.), Cambridge - all in Massachusetts; Charles River Laboratories, Montreal (J.D.); University of Colorado School of Medicine, Aurora (A.L.); Pendergast Consulting, Washington, DC (M.K.P.); Goldkind Consulting, Potomac, MD (S.F.G.); the Department of Neurology Feinberg School of Medicine, Northwestern University, Chicago (N.R.B., K.F., I.S., J.R.M.); the Department of Neurology, University of Rochester Medical Center, Rochester, NY (E.F.A.); Brain Hz Consulting, Del Mar, CA (C.R.); Tyndall Consulting, Wake Forest, NC (K.T.); and Brammer Bio, Alachua, FL (R.O.S.).

Genome sequencing is often pivotal in the diagnosis of rare diseases, but many of these conditions lack specific treatments. We describe how molecular diagnosis of a rare, fatal neurodegenerative condition led to the rational design, testing, and manufacture of milasen, a splice-modulating antisense oligonucleotide drug tailored to a particular patient. Proof-of-concept experiments in cell lines from the patient served as the basis for launching an "N-of-1" study of milasen within 1 year after first contact with the patient. There were no serious adverse events, and treatment was associated with objective reduction in seizures (determined by electroencephalography and parental reporting). This study offers a possible template for the rapid development of patient-customized treatments. (Funded by Mila's Miracle Foundation and others.).
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http://dx.doi.org/10.1056/NEJMoa1813279DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6961983PMC
October 2019

Heterogeneous clinical and functional features of GRIN2D-related developmental and epileptic encephalopathy.

Brain 2019 10;142(10):3009-3027

Department of Pediatrics and Pediatric Epilepsy Center, Peking University First Hospital, Beijing, China.

N-methyl d-aspartate receptors are ligand-gated ionotropic receptors mediating a slow, calcium-permeable component of excitatory synaptic transmission in the CNS. Variants in genes encoding NMDAR subunits have been associated with a spectrum of neurodevelopmental disorders. Here we report six novel GRIN2D variants and one previously-described disease-associated GRIN2D variant in two patients with developmental and epileptic encephalopathy. GRIN2D encodes for the GluN2D subunit protein; the GluN2D amino acids affected by the variants in this report are located in the pre-M1 helix, transmembrane domain M3, and the intracellular carboxyl terminal domain. Functional analysis in vitro reveals that all six variants decreased receptor surface expression, which may underline some shared clinical symptoms. In addition the GluN2D(Leu670Phe), (Ala675Thr) and (Ala678Asp) substitutions confer significantly enhanced agonist potency, and/or increased channel open probability, while the GluN2D(Ser573Phe), (Ser1271Phe) and (Arg1313Trp) substitutions result in a mild increase of agonist potency, reduced sensitivity to endogenous protons, and decreased channel open probability. The GluN2D(Ser573Phe), (Ala675Thr), and (Ala678Asp) substitutions significantly decrease current amplitude, consistent with reduced surface expression. The GluN2D(Leu670Phe) variant slows current response deactivation time course and increased charge transfer. GluN2D(Ala678Asp) transfection significantly decreased cell viability of rat cultured cortical neurons. In addition, we evaluated a set of FDA-approved NMDAR channel blockers to rescue functional changes of mutant receptors. This work suggests the complexity of the pathological mechanisms of GRIN2D-mediated developmental and epileptic encephalopathy, as well as the potential benefit of precision medicine.
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http://dx.doi.org/10.1093/brain/awz232DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6763743PMC
October 2019

Recurrent SLC1A2 variants cause epilepsy via a dominant negative mechanism.

Ann Neurol 2019 06 26;85(6):921-926. Epub 2019 Apr 26.

Division of Genetics and Genomics, Boston Children's Hospital, Harvard Medical School, Boston, MA.

SLC1A2 is a trimeric transporter essential for clearing glutamate from neuronal synapses. Recurrent de novo SLC1A2 missense variants cause a severe, early onset developmental and epileptic encephalopathy via an unclear mechanism. We demonstrate that all 3 variants implicated in this condition localize to the trimerization domain of SLC1A2, and that the Leu85Pro variant acts via a dominant negative mechanism to reduce, but not eliminate, wild-type SLC1A2 protein localization and function. Finally, we demonstrate that treatment of a 20-month-old SLC1A2-related epilepsy patient with the SLC1A2-modulating agent ceftriaxone did not result in a significant change in daily spasm count. ANN NEUROL 2019;85:921-926.
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http://dx.doi.org/10.1002/ana.25477DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6800210PMC
June 2019

A Recurrent De Novo PACS2 Heterozygous Missense Variant Causes Neonatal-Onset Developmental Epileptic Encephalopathy, Facial Dysmorphism, and Cerebellar Dysgenesis.

Am J Hum Genet 2018 05 12;102(5):995-1007. Epub 2018 Apr 12.

University of Groningen, University Medical Center Groningen, Department of Genetics, 9700 RB Groningen, the Netherlands.

Developmental and epileptic encephalopathies (DEEs) represent a large clinical and genetic heterogeneous group of neurodevelopmental diseases. The identification of pathogenic genetic variants in DEEs remains crucial for deciphering this complex group and for accurately caring for affected individuals (clinical diagnosis, genetic counseling, impacting medical, precision therapy, clinical trials, etc.). Whole-exome sequencing and intensive data sharing identified a recurrent de novo PACS2 heterozygous missense variant in 14 unrelated individuals. Their phenotype was characterized by epilepsy, global developmental delay with or without autism, common cerebellar dysgenesis, and facial dysmorphism. Mixed focal and generalized epilepsy occurred in the neonatal period, controlled with difficulty in the first year, but many improved in early childhood. PACS2 is an important PACS1 paralog and encodes a multifunctional sorting protein involved in nuclear gene expression and pathway traffic regulation. Both proteins harbor cargo(furin)-binding regions (FBRs) that bind cargo proteins, sorting adaptors, and cellular kinase. Compared to the defined PACS1 recurrent variant series, individuals with PACS2 variant have more consistently neonatal/early-infantile-onset epilepsy that can be challenging to control. Cerebellar abnormalities may be similar but PACS2 individuals exhibit a pattern of clear dysgenesis ranging from mild to severe. Functional studies demonstrated that the PACS2 recurrent variant reduces the ability of the predicted autoregulatory domain to modulate the interaction between the PACS2 FBR and client proteins, which may disturb cellular function. These findings support the causality of this recurrent de novo PACS2 heterozygous missense in DEEs with facial dysmorphim and cerebellar dysgenesis.
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http://dx.doi.org/10.1016/j.ajhg.2018.03.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5986694PMC
May 2018

Characterization of a novel variant in siblings with Asparagine Synthetase Deficiency.

Mol Genet Metab 2018 03 20;123(3):317-325. Epub 2017 Dec 20.

Department of Biochemistry & Molecular Biology, Genetics Institute, University of Florida College of Medicine, 1200 Newell Drive, FL 32608, USA. Electronic address:

Asparagine Synthetase Deficiency (ASD) is a recently described inborn error of metabolism caused by bi-allelic pathogenic variants in the asparagine synthetase (ASNS) gene. ASD typically presents congenitally with microcephaly and severe, often medically refractory, epilepsy. Development is generally severely affected at birth. Tone is abnormal with axial hypotonia and progressive appendicular spasticity. Hyperekplexia has been reported. Neuroimaging typically demonstrates gyral simplification, abnormal myelination, and progressive cerebral atrophy. The present report describes two siblings from consanguineous parents with a homozygous Arg49Gln variant associated with a milder form of ASD that is characterized by later onset of symptoms. Both siblings had a period of normal development before onset of seizures, and development regression. Primary fibroblast studies of the siblings and their parents document that homozygosity for Arg49Gln blocks cell growth in the absence of extracellular asparagine. Functional studies with these cells suggest no impact of the Arg49Gln variant on basal ASNS mRNA or protein levels, nor on regulation of the gene itself. Molecular modelling of the ASNS protein structure indicates that the Arg49Gln variant lies near the substrate binding site for glutamine. Collectively, the results suggest that the Arg49Gln variant affects the enzymatic function of ASNS. The clinical, cellular, and molecular observations from these siblings expand the known phenotypic spectrum of ASD.
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http://dx.doi.org/10.1016/j.ymgme.2017.12.433DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5832599PMC
March 2018

Compound heterozygosity with : Pushing the phenotypic envelope in genetic epilepsies.

Epilepsy Behav Case Rep 2019 1;11:125-128. Epub 2017 Feb 1.

Epilepsy Genetics Program, Division of Epilepsy and Clinical Neurophysiology, Department of Neurology, Boston Children's Hospital, and Harvard Medical School, Boston, MA 02115, United States.

pathogenic variants have been described in benign familial infantile epilepsy, episodic ataxia, paroxysmal kinesigenic dyskinesia, and hemiplegic migraines. We describe a patient with compound heterozygous variants, infantile epilepsy with status epilepticus, paroxysmal dyskinesia and episodic ataxia. Testing revealed a pathogenic duplication (c.649dupC), and a likely pathogenic missense variant (c.916G>A). His presentation meets the severe phenotypic category with a combination of at least 3 neurological symptoms: seizures and status epilepticus, prolonged episodic ataxia, and paroxysmal dyskinesia. This further expands the clinical findings related to , and suggests that compound heterozygous variants could confer a severe phenotype.
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http://dx.doi.org/10.1016/j.ebcr.2016.12.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6525261PMC
February 2017

De Novo TUBB2A Variant Presenting With Anterior Temporal Pachygyria.

J Child Neurol 2017 01 23;32(1):127-131. Epub 2016 Oct 23.

2 Department of Neurology, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA.

TUBB2A is a gene that has recently been reported in association with structural brain abnormalities. Only 3 cases have been reported to date with disparate brain morphologic abnormalities, although all patients have presented with developmental delay and infantile-onset epilepsy. We report a fourth patient with a de novo variant in TUBB2A that is predicted to be pathogenic, presenting with developmental delay, spastic diplegia, exaggerated startle, and anterior temporal pachygyria in the absence of epilepsy. This report serves to further delineate the phenotype of the TUBB2A-related disorders. Focal anterior temporal pachygyria may facilitate recognition of additional cases of this tubulinopathy.
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http://dx.doi.org/10.1177/0883073816672998DOI Listing
January 2017

Genetic and phenotypic diversity of NHE6 mutations in Christianson syndrome.

Ann Neurol 2014 Oct 19;76(4):581-93. Epub 2014 Sep 19.

Department of Molecular Biology, Cell Biology, and Biochemistry and Laboratory for Molecular Medicine, Institute for Brain Science, Brown University, Providence, RI; Developmental Disorders Genetics Research Program, Emma Pendleton Bradley Hospital and Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University, East Providence, RI.

Objective: Recently, Christianson syndrome (CS) has been determined to be caused by mutations in the X-linked Na(+) /H(+) exchanger 6 (NHE6). We aimed to determine the diagnostic criteria and mutational spectrum for CS.

Methods: Twelve independent pedigrees (14 boys, age = 4-19 years) with mutations in NHE6 were administered standardized research assessments, and mutations were characterized.

Results: The mutational spectrum was composed of 9 single nucleotide variants, 2 indels, and 1 copy number variation deletion. All mutations were protein-truncating or splicing mutations. We identified 2 recurrent mutations (c.1498 c>t, p.R500X; and c.1710 g>a, p.W570X). Otherwise, all mutations were unique. In our study, 7 of 12 mutations (58%) were de novo, in contrast to prior literature wherein mutations were largely inherited. We also report prominent neurological, medical, and behavioral symptoms. All CS participants were nonverbal and had intellectual disability, epilepsy, and ataxia. Many had prior diagnoses of autism and/or Angelman syndrome. Other neurologic symptoms included eye movement abnormalities (79%), postnatal microcephaly (92%), and magnetic resonance imaging evidence of cerebellar atrophy (33%). Regression was noted in 50%, with recurrent presentations involving loss of words and/or the ability to walk. Medical symptoms, particularly gastrointestinal symptoms, were common. Height and body mass index measures were below normal ranges in most participants. Behavioral symptoms included hyperkinetic behavior (100%), and a majority exhibited high pain threshold.

Interpretation: This is the largest cohort of independent CS pedigrees reported. We propose diagnostic criteria for CS. CS represents a novel neurogenetic disorder with general relevance to autism, intellectual disability, Angelman syndrome, epilepsy, and regression.
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http://dx.doi.org/10.1002/ana.24225DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4304796PMC
October 2014
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