BACKGROUND:Potocki-Lupski syndrome (PTLS) is a rare genetic disorder, with an estimated prevalence of 1:25 000. Detection of a duplication at position 17p11.2 comprising the RAI1 gene establishes the diagnosis. Deletion of this same region is responsible for Smith-Magenis syndrome (SMS). Hitherto, the non-specific clinical features included psychomotor and growth retardation and multiple congenital anomalies. Our aim was to further delineate the clinical spectrum of PLTS. METHODS:We gathered a series of 56 individuals carrying a 17p11.2 duplication, one of the largest reported to date. We collected detailed phenotypic data and established a phenotypic comparison with individuals already described in the literature. RESULTS:We corroborated the main clinical signs associated with PTLS and highlighted additional features present in a significant proportion in our series, such as intrauterine growth retardation or low birth weight, musculoskeletal and ophthalmological anomalies, and abnormalities of the skin appendages. In line with previous reports, behavioural disorders were frequently identified (23%). Yet unexpectedly, self-aggressive and hetero-aggressive behaviours, characteristic features of SMS, were found in a small number of individuals. Forty-six individuals harboured the recurrent duplication (85%), five had larger duplications (9%) and three had smaller duplications (6%). We did not identify inherited duplications when parental information was available (n=43). CONCLUSION:Our study refined the clinical features of PTLS and their relative frequencies. Our findings therefore contribute to improving management of people with PTLS. These open up new pathophysiological hypotheses involving RAI1 gene dosage of the genesis and control of behaviour, as well as new, more complex regulatory pathways.

The MYT1L-related neurodevelopmental disorder (MRND) is associated with global motor and language delay, intellectual disability, behavioural disturbances, epilepsy and frequent early-onset obesity. Eating disturbances have been reported but remain poorly characterized. A systematic characterization of the eating behaviour phenotype is essential to improve diagnosis and management. We conducted a multicentre study including 21 French-speaking individuals with a molecularly confirmed MRND and either overweight/obesity or eating behaviour disturbances. Eating behaviours were reported by relatives using validated questionnaires widely employed in rare obesity research: the Dykens Hyperphagia Questionnaire (HQ), the Trousseau Impulsivity Questionnaire, the Children’s Eating Behaviour Questionnaire (CEBQ), the Food Cravings Questionnaire-Trait-reduced (FCQ-T-r, adults only), and a Visual Analogue Scale (VAS) for hunger. When available, questionnaire results were compared with published studies using the same instruments. Persistent hyperphagic behaviours were identified in the majority of patients, with the HQ questionnaire highlighting sustained food-seeking behaviours and pervasive food preoccupation. The mean global score was 25.9, indicating a moderate yet sustained hyperphagic profile. CEBQ revealed a strong attraction to food combined with reduced satiety responsiveness and rapid eating. Hunger was reported as persistent throughout the day. In children food impulsivity was less frequent (5/14; 36

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.

Cohesin orchestrates gene expression via three-dimensional chromosome folding. Genes encoding cohesin and cohesin loaders have been associated with Mendelian disorders, whereas genes encoding cohesin release factors, including WAPL and its binding partners PDS5A and PDS5B, have not. We explored the relevance of cohesin release factors in Mendelian disease by phenotyping individuals with heterozygous predicted damaging variants in WAPL (n = 27), PDS5A (n = 8), and PDS5B (n = 8), by modeling WAPL deficiency in human cells and mice, and by aggregating disease association statistics from consortia studies. We identified a WAPL-related disorder featuring developmental delay, intellectual disability, and risk of other developmental anomalies. Similarities between individuals with damaging WAPL variants and those with large, recurrent 10q22.3q23.2 (10q) deletions encompassing WAPL nominate WAPL as a driver gene within this genomic disorder region. While individuals with PDS5A or PDS5B variants exhibited features of developmental disorders, neither cohort-based statistics nor subject phenotyping associated these genes with specific phenotypes. We used CRISPR to generate truncating variants in WAPL and 10q deletion or duplication in human induced pluripotent stem cells (iPSCs) and induced neurons. Transcriptomics identified significant overlap between WAPL haploinsufficiency and 10q deletion differentially expressed genes. Mice with 50% Wapl expression exhibited mild deficits of growth and learning/memory, whereas those with 25% residual Wapl displayed birth defects and postnatal lethality, revealing a dosage liability threshold below the level of heterozygosity. In summary, we delineated a genetic condition caused by cohesin release factor deficiency, nominated WAPL as a driver gene within a genomic disorder region, and further illuminated dosage sensitivity of human cohesin.

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.

LDB1 encodes transcriptional regulator protein LIM domain-binding protein 1, which plays an important role in neurogenesis. Few C-terminal likely gene-disrupting (LGD) variants have been reported in the literature in individuals with congenital ventriculomegaly. Through international collaboration, we now assembled a cohort of 16 individuals with de novo variants affecting various regions of LDB1. Eleven variants affect either the whole gene or the N-terminal dimerization domain (including gene deletions, as well as nonsense-mediated mRNA decay (NMD)-sensitive LGD and missense variants), and five variants (missense or NMD-escaping LGD variants) affect only the C terminus of LDB1 containing the LIM interaction domain. All individuals showed variable neurodevelopmental phenotypes, including developmental delay and behavioral anomalies. In line with literature reports, individuals harboring C-terminal variants additionally presented with ventriculomegaly, which suggests a potential genotype-phenotype correlation. In accordance, we found diverging pathomechanisms in vitro: N-terminal missense variants disrupt homodimerization of LDB1, likely leading to a loss of function, while C-terminal variants impair interaction with the essential partner LHX2 in a dominant-negative manner. These findings were confirmed in vivo in Drosophila melanogaster. Toxicity of overexpressed human LDB1 in Drosophila was not observed with N-terminal missense variants but was exacerbated by C-terminal variants. Similarly, phenotypes associated with LDB1/chi loss were rescued by overexpression of wild-type LDB1 but not by LDB1 harboring N-terminal missense variants or by C-terminal variants that even worsened phenotypes. In summary, our findings indicate that de novo variants in LDB1 are linked to two overlapping but distinct neurodevelopmental phenotypes based on variant location and propose two separate pathomechanisms underlying LDB1-related neurodevelopmental disorders.

Cohesin is a fundamental genome-organizing complex that orchestrates three-dimensional chromosome folding and gene expression via DNA loop extrusion. Alterations to genes encoding cohesin subunits and cohesin loaders cause Mendelian disorders, including Cornelia de Lange syndrome (CdLS). By contrast, disruption of factors that remove cohesin from DNA, including WAPL and its binding partners PDS5A and PDS5B, have not yet been associated with human disease. Here, we explored the relevance of these cohesin release factors in Mendelian disease by establishing a rare disease cohort of deeply phenotyped individuals with heterozygous, predicted damaging variants in WAPL (n=27), PDS5A (n=8), and PDS5B (n=8), by modeling WAPL deficiency in human cell lines and mice, and by aggregating rare disease association statistics from consortia studies. We identified a WAPL-related disorder characterized by developmental delay, intellectual disability, and risk of other developmental anomalies including clubfoot. Similarities between individuals with damaging WAPL variants and those with large, recurrent 10q22.3q23.2 (10q) deletions (which encompass WAPL) nominate WAPL as a driver gene within this genomic disorder region. While carriers of PDS5A or PDS5B variants exhibited features of developmental disorders, neither cohort-based statistics nor case phenotyping associated these genes with specific phenotypes. We used CRISPR engineering to generate truncating variants in WAPL, as well the 7.8 Mb 10q deletion or duplication in human iPSCs and induced neurons. Transcriptomic analyses identified differentially expressed genes in both models, with highly significant overlap between WAPL haploinsufficiency and 10q deletion signatures. Mice with 50% residual Wapl expression exhibited mild deficits of growth and learning/memory, whereas those with 25% residual Wapl expression displayed birth defects and postnatal lethality, revealing a dosage liability threshold below the level of heterozygosity. In summary, we delineated a novel genetic condition caused by cohesin release factor deficiency, nominated WAPL as a driver gene within a genomic disorder region, and further illuminated dosage sensitivity of human cohesin.

Sex-specific penetrance in autosomal-dominant Mendelian conditions is largely understudied. The neurodevelopmental disorder Pilarowski-Bjornsson syndrome (PILBOS) was initially described in females. Here, we describe the clinical and genetic characteristics of the largest PILBOS cohort to date, showing that both sexes can exhibit PILBOS features, although males are overrepresented. A mouse model carrying a human-derived Chd1 missense variant (Chd1R616Q/+) displays female-restricted phenotypes, including growth deficiency, anxiety, and hypotonia. Orchiectomy unmasks a growth-deficiency phenotype in male Chd1R616Q/+ mice, while testosterone rescues the phenotype in females, implicating androgens in phenotype modulation. In the gnomAD and UK Biobank databases, rare missense variants in CHD1 are overrepresented in males, supporting a male-protective effect. We identify 33 additional highly constrained autosomal genes with missense variant overrepresentation in males. Our results support androgen-regulated sexual dimorphism in PILBOS and open avenues toward understanding the mechanistic basis of sexual dimorphism in other autosomal Mendelian disorders.

PACS1-related disorder (PACS1-RD), also known as Schuurs-Hoeijmakers syndrome, is a rare autosomal dominant neurodevelopmental disorder predominantly caused by the recurrent de novo c.607 C > T p.(Arg203Trp) gain-of-function variant. Although core clinical features have been delineated, systematic data on developmental milestones, growth parameters, and clinical variability remain limited. We assembled a series of 24 previously unreported, unrelated individuals with PACS1-RD and compared their clinical and molecular features with 84 individuals from the literature. Genome-wide DNA methylation profiling was performed on peripheral blood DNA using bisulfite sequencing, interrogating ~860,000 CpG sites. Our study expands the phenotypic spectrum of PACS1-RD by reporting median age at independent walking and first spoken words (both 24 months), cross-sectional growth parameters, and previously undescribed clinical features, including congenital kidney malformations (25%) and feeding difficulties (75%). Compared with the literature, our series showed a higher prevalence of cryptorchidism (77.8%), congenital heart defect (45.8%), and hypotonia (75%). Methylation analysis identified a specific episignature for PACS1-RD, consistently observed in individuals carrying either the canonical p.(Arg203Trp) or the non-recurrent p.(Arg203Gln) variant. This episignature further enabled PACS1-RD diagnosis in one unsolved individual initially suspected of Kabuki syndrome. These findings refine the clinical delineation of PACS1-RD and establish an episignature that will support diagnosis in unresolved neurodevelopmental disorders and guide pathogenicity assessment of non-recurrent PACS1 variants.

Heterozygous loss-of-function variants in SUFU are associated with Gorlin syndrome (MIM:620343) and tumor predisposition, while biallelic missense variants underlie recessive Joubert syndrome (JS; MIM:617757). Interestingly, emerging evidence suggests that SUFU haploinsufficiency also contributes to neurodevelopmental disorders (NDDs). We investigated 5 unrelated families encompassing 4 singletons and 1 pair of monozygotic twins carrying heterozygous SUFU loss-of-function variants through clinical, neuropsychological, and neuroimaging assessments and compared their features with 47 published cases fulfilling NDDs inclusion criteria. A consistent neurodevelopmental phenotype was observed, characterized by global developmental delay, hypotonia, congenital ocular motor apraxia, macrocephaly, and mild cerebellar abnormalities, including vermian hypoplasia and posterior fossa anomalies, variably falling within the JS spectrum. Craniofacial features were variably observed in our cohort and are reported as supportive clinical observations. Intellectual disability was present in similar to 35% of affected individuals, while autism spectrum disorder and behavioral difficulties occurred less frequently. Notably, neoplastic manifestations were absent among our cases, indicating that oncological and neurodevelopmental outcomes may segregate independently. SUFU haploinsufficiency may underlie a distinct dominantly inherited neurodevelopmental syndrome spanning from isolated ocular motor apraxia to a mild Joubert-like phenotype with macrocephaly and variable cognitive/behavioral outcomes. These findings further refine the clinical description of the SUFU-related neurodevelopmental phenotype beyond tumor predisposition and support its inclusion in diagnostic panels for developmental delay, macrocephaly, and JS-spectrum disorders. Multidisciplinary surveillance, balancing neurodevelopmental and oncological aspects, is recommended.

Rationale & Objective: Molecular diagnosis of autosomal dominant tubulointerstitial kidney disease (ADTKD) due to variants in the MUC1 gene has long been challenging because variants lie in a large variable number of tandem repeat (VNTR) region, making identification impossible using standard short-read techniques. Previously, we addressed this diagnostic limitation by developing a computational pipeline named VNtyper for easier reliable detection of MUC1 VNTR pathogenic variants from short-read sequences. This led to unexpected diagnoses of ADTKD-MUC1 among patients with kidney disease referred for genetic testing, which we report here. Study Design: Cross-sectional observational study. Setting & Participants: 4,040 patients referred to Necker Enfants-Malades Hospital from 2017 to 2023 for genetic testing for (1) glomerular disease, (2) ciliopathy, (3) congenital anomalies of the kidneys and urinary tracts (CAKUT), (4) ADTKD, or (5) chronic kidney disease (CKD) of unknown origin, in whom MUC1 had not been previously tested by SNaPshot minisequencing. Exposure: Clinical suspicion of ADTKD. Outcome: ADTKD-MUC1 diagnosed using VNtyper. Analytical Approach: Data were collected from patients in whom ADTKD-MUC1 was newly diagnosed and patients in whom ADTKD was clinically suspected were compared with those in whom ADTKD was not. Results: We identified 40 patients with MUC1 variants by VNtyper, including 33 new index patients and 7 relatives. Of the 33 index cases, 20 had been suspected of having ADTKD based on clinical features, and in the other 13 ADTKD had not been considered. In patients in whom ADTKD had not been considered clinically, the detection rate was 0.05% (1 of 1,895) among patients with glomerular disease, 1.2% (4 of 329) among patients with ciliopathy, 0.09% (1 of 1,099) among patients with CAKUT and 2.5% (7 of 285) among patients with CKD of unknown origin. In 6 patients there was no family history of kidney disease, and we confirmed de novo presentation in 2 patients by segregation studies. Limitations: Observational study and selected referral population (may not represent the prevalence or phenotypes in the general kidney disease population). Conclusions: With VNtyper, we were able to diagnose new cases of ADTKD-MUC1 in a large cohort of patients with various phenotypes. Some patients had atypical phenotypes due to a variant in another gene, and some had no family history of kidney disease, suggesting de novo disease, which was confirmed in 2 patients.

Dystonia is a rare disease trait for which large-scale genomic investigations are still underrepresented. Genetic heterogeneity among patients with unexplained dystonia warrants interrogation of entire genome sequences, but this has not yet been systematically evaluated.To significantly enhance our understanding of the genetic contribution to dystonia, we (re)analysed 2874 whole-exome sequencing (WES), 564 whole-genome sequencing (WGS), as well as 80 fibroblast-derived proteomics datasets, representing the output of high-throughput analyses in 1990 patients and 973 unaffected relatives from 1877 families. Recruitment and precision-phenotyping procedures were driven by long-term collaborations of international experts with access to overlooked populations.By exploring WES data, we found that continuous scaling of sample sizes resulted in steady gains in the number of associated disease genes without plateauing. On average, every second diagnosis involved a gene not previously implicated in our cohort. Second-line WGS focused on a subcohort of undiagnosed individuals with high likelihood of having monogenic forms of dystonia, comprising large proportions of patients with early onset (81.3%), generalized symptom distribution (50.8%) and/or coexisting features (68.9%). We undertook extensive searches for variants in nuclear and mitochondrial genomes to uncover 38 (ultra)rare diagnostic-grade findings in 37 of 305 index patients (12.1%), many of which had remained undetected due to methodological inferiority of WES or pipeline limitations. WGS-identified elusive variations included alterations in exons poorly covered by WES, RNA-gene variants, mitochondrial-DNA mutations, small copy-number variants, complex rearranged genome structure and short tandem repeats. For improved variant interpretation in WGS-inconclusive cases, we employed systematic integration of quantitative proteomics. This aided in verifying diagnoses related to technically challenging variants and in upgrading a variant of uncertain significance (3 of 70 WGS-inconclusive index patients, 4.3%). Further, unsupervised proteomic outlier analysis supplemented with transcriptome sequencing revealed pathological gene underexpression induced by transcript disruptions in three more index patients with underlying (deep) intronic variants (3/70, 4.3%), highlighting the potential for targeted antisense-oligonucleotide therapy development. Finally, trio-WGS prioritized a de novo missense change in the candidate PRMT1, encoding a histone methyltransferase. Data-sharing strategies supported the discovery of three distinct PRMT1 de novo variants in four phenotypically similar patients, associated with loss-of-function effects in in vitro assays.This work underscores the importance of continually expanding sequencing cohorts to characterize the extensive spectrum of gene aberrations in dystonia. We show that a pool of unresolved cases is amenable to WGS and complementary multi-omic studies, directing advanced aetiopathological concepts and future diagnostic-practice workflows for dystonia. Using whole-genome sequencing and proteomics, Zech et al. have shown that many patients with suspected monogenic dystonia carry mutations that are undetectable with exome analysis alone. Complementary approaches, such as RNA sequencing and functional studies, can improve rates of diagnosis.

Rare genetic variants in ARID2 are responsible for a recently described neurodevelopmental condition called ARID2-related disorder (ARID2-RD). ARID2 belongs to PBAF, a unit of the SWI/SNF complex, which is a chromatin remodeling complex. This work aims to further delineate the phenotypic spectrum of ARID2-RD, providing clinicians with additional data for better care and aid in the future diagnosis of this condition. We obtained the genotypes and phenotypes of 27 previously unreported individuals with ARID2-RD and compared this series with findings in the literature. We also assessed peripheral blood DNA methylation profiles in individuals with ARID2-RD compared to episignatures of controls, unresolved cases, and other neurodevelopmental disorders. The main clinical features of ARID2-RD are developmental delay, speech disorders, intellectual disability (ID), behavior problems, short stature, and various dysmorphic and ectodermal features. Genome-wide differential methylation analysis revealed a global hypermethylated profile in ARID2-RD that could aid in reclassifying variants of uncertain significance. Our study doubles the number of reported individuals with ARID2 pathogenic variants to 53. It confirms loss-of-function as a pathomechanism and shows the absence of a clear genotype-phenotype correlation. We provide evidence for a unique DNA methylation episignature for ARID2-RD and further delineate the ARID2-associated phenotype.

Introduction:Microtubules are essential components of the neuronal cytoskeleton. The α- and β-tubulins, variably expressed in the central nervous system, play key roles in neurogenesis and brain development. Pathogenic variants in TUBB2A have recently been identified as an ultra-rare cause of pediatric neurodevelopmental disorders (NDDs). However, the neurological and behavioral manifestations, genotype-phenotype correlations, and underlying disease mechanisms remain poorly understood due to the limited number of reported families. Methods:We describe a cohort of families presenting with microcephaly, global developmental delay, speech impairment, seizures and/or EEG abnormalities, movement disorders and severe behavioral disorders. Clinical assessments and brain imaging studies were conducted over a 10-year follow-up period. Genetic analysis was performed via whole-exome sequencing (WES), and structural modeling was used to investigate the functional impact of the identified variants. Results:WES revealed a novel recurrent heterozygous pathogenic variant in TUBB2A (NM_001069.3:c.1172G > A; NP_001060.1:p.Arg391His), identified as the cause of disease in multiple affected individuals from unrelated families. Comparative analysis with previously reported TUBB2A de novo variants confirmed that this novel recurrent mutation affects a highly conserved Arg391 residue within the longitudinal E-site heterodimer interface. Computational modeling demonstrated that the variant disrupts α/β-tubulin heterodimer formation, impairing binding stability at this critical interaction site. Discussion:Our findings expand the phenotypic and genotypic spectrum of TUBB2A-related disorders and identify Arg391 as a mutational hotspot linked to severe brain developmental disorders due to aberrant tubulin dynamics, highlighting the disruption of the α/β-tubulin heterodimer formation as the disease mechanism associated to this novel hotspot variant. These results provide new insights into disease mechanisms and offer a foundation for potential future therapeutic approaches aimed at stabilizing α/β-tubulin interactions.

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.

Variable expressivity of disease-associated variants implies a role for secondary variants that modify clinical features. We assessed the effects of modifier variants on the clinical outcomes of 2,455 individuals with primary variants. Among 124 families with the 16p12.1 deletion, distinct rare and common variant classes conferred risks for specific developmental features, including short tandem repeats for neurological defects. Network analysis suggested distinct mechanisms involving 16p12.1 genes and secondary variants specific to each proband. Within disease and population cohorts of 976 individuals with the 16p12.1 deletion, we found opposing effects of secondary variants on clinical features across ascertainments. Additional analysis of 1,479 probands with other primary variants, such as the 16p11.2 deletion and CHD8 variants, and 1,528 probands without primary variants showed that phenotypic associations differed by primary variant context and were influenced by synergistic interactions between primary and secondary variants. Our study provides a paradigm to dissect the personalized genomic architecture of complex disorders.