Individuals with monoallelic gain-of-function variants in the histone lysine methyltransferase DOT1L display global developmental delay and varying congenital anomalies. However, the impact of monoallelic loss of DOT1L remains unclear. Here, we sought to define the effects of partial DOT1L loss by applying bulk and single-nucleus RNA-sequencing, ChIP-sequencing, imaging, multielectrode array recordings and behavioural analysis of zebrafish and multiple mouse models. We present a cohort of 16 individuals (12 females, 4 males) with neurodevelopmental disorders and monoallelic DOT1L variants, including a frameshift deletion, an in-frame deletion, a nonsense, and missense variants clustered in the catalytic domain. We demonstrate that specific variants cause loss of methyltransferase activity. In primary cortical neurons, Dot1l knockdown disrupts transcription of synaptic genes, neuron branching, expression of a synaptic protein and neuronal activity. Further in the cortex of heterozygous Dot1l mice, Dot1l loss causes sex-specific transcriptional responses and H3K79me2 depletion, including within downregulated genes. Lastly, using both zebrafish and mouse models, we found behavioural disruptions that include developmental deficits and sex-specific social behavioural changes. Overall, we define how DOT1L loss leads to neurological dysfunction by demonstrating that partial Dot1l loss impacts neuronal transcription, neuron morphology and behaviour across multiple models and systems.

PURPOSE:TCF7L2 (OMIM 602228; HGNC:11641) is a transcription factor and a critical effector of the Wnt/ β-Catenin pathway. In 2021, 11 pediatric patients with monoallelic predicted loss-of-function (pLOF) TCF7L2 variants and syndromic features were observed. Characterization of patients with pLOF TCF7L2 variants and neurodevelopmental features-herein referred to as TCF7L2-related neurodevelopmental disorder-is urgently needed. METHODS:We leveraged multiple methods (eg, GeneMatcher, DECIPHER, literature review, and public/private repositories) to identify an international cohort of 76 patients with pLOF TCF7L2 variants and neurodevelopmental features and phenotypically characterized them. We also retrospectively searched for an independent cohort of adults with pLOF TCF7L2 variants (n = 11) from more than 60,000 PennMedicine BioBank patients. RESULTS:Among 76 patients with pLOF TCF7L2 variants, speech delay (95.3%), craniofacial dysmorphisms (73.3%), ophthalmologic conditions (65.5%), autism (62.1%), and orthopedic abnormalities (52.6%) were the most commonly observed. Phenotypic differences did not cluster by variant type or genomic locus. Among PennMedicine BioBank patients, an association of nominal significance with type 2 diabetes with renal manifestations (odds ratio = 5.8; P = .03) was detected, warranting further investigation. CONCLUSION:This study represents the most comprehensive characterization of TCF7L2-related neurodevelopmental disorder to date, a novel neurodevelopmental disorder, defining its genotypic and phenotypic spectra. We opened a Simons Searchlight natural history study that is now available for patient enrollment to enhance the understanding of this condition.

Abstract Background Pathogenic variants in AGO2 , encoding a central component of the RNA-induced silencing complex (RISC), cause the neurodevelopmental disorder Lessel-Kreienkamp syndrome (LESKRES). The variant spectrum and associated molecular mechanisms underlying phenotypic variability and disease severity remain incompletely understood. Methods We investigated 45 newly identified individuals carrying 33 distinct AGO2 variants, 30 of which were previously unreported. Phenotypic data from these and previously reported cases ( n = 70) were integrated to delineate the LESKRES-associated clinical spectrum and genotype–phenotype correlations. Functional studies included shRNA-based silencing, co-immunoprecipitation, subcellular localization, and sequencing of AGO2-bound miRNAs. Results All individuals presented with a neurodevelopmental disorder of variable severity. Delayed speech and language development (97%), intellectual disability (97%), and motor delay (93%) were the most consistent features, frequently accompanied by muscular hypotonia, autistic traits, attention deficit hyperactivity disorder, visual impairment and structural brain anomalies. Systemic manifestations, including skeletal, craniofacial, cardiac, and male urogenital anomalies were common, underscoring AGO2’s multisystemic role. Moreover, we report occurrence of gonadal mosaicism and reveal the presence of interfamilial and variant-specific clinical heterogeneity. Variants clustered in defined regions of AGO2, including the L1 loop, helix-7, and multiple loops of the PIWI domain, highlight structural hotspots critical for RISC activity. Not all pathogenic variants impaired shRNA-mediated silencing; this was restricted to p.(Arg714Trp) and p.(Asn729His). Biochemical analyses revealed that p.(Asp619Asn) impaired GW182 binding and P-body assembly. Variants p.(Arg506Gln), p.(Glu531Gln) p.(Gly604Arg) and p.(Asp619Asn), reduced C-terminal phosphorylation, implicating defective AGO2 recycling. AGO2–miRNA co-immunoprecipitation and sequencing demonstrated variant-specific perturbations in miRNA association, strand selectivity, and isomiR generation. Variants near the hinge of the helix-7 region, especially p.(Phe182del), induced extensive changes in miRNA association and 3′-end modification, suggesting impaired anchoring within the miRNA-binding pocket. Conclusions Our findings substantially broaden the clinical and molecular landscape of LESKRES, establishing AGO2 as a pivotal regulator of neurodevelopment whose structural integrity is essential for precise miRNA-mediated gene regulation. Pathogenic variants disrupt distinct interconnected processes: P-body association, phosphorylation-dependent turnover, and miRNA interactions, culminating in dysregulated post-transcriptional gene silencing. These mechanistic insights link specific structural perturbations in AGO2 to graded clinical outcomes and underscore the critical role of AGO2 conformational dynamics in human neurodevelopment.

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental condition with complex genetic and environmental underpinnings. A clinically significant subset of children with ASD experience developmental regression (regASD), characterized by the acute loss of previously acquired skills. The mechanisms, predictors, and molecular basis of regASD remain poorly understood. We retrospectively and prospectively analyzed a cohort of 505 children diagnosed with ASD at the Center of Excellence for Autism and Neurodevelopmental Disorders (Paris, France) between 2017 and 2023. Clinical, neurodevelopmental, and genetic data were collected, including detailed developmental histories, standardized diagnostic assessments (ADI-R, ADOS-2, VABS), and chromosomal microarray analysis (CMA). Statistical analyses included classification tree algorithms and principal component analysis to identify clinical predictors of regression, and gene ontology enrichment to explore molecular pathways. Developmental regression was detected in 74 children (15%). Prior to regression, regASD children exhibited more favorable neurodevelopmental profiles, including lower rates of prematurity, higher birth weight and height, and earlier acquisition of first words, compared with nonregressive ASD (non-regASD) peers. However, after regression, regASD children had significantly more severe neurodevelopmental impairments across cognitive, adaptive, and social domains (p < 0.001). Routine clinical variables did not reliably predict the onset of regression. CMA revealed that regASD is associated with distinct genetic deletions enriched in immune, inflammatory (particularly Type I interferon), oxidative stress, angiogenesis, and synaptic pathways, with minimal overlap with non-regASD genetic profiles. Our findings are consistent with the hypothesis that regASD may represent a distinct clinical and molecular subgroup within ASD. The molecular signatures identified in regASD suggest involvement of immune and synaptic pathways, highlighting the need for further targeted research to clarify their potential therapeutic implications for this subgroup.

Small nuclear RNAs (snRNAs) are essential components of the spliceosome. De novo variants in snRNA genes RNU4-2 (ReNU syndrome), RNU5B-1 and RNU2-2 have been linked to dominant neurodevelopmental disorders (NDDs), revealing a large unexpected contribution of noncoding RNA genes to genetic diseases. Here, through international collaborations, we analyze systematically 200 potentially functional snRNA genes in a French cohort of 34,329 people with rare disorders. We report RNU2-2 variants in 141 individuals, including 35 with recurrent dominant pathogenic variants and 91 affected members from 73 families with biallelic variants. Recessive RNU2-2 NDD is at least twice as frequent as the dominant form and often involves a de novo variant in trans with an inherited allele, consistent with the high mutability of snRNA genes. Dominant and recessive RNU2-2 NDDs share overlapping clinical features, with frequent epilepsy. Blood transcriptomics and DNA methylation analyses revealed subtle, variant-specific effects on splicing and episignatures. Our results support a gradient-of-impact model bridging dominant and recessive inheritance, and establish RNU2-2 variants as a principal contributor to NDDs, nearly as prevalent as ReNU syndrome.

Nuclear factor I (NFI) transcription factors regulate neural stem and progenitor differentiation during brain development. While NFIA, NFIB, and NFIX are linked to neurodevelopmental disorders, the role of NFIC (MIM: 600729) in human disease remains unclear. This study aimed to determine whether NFIC contributes to a neurodevelopmental syndrome, define its phenotype, and assess dosage-dependent effects. We established the first cohort of 11 individuals, including NFIC deletions and single nucleotide variants. Genotype-phenotype correlations, including critical region mapping, were performed. Murine data and bioinformatics were integrated to explore underlying pathomechanisms. We report 11 individuals with NFIC variants, including four with de novo SNVs and seven with deletions encompassing the gene, of whom nine have not been previously reported. A core phenotype of syndromic intellectual disability and macrocephaly was delineated. Opposing cranial phenotypes relative to proximal 19p13.3 duplication cases support a dosage-sensitive effect and a mirror-syndrome model. NFIC-related disorder represents a novel neurodevelopmental syndrome characterized by intellectual disability and macrocephaly, highlighting the importance of NFIC dosage supporting a mirror-syndrome model.

Variants in BRSK2, encoding brain specific kinase-2, have recently been associated with an autosomal dominant neurodevelopmental disorder (NDD). We have assembled 52 cases with heterozygous BRSK2 variants and variable neurodevelopmental phenotypes with frequent neuropsychiatric and behavioral symptoms. The variant spectrum included 15 different truncating variants, seven (potential) splice variants, three structural variants, and 12 different missense variants. Of the missense variants, seven were in the kinase domain, and the others in the UBA and the KA1 domain or outside domains. Variants occurred de novo in 19 cases and were inherited in 18. We utilized Drosophila melanogaster as a model and assessed viability and performed climbing and bang sensitivity assays upon knockdown of the fly orthologue sff or upon overexpression of wildtype or mutant human BRSK2. Pan-neuronal knockdown of sff resulted in impaired locomotor behavior and seizure susceptibility. Ubiquitous or pan-neuronal overexpression of human wildtype BRSK2 in Drosophila resulted in lethality or locomotor impairment, respectively, indicating toxicity. Overexpressing mutant BRSK2 did not or incompletely affect viability and locomotor behavior for six of seven tested kinase domain missense variants and one KA1 domain variant, indicating a (partial) loss-of-function effect. Interestingly, overexpressing BRSK2 with the remaining missense variant from the kinase domain and the two most C-terminal missense variants resulted in possible gain of function. Our findings further delineate the clinical and molecular spectrum of BRSK2-associated NDD and provide further insights into the role of BRSK2/sff in nervous system function and dysfunction.

INTRODUCTION:People with multiple sclerosis (PwMS) are ageing and exposed to multiple impairments. We described the use of health care procedures in a physical and rehabilitation medicine setting for PwMS ≥70 years and identified specific participant clusters. METHODS:In this observational cohort study using a local data hub (2012 to March 2024), PwMS were identified with ICD-10 codes (G35). An age filter (≥70) was applied. Medical procedures were systematically coded according to a specific French classification over time, including dates of occurrence, and then extracted and grouped by impairment domains: upper motor neuron syndrome and orthopedic deformities (UMN-OD), respiratory and sleep disorders (RSD), and neurogenic lower urinary tract dysfunction (NLUTD). Clinical data were retrospectively collected from medical files. We conducted descriptive analyses and multiple-component and clustering analyses to identify and characterize the participants' profiles. RESULTS:Among 206 participants aged 75.7 (4.3) years, 62% (128) were women, 19% (39) had died, and MS had evolved for 43.3 (12.4) years. The Expanded Disability Status Scale (EDSS) was 7.5 (6.5-8.5), and the Charlson Comorbidity Index (CCI) was 6 (5-7). A total of 2794 procedures were performed for 187 participants, mainly in NLUTD (1424 for 170), which was associated with RSD (P = 0.001), but not UMN-OD (P = 0.262). Three groups were identified (Group 1 = isolated NLUTD, Group 2 = RSD and intrathecal baclofen procedures, and Group 3 = no in-hospital management). People in Group 2 had more severe comorbidities (P < 0.001) than those in the other two groups (P = 0.016). CONCLUSIONS:In PwMS ≥70 years, the hospital management of MS-related impairments was directly associated with disease severity and overall comorbidities. Participants who were followed only for NLUTD exhibited severity and comorbidity profiles similar to those of participants who did not require hospital procedures. DATA REGISTRATION:Our institutional health data warehouse and all derived extracted databases within the scope of the health team perimeter are approved by the French Data Protection Authority under the No. 1980120.

Primary mitochondrial diseases (PMDs) affect approximately 1 in 4300 individuals and cause early-onset neuromuscular and multisystem dysfunction with reduced lifespan. They result from pathogenic variants in mitochondrial or nuclear DNA that impair oxidative phosphorylation. Cytochrome c oxidase (COX; complex IV) deficiency is a well-established cause of PMD, leading to a broad spectrum of phenotypes. COXFA4 (cytochrome c oxidase subunit FA4), formerly NDUFA4, is a nuclear-encoded COX subunit, but its role in disease remains poorly defined. We report the largest genetically confirmed cohort of COXFA4-related PMD to date, comprising 13 individuals from 12 families with biallelic pathogenic COXFA4 variants. All present with Leigh-like encephalopathy and complete loss of COXFA4 protein; however, patient-derived fibroblasts retain residual COX activity, with upregulation of COXFA4L2 (cytochrome c oxidase subunit FA4-like 2), a poorly characterised paralog. Here, we show that COXFA4 is a late-stage COX assembly subunit and identify a paralog-mediated compensatory mechanism with translational potential.

BACKGROUND: Recent advances in sequencing technologies have enhanced patient diagnosis; however, causal pathogenic variants remain unidentified for a significant number of patients due to limited understanding of certain variants, regulatory sequences, or sequencing challenges, such as complex rearrangements. Investigating the epigenetic landscape has become essential to improve the diagnostic yield. Diseases caused by pathogenic variants in epigenetic regulators, often associated with growth abnormalities, intellectual disability, and facial dysmorphism, are prime models for studying episignatures. Among them, Snijders Blok-Campeau syndrome (ORPHA:599082), caused by pathogenic variants in the CHD3 gene, remains largely understudied. METHODS: A European cohort of 23 patients displaying typical Snijders Blok-Campeau syndrome traits and carrying pathogenic/likely pathogenic CHD3 variants was analysed using the Illumina EPIC array, identifying 270 differentially methylated positions distinguishing patients from 62 healthy matched controls. A subset of these regions serves as diagnostic tools for complex cases or variants of uncertain significance and helps uncover deregulated pathways linked to this syndrome. Four patients carrying pathogenic/likely pathogenic variants but with atypical clinical presentation, as well as 10 patients with variants of uncertain significance, were analysed as the testing set. RESULTS: Comparing methylomes of patients carrying pathogenic variants in CHD3, CHD7 (CHARGE syndrome, ORPHA:138), and CHD8 (Intellectual developmental disorder with autism and macrocephaly, ORPHA:642675) genes allows us to identify distinct subgroups with unique methylation profiles. This CHD3 DNA methylation signature aids in reclassifying variants and diagnosing atypical cases. CONCLUSIONS: Our findings advance the field of epigenetic signatures in rare diseases. We have opened new avenues for further investigation into subtypes defined by methylome assays (such as in the context of chromatinopathies), which could refine the phenotype spectrum and help predict patient outcomes.

RNA-binding proteins (RBPs) regulate gene expression, and a number of RBPs have been implicated in brain function and behavior. Here, we report 16 individuals with a neurodevelopmental disorder and de novo heterozygous variants in ELAVL2, encoding an RBP not previously linked to Mendelian disease. Thirteen individuals were identified through GeneMatcher. Their ELAVL2 variants include two structural, five nonsense, and six missense variants, supporting haploinsufficiency as the primary disease mechanism. The cohort presented with developmental delay, intellectual disability, autism spectrum disorder, seizures, sleep problems, sensory processing issues, emotional instability, and difficulty with socialization. Three additional variants (two missense and one terminal exon truncation), each previously reported in a different large cohort study, were also included for follow-up investigations. We provide multiple lines of evidence linking variants in ELAVL2 to the observed neurodevelopmental and behavioral phenotypes. First, we show that common genetic variants in ELAVL2 are significantly associated with intelligence, motor development, sleep-related traits, and sociability in the general population. Drosophila loss-of-function models provide further independent evidence for a conserved role in the regulation of seizure-like behavior, sensory processing, and sleep. Molecular studies confirm that some of the missense variants are deleterious, leading to decreased protein levels. Together, our integrative study combining Mendelian genetics, clinical and association studies, and animal and molecular modeling supports variants in ELAVL2 as a cause of a neurodevelopmental disorder, with haploinsufficiency as the disease mechanism, and identifies crucial roles of ELAVL2 in neuronal function, cognition, and behavior.

Purpose AUTS2-related syndrome is characterized by developmental delay, autism spectrum disorder, and intellectual disability. From alternative promoters, AUTS2 encodes 2 distinct long and short isoforms encoding a putative transcriptional activator. Methods Through a European collaborative study, we collected clinical and genotype data on the largest AUTS2-related syndrome cohort of 58 patients harboring genomic rearrangements or single-nucleotide variants (SNVs). Results Pathogenic SNVs were recurrently found in individuals from different countries, suggesting mutational hotspots. Independent of the underlying defect at the AUTS2 locus, we observed that autistic behavior, hyperactivity, learning difficulties, and speech delay are common features of AUTS2-related syndrome. Among patients with SNVs, individuals carrying pathogenic variants affecting both longer and shorter AUTS2 transcripts showed a recognizable phenotype with microcephaly, brachycephaly, microretrognathia, broad nasal base, and anteverted nares. Behavioral disorders were more common in patients with variants affecting only the longer isoform. Arthrogryposis and stiff movements were only observed in patients with SNVs. Conclusion This study provides a comprehensive clinical characterization of AUTS2-related syndrome, reveals few genotype-phenotype correlations, and suggests that the disruption of the 2 distinct AUTS2 transcripts has a different impact on the clinical phenotype.

Most current autism research focuses on categorical comparisons (e.g., autistic vs. neurotypical people) and usually examines only one biological domain (e.g., cognition, genetics, or brain imaging). Here, we present a comprehensive resource integrating quantitative phenotypic data, whole genome sequencing, brain magnetic resonance imaging, and electroencephalography. A total of 5,549 people were recruited in Europe through LEAP and InovAND, including 2,061 autistic people, 62 people with intellectual developmental disability who do not meet diagnostic criteria for autism, 2,551 undiagnosed relatives and 875 neurotypical people. Among these people, 2,531 have both clinical and genetic data, and 875 people additionally have neuroimaging data (EEG and/or MRI). We stratified people based on autistic traits and cognitive skills, revealing clusters with distinct genetic and brain signatures. Differences were observed in both rare and common variants, particularly in synaptic and chromatin remodeling genes pathways, and suggesting distinct trajectories of cortical maturation at early stages of development. This resource is available to support research into the complex links between genes, brain structures/functions, and autism. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was funded by Institut Pasteur, Universite Paris Cite, the Simons Foundation Autism Research Initiative (SFARI award #240059), the Bettencourt-Schueller Foundation, the GenMed Labex, and AIMS-2-TRIALS, which received support from the Innovative Medicines Initiative 2 Joint Undertaking under grant agreement No 777394 for the project AIMS-2-TRIALS. This Joint Undertaking receives support from the European Union's Horizon 2020 research and innovation program and EFPIA and AUTISM SPEAKS, Autistica, SFARI, and the Inception program (Investissement d'Avenir grant ANR-16-CONV-0005). This project has received funding from the European Union's Horizon 2020 Research and Innovation Program under grant 847818 (CANDY), and from Horizon Europe under grant 101057385 (R2D2-MH). Views and opinions expressed are, however, those of the authors only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them. This work benefited from the DNA & cell bank core facility, at the ICM-Paris Brain Institute. This work received support from the French government, managed by the National Research Agency (Agence Nationale de la Recherche), under the France 2030 program, reference ANR-23-IAHU-0010. Part of this work was funded by a grant from the Conseil Regional d'Ile de France (grant number EX024087). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study is multi-site; Ethical approval was obtained through ethics committees at each site: The London Queen Square Health Research Authority Research Ethics Committee of King's College London & University of Cambridge (KCL & UCAM) gave ethical approval for this work (13/LO/1156). The Radboud Universitair Medisch Centrum Instituut Waarborging Kwaliteit en Veiligheid Commissie Mensgebonden Onderzoek Regio Arnhem-Nijmegen (Radboud University Medical Centre Institute Ensuring Quality and Safety Committee on Research Involving Human Subjects Arnhem-Nijmegen) from Radboud University Nijmegen Medical Centre (RUNMC) & University Medical Centre Utrecht (UMCU) gave ethical approval for this work (2013/455). The UMM Universitatsmedizin Mannheim, Medizinishe Ethik Commission II (UMM University Medical Mannheim, Medical Ethics Commission II) from Central Institute of Mental Health (CIMH) gave ethical approval for this work (2014-540N-MA). The Universita Campus Bio Medica De Roma Comitato Etico (University Campus Bio-Medical Ethics Committee De Roma) from the University Campus Bio-Medico (UCBM) gave ethical approval for this work (18/14 PAR ComET CBM). The Centrala Etikprovningsnamnden (Central Ethical Review Board) from Karolinska Institutet (KI) gave ethical approval for this work (32 2010). The Ethics Committee overseeing the INOVAND cohort (Inserm C07 33) cohorts gave ethical approval for this work (CEER 2008 A00019 46). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The datasets generated and analyzed in this study, including all modalities from the LEAP (EUAIMS / AIMS2 TRIALS) and InovAND cohorts are securely stored on ELIXIR LU servers, part of the European infrastructure for life science information, based at the Luxembourg Centre for Systems Biomedicine (LCSB) and supported by the Luxembourg National Data Service (LNDS). The LEAP dataset (clinical, cognitive, eye-tracking, neuroimaging, and genetic data) is available via the ELIXIR Luxembourg data catalog. The InovAND dataset will be made available through the same repository upon publication. Access to both datasets is granted upon reasonable request following review and approval by the Data Access Committee, including scientific leads, ethics experts, and Autism community representatives. Requests should be submitted via the data catalog website with a detailed project proposal describing the intended use of the data and must be aligned with General Data Protection Regulation (GDPR) requirements as well as the AIMS2 TRIALS consortium or InovAND data sharing policies, respectively.

Introduction: While botulinum toxin type A (BoNT-A) is effective for poststroke spasticity, its accessibility in older adults remains unclear. We aimed to examine the association between BoNT-A use and age among stroke survivors. Methods: This nationwide, population-based, retrospective cohort study analyzed data from the French National Hospital Discharge Database. Stroke survivors admitted between 2014 and 2016 were followed until 2020. BoNT-A use was assessed across different age groups (18–64, 65–74, 75–84, ≥85 years). Multivariable logistic regression was performed to examine the association between BoNT-A use and age, adjusting for potential confounders, including sex, comorbidities, stroke unit hospitalization, and rehabilitation. Results: BoNT-A use was reported in 1,757 (2.88%), 862 (0.99%), and 183 (0.22%) of 60,928, 86,917, and 82,725 stroke survivors aged 65–74, 75–84, and ≥85 years, respectively. These rates were significantly lower than BoNT-A use in those aged <65 years (5.13%) (p < 0.001). After adjustment, the inverse relationship between age and BoNT-A use was maintained, demonstrating an age-dependent association in the 65–74, 75–84, and ≥85 age groups vs. 18–64 years. Odds ratios (ORs) (95% confidence intervals [CIs]) were 0.49 (0.47–0.53), 0.18 (0.17–0.19), and 0.05 (0.04–0.06), respectively. Stroke unit stays (OR, 1.33; 95% CI, 1.26–1.41) and neurological rehabilitation unit stays (OR, 16.69; 95% CI, 15.59–17.87) were significantly associated with a higher probability of receiving BoNT-A. Conclusions: BoNT-A use is notably low in older stroke survivors, highlighting the need to enhance equitable access to BoNT-A injections for this population.

Variants in spliceosomal small nuclear RNA (snRNA) genes RNU4-2 (ReNU syndrome), RNU5B-1, and RNU2-2 have recently been linked to dominant neurodevelopmental disorders (NDDs), revealing a major, previously overlooked role for noncoding snRNAs in human disease. Here, we systematically analysed 200 potentially functional snRNA genes in a French cohort comprising 26,911 individuals with rare disorders and through international collaborations. We identify de novo and biallelic variants in RNU2-2 associated with both dominant and recessive NDDs in 126 individuals from 108 unrelated families. Recessive RNU2-2 NDD is at least twice as frequent as the dominant NDD caused by n.4G>A and n.35A>G, and often arises from a de novo variant in trans with an inherited allele, reflecting the high mutability of snRNA genes. Dominant and recessive RNU2-2-NDDs share overlapping clinical features with frequent epilepsy. Blood transcriptomics and DNA methylation analyses revealed subtle, variant-specific effects on splicing and episignatures. Our findings support a gradient-of-impact model and a continuum between dominant and recessive inheritance, establishing RNU2-2 variants as a frequent cause of NDDs, nearly as prevalent as ReNU syndrome.

The major spliceosome contains five small nuclear RNAs (snRNAs; U1, U2, U4, U5 and U6) essential for splicing. Variants in RNU4-2, encoding U4, cause a neurodevelopmental disorder called ReNU syndrome. We investigated de novo variants in 50 snRNA-encoding genes in a French cohort of 23,649 individuals with rare disorders and gathered additional cases through international collaborations. Altogether, we identified 145 previously unreported probands with (likely) pathogenic variants in RNU4-2 and 21 individuals with de novo and/or recurrent variants in RNU5B-1 and RNU5A-1, encoding U5. Pathogenic variants typically arose de novo on the maternal allele and cluster in regions critical for splicing. RNU4-2 variants mainly localize to two structures, the stem III and T-loop/quasi-pseudoknot, which position the U6 ACAGAGA box for 5' splice site recognition and associate with different phenotypic severity. RNU4-2 variants result in specific defects in alternative 5' splice site usage and methylation patterns (episignatures) that correlate with variant location and clinical severity. This study establishes RNU5B-1 as a neurodevelopmental disorder gene, suggests RNU5A-1 as a strong candidate and highlights the role of de novo variants in snRNAs.

Germline variants that disrupt components of the epigenetic machinery cause syndromic neurodevelopmental disorders. Using exome and genome sequencing, we identified de novo variants in KDM2A, a lysine demethylase crucial for embryonic development, in 18 individuals with developmental delays and/or intellectual disabilities. The severity ranged from learning disabilities to severe intellectual disability. Other core symptoms included feeding difficulties; growth issues, such as intrauterine growth restriction, short stature, and microcephaly; and recurrent facial features, such as epicanthic folds, upslanted palpebral fissures, thin vermillion of the lips, and low-set ears. Expression of human disease-causing KDM2A variants in a Drosophila melanogaster model led to neural degeneration, motor defects, and reduced lifespan. Interestingly, pathogenic variants in KDM2A affected physiological attributes, including subcellular distribution, expression, and stability in human cells. Genetic epistasis experiments indicated that KDM2A variants act via a dual mechanism—loss of nuclear function for some variants tested and additional cytoplasmic gain-of-function toxicity for c.704C>T (p.Pro235Leu), as eliminating endogenous Drosophila Kdm2 did not produce noticeable neurodevelopmental phenotypes. Data from enzymatic-methylation sequencing support the suggested gene-disease association by showing aberrant methylome profiles in affected individuals’ peripheral blood. Combining our genetic, phenotypic, and functional findings, we establish de novo variants in KDM2A as causative for a syndromic neurodevelopmental disorder.

BACKGROUND:Excitatory amino acid transporter 2 (EAAT2) is the predominant glutamate transporter and a key mediator of excitatory neurotransmission in the human brain. Here we present a cohort of 18 individuals harbouring 13 different SLC1A2 variants, who all present with neurodevelopmental impairment with variable symptoms and disease severities, and we delineate the impact of these variants on EAAT2 function. METHODS:The consequences of nine novel missense SLC1A2 variants for expression, transport and anion channel properties of EAAT2 expressed in mammalian cells were characterized by confocal microscopy, enzyme-linked immunosorbent and [3H]-D-aspartate uptake assays, and electrophysiological recordings. FINDINGS:Ten of the 13 SLC1A2 variants mediated significant changes to EAAT2 expression and/or function. These molecular phenotypes were classified into three categories: overall loss-of-function (F249Sfs∗17, A432D, A439V, c.1421+1G>C), mild gain-of-anion-channel function (I276S, G360A), and mixed loss-of-transport/gain-of-anion-channel function (G82R, L85R, L85P, P289R). In contrast, L37P, H542R and I546T did not mediate significant changes to EAAT2 expression or function. Although specific clinical outcomes in individuals carrying variants within each category varied somewhat, the three categories overall translated into distinct clinical phenotypes in terms of phenotypic traits and severity. INTERPRETATION:The observed associations between functional effects and clinical phenotypes produced by these variants offer valuable insights for future predictions of progression and severity of SLC1A2-associated neurodevelopmental disorders. Furthermore, these associations between variant-induced changes in EAAT2 function and phenotypic traits could assist in tailoring personalized treatments of these disorders. FUNDING:This work was funded by the German Ministry of Education and Research and by the Lundbeck Foundation.

Neurodevelopmental proteasomopathies are a group of disorders caused by variants in proteasome subunit genes, that disrupt protein homeostasis and brain development through poorly characterized mechanisms. Here, we report 26 distinct variants in PSMC5, encoding the AAA⁺ ATPase subunit PSMC5/RPT6, in individuals with syndromic neurodevelopmental conditions. Combining genetic, multi-omics and biochemical approaches across cellular models and Drosophila, we unveil the essential role of proteasomes in sustaining key cellular processes. Loss of PSMC5/RPT6 function impairs proteasome activity, leading to protein aggregation, disruption of mitochondrial homeostasis, and dysregulation of lipid metabolism and immune signaling. It also compromises synaptic balance, neuritogenesis, and neural progenitor cell stemness, causing deficits in higher-order functions, including learning and locomotion. Pharmacological targeting of integrated stress response kinases reveals a mechanistic link between proteotoxic stress and spontaneous type I interferon activation. These findings expand our understanding of proteasome-dependent quality control in neurodevelopment and suggest potential therapeutic strategies for neurodevelopmental proteasomopathies.

In 2016, Sifrim and colleagues described the first group of patients carrying heterozygous pathogenic variants in CDK13 and sharing major clinical features mainly consisting of congenital heart defects, intellectual disability and peculiar facial features (Congenital Heart Defects, Dysmorphic Facial Features, and Intellectual Developmental Disorder; CHDFIDD, OMIM # 617360). This condition is generally referred to as CDK13-related disorder, and since then other reports have provided further clinical and molecular information. Here we describe a group of 27 previously unreported patients to more accurately profile the clinical spectrum associated with CDK13 variants, disclosing novel associated findings, such as complex craniosynostosis and variable skeletal features (e.g., cranio-cervical anomalies). We also focused on the ocular phenotype that appears to include bilateral congenital glaucoma, posterior embriotoxon, buphthalmos and Duane anomaly. Finally, we observed two cases of mother-to-daughter transmission. Our work clarifies some novel features of CHDFIDD, defines the differential diagnosis of this disorder, and provides recommendations for its clinical management.