Large-scale discovery of novel genetic causes of developmental disorders

Comprehensive Clinical and Genetic Characterization of a Spanish Cohort of 22 Patients With Bainbridge-Ropers Syndrome

Bainbridge-Ropers Syndrome (BRPS) is a genetic condition resulting from truncating variants in the ASXL3 gene. The clinical features include neurodevelopmental and language impairments, behavioral issues, hypotonia, feeding difficulties, and distinctive facial features. In this retrospective study, we analyzed 22 Spanish individuals with BRPS, aiming to perform a detailed clinical and molecular description and establish a genotype-phenotype correlation. We identified 19 ASXL3 variants, nine of which are novel. We documented recurrence in nontwin siblings due to parental mosaicism. The predominant prenatal finding was intrauterine growth restriction (35%) followed, after birth, by feeding difficulties (90.5%), hypotonia (85.7%), and gastroesophageal reflux disease (82.4%). Later in life, intellectual disability, language impairment, autism spectrum disorder (75%), and joint laxity (73.7%) were noted. Individuals with variants in the 3' mutational cluster region (MCR) of exon 12 exhibited more perinatal feeding problems, and those with variants in the 5' MCR of exon 11 displayed lower percentiles in height and occipitofrontal circumference, as well as higher frequency of arched eyebrows. This study is the first characterization of a Spanish BRPS cohort, with more than 50 clinical features analyzed, representing the most detailed phenotypic analysis to date.

Lithium normalizes ASD-related neuronal, synaptic, and behavioral phenotypes in DYRK1A-knockin mice

Dyrk1A deficiency is linked to various neurodevelopmental disorders, including developmental delays, intellectual disability (ID) and autism spectrum disorders (ASD). Haploinsufficiency of Dyrk1a in mice reportedly leads to ASD-related phenotypes. However, the key pathological mechanisms remain unclear and human DYRK1A mutations remain uncharacterized in mice. Here, we generated and studied Dyrk1a-knockin mice carrying a human ASD patient mutation (Ile48LysfsX2; Dyrk1a-I48K mice). These mice display severe microcephaly, social and cognitive deficits, dendritic shrinkage, excitatory synaptic deficits, and altered phospho-proteomic patterns enriched for multiple signaling pathways and synaptic proteins. Early chronic lithium treatment of newborn mutant mice rescues the brain volume, behavior, dendritic, synaptic, and signaling/synapse phospho-proteomic phenotypes at juvenile and adult stages. These results suggest that signaling/synaptic alterations contribute to the phenotypic alterations seen in Dyrk1a-I48K mice, and that early correction of these alterations by lithium treatment has long-lasting effects in preventing juvenile and adult-stage phenotypes.

Contribution of families using the GenIDA database to the description of MED13L syndrome and literature review

The GenIDA project aims to improve the understanding and management of rare genetic forms of intellectual disability by fostering collaboration among patients, caregivers, healthcare professionals, and research professionals. Clinical data is provided by patients' families via a structured questionnaire to identify medically relevant insights and better understand the natural history of rare diseases. This study focused on MED13L syndrome, analyzing data from 41 patients in the GenIDA database and comparing it with 102 cases from the scientific literature and 6 new descriptions of patients from our medical center.The GenIDA series confirmed the key features of MED13L syndrome, including global developmental delay, poor speech, intellectual disability, and cardiac defects (OMIM #616789), at frequencies similar to those reported in the literature. The GenIDA series identified a higher prevalence of visual impairment (76%) and highlighted under-recognized musculoskeletal issues, such as foot deformities, which had previously received little attention. This study highlights the value of family-reported data in describing the full phenotype of rare syndromes. A comprehensive review of published cases showed that patients with missense variants have more severe impairments, including increased cardiac defects, global developmental delay, and a higher incidence of epilepsy, than patients with premature truncated variants.These findings highlight the importance of family involvement in rare disease research and the need for further studies to explore genotype-phenotype correlations to improve patient care and outcomes.

Variants in BSN, encoding the presynaptic protein Bassoon, result in a distinct neurodevelopmental disorder with a broad phenotypic range

Disease-causing variants in synaptic function genes are a common cause of neurodevelopmental disorders (NDDs) and epilepsy. Here, we describe 14 individuals with de novo disruptive variants in BSN, which encodes the presynaptic protein Bassoon. To expand the phenotypic spectrum, we identified 15 additional individuals with protein-truncating variants (PTVs) from large biobanks. Clinical features were standardized using the Human Phenotype Ontology (HPO) across all 29 individuals, which revealed common clinical characteristics including epilepsy (13/29, 45%), febrile seizures (7/29, 25%), generalized tonic-clonic seizures (5/29, 17%), and focal-onset seizures (3/29, 10%). Behavioral phenotypes were present in almost half of all individuals (14/29, 48%), which included ADHD (7/29, 25%) and autistic behavior (5/29, 17%). Additional common features included developmental delay (11/29, 38%), obesity (10/29, 34%), and delayed speech (8/29, 28%). In adults with BSN PTVs, milder features were common, suggesting phenotypic variability, including a range of individuals without obvious neurodevelopmental features (7/29, 24%). To detect gene-specific signatures, we performed association analysis in a cohort of 14,895 individuals with NDDs. A total of 66 clinical features were associated with BSN, including febrile seizures (p = 1.26e-06) and behavioral disinhibition (p = 3.39e-17). Furthermore, individuals carrying BSN variants were phenotypically more similar than expected by chance (p = 0.00014), exceeding phenotypic relatedness in 179/256 NDD-related conditions. In summary, integrating information derived from community-based gene matching and large data repositories through computational phenotyping approaches, we identify BSN variants as the cause of a synaptic disorder with a broad phenotypic range across the age spectrum.

Sex-specific perturbations of neuronal development caused by mutations in the autism risk gene DDX3X

DDX3X is an X-linked RNA helicase that escapes X chromosome inactivation and is expressed at higher levels in female brains. Mutations in DDX3X are associated with intellectual disability (ID) and autism spectrum disorder (ASD) and are predominantly identified in females (DDX3X syndrome). Using cellular and mouse models, we show that Ddx3x mediates sexual dimorphisms in brain development at a molecular, cellular, and behavioral level. During cortical neuronal development, Ddx3x sustains a female-biased signature of enhanced ribosomal biogenesis and mRNA metabolism. Compared to male neurons, female neurons display larger nucleoli, higher expression of a set of ribosomal proteins, and a higher cytoplasm-to-nucleus ratio of ribosomal RNA. All these sex dimorphisms are obliterated by Ddx3x loss. Ddx3x regulates dendritic arborization complexity in a sex- and dose-dependent manner in both female and male neurons. Ddx3x modulates the development of dendritic spines but only in female neurons. Further, ablating Ddx3x conditionally in forebrain neurons is sufficient to yield sex-specific changes in developmental outcomes and motor function. Together, these findings pose Ddx3x as a mediator of sexual differentiation during neurodevelopment and open new avenues to understand sex differences in health and disease.

The Phenotypic and Genotypic Spectrum of BRPF1-Related Disorder: 29 New Patients and Literature Review

Intellectual Developmental Disorder with Dysmorphic Facies and Ptosis (IDDDFP) is a rare autosomal dominant syndrome caused by pathogenic variants in the BRPF1 gene, which is critical for chromatin regulation. This study expands the clinical and molecular spectrum of IDDDFP by analysing 29 new patients from 20 families with confirmed BRPF1 variants. Our cohort presented with a wide range of clinical features including developmental delay, intellectual disability (ID) and characteristic dysmorphic facial features such as ptosis, blepharophimosis and a broad nasal bridge. New phenotypic features identified include palpebral oedema, laterally elongated eyebrows, low hanging columella and hypertrichosis. Neuropsychological assessment reveals a predominance of mild to moderate ID, with cognitive profiles showing variability in verbal and visual processing. Structural abnormalities such as agenesis of the corpus callosum and ocular defects were noted, consistent with previous studies but with some differences. Familial analysis revealed variability in clinical expression. Our findings highlight the diverse clinical manifestations of BRPF1-related disorders and suggest that comprehensive ophthalmological evaluation is essential for the management of these patients.

DEAD/DEAH-box RNA helicases shape the risk of neurodevelopmental disorders

The DEAD/DEAH-box family of RNA helicases (RHs) is among the most abundant and conserved in eukaryotes. These proteins catalyze the remodeling of RNAs to regulate their splicing, stability, localization, and translation. Rare genetic variants in DEAD/DEAH-box proteins have recently emerged as being associated with neurodevelopmental disorders (NDDs). Analyses in cellular and animal models have uncovered fundamental roles for these proteins during brain development. We discuss the genetic and functional evidence that implicates DEAD/DEAH-box proteins in brain development and NDDs, with a focus on how structural insights from paralogous genes can be leveraged to advance our understanding of the pathogenic mechanisms at play.

Visual and auditory attention in individuals with DYRK1A and SCN2A disruptive variants

This preliminary study sought to assess biomarkers of attention using electroencephalography (EEG) and eye tracking in two ultra-rare monogenic populations associated with autism spectrum disorder (ASD). Relative to idiopathic ASD (n = 12) and neurotypical comparison (n = 49) groups, divergent attention profiles were observed for the monogenic groups, such that individuals with DYRK1A (n = 9) exhibited diminished auditory attention condition differences during an oddball EEG paradigm whereas individuals with SCN2A (n = 5) exhibited diminished visual attention condition differences noted by eye gaze tracking when viewing social interactions. Findings provide initial support for alignment of auditory and visual attention markers in idiopathic ASD and neurotypical development but not monogenic groups. These results support ongoing efforts to develop translational ASD biomarkers within the attention domain.

A systematic review of hereditary neurological disorders diagnosed by whole exome sequencing in Pakistani population: updates from 2014 to November 2024

Hereditary neurological disorders (HNDs) are a group of heterogeneous disorders characterized by significant genetic and clinical variability. HNDs are caused by dysfunction of the central or peripheral nervous system due to aberrant electrical impulses. More than 600 types of HNDs have been documented, and overall, these are the second leading cause of death worldwide. This systematic review is based on a retrospective analysis of research articles reporting HNDs diagnosed using whole exome sequencing in Pakistani families from 2014 to November 2024. Original research articles were retrieved through online surveys, notably Google Scholar, PubMed, and the Web of Science. Based on stringent selection criteria, 89 research articles and 188 variants published around 10 years were considered. Variants and research articles were cross-checked and further validated in different online databases/resources to confirm their genomic nomenclature and pathogenicity according to the ACMG guidelines. A total of 188 variants in 143 distinct genes in Pakistani families identified through whole exome sequencing have been reported to date that caused genetic and clinically heterogeneous HNDs. Consanguineous parentage was found in around 90% of cases, and approximately 91% of causative alleles were reported in homozygous state showing a predominant burden of HNDs because of blood-related marriages. The most frequent type of pathogenic variants were single nucleotide substitutions (92 missense and 39 nonsense). Among 188 variants, 76 variants were reported in 2024 and 44 variants were observed in 2023. Pakistan is the fifth most populous country in the world having an extreme prevalence of consanguinity resulting in the expression of pathogenic variants due to homozygosity. Therefore, there is a prevalence of genetic disorders particularly rare monogenic or Mendelian disorders. Next-generation sequencing approach is strongly recommended for diagnosis, early therapeutic intervention and genetic counselling.

Genetic advances in neurodevelopmental disorders

Neurodevelopmental disorders (NDDs) are a group of highly heterogeneous diseases that affect children's social, cognitive, and emotional functioning. The etiology is complicated with genetic factors playing an important role. During the past decade, large-scale whole exome sequencing (WES) and whole genome sequencing (WGS) have vastly advanced the genetic findings of NDDs. Various forms of variants have been reported to contribute to NDDs, such as de novo mutations (DNMs), copy number variations (CNVs), rare inherited variants (RIVs), and common variation. By far, over 200 high-risk NDD genes have been identified, which are involved in biological processes including synaptic function, transcriptional and epigenetic regulation. In addition, monogenic, oligogenic, polygenetic, and omnigenic models have been proposed to explain the genetic architecture of NDDs. However, the majority of NDD patients still do not have a definitive genetic diagnosis. In the future, more types of risk factors, as well as noncoding variants, are await to be identified, and including their interplay mechanisms are key to resolving the etiology and heterogeneity of NDDs.

Should Scotland provide genome-wide sequencing for the diagnosis of rare developmental disorders? A cost-effectiveness analysis

AIMS

This study aims to evaluate the cost effectiveness of genetic and genomic testing strategies for the diagnosis of rare developmental disorders in NHS Scotland.

METHODS

Six genetic and genomic testing strategies were evaluated using a decision tree model. First-line, second-line and last-resort trio genome sequencing (GS), and second-line and last-resort trio exome sequencing (ES) were compared with standard genetic testing. The cost effectiveness of each strategy was expressed in terms of incremental cost per additional diagnosis. The impact of uncertainty on cost-effectiveness results was explored using deterministic and probabilistic sensitivity analysis.

RESULTS

2nd-line ES was a cost-saving option, increasing diagnostic yield by 13.9% and decreasing cost by £1027 per trio compared to standard genetic testing. Compared to ES, strategies involving GS increased costs significantly, with only a moderate or zero improvement in diagnostic yield. Sensitivity analysis indicated that significant reductions in cost or improvements in diagnostic yield are required before 1st-line GS becomes cost effective.

CONCLUSION

2nd-line ES (after chromosomal microarray; replacing gene panel testing) for the diagnosis of developmental disorders is a cost-saving option for the Scottish NHS. Ongoing economic evaluation is required to monitor the evolving cost and diagnostic yield of GS and ES over time.

Proteome-wide model for human disease genetics

Identifying variants driving disease accelerates both genetic diagnosis and therapeutic development, but missense variants still present a bottleneck as their effects are less straightforward than truncations or nonsense mutations. While computational prediction methods are sufficiently accurate to be of clinical value for variants in known disease genes, they do not generalize well to other genes as the scores are not calibrated across the proteome 1-6 . To address this, we developed a deep generative model, popEVE, that combines evolutionary information with population sequence data 7 and achieves state-of-the-art performance on a suite of proteome-wide prediction tasks, without overestimating the prevalence of deleterious variants in the population. popEVE identifies 442 genes in a developmental disorder cohort 8 , including evidence of 123 novel candidates, many without the need for cohort-wide enrichment. Candidate genes are functionally similar to known developmental disorder genes and case variants tend to fall in functionally important regions of these genes. Finally, we show that these findings can be reproduced from analysis of the patient exomes alone, demonstrating that popEVE provides a new avenue for genetic analysis in situations where traditional methods fail, including genetic diagnosis of rare-as-one diseases, even in the absence of parent sequencing.

Use of polyadenosine tail mimetics to enhance mRNA expression from genes associated with haploinsufficiency disorders

Polyadenosine (poly(A)) tails are nearly ubiquitous in human messenger RNA (mRNA) governing mRNA stability and translation. Crucially, the poly(A) tail regulates cytoplasmic gene expression by undergoing controlled removal upon exposure to the cytoplasm. Upon removal, mRNA ceases protein production and may subsequently be degraded or silenced. We have generated a therapeutic modality that tethers a poly(A) tail mimetic on the 3' end of specifically targeted mRNAs, thereby enhancing their expression beyond their normal utility. This technology, which we term mRNA boosters, lends itself to uses on haploinsufficiency disorders, where reduced gene expression manifests in a disease state. By polyadenylating short RNA sequences antisense to the 3' untranslated region (UTR) of specific mRNAs, we demonstrate that we can selectively and significantly enhance mRNA expression both in vitro and in vivo. We showcase the effectiveness of this technology on genes linked to autism spectrum disorders such as SYNGAP1, M E CP2, PURA, and CTNNB1, illustrating increased expression in both human cell cultures and animal models. These findings indicate that small poly(A) tail mimetics can substantially enhance mRNA expression, providing the potential to efficaciously treat haploinsufficiency disorders.

Diagnostic Utility of Trio-Exome Sequencing for Children With Neurodevelopmental Disorders

Importance

Copy number variants (CNVs) and single-nucleotide variations (SNVs) or insertions and deletions are key genetic contributors to neurodevelopmental disorders (NDDs). Traditionally, chromosome microarray and exome sequencing (ES) have been used to detect CNVs and single gene variants, respectively.

Objective

To identify genetic variants causing NDDs and evaluate the diagnostic yield and clinical utility of ES by simultaneously analyzing CNVs and SNVs in patients with NDDs and their biologic parents (trios).

Design, Setting, and Participants

This retrospective cohort study included pediatric patients with suspected NDDs who visited Shanghai Children's Hospital between January 1, 2018, and December 31, 2023. ES was used to investigate trios (trio-ES) including patients with NDDs who remained undiagnosed after phenotype identification and underwent gene panel testing, multiplex ligation-dependent probe amplification, or karyotyping. Comprehensive clinical and laboratory data were collected. Data were analyzed from July 2022 to December 2023.

Exposure

NDDs, characterized by global developmental delay or intellectual disability.

Main Outcomes and Measures

The study measured the overall diagnostic yield of SNVs and CNVs in the NDD cohort as well as within NDD syndromic subtypes.

Results

Of the 1106 patients with NDDs, 731 (66.1%) were male. The mean (SD) age of patients at diagnosis was 3.80 (2.82) years. The overall diagnostic yield of trio-ES was 46.1% (510 diagnoses among 1106 patients), with 149 CNVs (13.5%), 355 SNVs (32.1%), and 4 cases of uniparental disomy (0.4%). Codiagnosis of SNVs and CNVs occurred in 2 cases (0.2%). Among the trios, 812 candidate germline variants were identified, including 634 SNVs (78.1%), 174 CNVs (21.4%), and 4 cases of uniparental disomy (0.5%). Of these, 423 SNVs (66.7%) and 157 CNVs (90.2%) were diagnostic variants, while 211 SNVs (33.3%) and 17 CNVs (9.8%) were variants of uncertain significance. Sixteen CNVs smaller than 20 kilobase were detected using ES.

Conclusions and Relevance

In this cohort study, trio-ES, by simultaneously detecting SNVs and CNVs, achieved a diagnostic yield of 46.1%. Trio-ES may be particularly applicable for identifying small CNVs and recessive genetic diseases involving both SNVs and CNVs. These findings suggest that in clinical practice, simultaneously analyzing SNVs and CNVs using trio-ES data has a favorable genetic diagnostic yield for children with NDDs.

Genome-wide association testing beyond SNPs

Decades of genetic association testing in human cohorts have provided important insights into the genetic architecture and biological underpinnings of complex traits and diseases. However, for certain traits, genome-wide association studies (GWAS) for common SNPs are approaching signal saturation, which underscores the need to explore other types of genetic variation to understand the genetic basis of traits and diseases. Copy number variation (CNV) is an important source of heritability that is well known to functionally affect human traits. Recent technological and computational advances enable the large-scale, genome-wide evaluation of CNVs, with implications for downstream applications such as polygenic risk scoring and drug target identification. Here, we review the current state of CNV-GWAS, discuss current limitations in resource infrastructure that need to be overcome to enable the wider uptake of CNV-GWAS results, highlight emerging opportunities and suggest guidelines and standards for future GWAS for genetic variation beyond SNPs at scale.

BCL11A intellectual developmental disorder: defining the clinical spectrum and genotype-phenotype correlations

An increasing number of individuals with intellectual developmental disorder (IDD) and heterozygous variants in BCL11A are identified, yet our knowledge of manifestations and mutational spectrum is lacking. To address this, we performed detailed analysis of 42 individuals with BCL11A-related IDD (BCL11A-IDD, a.k.a. Dias-Logan syndrome) ascertained through an international collaborative network, and reviewed 35 additional previously reported patients. Analysis of 77 affected individuals identified 60 unique disease-causing variants (30 frameshift, 7 missense, 6 splice-site, 17 stop-gain) and 8 unique BCL11A microdeletions. We define the most prevalent features of BCL11A-IDD: IDD, postnatal-onset microcephaly, hypotonia, behavioral abnormalities, autism spectrum disorder, and persistence of fetal hemoglobin (HbF), and identify autonomic dysregulation as new feature. BCL11A-IDD is distinguished from 2p16 microdeletion syndrome, which has a higher incidence of congenital anomalies. Our results underscore BCL11A as an important transcription factor in human hindbrain development, identifying a previously underrecognized phenotype of a small brainstem with a reduced pons/medulla ratio. Genotype-phenotype correlation revealed an isoform-dependent trend in severity of truncating variants: those affecting all isoforms are associated with higher frequency of hypotonia, and those affecting the long (BCL11A-L) and extra-long (-XL) isoforms, sparing the short (-S), are associated with higher frequency of postnatal microcephaly. With the largest international cohort to date, this study highlights persistence of fetal hemoglobin as a consistent biomarker and hindbrain abnormalities as a common feature. It contributes significantly to our understanding of BCL11A-IDD through an extensive unbiased multi-center assessment, providing valuable insights for diagnosis, management and counselling, and into BCL11A's role in brain development.

An AI-based approach driven by genotypes and phenotypes to uplift the diagnostic yield of genetic diseases

Identifying disease-causing variants in Rare Disease patients' genome is a challenging problem. To accomplish this task, we describe a machine learning framework, that we called "Suggested Diagnosis", whose aim is to prioritize genetic variants in an exome/genome based on the probability of being disease-causing. To do so, our method leverages standard guidelines for germline variant interpretation as defined by the American College of Human Genomics (ACMG) and the Association for Molecular Pathology (AMP), inheritance information, phenotypic similarity, and variant quality. Starting from (1) the VCF file containing proband's variants, (2) the list of proband's phenotypes encoded in Human Phenotype Ontology terms, and optionally (3) the information about family members (if available), the "Suggested Diagnosis" ranks all the variants according to their machine learning prediction. This method significantly reduces the number of variants that need to be evaluated by geneticists by pinpointing causative variants in the very first positions of the prioritized list. Most importantly, our approach proved to be among the top performers within the CAGI6 Rare Genome Project Challenge, where it was able to rank the true causative variant among the first positions and, uniquely among all the challenge participants, increased the diagnostic yield of 12.5% by solving 2 undiagnosed cases.

A meta-analysis of diagnostic yield and clinical utility of genome and exome sequencing in pediatric rare and undiagnosed genetic diseases

PURPOSE

To systematically evaluate the diagnostic yield and clinical utility of genome sequencing (GS) and exome sequencing (ES; genome-wide sequencing [GWS]) in pediatric patients with rare and undiagnosed genetic diseases.

METHODS

We conducted a meta-analysis of studies published between 2011 and 2023. To address study heterogeneity, comparative analyses included within-cohort studies using random-effects models.

RESULTS

We identified 108 studies including 24,631 probands with diverse clinical indications. The pooled diagnostic yield among within-cohort studies (N = 13) for GWS was 34.2% (95% CI: 27.6-41.5; I2: 86%) vs 18.1% (95% CI: 13.1-24.6; I2: 89%) for non-GWS, with 2.4-times odds of diagnosis (95% CI: 1.40-4.04; P < .05). The pooled diagnostic yield among within-cohort studies (N = 3) for GS was 30.6% (95% CI: 18.6-45.9; I2: 79%) vs 23.2% (95% CI: 18.5-28.7; I2: 58%) for ES, with 1.7-times the odds of diagnosis (95% CI: 0.94-2.92; P = .13). In first-line testing, the diagnostic yield tended to be higher for GS than for ES across clinical subgroups. The pooled clinical utility among patients with a positive diagnosis was 58.7% (95% CI: 47.3-69.2; I2: 81%) for GS and 54.5% (95% CI: 40.7-67.6; I2: 87%) for ES.

CONCLUSION

GS appears to have a higher diagnostic yield than ES, with similar clinical utility per positive diagnosis.

Novel De Novo Intronic Variant of SYNGAP1 Associated With the Neurodevelopmental Disorders

BACKGROUND

SYNGAP1 encodes a Ras/Rap GTPase-activating protein that is predominantly expressed in the brain with the functional roles in regulating synaptic plasticity, spine morphogenesis, and cognition function. Pathogenic variants in SYNGAP1 have been associated with a spectrum of neurodevelopmental disorders characterized by developmental delays, intellectual disabilities, epilepsy, hypotonia, and the features of autism spectrum disorder. The aim of this study was to identify a novel SYNGAP1 gene variant linked to neurodevelopmental disorders and to evaluate the pathogenicity of the detected variant.

METHODS

A novel de novo intronic variant in SYNGAP1 was identified by Whole exome sequencing (WES) and confirmed by Sanger sequencing. Minigene assays were conducted to assess whether the intronic variant in SYNGAP1 influenced the normal splicing of mRNA.

RESULTS

A novel de novo intronic variant in SYNGAP1 (c.3582+2T>G) was indentified with clinical features suggestive of neurodevelopmental related disorders. Minigene splicing analysis demonstrated that this noncanonical splice site variant led to the activation of a cryptic acceptor splice site. Consequently, 101 base pairs of intron 16 were aberrantly retained in the mRNA, leading to a frameshift. This frameshift resulted in the introduction of a premature stop codon (TGA) in the coding sequence and the production of a truncated SYNGAP1 protein, potentially leding to loss of function and subsequent disruption of its biological roles.

CONCLUSION

Our findings highlight the significance of de novo pathogenic SYNGAP1 variants at the intron 16/exon 17 junction in the SYNGAP1-related neurodevelopmental disorders, providing novel insights into the genetic basis and diagnosis of these disabilities.

CAMK2; four genes, one syndrome? Delineation of genotype-phenotype correlations

Neurodevelopmental disorders are a heterogenous group of brain disorders impacting cognitive, adaptive, motor, and speech language development. With advancements in diagnostics an increasing number of causative genes are discovered, including synaptic genes. The calcium calmodulin dependent protein kinase type 2 (CAMK2) family is the most abundant kinase family in the synapse and has recently been established to cause NDD, with a growing number of unrelated NDD-individuals who carry pathogenic variations in one of the four CAMK2 genes. However, there is still much to learn about the specific phenotypic manifestations per CAMK2 paralog and per variant type, including the mechanism of how variants in these genes impact CAMK2 protein and synaptic functioning, and result in neurodevelopmental disorders. This review provides an overview of all CAMK2 cases published to date and reveals first genotype-phenotype correlations that can serve as a starting point to explain CAMK2 related symptoms, offering direction for future research.

ChromBPNet: bias factorized, base-resolution deep learning models of chromatin accessibility reveal cis-regulatory sequence syntax, transcription factor footprints and regulatory variants

Despite extensive mapping of cis-regulatory elements (cREs) across cellular contexts with chromatin accessibility assays, the sequence syntax and genetic variants that regulate transcription factor (TF) binding and chromatin accessibility at context-specific cREs remain elusive. We introduce ChromBPNet, a deep learning DNA sequence model of base-resolution accessibility profiles that detects, learns and deconvolves assay-specific enzyme biases from regulatory sequence determinants of accessibility, enabling robust discovery of compact TF motif lexicons, cooperative motif syntax and precision footprints across assays and sequencing depths. Extensive benchmarks show that ChromBPNet, despite its lightweight design, is competitive with much larger contemporary models at predicting variant effects on chromatin accessibility, pioneer TF binding and reporter activity across assays, cell contexts and ancestry, while providing interpretation of disrupted regulatory syntax. ChromBPNet also helps prioritize and interpret regulatory variants that influence complex traits and rare diseases, thereby providing a powerful lens to decode regulatory DNA and genetic variation.

Transcriptome-wide outlier approach identifies individuals with minor spliceopathies

RNA-sequencing has improved the diagnostic yield of individuals with rare diseases. Current analyses predominantly focus on identifying outliers in single genes that can be attributed to cis-acting variants within the gene locus. This approach overlooks causal variants with trans-acting effects on splicing transcriptome-wide, such as variants impacting spliceosome function. We present a transcriptomics-first method to diagnose individuals with rare diseases by examining transcriptome-wide patterns of splicing outliers. Using splicing outlier detection methods (FRASER and FRASER2) we characterized splicing outliers from whole blood for 390 individuals from the Genomics Research to Elucidate the Genetics of Rare Diseases (GREGoR) and Undiagnosed Diseases Network (UDN) consortia. We examined all samples for excess intron retention outliers in minor intron containing genes (MIGs). Minor introns, which make up about 0.5% of all introns in the human genome, are removed by small nuclear RNAs (snRNAs) in the minor spliceosome. This approach identified five individuals with excess intron retention outliers in MIGs, all of which were found to harbor rare, biallelic variants in minor spliceosome snRNAs. Four individuals had rare, compound heterozygous variants in RNU4ATAC, which aided the reclassification of four variants. Additionally, one individual had rare, highly conserved, compound heterozygous variants in RNU6ATAC that may disrupt the formation of the catalytic spliceosome, suggesting a novel gene-disease candidate. These results demonstrate that examining RNA-sequencing data for transcriptome-wide signatures can increase the diagnostic yield of individuals with rare diseases, provide variant-to-function interpretation of spliceopathies, and uncover novel disease gene associations.

The human and non-human primate developmental GTEx projects

Many human diseases are the result of early developmental defects. As most paediatric diseases and disorders are rare, children are critically underrepresented in research. Functional genomics studies primarily rely on adult tissues and lack critical cell states in specific developmental windows. In parallel, little is known about the conservation of developmental programmes across non-human primate (NHP) species, with implications for human evolution. Here we introduce the developmental Genotype-Tissue Expression (dGTEx) projects, which span humans and NHPs and aim to integrate gene expression, regulation and genetics data across development and species. The dGTEx cohort will consist of 74 tissue sites across 120 human donors from birth to adulthood, and developmentally matched NHP age groups, with additional prenatal and adult animals, with 126 rhesus macaques (Macaca mulatta) and 72 common marmosets (Callithrix jacchus). The data will comprise whole-genome sequencing, extensive bulk, single-cell and spatial gene expression profiles, and chromatin accessibility data across tissues and development. Through community engagement and donor diversity, the human dGTEx study seeks to address disparities in genomic research. Thus, dGTEx will provide a reference human and NHP dataset and tissue bank, enabling research into developmental changes in expression and gene regulation, childhood disorders and the effect of genetic variation on development.

Exome sequencing of UK birth cohorts

Birth cohort studies involve repeated surveys of large numbers of individuals from birth and throughout their lives. They collect information useful for a wide range of life course research domains, and biological samples which can be used to derive data from an increasing collection of omic technologies. This rich source of longitudinal data, when combined with genomic data, offers the scientific community valuable insights ranging from population genetics to applications across the social sciences. Here we present quality-controlled whole exome sequencing data from three UK birth cohorts: the Avon Longitudinal Study of Parents and Children (8,436 children and 3,215 parents), the Millenium Cohort Study (7,667 children and 6,925 parents) and Born in Bradford (8,784 children and 2,875 parents). The overall objective of this coordinated effort is to make the resulting high-quality data widely accessible to the global research community in a timely manner. We describe how the datasets were generated and subjected to quality control at the sample, variant and genotype level. We then present some preliminary analyses to illustrate the quality of the datasets and probe potential sources of bias. We introduce measures of ultra-rare variant burden to the variables available for researchers working on these cohorts, and show that the exome-wide burden of deleterious protein-truncating variants, S het burden, is associated with educational attainment and cognitive test scores. The whole exome sequence data from these birth cohorts (CRAM & VCF files) are available through the European Genome-Phenome Archive, and here we provide guidance for their use.

The genetic landscape of autism spectrum disorder in an ancestrally diverse cohort

Autism spectrum disorder (ASD) comprises neurodevelopmental disorders with wide variability in genetic causes and phenotypes, making it challenging to pinpoint causal genes. We performed whole exome sequencing on a modest, ancestrally diverse cohort of 195 families, including 754 individuals (222 with ASD), and identified 38,834 novel private variants. In 68 individuals with ASD (~30%), we identified 92 potentially pathogenic variants in 73 known genes, including BCORL1, CDKL5, CHAMP1, KAT6A, MECP2, and SETD1B. Additionally, we identified 158 potentially pathogenic variants in 120 candidate genes, including DLG3, GABRQ, KALRN, KCTD16, and SLC8A3. We also found 34 copy number variants in 31 individuals overlapping known ASD loci. Our work expands the catalog of ASD genetics by identifying hundreds of variants across diverse ancestral backgrounds, highlighting convergence on nervous system development and signal transduction. These findings provide insights into the genetic underpinnings of ASD and inform molecular diagnosis and potential therapeutic targets.

Examining the role of common variants in rare neurodevelopmental conditions

Although rare neurodevelopmental conditions have a large Mendelian component1, common genetic variants also contribute to risk2,3. However, little is known about how this polygenic risk is distributed among patients with these conditions and their parents nor its interplay with rare variants. It is also unclear whether polygenic background affects risk directly through alleles transmitted from parents to children, or whether indirect genetic effects mediated through the family environment4 also play a role. Here we addressed these questions using genetic data from 11,573 patients with rare neurodevelopmental conditions, 9,128 of their parents and 26,869 controls. Common variants explained around 10% of variance in risk. Patients with a monogenic diagnosis had significantly less polygenic risk than those without, supporting a liability threshold model5. A polygenic score for neurodevelopmental conditions showed only a direct genetic effect. By contrast, polygenic scores for educational attainment and cognitive performance showed no direct genetic effect, but the non-transmitted alleles in the parents were correlated with the child's risk, potentially due to indirect genetic effects and/or parental assortment for these traits4. Indeed, as expected under parental assortment, we show that common variant predisposition for neurodevelopmental conditions is correlated with the rare variant component of risk. These findings indicate that future studies should investigate the possible role and nature of indirect genetic effects on rare neurodevelopmental conditions, and consider the contribution of common and rare variants simultaneously when studying cognition-related phenotypes.

Differential expression analyses and detection of SNP loci associated with environmental variables: Are salinity and temperature factors involved in population differentiation and speciation in Odontesthes?

Environmental factors play a key role in individual adaptation to different local conditions. Because of this, studies about the physiological and genetic responses of individuals exposed to different natural environments offer clues about mechanisms involved in population differentiation, and as a subsequent result, speciation. Marine environments are especially suited to survey this kind of phenomena because they commonly harbor species adapted to different local conditions along a geographic continuum. Silversides belonging to Odontesthes are commonly distributed in tropical and temperate regions of South America and exhibit noticeable phenotypic plasticity, which allows them to adapt to contrasting environments. In this study, the genetic expression of O. argentinensis sampled along the Uruguayan Atlantic coast and estuarine adjacent areas was investigated. In addition, the correlation between individual genotypes and environmental variables was also analysed in O. argentinensis and O. bonariensis. Results obtained suggest a differential expression pattern of low magnitude among individuals from the different areas sampled and a correlation between several SNP loci and environmental variables. The analyses carried out did not show a clear differentiation among individuals sampled along different salinity regimens, but enriched GOTerms seem to be driven by water oxygen content. On the other hand, a total of 46 SNPs analysed in O. argentinensis and O. bonariensis showed a correlation with salinity and temperature. Although none of the correlated SNPs and corresponding genes from our both analyses were directly associated with hypoxia, genes related to the cardiovascular system and muscle cell differentiation were found. All these genes are interesting candidates for future studies since they are closely related to the differentially expressed genes. Although salinity was also mentioned as an important parameter limiting introgression between O. argentinensis and O. bonariensis, it was found that salinity does not drive differential expression in O. argentinensis, but rather oxygen levels. Moreover, salinity does not directly affect the structure and genetic divergence of the populations, they appear to be structured based on their degree of isolation and geographical distance between them. Further studies, like genome-wide analyses, could help to elucidate additional genes adapted to the different environments in these silverside species.

[Genetic diseases of epigenetic machinery]

The development of sequencing technologies and their increased accessibility in clinical services and genetic laboratories have considerably accelerated the identification of genetic variants associated with rare diseases (RDs). Among these, Mendelian disorders of the epigenetic machinery (MDEM) are rare monogenic diseases characterized by the presence of mutations in genes encoding epigenetic regulators that play a key role in organismal development and cellular functions. Loss of function of these regulators is expected to lead to epigenetic modifications that profoundly affect genome expression and cellular identity. Disruptions in DNA methylation profiles have been documented in MDEMs, emerging as a useful diagnostic tool. The current challenge is to determine whether and how these epigenomic alterations drive the mechanisms underlying the clinical manifestations in patients suffering from this class of diseases. Studying MDEMs may therefore shed light on the important role of epigenetic information in health and disease, particularly the mechanisms involved in the development and understanding of complex pathologies, such as neurodevelopmental disorders and cancer.

Unveiling a de novo SYNGAP1 variant: Clinical progression and management challenges in a case of developmental and epileptic encephalopathy - A case report

Developmental and epileptic encephalopathies (DEEs), such as SYNGAP1-related DEE, are marked by severe developmental delays and pharmaco-resistant seizures due to specific genetic variants. This case report focuses on a 9-year-old male with a de novo SYNGAP1 variant (c.1267del, p.Tyr423Metfs*17), illustrating the diagnostic and treatment challenges. Initially experiencing developmental delays and later, misdiagnosed tics, he was diagnosed with epilepsy with eyelid myoclonia at seven. His case includes key SYNGAP1 encephalopathy symptoms: intellectual disability, behavioral issues, and generalized epilepsy resistant to antiseizure medication. The identification of a specific variant adds to our knowledge, suggesting the necessity of considering SYNGAP1-related DEE for unexplained neurodevelopmental delays and seizures. This case underlines the need for a personalized treatment approach focusing on quality of life and symptom management, advancing our understanding and treatment practices for genetic developmental and epileptic encephalopathy.

Activity-assembled nBAF complex mediates rapid immediate early gene transcription by regulating RNA polymerase II productive elongation

Signal-dependent RNA polymerase II (RNA Pol II) productive elongation is an integral component of gene transcription, including that of immediate early genes (IEGs) induced by neuronal activity. However, it remains unclear how productively elongating RNA Pol II overcomes nucleosomal barriers. Using RNAi, three degraders, and several small-molecule inhibitors, we show that the mammalian switch/sucrose non-fermentable (SWI/SNF) complex of neurons (neuronal BRG1/BRM-associated factor or nBAF) is required for activity-induced transcription of neuronal IEGs, including Arc. The nBAF complex facilitates promoter-proximal RNA Pol II pausing and signal-dependent RNA Pol II recruitment (loading) and, importantly, mediates productive elongation in the gene body via interaction with the elongation complex and elongation-competent RNA Pol II. Mechanistically, RNA Pol II elongation is mediated by activity-induced nBAF assembly (especially ARID1A recruitment) and its ATPase activity. Together, our data demonstrate that the nBAF complex regulates several aspects of RNA Pol II transcription and reveal mechanisms underlying activity-induced RNA Pol II elongation. These findings may offer insights into human maladies etiologically associated with mutational interdiction of BAF functions.

Sex-specific perturbations of neuronal development caused by mutations in the autism risk gene DDX3X

DDX3X is an X-linked RNA helicases that escapes X chromosome inactivation and is expressed at higher levels in female brains. Mutations in DDX3X are associated with intellectual disability (ID) and autism spectrum disorder (ASD) and are predominantly identified in females. Using cellular and mouse models, we show that Ddx3x mediates sexual dimorphisms in brain development at a molecular, cellular, and behavioral level. During cortical neuronal development, Ddx3x sustains a female-biased signature of enhanced ribosomal biogenesis and mRNA translation. Female neurons display higher levels of ribosomal proteins and larger nucleoli, and these sex dimorphisms are obliterated by Ddx3x loss. Ddx3x regulates dendritic outgrowth in a sex- and dose-dependent manner in both female and male neurons, and dendritic spine development only in female neurons. Further, ablating Ddx3x conditionally in forebrain neurons is sufficient to yield sex-specific changes in developmental outcomes and motor function. Together, these findings pose Ddx3x as a mediator of sexual differentiation during neurodevelopment and open new avenues to understand sex differences in health and disease.

Long-read genome sequencing and variant reanalysis increase diagnostic yield in neurodevelopmental disorders

Variant detection from long-read genome sequencing (lrGS) has proven to be more accurate and comprehensive than variant detection from short-read genome sequencing (srGS). However, the rate at which lrGS can increase molecular diagnostic yield for rare disease is not yet precisely characterized. We performed lrGS using Pacific Biosciences "HiFi" technology on 96 short-read-negative probands with rare diseases that were suspected to be genetic. We generated hg38-aligned variants and de novo phased genome assemblies, and subsequently annotated, filtered, and curated variants using clinical standards. New disease-relevant or potentially relevant genetic findings were identified in 16/96 (16.7%) probands, nine of which (8/96, ∼9.4%) harbored pathogenic or likely pathogenic variants. Nine probands (∼9.4%) had variants that were accurately called in both srGS and lrGS and represent changes to clinical interpretation, mostly from recently published gene-disease associations. Seven cases included variants that were only correctly interpreted in lrGS, including copy-number variants (CNVs), an inversion, a mobile element insertion, two low-complexity repeat expansions, and a 1 bp deletion. While evidence for each of these variants is, in retrospect, visible in srGS, they were either not called within srGS data, were represented by calls with incorrect sizes or structures, or failed quality control and filtration. Thus, while reanalysis of older srGS data clearly increases diagnostic yield, we find that lrGS allows for substantial additional yield (7/96, 7.3%) beyond srGS. We anticipate that as lrGS analysis improves, and as lrGS data sets grow allowing for better variant-frequency annotation, the additional lrGS-only rare disease yield will grow over time.

The Neurodevelopmental Protein POGZ Suppresses Metastasis in Triple-Negative Breast Cancer by Attenuating TGFβ Signaling

The pogo transposable element-derived zinc finger protein, POGZ, is notably associated with neurodevelopmental disorders through its role in gene transcription. Many proteins involved in neurological development are often dysregulated in cancer, suggesting a potential role for POGZ in tumor biology. Here, we provided experimental evidence that POGZ influences the growth and metastatic spread of triple-negative breast cancers (TNBC). In well-characterized models of TNBC, POGZ exerted a dual role, both as a tumor promoter and metastasis suppressor. Mechanistically, loss of POGZ potentiated TGFβ pathway activation to exert cytostatic effects while simultaneously increasing the mesenchymal and migratory properties of breast tumors. Although POGZ levels are elevated in human breast cancers, the most aggressive forms of TNBC tumors, including those with increased mesenchymal and metastatic properties, exhibit dampened POGZ levels, and low POGZ expression was associated with inferior clinical outcomes in these tumor types. Taken together, these data suggest that POGZ is a critical suppressor of the early stages of the metastatic cascade. Significance: The POGZ neurodevelopmental protein plays dual functions in triple-negative breast cancers as a tumor promoter and metastasis suppressor, inhibiting TGFβ-regulated EMT to limit breast cancer metastatic progression.

Four heterozygous de novo variants in ASXL3 identified with Bainbridge-Ropers syndrome and further dissecting published genotype-phenotype spectrum

Bainbridge-Ropers syndrome (BRPS) is a recently described neurodevelopmental genetic disorder associated with de novo truncating variants in additional sex combs like 3 (ASXL3) on chromosome 18q12.1. Trio-based exome sequencing was conducted on patients admitted to the Children's Hospital Affiliated to Shandong University and diagnosed with unexplained intellectual disabilities or developmental delay between June 2022 and January 2024. De novo truncation of ASXL3 was identified in four patients, and the pathogenic variants and their de novo status were validated using Sanger sequencing. Comprehensive clinical phenotype-genotype information of all previously reported patients with BRPS was collected and summarized. The common clinical manifestations observed in the four patients included language and intellectual disabilities or psychomotor retardation. Genetic analysis revealed that patient 1 carried a de novo heterozygous variant, c.1667_1668del (p.Thr556Arpfs*3), whereas patient 2 had a novel heterozygous frameshift variant of ASXL3, c.3324del (p.Lys1109Serfs*34). These two variants have not been documented to date. Additionally, patients 3 and 4 exhibited a de novo variant, c.4678C > T (p.Arg1560Ter). Based on the combined assessment of clinical phenotypes and genetic testing results, it was postulated that all four children presented with BRPS syndrome caused by pathogenic variations in ASXL3. The present study complements the range of ASXL3 mutational and phenotypic spectra in the population, highlighting subtle distinctions in clinical manifestations between Chinese patients and other racial groups. The reporting of additional cases will contribute to further elucidating the function of ASXL3 and establishing a solid foundation for clinical diagnosis and treatment.

Common variants increase risk for congenital diaphragmatic hernia within the context of de novo variants

Congenital diaphragmatic hernia (CDH) is a severe congenital anomaly often accompanied by other structural anomalies and/or neurobehavioral manifestations. Rare de novo protein-coding variants and copy-number variations contribute to CDH in the population. However, most individuals with CDH remain genetically undiagnosed. Here, we perform integrated de novo and common-variant analyses using 1,469 CDH individuals, including 1,064 child-parent trios and 6,133 ancestry-matched, unaffected controls for the genome-wide association study. We identify candidate CDH variants in 15 genes, including eight novel genes, through deleterious de novo variants. We further identify two genomic loci contributing to CDH risk through common variants with similar effect sizes among Europeans and Latinx. Both loci are in putative transcriptional regulatory regions of developmental patterning genes. Estimated heritability in common variants is ∼19%. Strikingly, there is no significant difference in estimated polygenic risk scores between isolated and complex CDH or between individuals harboring deleterious de novo variants and individuals without these variants. The data support a polygenic model as part of the CDH genetic architecture.

Specific catalytically impaired DDX3X mutants form sexually dimorphic hollow condensates

Mutations in the RNA helicase DDX3X, implicated in various cancers and neurodevelopmental disorders, often impair RNA unwinding and translation. However, the mechanisms underlying the impairment and the differential interactions of DDX3X mutants with wild-type (WT) X-linked DDX3X and Y-linked homolog DDX3Y remain elusive. This study reveals that specific DDX3X mutants more frequently found in disease form distinct hollow condensates in cells. Using a combined structural, biochemical, and single-molecule microscopy study, we show that reduced ATPase and RNA release activities contribute to condensate formation and these catalytic deficits result from inhibiting the catalytic cycle at multiple steps. Proteomic investigations further demonstrate that these hollow condensates sequester WT DDX3X/DDX3Y and other proteins crucial for diverse signaling pathways. WT DDX3X enhances the dynamics of heterogeneous mutant/WT hollow condensates more effectively than DDX3Y. These findings offer valuable insights into the catalytic defects of specific DDX3X mutants and their differential interactions with wild-type DDX3X and DDX3Y, potentially explaining sex biases in disease.

Deficiency of DDX3X results in neurogenesis defects and abnormal behaviors via dysfunction of the Notch signaling

The molecular mechanisms underlying the neurodevelopmental disorders (NDDs) caused by DDX3X variants remain poorly understood. In this study, we validated that de novo DDX3X variants are enriched in female developmental delay (DD) patients and mainly affect the evolutionarily conserved amino acids based on a meta-analysis of 46,612 NDD trios. We generated a ddx3x deficient zebrafish allele, which exhibited reduced survival rate, DD, microcephaly, adaptation defects, anxiolytic behaviors, social interaction deficits, and impaired spatial recognitive memory. As revealed by single-nucleus RNA sequencing and biological validations, ddx3x deficiency leads to reduced neural stem cell pool, decreased total neuron number, and imbalanced differentiation of excitatory and inhibitory neurons, which are responsible for the behavioral defects. Indeed, the supplementation of L-glutamate or glutamate receptor agonist ly404039 could partly rescue the adaptation and social deficits. Mechanistically, we reveal that the ddx3x deficiency attenuates the stability of the crebbp mRNA, which in turn causes downregulation of Notch signaling and defects in neurogenesis. Our study sheds light on the molecular pathology underlying the abnormal neurodevelopment and behavior of NDD patients with DDX3X mutations, as well as providing potential therapeutic targets for the precision treatment.

Large-scale evaluation of outcomes after a genetic diagnosis in children with severe developmental disorders

Purpose

We sought to evaluate outcomes for clinical management after a genetic diagnosis from the Deciphering Developmental Disorders study.

Methods

Individuals in the Deciphering Developmental Disorders study who had a pathogenic/likely pathogenic genotype in the DECIPHER database were selected for inclusion (n = 5010). Clinical notes from regional clinical genetics services notes were reviewed to assess predefined clinical outcomes relating to interventions, prenatal choices, and information provision.

Results

Outcomes were recorded for 4237 diagnosed probands (85% of those eligible) from all 24 recruiting centers across the United Kingdom and Ireland. Clinical management was reported to have changed in 28% of affected individuals. Where individual-level interventions were recorded, additional diagnostic or screening tests were started in 903 (21%) probands through referral to a range of different clinical specialties, and stopped or avoided in a further 26 (0.6%). Disease-specific treatment was started in 85 (2%) probands, including seizure-control medications and dietary supplements, and contra-indicated medications were stopped or avoided in a further 20 (0.5%). The option of prenatal/preimplantation genetic testing was discussed with 1204 (28%) families, despite the relatively advanced age of the parents at the time of diagnosis. Importantly, condition-specific information or literature was given to 3214 (76%) families, and 880 (21%) were involved in family support groups. In the most common condition (KBG syndrome; 79 [2%] probands), clinical interventions only partially reflected the temporal development of phenotypes, highlighting the importance of consensus management guidelines and patient support groups.

Conclusion

Our results underscore the importance of achieving a clinico-molecular diagnosis to ensure timely onward referral of patients, enabling appropriate care and anticipatory surveillance, and for accessing relevant patient support groups.

Epigenomic newborn screening for conditions with intellectual disability and autistic features in Australian newborns

This study describes a protocol to assess a novel workflow called Epi-Genomic Newborn Screening (EpiGNs) on 100,000 infants from the state of Victoria, Australia. The workflow uses a first-tier screening approach called methylation-specific quantitative melt analysis (MS-QMA), followed by second and third tier testing including targeted methylation and copy number variation analyzes with droplet digital PCR, EpiTYPER system and low-coverage whole genome sequencing. EpiGNs utilizes only two 3.2 mm newborn blood spot punches to screen for genetic conditions, including fragile X syndrome, Prader-Willi syndrome, Angelman syndrome, Dup15q syndrome and sex chromosome aneuploidies. The program aims to: identify clinically actionable methylation screening thresholds for the first-tier screen and estimate prevalence for the conditions screened.

Regulation of cellular and systemic sphingolipid homeostasis

One hundred and fifty years ago, Johann Thudichum described sphingolipids as unusual "Sphinx-like" lipids from the brain. Today, we know that thousands of sphingolipid molecules mediate many essential functions in embryonic development and normal physiology. In addition, sphingolipid metabolism and signalling pathways are dysregulated in a wide range of pathologies, and therapeutic agents that target sphingolipids are now used to treat several human diseases. However, our understanding of sphingolipid regulation at cellular and organismal levels and their functions in developmental, physiological and pathological settings is rudimentary. In this Review, we discuss recent advances in sphingolipid pathways in different organelles, how secreted sphingolipid mediators modulate physiology and disease, progress in sphingolipid-targeted therapeutic and diagnostic research, and the trans-cellular sphingolipid metabolic networks between microbiota and mammals. Advances in sphingolipid biology have led to a deeper understanding of mammalian physiology and may lead to progress in the management of many diseases.

Key roles of C2/GAP domains in SYNGAP1-related pathophysiology

Mutations in SYNGAP1 are a common genetic cause of intellectual disability (ID) and a risk factor for autism. SYNGAP1 encodes a synaptic GTPase-activating protein (GAP) that has both signaling and scaffolding roles. Most pathogenic variants of SYNGAP1 are predicted to result in haploinsufficiency. However, some affected individuals carry missense mutations in its calcium/lipid binding (C2) and GAP domains, suggesting that many clinical features result from loss of functions carried out by these domains. To test this hypothesis, we targeted the exons encoding the C2 and GAP domains of SYNGAP. Rats heterozygous for this deletion exhibit reduced exploration and fear extinction, altered social investigation, and spontaneous seizures-key phenotypes shared with Syngap heterozygous null rats. Together, these findings indicate that the reduction of SYNGAP C2/GAP domain function is a main feature of SYNGAP haploinsufficiency. This rat model provides an important system for the study of ID, autism, and epilepsy.

Oxygen-induced stress reveals context-specific gene regulatory effects in human brain organoids

The interaction between genetic variants and environmental stressors is key to understanding the mechanisms underlying neurological diseases. In this study, we used human brain organoids to explore how varying oxygen levels expose context-dependent gene regulatory effects. By subjecting a genetically diverse panel of 21 brain organoids to hypoxic and hyperoxic conditions, we identified thousands of gene regulatory changes that are undetectable under baseline conditions, with 1,745 trait-associated genes showing regulatory effects only in response to oxygen stress. To capture more nuanced transcriptional patterns, we employed topic modeling, which revealed context-specific gene regulation linked to dynamic cellular processes and environmental responses, offering a deeper understanding of how gene regulation is modulated in the brain. These findings underscore the importance of genotype-environment interactions in genetic studies of neurological disorders and provide new insights into the hidden regulatory mechanisms influenced by environmental factors in the brain.

DDX3X syndrome: From clinical phenotypes to biological insights

DDX3X syndrome is a neurodevelopmental disorder accounting for up to 3% of cases of intellectual disability (ID) and affecting primarily females. Individuals diagnosed with DDX3X syndrome can also present with behavioral challenges, motor delays and movement disorders, epilepsy, and congenital malformations. DDX3X syndrome is caused by mutations in the X-linked gene DDX3X, which encodes a DEAD-box RNA helicase with critical roles in RNA metabolism, including mRNA translation. Emerging discoveries from animal models are unveiling a fundamental role of DDX3X in neuronal differentiation and development, especially in the neocortex. Here, we review the current knowledge of genetic and neurobiological mechanisms underlying DDX3X syndrome and their relationship with clinical phenotypes.

O-GlcNAc transferase congenital disorder of glycosylation (OGT-CDG): Potential mechanistic targets revealed by evaluating the OGT interactome

O-GlcNAc transferase (OGT) is the sole enzyme responsible for the post-translational modification of O-GlcNAc on thousands of target nucleocytoplasmic proteins. To date, nine variants of OGT that segregate with OGT Congenital Disorder of Glycosylation (OGT-CDG) have been reported and characterized. Numerous additional variants have been associated with OGT-CDG, some of which are currently undergoing investigation. This disorder primarily presents with global developmental delay and intellectual disability (ID), alongside other variable neurological features and subtle facial dysmorphisms in patients. Several hypotheses aim to explain the etiology of OGT-CDG, with a prominent hypothesis attributing the pathophysiology of OGT-CDG to mutations segregating with this disorder disrupting the OGT interactome. The OGT interactome consists of thousands of proteins, including substrates as well as interactors that require noncatalytic functions of OGT. A key aim in the field is to identify which interactors and substrates contribute to the primarily neural-specific phenotype of OGT-CDG. In this review, we will discuss the heterogenous phenotypic features of OGT-CDG seen clinically, the variable biochemical effects of mutations associated with OGT-CDG, and the use of animal models to understand this disorder. Furthermore, we will discuss how previously identified OGT interactors causal for ID provide mechanistic targets for investigation that could explain the dysregulated gene expression seen in OGT-CDG models. Identifying shared or unique altered pathways impacted in OGT-CDG patients will provide a better understanding of the disorder as well as potential therapeutic targets.

To Ub or not to Ub: The epic dilemma of histones that regulate gene expression and epigenetic cross-talk

A dynamic array of histone post-translational modifications (PTMs) regulate diverse cellular processes in the eukaryotic chromatin. Among them, histone ubiquitination is particularly complex as it alters nucleosome surface area fostering intricate cross-talk with other chromatin modifications. Ubiquitin signaling profoundly impacts DNA replication, repair, and transcription. Histones can undergo varied extent of ubiquitination such as mono, multi-mono, and polyubiquitination, which brings about distinct cellular fates. Mechanistic studies of the ubiquitin landscape in chromatin have unveiled a fascinating tapestry of events that orchestrate gene regulation. In this review, we summarize the key contributors involved in mediating different histone ubiquitination and deubiquitination events, and discuss their mechanism which impacts cell transcriptional identity and DNA damage response. We also focus on the proteins bearing epigenetic reader modules critical in discerning site-specific histone ubiquitination, pivotal for establishing complex epigenetic crosstalk. Moreover, we highlight the role of histone ubiquitination in different human diseases including neurodevelopmental disorders and cancer. Overall the review elucidates the intricate orchestration of histone ubiquitination impacting diverse cellular functions and disease pathogenesis, and provides insights into the current challenges of targeting them for therapeutic interventions.

The molecular genetics of PI3K/PTEN/AKT/mTOR pathway in the malformations of cortical development

Malformations of cortical development (MCD) are a group of developmental disorders characterized by abnormal cortical structures caused by genetic or harmful environmental factors. Many kinds of MCD are caused by genetic variation. MCD is the common cause of intellectual disability and intractable epilepsy. With rapid advances in imaging and sequencing technologies, the diagnostic rate of MCD has been increasing, and many potential genes causing MCD have been successively identified. However, the high genetic heterogeneity of MCD makes it challenging to understand the molecular pathogenesis of MCD and to identify effective targeted drugs. Thus, in this review, we outline important events of cortical development. Then we illustrate the progress of molecular genetic studies about MCD focusing on the PI3K/PTEN/AKT/mTOR pathway. Finally, we briefly discuss the diagnostic methods, disease models, and therapeutic strategies for MCD. The information will facilitate further research on MCD. Understanding the role of the PI3K/PTEN/AKT/mTOR pathway in MCD could lead to a novel strategy for treating MCD-related diseases.

Cell type-specific dysregulation of gene expression due to Chd8 haploinsufficiency during mouse cortical development

Disruptive variants in the chromodomain helicase CHD8, which acts as a transcriptional regulator during neurodevelopment, are strongly associated with risk for autism spectrum disorder (ASD). Loss of CHD8 function is hypothesized to perturb gene regulatory networks in the developing brain, thereby contributing to ASD etiology. However, insight into the cell type-specific transcriptional effects of CHD8 loss of function remains limited. We used single-cell and single-nucleus RNA-sequencing to globally profile gene expression and identify dysregulated genes in the embryonic and juvenile wild type and Chd8 +/- mouse cortex, respectively. Chd8 and other ASD risk-associated genes showed a convergent expression trajectory that was largely conserved between the mouse and human developing cortex, increasing from the progenitor zones to the cortical plate. Genes associated with risk for neurodevelopmental disorders and genes involved in neuron projection development, chromatin remodeling, signaling, and migration were dysregulated in Chd8 +/- embryonic day (E) 12.5 radial glia. Genes implicated in synaptic organization and activity were dysregulated in Chd8 +/- postnatal day (P) 25 deep- and upper-layer excitatory cortical neurons, suggesting a delay in synaptic maturation or impaired synaptogenesis due to CHD8 loss of function. Our findings reveal a complex pattern of transcriptional dysregulation in Chd8 +/- developing cortex, potentially with distinct biological impacts on progenitors and maturing neurons in the excitatory neuronal lineage.

Behavioural and neurodevelopmental characteristics of SYNGAP1

BACKGROUND

SYNGAP1 variants are associated with varying degrees of intellectual disability (ID), developmental delay (DD), epilepsy, autism, and behavioural difficulties. These features may also be observed in other monogenic conditions. There is a need to systematically compare the characteristics of SYNGAP1 with other monogenic causes of ID and DD to identify features unique to the SYNAGP1 phenotype. We aimed to contrast the neurodevelopmental and behavioural phenotype of children with SYNGAP1-related ID (SYNGAP1-ID) to children with other monogenic conditions and a matched degree of ID.

METHODS

Participants were identified from the IMAGINE-ID study, a UK-based, national cohort study of neuropsychiatric risk in children with ID of known genetic origin. Thirteen children with SYNGAP1 variants (age 4-16 years; 85% female) were matched (2:1) with 26 controls with other monogenic causes of ID for chronological and mental age, sex, socio-economic deprivation, adaptive behaviour, and physical health difficulties. Caregivers completed the Development and Wellbeing Assessment (DAWBA) and physical health questionnaires.

RESULTS

Our results demonstrate that seizures affected children with SYNGAP1-ID (84.6%) more frequently than the ID-comparison group (7.6%; p =  < 0.001). Fine-motor development was disproportionally impaired in SYNGAP1-ID, with 92.3% of children experiencing difficulties compared to 50% of ID-comparisons(p = 0.03). Gross motor and social development did not differ between the two groups. Children with SYNGAP1-ID were more likely to be non-verbal (61.5%) than ID-comparisons (23.1%; p = 0.01). Those children able to speak, spoke their first words at the same age as the ID-comparison group (mean = 3.25 years), yet achieved lower language competency (p = 0.04). Children with SYNGAP1-ID compared to the ID-comparison group were not more likely to meet criteria for autism (SYNGAP1-ID = 46.2%; ID-comparison = 30.7%; p = .35), attention-deficit hyperactivity disorder (15.4%;15.4%; p = 1), generalised anxiety (7.7%;15.4%; p = .49) or oppositional defiant disorder (7.7%;0%; p = .15).

CONCLUSION

For the first time, we demonstrate that SYNGAP1-ID is associated with fine motor and language difficulties beyond those experienced by children with other genetic causes of DD and ID. Targeted occupational and speech and language therapies should be incorporated early into SYNGAP1-ID management.

Investigation of Pogz Gene Variants in Non-Syndromic Autism Spectrum Disorder

Introduction

Genetic factors play an important role in the etiopathogenesis of autism spectrum disorder (ASD). The Pogo Transposable Element with ZNF Domain protein (POGZ) gene (MIM*614787) has been reported to be one of the most frequently mutated genes associated with ASD. This study aims to analyze the exonic regions of the POGZ gene in individuals diagnosed with non-syndromic ASD.

Methods

Fifty-one non-syndromic cases diagnosed with ASD according to the DSM-V diagnostic criteria, aged 2-18 years, were included in the study. The healthy control group consisted of 50 children of similar age groups without neurodevelopmental problems. Amplicons produced using deep intronic primers covering the mRNA-encoded regions of the POGZ gene from at least 50 base pairs were sequenced by Next Generation Sequencing Analysis.

Results

No pathogenic or likely pathogenic variants reported in open-access databases (ClinVar, HGMD, etc.) were detected in the case group. In the ASD and healthy control groups, rs113396244, rs11204811, rs779479223, rs772352054, rs3831142, rs112072925, rs227453 and rs142860188 variants were determined. The rs3831142, rs112072925, rs2274535, rs142860188 variants were found statistically significant in the ASD group. The distribution of the cases with detected single nucleotide polymorphisms (SNPs) according to gender was not statistically significant.

Conclusion

The variants identified as statistically significant within the patient group are situated in regions that encompass both the HP1-ZNF and DDE domains of the protein. Given the crucial role that the DDE domain plays, particularly in fetal brain development and neurogenesis, these four variants may potentially possess modifying and/or predisposing effects in the context of ASD.

Bayesian Rare Variant Analysis Identifies Novel Schizophrenia Putative Risk Genes

The genetics of schizophrenia is so complex that it involves both common variants and rare variants. Rare variant association studies of schizophrenia are challenging because statistical methods for rare variant analysis are under-powered due to the rarity of rare variants. The recent Schizophrenia Exome meta-analysis (SCHEMA) consortium, the largest consortium in this field to date, has successfully identified 10 schizophrenia risk genes from ultra-rare variants by burden test, while more risk genes remain to be discovered by more powerful rare variant association test methods. In this study, we use a recently developed Bayesian rare variant association method that is powerful for detecting sparse rare risk variants that implicates 88 new candidate risk genes associated with schizophrenia from the SCHEMA case-control sample. These newly identified genes are significantly enriched in autism risk genes and GO enrichment analysis indicates that new candidate risk genes are involved in mechanosensory behavior, regulation of cell size, neuron projection morphogenesis, and plasma-membrane-bounded cell projection morphogenesis, that may provide new insights on the etiology of schizophrenia.