Missense variants in ANO4 cause sporadic encephalopathic or familial epilepsy with evidence for a dominant-negative effect.

Anoctamins are a family of Ca2+-activated proteins that may act as ion channels and/or phospholipid scramblases with limited understanding of function and disease association. Here, we identified five de novo and two inherited missense variants in ANO4 (alias TMEM16D) as a cause of fever-sensitive developmental and epileptic or epileptic encephalopathy (DEE/EE) and generalized epilepsy with febrile seizures plus (GEFS+) or temporal lobe epilepsy. In silico modeling of the ANO4 structure predicted that all identified variants lead to destabilization of the ANO4 structure. Four variants are localized close to the Ca2+ binding sites of ANO4, suggesting impaired protein function. Variant mapping to the protein topology suggests a preliminary genotype-phenotype correlation. Moreover, the observation of a heterozygous ANO4 deletion in a healthy individual suggests a dysfunctional protein as disease mechanism rather than haploinsufficiency. To test this hypothesis, we examined mutant ANO4 functional properties in a heterologous expression system by patch-clamp recordings, immunocytochemistry, and surface expression of annexin A5 as a measure of phosphatidylserine scramblase activity. All ANO4 variants showed severe loss of ion channel function and DEE/EE associated variants presented mild loss of surface expression due to impaired plasma membrane trafficking. Increased levels of Ca2+-independent annexin A5 at the cell surface suggested an increased apoptosis rate in DEE-mutant expressing cells, but no changes in Ca2+-dependent scramblase activity were observed. Co-transfection with ANO4 wild-type suggested a dominant-negative effect. In summary, we expand the genetic base for both encephalopathic sporadic and inherited fever-sensitive epilepsies and link germline variants in ANO4 to a hereditary disease.

Stretch-activated ion channel TMEM63B associates with developmental and epileptic encephalopathies and progressive neurodegeneration.

By converting physical forces into electrical signals or triggering intracellular cascades, stretch-activated ion channels allow the cell to respond to osmotic and mechanical stress. Knowledge of the pathophysiological mechanisms underlying associations of stretch-activated ion channels with human disease is limited. Here, we describe 17 unrelated individuals with severe early-onset developmental and epileptic encephalopathy (DEE), intellectual disability, and severe motor and cortical visual impairment associated with progressive neurodegenerative brain changes carrying ten distinct heterozygous variants of TMEM63B, encoding for a highly conserved stretch-activated ion channel. The variants occurred de novo in 16/17 individuals for whom parental DNA was available and either missense, including the recurrent p.Val44Met in 7/17 individuals, or in-frame, all affecting conserved residues located in transmembrane regions of the protein. In 12 individuals, hematological abnormalities co-occurred, such as macrocytosis and hemolysis, requiring blood transfusions in some. We modeled six variants (p.Val44Met, p.Arg433His, p.Thr481Asn, p.Gly580Ser, p.Arg660Thr, and p.Phe697Leu), each affecting a distinct transmembrane domain of the channel, in transfected Neuro2a cells and demonstrated inward leak cation currents across the mutated channel even in isotonic conditions, while the response to hypo-osmotic challenge was impaired, as were the Ca2+ transients generated under hypo-osmotic stimulation. Ectopic expression of the p.Val44Met and p.Gly580Cys variants in Drosophila resulted in early death. TMEM63B-associated DEE represents a recognizable clinicopathological entity in which altered cation conductivity results in a severe neurological phenotype with progressive brain damage and early-onset epilepsy associated with hematological abnormalities in most individuals.

Biallelic variants in ERLIN1: a series of 13 individuals with spastic paraparesis.

Biallelic variants in the ERLIN1 gene were recently reported as the cause of two motor neuron degeneration diseases, SPG62 and a recessive form of amyotrophic lateral sclerosis. However, only 12 individuals from five pedigrees have been identified so far. Thus, the description of the disease remains limited. Following the discovery of a homozygous pathogenic variant in a girl with SPG62, presenting with intellectual disability, and epilepsy, we gathered the largest series of SPG62 cases reported so far (13 individuals) to better understand the phenotype associated with ERLIN1. We collected molecular and clinical data for 13 individuals from six families with ERLIN1 biallelic variants. We performed RNA-seq analyses to characterize intronic variants and used Alphafold and a transcripts database to characterize the molecular consequences of the variants. We identified three new variants suspected to alter the bell-shaped ring formed by the ERLIN1/ERLIN2 complex. Affected individuals had childhood-onset paraparesis with slow progression. Six individuals presented with gait ataxia and three had superficial sensory loss. Aside from our proband, none had intellectual disability or epilepsy. Biallelic pathogenic ERLIN1 variants induce a rare, predominantly pure, spastic paraparesis, with possible cerebellar and peripheral nerve involvement.

Variants in the degron of AFF3 are associated with intellectual disability, mesomelic dysplasia, horseshoe kidney, and epileptic encephalopathy.

The ALF transcription factor paralogs, AFF1, AFF2, AFF3, and AFF4, are components of the transcriptional super elongation complex that regulates expression of genes involved in neurogenesis and development. We describe an autosomal dominant disorder associated with de novo missense variants in the degron of AFF3, a nine amino acid sequence important for its binding to ubiquitin ligase, or with de novo deletions of this region. The sixteen affected individuals we identified, along with two previously reported individuals, present with a recognizable pattern of anomalies, which we named KINSSHIP syndrome (KI for horseshoe kidney, NS for Nievergelt/Savarirayan type of mesomelic dysplasia, S for seizures, H for hypertrichosis, I for intellectual disability, and P for pulmonary involvement), partially overlapping the AFF4-associated CHOPS syndrome. Whereas homozygous Aff3 knockout mice display skeletal anomalies, kidney defects, brain malformations, and neurological anomalies, knockin animals modeling one of the microdeletions and the most common of the missense variants identified in affected individuals presented with lower mesomelic limb deformities like KINSSHIP-affected individuals and early lethality, respectively. Overexpression of AFF3 in zebrafish resulted in body axis anomalies, providing some support for the pathological effect of increased amount of AFF3. The only partial phenotypic overlap of AFF3- and AFF4-associated syndromes and the previously published transcriptome analyses of ALF transcription factors suggest that these factors are not redundant and each contributes uniquely to proper development.

Differences in Survival across Monogenic Forms of Parkinson's Disease.

OBJECTIVE: Survival of patients with monogenic Parkinson's disease may depend on the causative genes associated with the disease. In this study, we compare survival of patients with Parkinson's disease according to the presence of SNCA, PRKN, LRRK2, or GBA mutations. METHODS: Data from the French Parkinson Disease Genetics national multicenter cohort study were used. Patients with sporadic and familial Parkinson's disease were recruited between 1990 and 2021. Patients were genotyped for the presence of mutations in the SNCA, PRKN, LRRK2, or GBA genes. Vital status was collected from the National death register for participants born in France. Hazard ratios (HRs) and 95% confidence intervals (CIs) were computed using multivariable Cox proportional hazards regression. RESULTS: Of the 2,037 patients with Parkinson's disease, 889 had died after a follow-up of up to 30 years. Patients with PRKN (n = 100, HR = 0.41; p = 0.001) and LRRK2 mutations (n = 51, HR = 0.49; p = 0.023) had longer survival than those without any mutation, whereas patients with SNCA (n = 20, HR = 9.88; p < 0.001) or GBA mutations (n = 173, HR = 1.33; p = 0.048) had shorter survival. INTERPRETATION: Survival differs across genetic forms of Parkinson's disease, with higher mortality for patients with SNCA or GBA mutations, and lower mortality for those with PRKN or LRRK2 mutations. Differences in severity and disease progression among monogenic forms of Parkinson's disease likely explain these findings, which has important consequences for genetic counselling and choice of end points for future clinical trials for targeted therapies. ANN NEUROL 2023;94:123-132.

PTPA variants and impaired PP2A activity in early-onset parkinsonism with intellectual disability.

The protein phosphatase 2A complex (PP2A), the major Ser/Thr phosphatase in the brain, is involved in a number of signalling pathways and functions, including the regulation of crucial proteins for neurodegeneration, such as alpha-synuclein, tau and LRRK2. Here, we report the identification of variants in the PTPA/PPP2R4 gene, encoding a major PP2A activator, in two families with early-onset parkinsonism and intellectual disability. We carried out clinical studies and genetic analyses, including genome-wide linkage analysis, whole-exome sequencing, and Sanger sequencing of candidate variants. We next performed functional studies on the disease-associated variants in cultured cells and knock-down of ptpa in Drosophila melanogaster. We first identified a homozygous PTPA variant, c.893T>G (p.Met298Arg), in patients from a South African family with early-onset parkinsonism and intellectual disability. Screening of a large series of additional families yielded a second homozygous variant, c.512C>A (p.Ala171Asp), in a Libyan family with a similar phenotype. Both variants co-segregate with disease in the respective families. The affected subjects display juvenile-onset parkinsonism and intellectual disability. The motor symptoms were responsive to treatment with levodopa and deep brain stimulation of the subthalamic nucleus. In overexpression studies, both the PTPA p.Ala171Asp and p.Met298Arg variants were associated with decreased PTPA RNA stability and decreased PTPA protein levels; the p.Ala171Asp variant additionally displayed decreased PTPA protein stability. Crucially, expression of both variants was associated with decreased PP2A complex levels and impaired PP2A phosphatase activation. PTPA orthologue knock-down in Drosophila neurons induced a significant impairment of locomotion in the climbing test. This defect was age-dependent and fully reversed by L-DOPA treatment. We conclude that bi-allelic missense PTPA variants associated with impaired activation of the PP2A phosphatase cause autosomal recessive early-onset parkinsonism with intellectual disability. Our findings might also provide new insights for understanding the role of the PP2A complex in the pathogenesis of more common forms of neurodegeneration.

TMEM63C mutations cause mitochondrial morphology defects and underlie hereditary spastic paraplegia.

The hereditary spastic paraplegias (HSP) are among the most genetically diverse of all Mendelian disorders. They comprise a large group of neurodegenerative diseases that may be divided into 'pure HSP' in forms of the disease primarily entailing progressive lower-limb weakness and spasticity, and 'complex HSP' when these features are accompanied by other neurological (or non-neurological) clinical signs. Here, we identified biallelic variants in the transmembrane protein 63C (TMEM63C) gene, encoding a predicted osmosensitive calcium-permeable cation channel, in individuals with hereditary spastic paraplegias associated with mild intellectual disability in some, but not all cases. Biochemical and microscopy analyses revealed that TMEM63C is an endoplasmic reticulum-localized protein, which is particularly enriched at mitochondria-endoplasmic reticulum contact sites. Functional in cellula studies indicate a role for TMEM63C in regulating both endoplasmic reticulum and mitochondrial morphologies. Together, these findings identify autosomal recessive TMEM63C variants as a cause of pure and complex HSP and add to the growing evidence of a fundamental pathomolecular role of perturbed mitochondrial-endoplasmic reticulum dynamics in motor neurone degenerative diseases.

Delineating the genotypic and phenotypic spectrum of HECW2-related neurodevelopmental disorders.

BACKGROUND: Variants in HECW2 have recently been reported to cause a neurodevelopmental disorder with hypotonia, seizures and impaired language; however, only six variants have been reported and the clinical characteristics have only broadly been defined. METHODS: Molecular and clinical data were collected from clinical and research cohorts. Massive parallel sequencing was performed and identified individuals with a HECW2-related neurodevelopmental disorder. RESULTS: We identified 13 novel missense variants in HECW2 in 22 unpublished cases, of which 18 were confirmed to have a de novo variant. In addition, we reviewed the genotypes and phenotypes of previously reported and new cases with HECW2 variants (n=35 cases). All variants identified are missense, and the majority of likely pathogenic and pathogenic variants are located in or near the C-terminal HECT domain (88.2%). We identified several clustered variants and four recurrent variants (p.(Arg1191Gln);p.(Asn1199Lys);p.(Phe1327Ser);p.(Arg1330Trp)). Two variants, (p.(Arg1191Gln);p.(Arg1330Trp)), accounted for 22.9% and 20% of cases, respectively. Clinical characterisation suggests complete penetrance for hypotonia with or without spasticity (100%), developmental delay/intellectual disability (100%) and developmental language disorder (100%). Other common features are behavioural problems (88.9%), vision problems (83.9%), motor coordination/movement (75%) and gastrointestinal issues (70%). Seizures were present in 61.3% of individuals. Genotype-phenotype analysis shows that HECT domain variants are more frequently associated with cortical visual impairment and gastrointestinal issues. Seizures were only observed in individuals with variants in or near the HECT domain. CONCLUSION: We provide a comprehensive review and expansion of the genotypic and phenotypic spectrum of HECW2 disorders, aiding future molecular and clinical diagnosis and management.

Heterozygous variants in CTR9, which encodes a major component of the PAF1 complex, are associated with a neurodevelopmental disorder.

PURPOSE: CTR9 is a subunit of the PAF1 complex (PAF1C) that plays a crucial role in transcription regulation by binding CTR9 to RNA polymerase II. It is involved in transcription-coupled histone modification through promoting H3K4 and H3K36 methylation. We describe the clinical and molecular studies in 13 probands, harboring likely pathogenic CTR9 missense variants, collected through GeneMatcher. METHODS: Exome sequencing was performed in all individuals. CTR9 variants were assessed through 3-dimensional modeling of the activated human transcription complex Pol II-DSIF-PAF-SPT6 and the PAF1/CTR9 complex. H3K4/H3K36 methylation analysis, mitophagy assessment based on tetramethylrhodamine ethyl ester perchlorate immunofluorescence, and RNA-sequencing in skin fibroblasts from 4 patients was performed. RESULTS: Common clinical findings were variable degrees of intellectual disability, hypotonia, joint hyperlaxity, speech delay, coordination problems, tremor, and autism spectrum disorder. Mild dysmorphism and cardiac anomalies were less frequent. For 11 CTR9 variants, de novo occurrence was shown. Three-dimensional modeling predicted a likely disruptive effect of the variants on local CTR9 structure and protein interaction. Additional studies in fibroblasts did not unveil the downstream functional consequences of the identified variants. CONCLUSION: We describe a neurodevelopmental disorder caused by (mainly) de novo variants in CTR9, likely affecting PAF1C function.

Heterozygous variants in MYH10 associated with neurodevelopmental disorders and congenital anomalies with evidence for primary cilia-dependent defects in Hedgehog signaling.

PURPOSE: Nonmuscle myosin II complexes are master regulators of actin dynamics that play essential roles during embryogenesis with vertebrates possessing 3 nonmuscle myosin II heavy chain genes, MYH9, MYH10, and MYH14. As opposed to MYH9 and MYH14, no recognizable disorder has been associated with MYH10. We sought to define the clinical characteristics and molecular mechanism of a novel autosomal dominant disorder related to MYH10. METHODS: An international collaboration identified the patient cohort. CAS9-mediated knockout cell models were used to explore the mechanism of disease pathogenesis. RESULTS: We identified a cohort of 16 individuals with heterozygous MYH10 variants presenting with a broad spectrum of neurodevelopmental disorders and variable congenital anomalies that affect most organ systems and were recapitulated in animal models of altered MYH10 activity. Variants were typically de novo missense changes with clustering observed in the motor domain. MYH10 knockout cells showed defects in primary ciliogenesis and reduced ciliary length with impaired Hedgehog signaling. MYH10 variant overexpression produced a dominant-negative effect on ciliary length. CONCLUSION: These data presented a novel genetic cause of isolated and syndromic neurodevelopmental disorders related to heterozygous variants in the MYH10 gene with implications for disrupted primary cilia length control and altered Hedgehog signaling in disease pathogenesis.

Understanding the new BRD4-related syndrome: Clinical and genomic delineation with an international cohort study.

BRD4 is part of a multiprotein complex involved in loading the cohesin complex onto DNA, a fundamental process required for cohesin-mediated loop extrusion and formation of Topologically Associating Domains. Pathogenic variations in this complex have been associated with a growing number of syndromes, collectively known as cohesinopathies, the most classic being Cornelia de Lange syndrome. However, no cohort study has been conducted to delineate the clinical and molecular spectrum of BRD4-related disorder. We formed an international collaborative study, and collected 14 new patients, including two fetuses. We performed phenotype and genotype analysis, integrated prenatal findings from fetopathological examinations, phenotypes of pediatric patients and adults. We report the first cohort of patients with BRD4-related disorder and delineate the dysmorphic features at different ages. This work extends the phenotypic spectrum of cohesinopathies and characterize a new clinically relevant and recognizable pattern, distinguishable from the other cohesinopathies.

Characterization of Recessive Parkinson Disease in a Large Multicenter Study.

Studies of the phenotype and population distribution of rare genetic forms of parkinsonism are required, now that gene-targeting approaches for Parkinson disease have reached the clinical trial stage. We evaluated the frequencies of PRKN, PINK1, and DJ-1 mutations in a cohort of 1,587 cases. Mutations were found in 14.1% of patients; 27.6% were familial and 8% were isolated. PRKN was the gene most frequently mutated in Caucasians, whereas PINK1 mutations predominated in Arab-Berber individuals. Patients with PRKN mutations had an earlier age at onset, and less asymmetry, levodopa-induced motor complications, dysautonomia, and dementia than those without mutations. ANN NEUROL 2020;88:843-850.

Further delineation of the phenotypic spectrum associated with hemizygous loss-of-function variants in NONO.

The non-POU domain containing, octamer-binding gene, NONO, is located on chromosome Xq13.1 and encodes a member of a small family of RNA and DNA binding proteins that perform a variety of tasks involved in RNA synthesis, transcriptional regulation and DNA repair. Hemizygous loss-of-function variants in NONO have been shown to cause mental retardation, X-linked, syndromic 34 in males. Features of this disorder can include a range of neurodevelopmental phenotypes, left ventricular noncompaction (LVNC), congenital heart defects, and CNS anomalies. To date only eight cases have been described in the literature. Here we report two unrelated patients and a miscarried fetus with loss-of-function variants in NONO. Their phenotypes, and a review of previously reported cases, demonstrate that hemizygous loss-of-function variants in NONO cause a recognizable genetic syndrome. The cardinal features of this condition include developmental delay, intellectual disability, hypotonia, macrocephaly, structural abnormalities affecting the corpus callosum and/or cerebellum, LVNC, congenital heart defects, and gastrointestinal/feeding issues. This syndrome also carries an increased risk for strabismus and cryptorchidism and is associated with dysmorphic features that include an elongated face, up/down-slanted palpebral fissures, frontal bossing, and malar hypoplasia.

Variants in TCF20 in neurodevelopmental disability: description of 27 new patients and review of literature.

PURPOSE: To define the clinical characteristics of patients with variants in TCF20, we describe 27 patients, 26 of whom were identified via exome sequencing. We compare detailed clinical data with 17 previously reported patients. METHODS: Patients were ascertained through molecular testing laboratories performing exome sequencing (and other testing) with orthogonal confirmation; collaborating referring clinicians provided detailed clinical information. RESULTS: The cohort of 27 patients all had novel variants, and ranged in age from 2 to 68 years. All had developmental delay/intellectual disability. Autism spectrum disorders/autistic features were reported in 69%, attention disorders or hyperactivity in 67%, craniofacial features (no recognizable facial gestalt) in 67%, structural brain anomalies in 24%, and seizures in 12%. Additional features affecting various organ systems were described in 93%. In a majority of patients, we did not observe previously reported findings of postnatal overgrowth or craniosynostosis, in comparison with earlier reports. CONCLUSION: We provide valuable data regarding the prognosis and clinical manifestations of patients with variants in TCF20.

LSM7 variants involving key amino-acids for LSM complex function cause a neurodevelopmental disorder with leukodystrophy and cerebellar atrophy.

Cerebellar atrophy and hypoplasia are usually identified on MRI performed on children presenting signs of cerebellar ataxias, developmental delay and intellectual disability. These signs can be associated with hypo- or de-myelinating leukodystrophies. A recent study reported two cases: one child diagnosed with leukodystrophy and cerebellar atrophy, harboring a homozygous variant in LSM7 and another one who died in utero, presumed to have another homozygous variant in LSM7, based on parents' genotype. LSM7 encodes a subunit of the LSM complex, involved in pre-RNA maturation and mRNA degradation. Consequently, it has been suggested as a strong candidate disease gene. This hypothesis was supported by functional investigations of the variants. Presently, we report a patient with neurodevelopmental defects, leukodystrophy and cerebellar atrophy, harboring compound heterozygous missense variants in the LSM7 gene. One of these variants is the same as the one carried by the first case previously reported. The other one is at the same position as the variant potentially carried by the second case previously reported. Based on comparable neuroimaging, clinical features and the involvement of the same amino-acids previously demonstrated as key for LSM complex function, we confirm that LSM7 disruption causes a neurodevelopmental disorder characterized by leukodystrophy and cerebellar atrophy.

Genotype-phenotype correlation in PRKN-associated Parkinson's disease.

Bi-allelic pathogenic variants in PRKN are the most common cause of autosomal recessive Parkinson's disease (PD). 647 patients with PRKN-PD were included in this international study. The pathogenic variants present were characterised and investigated for their effect on phenotype. Clinical features and progression of PRKN-PD was also assessed. Among 133 variants in index cases (n = 582), there were 58 (43.6%) structural variants, 34 (25.6%) missense, 20 (15%) frameshift, 10 splice site (7.5%%), 9 (6.8%) nonsense and 2 (1.5%) indels. The most frequent variant overall was an exon 3 deletion (n = 145, 12.3%), followed by the p.R275W substitution (n = 117, 10%). Exon3, RING0 protein domain and the ubiquitin-like protein domain were mutational hotspots with 31%, 35.4% and 31.7% of index cases presenting mutations in these regions respectively. The presence of a frameshift or structural variant was associated with a 3.4 ± 1.6 years or a 4.7 ± 1.6 years earlier age at onset of PRKN-PD respectively (p < 0.05). Furthermore, variants located in the N-terminus of the protein, a region enriched with frameshift variants, were associated with an earlier age at onset. The phenotype of PRKN-PD was characterised by slow motor progression, preserved cognition, an excellent motor response to levodopa therapy and later development of motor complications compared to early-onset PD. Non-motor symptoms were however common in PRKN-PD. Our findings on the relationship between the type of variant in PRKN and the phenotype of the disease may have implications for both genetic counselling and the design of precision clinical trials.

PSMF1 variants cause a phenotypic spectrum from early-onset Parkinson's disease to perinatal lethality by disrupting mitochondrial pathways.

Dissecting biological pathways highlighted by Mendelian gene discovery has provided critical insights into the pathogenesis of Parkinson's disease (PD) and neurodegeneration. This approach ultimately catalyzes the identification of potential biomarkers and therapeutic targets. Here, we identify PSMF1 as a new gene implicated in PD and childhood neurodegeneration. We find that biallelic PSMF1 missense and loss-of-function variants co-segregate with phenotypes from early-onset PD and parkinsonism to perinatal lethality with neurological manifestations across 15 unrelated pedigrees with 22 affected subjects, showing clear genotype-phenotype correlation. PSMF1 encodes the proteasome regulator PSMF1/PI31, a highly conserved, ubiquitously expressed partner of the 20S proteasome and neurodegeneration-associated F-box-O 7 and valosin-containing proteins. We demonstrate that PSMF1 variants impair mitochondrial membrane potential, dynamics and mitophagy in patient-derived fibroblasts. Additionally, we develop models of psmf1 knockdown Drosophila and Psmf1 conditional knockout mouse exhibiting age-dependent motor impairment, with diffuse gliosis in mice. These findings unequivocally link defective PSMF1 to early-onset PD and neurodegeneration and suggest mitochondrial dysfunction as a mechanistic contributor.

The Whole-Exome Sequencing of a Cohort of 19 Families with Adolescent Idiopathic Scoliosis (AIS): Candidate Pathways.

A significant genetic involvement has been known for decades to exist in adolescent idiopathic scoliosis (AIS), a spine deformity affecting 1-3% of the world population. However, though biomechanical and endocrinological theories have emerged, no clear pathophysiological explanation has been found. Data from the whole-exome sequencing performed on 113 individuals in 19 multi-generational families with AIS have been filtered and analyzed via interaction pathways and functional category analysis (Varaft, Bingo and Panther). The subsequent list of 2566 variants has been compared to the variants already described in the literature, with an 18% match rate. The familial analysis in two families reveals mutations in the BICD2 gene, supporting the involvement of the muscular system in AIS etiology. The cellular component analysis revealed significant enrichment in myosin-related and neuronal activity-related categories. All together, these results reinforce the suspected role of the neuronal and muscular systems, highlighting the calmodulin pathway and suggesting a role of DNA-binding activities in AIS physiopathology.

Detection of ATXN2 Expansions in an Exome Dataset: An Underdiagnosed Cause of Parkinsonism.

Background: CAG-repeat expansions in Ataxin 2 (ATXN2) are known to cause spinocerebellar ataxia type 2 (SCA2), but CAA interrupted expansions may also result in autosomal dominant Parkinson's disease (AD PD). However, because of technical limitations, such expansions are not explored in whole exome sequencing (WES) data. Objectives: To identify ATXN2 expansions using WES data from PD cases. Methods: We explored WES data from a cohort of 477 index cases with PD using ExpansionHunter (Illumina DRAGEN Bio-IT Platform, San Diego, CA). Putative expansions were confirmed by combining polymerase chain reaction and fragment length analysis followed by sub-cloning and sequencing methods. Results: Using ExpansionHunter, we identified three patients from two families with AD PD carrying either ATXN2 22/39 or 22/37 repeats, both interrupted by four CAA repeats. Conclusion: These findings demonstrate the usefulness of WES to detect pathogenic CAG repeat expansions, which were found in 1.7% of AD PD in the ATXN2 gene in our exome dataset.