Biology subjects

Kleefstra, T.

Publications and source records attributed to Kleefstra, T..

10 recordsLinked to original sources

bioRxiv2026

SysNDD: A Systematic Database for Neurodevelopmental Disorders

Neurodevelopmental disorders (NDDs) are clinically and genetically heterogeneous, and evidence linking additional genes to disease evolves rapidly. We developed SysNDD, an open-access, expert-curated resource that represents distinct gene-inheritance-disease associations as entities with standardized confidence, phenotype, and variant annotations. Each entity retains its curation history, so its evidence category can change as evidence accumulates. Currently, SysNDD contains 4,275 entities curated from 4,932 publications. Of these, 3,758 entities involving 3,271 genes describe NDDs; the remainder record non-NDD disorders, nearly all linked to NDD-associated genes, included for completeness. Regarding NDD evidence categories, 1,838 genes are Definitive, 179 Moderate, 1,248 Limited, and 6 Refuted. The entity model captures inheritance-specific disorders, including 220 genes with both autosomal dominant and autosomal recessive NDD associations. Comparison with seven other NDD gene resources showed complementary coverage, and evidence categories largely agreed with those of ClinGen, Gene2Phenotype, and PanelApp for shared gene-disease pairs. NDD genes formed distinct molecular modules, whereas associated disorders formed broad, overlapping phenotype groups that corresponded to those modules only selectively. SysNDD provides a continuously maintained, programmatically accessible framework for gene-disease evidence assessment, inheritance-aware interpretation, and systematic NDD research.

genetics↗

bioRxiv2026

The evolutionarily conserved EHMT1/G9a histone methyltransferase family regulates sleep maintenance through ROS homeostasis in insulin-producing cells

Sleep disturbances are a common, still poorly characterized feature of Kleefstra syndrome (KLEFS1), a neurodevelopmental disorder caused by rare variants in the epigenetic regulator EHMT1. The gap in understanding the characteristics and origin of these sleep disturbances poses a major barrier for therapy development. In this cross-species study, we reveal that 70% of individuals with KLEFS1 experience severe sleep maintenance insomnia, marked by fragmented sleep due to frequent night awakenings. Furthermore, common genetic variation at the EHMT1 locus was associated with short sleep and insomnia symptoms in the general population. Drosophila mutants of the EHMT1 orthologue G9a recapitulate these phenotypes, exhibiting reduced and fragmented sleep. We show that G9a is required in insulin-producing cells (IPCs) and the fat body, in the latter during development, to ensure adult sleep integrity. Untargeted metabolomics revealed widespread metabolic dysregulation in G9a mutants, particularly affecting methionine metabolism. Mutants exhibited reduced methionine and elevated methionine sulfoxide (Met-SO), pointing to increased reactive oxygen species (ROS). Redox sensors revealed increased H2O2-dependent oxidation in the larval brain and an elevated glutathione redox potential in IPCs during development but not in adulthood. IPC-specific knockdown of MsrA, the enzyme that reduces Met-SO back to methionine, reproduced sleep fragmentation. Developmental, but not acute, antioxidant treatment fully restored adult sleep consolidation, demonstrating that G9a safeguards sleep via ROS homeostasis in early life. Finally, we show that a Drosophila sleep-restriction paradigm based on human sleep-restriction therapy can override the developmental defects and restore sleep continuity in adulthood. Our findings establish an evolutionarily conserved role for EHMT1/G9a in sleep regulation and provide a mechanistic framework to understand and treat sleep disturbances in KLEFS1.

genetics↗

bioRxiv2025

De novo heterozygous variants in EHMT2 genocopy Kleefstra syndrome via loss of G9a methyltransferase activity

EHMT1 and EHMT2 genes encode human euchromatin histone lysine methyltransferase 1 and 2 (EHMT1 alias GLP; EHMT2 alias G9a) that form heteromeric GLP/G9a complexes with essential roles in epigenetic regulation of gene expression. While EHMT1 haploinsufficiency has been established as the cause of Kleefstra syndrome 1, the pathogenesis of G9a dysfunction in human disease remains largely unknown. We identified seven de novo EHMT2 variants in patients with clinical presentation, episignatures, histone modifications and transcriptomic profiles similar to those of Kleefstra syndrome 1. In vitro studies revealed that these variants encode for structurally stable G9a proteins that are catalytically incompetent due to aberrant interactions either with histone H3 tail or with S-adenosylmethionine. Heterozygous mice carrying a patient-derived variant exhibited growth retardation, facial/skull dysmorphia and aberrant behavior. Here we report pathogenic EHMT2 variants that likely exert dominant-negative effect on GLP/G9a complexes and thus genocopy the EHMT1 haploinsufficiency via a distinct molecular mechanism, defining an autosomal dominant EHMT2-related Kleefstra syndrome.

genetics↗

bioRxiv2022

The role of the gut microbiota in patients with Kleefstra syndrome

Kleefstra Syndrome (KS) is a rare monogenetic syndrome, caused by haploinsufficiency of the EHMT1 gene, an important regulator of neurodevelopment. The clinical features of KS include intellectual disability, autistic behavior and gastrointestinal problems. The gut microbiota may constitute a, yet unexplored, mechanism underlying clinical variation, as they are an important modifier of the gut-brain-axis. To test whether variation in the gut microbiota is part of KS, we investigated the gut microbiota composition of 23 individuals with KS (patients) and 40 of their family members. Both alpha and beta diversity of patients were different from their family members. Genus Coprococcus 3 was lower in abundance in patients compared to family members. Moreover, abundance of genus Merdibacter was lower in patients versus family members, but only in the participants reporting intestinal complaints. Within the patient group, behavioral problems explained 7% variance in the beta diversity. Also, within this group, we detected higher levels of Coprococcus 3 and Atopobiaceae - uncultured associated with higher symptoms severity. Our results show significant differences in the gut microbiota composition of patients with KS compared to their family members, suggesting that these differences are part of the KS phenotype.

microbiology↗

bioRxiv2021

Loss-of-function variants in the schizophrenia risk gene SETD1A alter neuronal network activity in human neurons through cAMP/PKA pathway

Heterozygous loss-of-function (LoF) mutations in SETD1A, which encodes a subunit of histone H3 lysine 4 methyltransferase, were shown to cause a novel neurodevelopmental syndrome and increase the risk for schizophrenia. We generated excitatory/inhibitory neuronal networks from human induced pluripotent stem cells with a SETD1A heterozygous LoF mutation (SETD1A+/-) using CRISPR/Cas9. Our data show that SETD1A haploinsufficiency resulted in morphologically increased dendritic complexity and functionally increased bursting activity. This network phenotype was primarily driven by SETD1A haploinsufficiency in glutamatergic neurons. In accordance with the functional changes, transcriptomic profiling revealed perturbations in gene sets associated with glutamatergic synaptic function. At the molecular level, we identified specific changes in the cAMP/PKA pathway pointing toward a hyperactive cAMP pathway in SETD1A+/- neurons. Finally, by pharmacologically targeting the cAMP pathway we were able to rescue the network deficits in SETD1A+/- cultures. Our results demonstrate a link between SETD1A and the cAMP-dependent pathway in human neurons.

neuroscience↗

bioRxiv2021

KMT2D haploinsufficiency in Kabuki Syndrome disrupts neuronal function through transcriptional and chromatin rewiring independent of H3K4-monomethylation

Kabuki syndrome (KS) is a rare multisystem disorder, characterized by intellectual disability, growth delay, and distinctive craniofacial features. It is mostly caused by de novo mutations of KMT2D, which is responsible for histone H3lysine 4 mono-methylation (H3K4me1) that marks active and poised enhancers. We assessed the impact of KMT2D mutations on chromatin and transcriptional regulation in a cohort of multiple KS1 tissues, including primary patient samples and disease-relevant lineages, namely cortical neurons (iN), neural crest stem cells (NCSC), and mesenchymal cells (MC). In parallel, we generated an isogenic line derived from human embryonic stem cells (hESC) for the stepwise characterization of neural precursors and mature neurons. We found that transcriptional dysregulation was particularly pronounced in cortical neurons and widely affected synapse activity pathways. This was consistent with highly specific alterations of spontaneous network-bursts patterns evidenced by Micro-electrode-array (MEA)-based neural network. Profiling of H3K4me1 unveiled the almost complete uncoupling between this chromatin mark and the effects on transcription, which is instead reflected by defects in H3K27ac. Finally, we identified the direct targets of KMT2D in mature cortical neurons, uncovering TEAD2 as the main mediator of KMT2D haploinsufficiency. Our results uncover the multi-tissue architecture of KS1 dysregulation and define a unique electrical phenotype and its molecular underpinnings for the cortical neuronal lineage.

genetics↗

bioRxiv2021

Human neuronal networks on micro-electrode arrays are a highly robust tool to study disease-specific genotype-phenotype correlations in vitro

Micro-electrode arrays (MEAs) are increasingly used to characterize neuronal network activity of human induced pluripotent stem-cell (hiPSC)-derived neurons. Despite their gain in popularity, MEA recordings from hiPSC-derived neuronal networks are not always used to their full potential in respect to experimental design, execution and data analysis. Therefore, we benchmarked the robustness and sensitivity of MEA-derived neuronal activity patterns derived from ten healthy individual control lines. We provide recommendations on experimental design and analysis to achieve standardization. With such standardization, MEAs can be used as a reliable platform to distinguish (disease-specific) network phenotypes. In conclusion, we show that MEAs are a powerful and robust tool to uncover functional neuronal network phenotypes from hiPSC-derived neuronal networks, and provide an important resource to advance the hiPSC field towards the use of MEAs for disease-phenotyping and drug discovery.

neuroscience↗

bioRxiv2019

Neuronal network dysfunction in a human model for Kleefstra syndrome mediated by enhanced NMDAR signaling

Epigenetic regulation of gene transcription plays a critical role in neural network development and in the etiology of Intellectual Disability (ID) and Autism Spectrum Disorder (ASD). However, little is known about the mechanisms by which epigenetic dysregulation leads to neural network defects. Kleefstra syndrome (KS), caused by mutation in the histone methyltransferase EHMT1, is a neurodevelopmental disorder with the clinical features of both ID and ASD. To study the impact of decreased EHMT1 function in human cells, we generated excitatory cortical neurons from induced pluripotent stem (iPS) cells derived from KS patients. In addition, we created an isogenic set by genetically editing healthy iPS cells. Characterization of the neurons at the single-cell and neuronal network level revealed consistent discriminative properties that distinguished EHMT1-mutant from wildtype neurons. Mutant neuronal networks exhibited network bursting with a reduced rate, longer duration, and increased temporal irregularity compared to control networks. We show that these changes were mediated by the upregulation of the NMDA receptor (NMDAR) subunit 1 and correlate with reduced deposition of the repressive H3K9me2 mark, the catalytic product of EHMT1, at the GRIN1 promoter. Furthermore, we show that EHMT1 deficiency in mice leads to similar neuronal network impairments and increased NMDAR function. Finally, we could rescue the KS patient-derived neuronal network phenotypes by pharmacological inhibition of NMDARs. Together, our results demonstrate a direct link between EHMT1 deficiency in human neurons and NMDAR hyperfunction, providing the basis for a more targeted therapeutic approach to treating KS.

neuroscience↗

bioRxiv2018

Distinct pathogenic genes causing intellectual disability and autism exhibit overlapping effects on neuronal network development

An intriguing question in medical biology is how mutations in functionally distinct genes can lead to similar clinical phenotypes. For example, patients with mutations in distinct epigenetic regulators EHMT1, MBD5, MLL3 or SMARCB1 share the core clinical features of intellectual disability (ID), autism spectrum disorder (ASD) and facial dysmorphisms. To elucidate how these phenotypic similarities are reflected by convergence at the molecular, cellular and neuronal network level, we directly compared the effects of their loss of function in neurons. Interestingly, knockdown of each gene resulted in hyperactive neuronal networks with altered patterns of synchronized activity. At the single-cell level, we found genotype-specific changes in intrinsic excitability and excitatory-inhibitory balance, but in all cases leading to increased excitability. Congruent with our physiological findings, we identified dysregulated genes that converge on biological and cellular pathways related to neuronal excitability and synaptic function, including genes previously implicated in ID/ASD. Yet, our data suggests that the common cellular phenotypes depend on the ensemble of dysregulated genes engaged in neuronal excitability rather than the direction of transcriptional changes of individual genes. The demonstration of increasing convergence from molecular pathways to neuronal networks may be a paradigm for other types of ID/ASD.

neuroscience↗

bioRxiv2018

Identification of rare de novo epigenetic variations in congenital disorders

Certain human traits such as neurodevelopmental disorders (NDs) and congenital anomalies (CAs) are believed to be primarily genetic in origin. With recent dramatic advances in genomic technologies, genome-wide surveys of cohorts of patients with ND/CAs for point mutations and structural variations have greatly advanced our understanding of their genetic etiologies1,2. However, even after whole genome sequencing (WGS), a substantial fraction of such disorders remain unexplained3. In contrast, the possibility that constitutive epigenetic variations (epivariations) might underlie such traits has not been well explored. We hypothesized that some cases of ND/CA are caused by aberrations of DNA methylation that lead to a dysregulation of normal genome function. By comparing DNA methylation profiles from 489 individuals with ND/CAs against 1,534 population controls, we identified epivariations as a frequent occurrence in the human genome. De novo epivariations were significantly enriched in cases when compared to controls. RNAseq data from population studies showed that epivariations often have an impact on gene expression comparable to loss-of-function mutations. Additionally, we detected and replicated an enrichment of rare sequence mutations overlapping CTCF binding sites close to epivariations. Thus, some epivariations occur secondary to cis-linked mutations in regulatory regions, providing a rationale for interpreting non-coding genetic variation. We propose that epivariations likely represent the causative genomic defect in 5-10% of patients with unexplained ND/CAs. This constitutes a yield comparable to CNV microarrays, and as such has significant diagnostic relevance.

genomics↗