RORA-neurodevelopmental disorder:A unique triad of developmental disabilities, cerebellar anomalies, and myoclonic seizures

Purpose: RORA encodes the RAR-related orphan receptor-α, playing a pivotal role in cerebellar maturation and function. Here, we report the largest series of individuals with RORA-related-neurodevelopmental disorder. Methods: Forty individuals (30 unrelated; 10 siblings from 4 families) carrying RORA pathogenic/likely pathogenic variants were collected through an international collaboration. Results: The 33 variants (29 de novo, 4 inherited, and 1 shared), identified by genome/exome sequencing (n = 21), chromosomal microarray analysis (n = 7), or gene panels (n = 4), included frameshift (n = 18/33), missense (n = 9/33), and stop codon (n = 6/33). Developmental disability (n = 32/37), intellectual disability (n = 22/32), and cerebellar signs (n = 25/34) were the most striking clinical features. Cerebellar symptoms were divided into early-onset, late-onset, and progressive subgroups. Cerebellar hypoplasia, atrophy, or both (n = 16/25) were more frequent in individuals with missense variants in the DNA-binding domain. Epilepsy (n = 18/38), with prominent myoclonic seizure types (n = 11/18), was classified in (1) genetic generalized epilepsy (n = 10/18) with a syndromic diagnosis identifiable for 6: epilepsy with eyelid myoclonia (n = 5/6) and epilepsy with myoclonic absence (n = 1/6); (2) developmental and epileptic encephalopathy (n = 5/18); and (3) unclassified (n = 3/18). A participant with rapid deterioration of visual acuity and cone/rod dystrophy was reported. Conclusion: Missense variants in DNA-binding domain correlate to a more severe cerebellar phenotype. The RORA-related-neurodevelopmental disorder triad comprises developmental disability, cerebellar features, and a spectrum of myoclonic epilepsy.</p

Loss-of-function mutations in UDP-Glucose 6-Dehydrogenase cause recessive developmental epileptic encephalopathy

Developmental epileptic encephalopathies are devastating disorders characterized by intractable epileptic seizures and developmental delay. Here, we report an allelic series of germline recessive mutations in UGDH in 36 cases from 25 families presenting with epileptic encephalopathy with developmental delay and hypotonia. UGDH encodes an oxidoreductase that converts UDP-glucose to UDP-glucuronic acid, a key component of specific proteoglycans and glycolipids. Consistent with being loss-of-function alleles, we show using patients’ primary fibroblasts and biochemical assays, that these mutations either impair UGDH stability, oligomerization, or enzymatic activity. In vitro, patient-derived cerebral organoids are smaller with a reduced number of proliferating neuronal progenitors while mutant ugdh zebrafish do not phenocopy the human disease. Our study defines UGDH as a key player for the production of extracellular matrix components that are essential for human brain development. Based on the incidence of variants observed, UGDH mutations are likely to be a frequent cause of recessive epileptic encephalopathy

Loss-of-function mutations in UDP-Glucose 6-Dehydrogenase cause recessive developmental epileptic encephalopathy

AbstractDevelopmental epileptic encephalopathies are devastating disorders characterized by intractable epileptic seizures and developmental delay. Here, we report an allelic series of germline recessive mutations in UGDH in 36 cases from 25 families presenting with epileptic encephalopathy with developmental delay and hypotonia. UGDH encodes an oxidoreductase that converts UDP-glucose to UDP-glucuronic acid, a key component of specific proteoglycans and glycolipids. Consistent with being loss-of-function alleles, we show using patients’ primary fibroblasts and biochemical assays, that these mutations either impair UGDH stability, oligomerization, or enzymatic activity. In vitro, patient-derived cerebral organoids are smaller with a reduced number of proliferating neuronal progenitors while mutant ugdh zebrafish do not phenocopy the human disease. Our study defines UGDH as a key player for the production of extracellular matrix components that are essential for human brain development. Based on the incidence of variants observed, UGDH mutations are likely to be a frequent cause of recessive epileptic encephalopathy.</jats:p

A Solve-RD ClinVar-based reanalysis of 1522 index cases from ERN-ITHACA reveals common pitfalls and misinterpretations in exome sequencing

Purpose Within the Solve-RD project (https://solve-rd.eu/), the European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies aimed to investigate whether a reanalysis of exomes from unsolved cases based on ClinVar annotations could establish additional diagnoses. We present the results of the “ClinVar low-hanging fruit” reanalysis, reasons for the failure of previous analyses, and lessons learned. Methods Data from the first 3576 exomes (1522 probands and 2054 relatives) collected from European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies was reanalyzed by the Solve-RD consortium by evaluating for the presence of single-nucleotide variant, and small insertions and deletions already reported as (likely) pathogenic in ClinVar. Variants were filtered according to frequency, genotype, and mode of inheritance and reinterpreted. Results We identified causal variants in 59 cases (3.9%), 50 of them also raised by other approaches and 9 leading to new diagnoses, highlighting interpretation challenges: variants in genes not known to be involved in human disease at the time of the first analysis, misleading genotypes, or variants undetected by local pipelines (variants in off-target regions, low quality filters, low allelic balance, or high frequency). Conclusion The “ClinVar low-hanging fruit” analysis represents an effective, fast, and easy approach to recover causal variants from exome sequencing data, herewith contributing to the reduction of the diagnostic deadlock

FARS-ADL across Ataxias: Construct Validity, Sensitivity to Change, and Minimal Important Change

BackgroundPatient-focused outcomes present a central need for trial-readiness across all ataxias. The Activities of Daily Living part of the Friedreich Ataxia Rating Scale (FARS-ADL) captures functional impairment and longitudinal change but is only validated in Friedreich Ataxia. ObjectiveValidation of FARS-ADL regarding disease severity and patient-meaningful impairment, and its sensitivity to change across genetic ataxias. MethodsReal-world registry data of FARS-ADL in 298 ataxia patients across genotypes were analyzed, including (1) cross-correlation with FARS-stage, Scale for the Assessment and Rating of Ataxia (SARA), Patient-Reported Outcome Measure (PROM)-ataxia, and European Quality of Life 5 Dimensions visual analogue scale (EQ5D-VAS);(2) sensitivity to change within a trial-relevant 1-year median follow-up, anchored in Patient Global Impression of Change (PGI-C);and (3) general linear modeling of factors age, sex, and depression (nine-item Patient Health Questionnaire [PHQ-9]). Results FARS-ADL correlated with overall disability (rho(FARS-stage) = 0.79), clinical disease severity (rho(SARA) = 0.80), and patient-reported impairment (rho(PROM-ataxia) = 0.69, rho(EQ5D-VAS) = -0.37), indicating comprehensive construct validity. Also at item level, and validated within genotype (SCA3, RFC1), FARS-ADL correlated with the corresponding SARA effector domains;and all items correlated to EQ5D-VAS quality of life. FARS-ADL was sensitive to change at a 1-year interval, progressing only in patients with worsening PGI-C. Minimal important change was 1.1. points based on intraindividual variability in patients with stable PGI-C. Depression was captured using FARS-ADL (+0.3 points/PHQ-9 count) and EQ5D-VAS, but not FARS-stage or SARA. ConclusionFARS-ADL reflects both disease severity and patient-meaningful impairment across genetic ataxias, with sensitivity to change in trial-relevant timescales in patients perceiving change. It thus presents a promising patient-focused outcome for upcoming ataxia trials. (c) 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

PolyQ-expanded ataxin-3 protein levels in peripheral blood mononuclear cells correlate with clinical parameters in SCA3: a pilot study

AbstractIn view of upcoming clinical trials, quantitative molecular markers accessible in peripheral blood are of critical importance as prognostic or pharmacodynamic markers in genetic neurodegenerative diseases such as Spinocerebellar Ataxia Type 3 (SCA3), in particular for signaling target engagement. In this pilot study, we focused on the quantification of ataxin-3, the protein altered in SCA3, in human peripheral blood mononuclear cells (PBMCs) acquired from preataxic and ataxic SCA3 mutation carriers as well as healthy controls, as a molecular marker directly related to SCA3 pathophysiology. We established two different highly sensitive TR-FRET-based immunoassays to measure the protein levels of either total full-length, non-expanded and expanded, ataxin-3 or specifically polyQ-expanded ataxin-3. In PBMCs, a clear discrimination between SCA3 mutation carrier and controls were seen measuring polyQ-expanded ataxin-3 protein level. Additionally, polyQ-expanded ataxin-3 protein levels correlated with disease progression and clinical severity as assessed by the Scale for the Assessment and Rating of Ataxia. Total full-length ataxin-3 protein levels were directly influenced by the expression levels of the polyQ-expanded ataxin-3 protein, but were not correlated with clinical parameters. Assessment of ataxin-3 levels in fibroblasts or induced pluripotent stem cells allowed to distinguish mutation carriers from controls, thus providing proof-of-principle validation of our PBMC findings across cell lines. Total full-length or polyQ-expanded ataxin-3 protein was not detectable by TR-FRET assays in other biofluids like plasma or cerebrospinal fluid, indicating the need for ultra-sensitive assays for these biofluids. Standardization studies revealed that tube systems, blood sampling, and PBMC preparation may influence ataxin-3 protein levels indicating a high demand for standardized protocols in biomarker studies. In conclusion, the polyQ-expanded ataxin-3 protein is a promising candidate as a molecular target engagement marker in SCA3 in future clinical trials, determinable even in—easily accessible—peripheral blood biomaterials. These results, however, require validation in a larger cohort and further standardization of modifying conditions.</jats:p

ARSA Variants Associated With Cognitive Decline and Long-Term Preservation of Motor Function in Metachromatic Leukodystrophy

Patients with metachromatic leukodystrophy (MLD) show variable motor and cognitive decline. The ARSA variants c.256C&gt;T, p.(Arg86Trp), c.257G&gt;A, p.(Arg86Gln) and c.542T&gt;G, p.(Ile181Ser) are associated with predominantly cognitive decline. This multinational study analyzed MLD onset type, presenting signs/symptoms, cognitive function, gross motor function, central motor tract involvement, MRI severity score, peripheral neuropathy, and survival of 47 patients (three homozygous for c.256C&gt;T and five, twelve and 27 compound heterozygous for c.256C&gt;T, c.257G&gt;A, or c.542T&gt;G and another ARSA variant, respectively). Eleven underwent hematopoietic stem cell transplantation (HSCT). Onset was late-juvenile (46.8%) or adult (44.7%) with predominantly cognitive decline (n = 40/41 symptomatic patients). At diagnosis, untreated patients typically retained independent walking (100%), sparing of central motor tracts (87.5%), and absence of demyelinating neuropathy (95.5%), which persisted in follow-up for most (76.5%, 71.4%, and 64.7%, respectively). Early-juvenile onset and rapid motor decline occurred only in patients compound heterozygous for c.256C&gt;T and a severe second variant (n = 4), showing central motor tract involvement at diagnosis. One untreated and one treated patient died of disease progression, and another from HSCT complications. All other treated patients retained independent walking, and four of five tested normal cognitive function. Median MRI severity score remained lower in treated (13) than untreated patients (25). The phenotype of c.256C&gt;T carriers depends on the severity of the second ARSA variant. Patients harboring c.257G&gt;A or c.542T&gt;G show late-juvenile or adult onset with cognitive decline and preserved motor function, usually associated with sparing of central motor tracts. In these patients, cognitive function and MRI severity score should be preferred treatment outcomes.</p

Polyglutamine-expanded ataxin-3: a target engagement marker for Spinocerebellar ataxia type 3 in peripheral blood

Abstract Spinocerebellar ataxia type 3 is a rare neurodegenerative disease, caused by a CAG repeat expansion leading to polyglutamine elongation in the ataxin-3 protein. While no curative therapy is yet available, preclinical gene silencing approaches to reduce polyglutamine-toxicity demonstrate promising results. In view of upcoming clinical trials, quantitative and easily accessible molecular markers are of critical importance as pharmacodynamic and particularly as target engagement markers. We developed a novel ultrasensitive immunoassay to measure specifically polyQ-expanded ataxin-3 in plasma and cerebrospinal fluid. Statistical analyses revealed a correlation with clinical parameters and a stability of polyglutamine-expanded ataxin-3 during conversion from the pre-ataxic to the ataxic phase.</jats:p

Heterozygous RAB3A variants cause cerebellar ataxia by a partial loss-of-function mechanism

RAB3A encodes a small GTP-binding protein that is abundant in brain synaptic vesicles and crucial for the release of neurotransmitters and synaptic plasticity. Here, we identified RAB3A as a candidate gene for autosomal dominant cerebellar ataxia by two independent approaches: linkage in a large dominant ataxia family and, in parallel, an untargeted computational genetic association approach, analysing the 100 000 Genomes Project datasets. To validate the role of RAB3A in ataxia, we next screened large rare disease databases for rare heterozygous RAB3A variants in probands with ataxia features.In total, we identified 18 individuals from 10 unrelated families all sharing a cerebellar ataxia phenotype. Notably, 9 of the 10 families carried a recurrent variant in RAB3A, p.Arg83Trp, including one de novo occurrence. In addition, our screening revealed three families with a neurodevelopmental phenotype and three unique RAB3A variants, which were either de novo or loss-of-function variants. In line with the different RAB3A variant types, protein domains and predicted functional consequences, a comprehensive set of complementary methods was used to characterize the identified variants functionally. As expected, GTPase-activating protein (GAP)-dependent GTP hydrolysis was reduced for those two missense variants located in the GAP-binding domain of RAB3A (Arg83Trp and Tyr91Cys). In a Drosophila Rab3 loss-of-function model, these two missense variants also failed to rescue a synaptic phenotype. Overexpression of Rab3 variants in Drosophila wild-type background did not cause an obvious phenotype, making a dominant negative effect of these variants unlikely. Lastly, exploring interactors of RAB3A variants by using co-immunoprecipitation and mass spectrometry showed differential changes in variant-specific interactions with known RAB3A key regulatory and effector proteins.In sum, our results establish RAB3A as a neurological disease gene. It represents an autosomal dominant gene for cerebellar ataxia with different variants associated with disease, including the frequent reoccurring variant p.Arg83Trp. Our study sheds light on the variant-specific interactome of RAB3A. Finally, we suggest an association of RAB3A with a neurodevelopmental phenotype, as reported for variants in several RAB3A interaction partners and as seen in Rab3A-deficent mice, although this possible association warrants further investigation by future studies. Using an untargeted computational genetic association approach and classical linkage analysis, Hengel et al. identify RAB3A as a gene linked to autosomal dominant cerebellar ataxia. They show that one particular RAB3A variant is present in multiple affected families, and investigate the mechanism by which it disrupts protein function

Body Mass Index Decline Is Related to Spinocerebellar Ataxia Disease Progression

Background Spinocerebellar ataxias (SCAs) are dominantly inherited, progressive ataxia disorders. Disease progression could be preceded by weight loss. Objectives We aimed to study the course of weight loss in patients who had the most common SCAs (SCA1, SCA2 SCA3, and SCA6). Additional objectives were to identify subgroups of weight evolution, to determine the factors influencing these evolutions, and to assess the impact of these evolutions on disease progression. Methods In total, 384 patients from the EUROSCA prospective cohort study were analyzed who had SCA1, SCA2, SCA3, or SCA6 and at least 3 measurements of weight. Age was used as a time scale. Clinical outcomes were body mass index (BMI) and the Scale for the Assessment and Rating Ataxia (SARA), with scores ranging from 0 to 40. We used a linear mixed model to analyze the course of BMI and a latent class mixed model to identify subgroup BMI evolution. Results Overall, BMI declined over time (−0.11 ± 0.03 kg/m2 per decade; P = 0.0009). Three subgroups of BMI evolution were identified: “decreasing BMI” (n = 88; 23%), “increasing BMI” (n = 70; 18%) and “stable BMI” (n = 226; 59%). Patients in the decreasing BMI group were more severely affected at baseline with higher SARA scores and a higher frequency of non-ataxia signs (especially motor symptoms) compared with those in the other groups. Weight loss was associated with faster disease progression (5.7 ± 0.7 SARA points per decade; P = 0.036). Conclusions The current data have substantial implications for the design of future interventional studies in SCA, as they provide a basis for patient stratification and emphasize the usefulness of BMI as a biomarker for monitoring disease progression