Euchromatin Histone Methyltransferase Research Articles

Abstract B009: Dual PARP and EHMT1/2 inhibition induces an interferon response and anti-tumor immunity in ovarian cancer

Abstract Ovarian cancer has a high propensity to develop therapy resistance. Epigenetic therapies can sensitize ovarian cancer cells to first-line treatments such as platinum-based chemotherapy and Poly (ADP-ribose) polymerase inhibitors (PARPi). Particularly, the reduction of histone 3 lysine 9 dimethylation (H3K9me2) via a euchromatin histone methyltransferase inhibitor (EHMTi) has been shown to sensitize PARPi-resistant cells to PARPi therapy. Additionally, cell growth defects were observed in PARPi-resistant cells treated with dual PARPi/EHMTi treatment compared to DMSO or single agent treatments. To determine the mechanism by which dual therapy sensitizes cells and reduces cell viability, bulk RNA-sequencing was performed on several PARPi-resistant cell lines treated with DMSO, PARPi, EHMTi, or dual PARPi/EHMTi. Transcriptomic analyses revealed that dual therapy increased interferon (IFN) signaling-related genes compared to DMSO or single agent treatments. Additionally, expression of transposable element (TE) transcripts, which can form double-stranded RNA (dsRNA) and induce an IFN response, was also increased in dual treated cells compared to controls. To determine if the reduction in cell viability is dependent on TEs and IFN signaling (i.e., viral mimicry), CRISPRi technology was used to silence intracellular sensors of dsRNA, RIGI and MDA5. Cell growth assays of these silenced cells showed that the reduction in cell growth observed with dual treatment was partially dependent on MDA5 expression. Based on the observed increase in IFN signaling and T cell recruiting cytokines, we performed an animal study using an immunogenic, PARPi-resistant model of ovarian cancer to determine if this dual therapy has any anti-tumor effects. Indeed, we observed that single and dual EHMTi therapy significantly reduced tumor burden and that this reduction was partially dependent on CD8 T cells. Lastly, to determine if dual therapy also induces a viral mimicry response in the human tumor microenvironment, we created ex vivo cultures of tumors resected from patients with ovarian cancer. We then treated the ex vivo tissues with DMSO, PARPi, EHMTi, and dual PARPi/EHMTi, and performed bulk RNA-sequencing and multispectral immunohistochemistry. From these analyses, we found that dual therapy upregulated TE transcripts and multiple immune-related pathways, and increased T cell activity in the tumor microenvironment. Altogether, our data suggest that dual therapy activates viral mimicry and promotes anti-tumor immunity in both PARPi-resistant and -sensitive ovarian cancer. Citation Format: Lily Nguyen, Zachary L. Watson, Elizabeth R. Woodruff, Kimberly R. Jordan, Edward Chuong, Benjamin G. Bitler. Dual PARP and EHMT1/2 inhibition induces an interferon response and anti-tumor immunity in ovarian cancer [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr B009.

Kleefstra syndrome and sleep disorders: An Italian case report

Kleefstra Syndrome (KS)is a rare genetic syndrome affecting approximately 1 in 200,000 individuals and is caused by either a deletion of the subtelomeric region of chromosome 9q (50%) or by a loss of function mutation in the Euchromatin Histone Methyl Transferase 1 (EHMT1) gene (50%). In this case report we analyze the case of an 8-year-old boy affected by KS from the parent’s point of view. The focus of the report is the detailed narrative analysis of the parent’s experience written directly by the mother and the complex intervention to reduce a severe sleep disturbance associated with the syndrome. A clinical assessment was carried out, focused on understanding the extent and frequency of the awakenings with a specific assessment questionnaire. The association of therapy with melatonine and trazodone was highly decisive and improved the well-being of the child and the family. The Author is carrying out further studies for the drafting of guidelines for sleep disorders in KS.

Multiple Mongolian spots in an individual with Kleefstra syndrome caused by a novel nonsense euchromatin histone methyltransferase 1 variant.

Multiple Mongolian spots in an individual with Kleefstra syndrome caused by a novel nonsense euchromatin histone methyltransferase 1 variant.

Functional validation of variants of unknown significance using CRISPR gene editing and transcriptomics: A Kleefstra syndrome case study

There are an estimated > 400 million people living with a rare disease globally, with genetic variants the cause of approximately 80% of cases. Next Generation Sequencing (NGS) rapidly identifies genetic variants however they are often of unknown significance. Low throughput functional validation in specialist laboratories is the current ad hoc approach for functional validation of genetic variants, which creating major bottlenecks in patient diagnosis. This study investigates the application of CRISPR gene editing followed by genome wide transcriptomic profiling to facilitate patient diagnosis.As proof-of-concept, we introduced a variant in the Euchromatin histone methyl transferase (EHMT1) gene into HEK293T cells.We identified changes in the regulation of the cell cycle, neural gene expression and suppression of gene expression changes on chromosome 19 and chromosome X, that are in keeping with Kleefstra syndrome clinical phenotype and/or provide insight into disease mechanism.This study demonstrates the utility of genome editing followed by functional readouts to rapidly and systematically validating the function of variants of unknown significance in patients suffering from rare diseases.

CRISPR single base editing, neuronal disease modelling and functional genomics for genetic variant analysis: pipeline validation using Kleefstra syndrome EHMT1 haploinsufficiency

BackgroundOver 400 million people worldwide are living with a rare disease. Next Generation Sequencing (NGS) identifies potential disease causative genetic variants. However, many are identified as variants of uncertain significance (VUS) and require functional laboratory validation to determine pathogenicity, and this creates major diagnostic delays.MethodsIn this study we test a rapid genetic variant assessment pipeline using CRISPR homology directed repair to introduce single nucleotide variants into inducible pluripotent stem cells (iPSCs), followed by neuronal disease modelling, and functional genomics on amplicon and RNA sequencing, to determine cellular changes to support patient diagnosis and identify disease mechanism.ResultsAs proof-of-principle, we investigated an EHMT1 (Euchromatin histone methyltransferase 1; EHMT1 c.3430C > T; p.Gln1144*) genetic variant pathogenic for Kleefstra syndrome and determined changes in gene expression during neuronal progenitor cell differentiation. This pipeline rapidly identified Kleefstra syndrome in genetic variant cells compared to healthy cells, and revealed novel findings potentially implicating the key transcription factors REST and SP1 in disease pathogenesis.ConclusionThe study pipeline is a rapid, robust method for genetic variant assessment that will support rare diseases patient diagnosis. The results also provide valuable information on genome wide perturbations key to disease mechanism that can be targeted for drug treatments.

Euchromatin histone methyltransferase II (EHMT2) regulates the expression of ras-related GTP binding C (RRAGC) protein

Dimethylation of the histone H3 protein at lysine residue 9 (H3K9) is mediated by euchromatin histone methyltransferase II (EHMT2) and results in transcriptional repression of target genes. Recently, chemical inhibition of EHMT2 was shown to induce various physiological outcomes, including endoplasmic reticulum stress-associated genes transcription in cancer cells. To identify genes that are transcriptionally repressed by EHMT2 during apoptosis, and cell stress responses, we screened genes that are upregulated by BIX-01294, a chemical inhibitor of EHMT2. RNA sequencing analyses revealed 77 genes that were upregulated by BIX-01294 in all four hepatic cell carcinoma (HCC) cell lines. These included genes that have been impli-cated in apoptosis, the unfolded protein response (UPR), and others. Among these genes, the one encoding the stress-response protein Ras-related GTPase C (RRAGC) was upregulated in all BIX-01294-treated HCC cell lines. We confirmed the regulatory roles of EHMT2 in RRAGC expression in HCC cell lines using proteomic analyses, chromatin immune precipitation (ChIP) assay, and small guide RNA-mediated loss-of-function experiments. Upregulation of RRAGC was limited by the reactive oxygen species (ROS) scavenger N-acetyl cysteine (NAC), suggesting that ROS are involved in EHMT2-mediated transcriptional regulation of stress-response genes in HCC cells. Finally, combined treatment of cells with BIX-01294 and 5-Aza-cytidine induced greater upregulation of RRAGC protein expression. These findings suggest that EHMT2 suppresses expression of the RRAGC gene in a ROS-dependent manner and imply that EHMT2 is a key regulator of stress-responsive gene expression in liver cancer cells.

Anesthetic Management of an Infant With Kleefstra Syndrome During Direct Laryngoscopy and Rigid Bronchoscopy: A Case Report.

Kleefstra syndrome (KS) is an autosomal dominant disorder caused by a chromosomal deletion at 9q34.3 resulting in pathogenic variants of the gene that codes for the enzyme, euchromatin histone methyltransferase 1 (EHMT1). KS is a rare, yet clinically relevant congenital disorder for anesthesiologists because of its potential for cardiac and craniofacial involvement. We present a 3-month-old patient with KS who required anesthetic care for diagnostic laryngoscopy and rigid bronchoscopy. The end-organ effects of KS are reviewed and our anesthetic care presented.

Prenatal diagnosis of Kleefstra syndrome

Abstract Objectives To describe the prenatal diagnosis of Kleefstra syndrome (KS), a rare panethnic disorder characterized by mental and developmental delays, distinct facial features, congenital heart and urogenital defects, among others. KS is caused by haploinsusufficiency and loss of function of euchromatin histone methyltransferase 1 (EHMT1) due to deletions or mutations in the chromosomal region 9q34.3. Case presentation The prenatal diagnosis of KS in this case report includes the description of subtle fetal phenotypic abnormalities detected by the fetal ultrasound examination as well as the results of the amniotic fluid microarray analysis that confirmed a fetal denovo deletion in the chromosomal region 9q34.3. These results confirmed the prenatal diagnosis of KS. Conclusions This case is noteworthy because of the late development of very subtle ultrasound abnormalities that triggered prenatal diagnostic studies in amniotic fluid cells, including SNP microarray analysis, that defined the diagnosis of KS. It allowed us to obtain the necessary antepartum consultations with neonatology, other pediatric subspecialties and arrange for the patient’s appropriate place of delivery to optimize the fetal and neonatal outcome.

Identification of novel quinoline inhibitor for EHMT2/G9a through virtual screening

G9a (also known as EHMT2 - Euchromatin histone methyltransferase 2) is a protein lysine methyltransferase which introduces methylation modification in variety of proteins including histones. G9a catalyzes the dimethylation of lysine 9 on histone 3 (H3K9me2) which is a repressive epigenetic modification. H3K9me2 is associated with the silencing of several genes including tumor suppressor genes in many cancers and hence G9a is a well characterized drug target for cancer therapy. Here, we report the discovery of CSV0C018875 as a novel quinoline based G9a inhibitor through virtual screening strategy from a HTS database. Sub-structure querying based on the known G9a inhibitors, followed by docking based virtual screening, led to the identification of CSV0C018875 as G9a inhibitor. We found that CSV0C018875 inhibits the activity of G9a in both enzyme and cell based assays. Importantly, the toxicity of CSV0C018875 is much lesser than that of the well-studied G9a inhibitor, BIX-01294. Molecular dynamics simulations shows that CSV0C018875 binds deeper inside the active site cavity of G9a, which facilitates the tight binding and also increases the compounds residence time, which in turn reflects better G9a inhibition. The novel quinoline CSV0C018875 could be further optimized to improve the ADME as well pharmacodynamic property.

Down-regulation of Survivin by BIX-01294 Pretreatment Overcomes Resistance of Hepatocellular Carcinoma Cells to TRAIL.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a cancer-selective, cell-death-inducing agent with little toxicity to normal cells. However, various human cancers and cancer cell lines have been reported to be resistant to TRAIL. Molecular clarification of resistance mechanism is needed. Compound screening, proliferation assays, western blotting, and flow cytometry were used to examine the sensitizer activity of methyl transferase inhibitor BIX-01294 in combination with TRAIL, in hepatocellular carcinoma (HCC) cells. RNA sequencing analysis and single guide (sg)RNA-mediated gene deletion were used to investigate the role of survivin in sensitization. In HCC cells, BIX-01294 enhanced TRAIL sensitivity by reducing survivin expression at the RNA level. Small interference RNA-mediated gene knockdown demonstrated the mechanism of sensitization to be via the reduction of survivin. Euchromatin histone methyltransferase 2 (EHMT2) inhibition by BIX-01294 may be a potent anti-tumor therapeutic strategy for human HCC.

Zespół Kleefstra – opis przypadku

Kleefstra Syndrome is a rare genetic neurodevelopmental disorder characterized by the presence of multiple congenital defects. Patients present a large variety of clinical symptoms: delay in psychomotor and speech development, intellectual disability, muscular hypotension and characteristic facial dysmorphic features. The cause of the syndrome is submicroscopic deletion in the chromosomal region 9q34.3 or an intragenic mutation of the euchromatin histone methyltransferase 1 (EHMT1) gene. Early diagnosis is extremely important for children and their families as it allows quick implementation of appropriate therapeutic management and comprehensive care, which has a great impact on improving the quality of life and prognosis for patients with Kleefstra syndrome. We present the case of a 9-year-old girl with Kleefstra Syndrome in whom the diagnosis of the genetic syndrome was proved at the age of 2 years by chromosome analysis using CGH, which showed deletion in the terminal band 9q34.3 of the long arm of chromosome 9.

Pulmonary hypertension in patients with 9q34.3 microdeletion-associated Kleefstra syndrome.

Kleefstra Syndrome is a rare genetic disorder caused by mutations in EHMT1, Euchromatin Histone Methyl Transferase 1, or deletions encompassing EHMT1 on 9q34.3. Congenital heart defects are among the major findings in patients with 9q34.3 microdeletion/Kleefstra Syndrome along with recognizable facial appearance, developmental delay/intellectual disability including severely delayed or absent speech, hypotonia, seizures, behavioral and sleep abnormalities. Pulmonary hypertension (PH) is a rare condition associated with increased pulmonary artery and right heart pressures that can lead to right heart failure and death if untreated. PH can be idiopathic, heritable, or associated with co-morbid conditions including congenital heart disease (CHD), lung diseases and other metabolic disorders. Genetic factors play important roles in heritable and idiopathic PH development and are particularly relevant but more diverse in etiology in children. PH is also reported in some chromosomal disorders such as Down syndrome in which congenital heart defects are common; however, PH has rarely been reported in patients with 9q34.3 microdeletion/Kleefstra Syndrome. Here, we present three patients with 9q34.3 microdeletions with CHD and PH along with review of five similar cases reported in the literature and discuss the potential association of PH with Kleefstra syndrome.

Inhibition of euchromatin histone-lysine N-methyltransferase 2 sensitizes breast cancer cells to tumor necrosis factor-related apoptosis-inducing ligand through reactive oxygen species-mediated activating transcription factor 4-C/EBP homologous protein-death receptor 5 pathway activation.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been characterized as an anti-cancer therapeutic agent with prominent cancer cell selectivity over normal cells. However, breast cancer cells are generally resistant to TRAIL, thus limiting its therapeutic potential. In this study, we found that BIX-01294, a selective inhibitor of euchromatin histone methyltransferase 2/G9a, is a strong TRAIL sensitizer in breast cancer cells. The combination of BIX-01294 and TRAIL decreased cell viability and led to an increase in the annexin V/propidium iodide-positive cell population, DNA fragmentation, and caspase activation. BIX-01294 markedly increased death receptor 5 (DR5) expression, while silencing of DR5 using small interfering RNAs abolished the TRAIL-sensitizing effect of BIX-01294. Specifically, BIX-01294 induced C/EBP homologous protein (CHOP)-mediated DR5 gene transcriptional activation and DR5 promoter activation was induced by upregulation of the protein kinase R-like endoplasmic reticulum kinase-mediated activating transcription factor 4 (ATF4). Moreover, inhibition of reactive oxygen species by N-acetyl-L-cysteine efficiently blocked BIX-01294-induced DR5 upregulation by inhibiting ATF4/CHOP expression, leading to diminished sensitization to TRAIL. These findings suggest that BIX-01294 sensitizes breast cancer cells to TRAIL by upregulating ATF4/CHOP-dependent DR5 expression with a reactive oxygen species-dependent manner. Furthermore, combination treatment with BIX-01294 and TRAIL suppressed tumor growth and induced apoptosis in vivo. In conclusion, we found that epigenetic regulation can contribute to the development of resistance to cancer therapeutics such as TRAIL, and further studies of unfolded protein responses and the associated epigenetic regulatory mechanisms may lead to the discovery of new molecular targets for effective cancer therapy.

EHMT1 mosaicism in apparently unaffected parents is associated with autism spectrum disorder and neurocognitive dysfunction

BackgroundGenetic mosaicism is only detected occasionally when there are no obvious health or developmental issues. Most cases concern healthy parents in whom mosaicism is identified upon targeted testing of a genetic defect that was initially detected in their children. A germline genetic defect affecting the euchromatin histone methyltransferase 1 (EHMT1) gene causes Kleefstra syndrome, which is associated with the typical triad of distinct facial appearance, (childhood) hypotonia, and intellectual disability. A high degree of psychopathology is associated with this syndrome. A few parents with a mosaic EHMT1 mutation have been detected upon testing after a child was diagnosed with a germline EHMT1 defect. At first glance, carriers of a mosaic EHMT1 mutation appeared to function normally. However, recent studies have shown that de novo, postzygotic mutations in important developmental genes significantly contribute to autism spectrum disorder (ASD). Therefore, we hypothesized that EHMT1 mosaicism could cause neuropsychiatric defects. To investigate this, we performed a detailed investigation of cognitive neuropsychiatric parameters in parents identified with EHMT1 mosaicism.MethodsThree adults (two males, one female) with a genetically confirmed diagnosis of EHMT1 mosaicism were examined by means of a battery of tests and observational instruments covering both neurocognitive and psychiatric features. The battery included the following instruments: the Autism Diagnostic Observation Schedule (ADOS), the mini Psychiatric Assessment Schedules for Adults with Developmental Disabilities (mini PAS-ADD), the Vineland Adaptive Behavior Scales (VABS), and the Cambridge Neuropsychological Test Automated Battery (CANTAB). These measures were compared with our previously reported data from Kleefstra syndrome patients with confirmed (germline) EHMT1 defects.ResultsAll three subjects achieved maximum total scores on the VABS, indicative of adequate (adaptive) functioning. In all, scores above cutoff were found on the ADOS for ASD and on the mini PAS-ADD for major depressive disorder (lifetime). Finally, results on the CANTAB showed impaired cognitive flexibility in all subjects.ConclusionIndividuals with EHMT1 mosaicism seem to have increased vulnerability for developing severe psychopathology, especially ASD and mood disorders. Although at first glance they appear to be well-adapted in their daily functioning, they may experience significant psychiatric symptoms and show reduced cognitive flexibility in comparison to the general population.

Neurons derived from induced pluripotent stem cells on microelectrode arrays: a human model for neurodevelopmental disorders

Neurons derived from induced pluripotent stem cells on microelectrode arrays: a human model for neurodevelopmental disorders

Functional convergence of histone methyltransferases EHMT1 and KMT2C involved in intellectual disability and autism spectrum disorder.

Kleefstra syndrome, caused by haploinsufficiency of euchromatin histone methyltransferase 1 (EHMT1), is characterized by intellectual disability (ID), autism spectrum disorder (ASD), characteristic facial dysmorphisms, and other variable clinical features. In addition to EHMT1 mutations, de novo variants were reported in four additional genes (MBD5, SMARCB1, NR1I3, and KMT2C), in single individuals with clinical characteristics overlapping Kleefstra syndrome. Here, we present a novel cohort of five patients with de novo loss of function mutations affecting the histone methyltransferase KMT2C. Our clinical data delineates the KMT2C phenotypic spectrum and reinforces the phenotypic overlap with Kleefstra syndrome and other related ID disorders. To elucidate the common molecular basis of the neuropathology associated with mutations in KMT2C and EHMT1, we characterized the role of the Drosophila KMT2C ortholog, trithorax related (trr), in the nervous system. Similar to the Drosophila EHMT1 ortholog, G9a, trr is required in the mushroom body for short term memory. Trr ChIP-seq identified 3371 binding sites, mainly in the promoter of genes involved in neuronal processes. Transcriptional profiling of pan-neuronal trr knockdown and G9a null mutant fly heads identified 613 and 1123 misregulated genes, respectively. These gene sets show a significant overlap and are associated with nearly identical gene ontology enrichments. The majority of the observed biological convergence is derived from predicted indirect target genes. However, trr and G9a also have common direct targets, including the Drosophila ortholog of Arc (Arc1), a key regulator of synaptic plasticity. Our data highlight the clinical and molecular convergence between the KMT2 and EHMT protein families, which may contribute to a molecular network underlying a larger group of ID/ASD-related disorders.

Haploinsufficiency of EHMT1 improves pattern separation and increases hippocampal cell proliferation

Heterozygous mutations or deletions of the human Euchromatin Histone Methyltransferase 1 (EHMT1) gene are the main causes of Kleefstra syndrome, a neurodevelopmental disorder that is characterized by impaired memory, autistic features and mostly severe intellectual disability. Previously, Ehmt1+/− heterozygous knockout mice were found to exhibit cranial abnormalities and decreased sociability, phenotypes similar to those observed in Kleefstra syndrome patients. In addition, Ehmt1+/− knockout mice were impaired at fear extinction and novel- and spatial object recognition. In this study, Ehmt1+/− and wild-type mice were tested on several cognitive tests in a touchscreen-equipped operant chamber to further investigate the nature of learning and memory changes. Performance of Ehmt1+/− mice in the Visual Discrimination & Reversal learning, object-location Paired-Associates learning- and Extinction learning tasks was found to be unimpaired. Remarkably, Ehmt1+/− mice showed enhanced performance on the Location Discrimination test of pattern separation. In line with improved Location Discrimination ability, an increase in BrdU-labelled cells in the subgranular zone of the dentate gyrus was observed. In conclusion, reduced levels of EHMT1 protein in Ehmt1+/− mice does not result in general learning deficits in a touchscreen-based battery, but leads to increased adult cell proliferation in the hippocampus and enhanced pattern separation ability.

Euchromatin histone methyltransferase 1 regulates cortical neuronal network development.

Heterozygous mutations or deletions in the human Euchromatin histone methyltransferase 1 (EHMT1) gene cause Kleefstra syndrome, a neurodevelopmental disorder that is characterized by autistic-like features and severe intellectual disability (ID). Neurodevelopmental disorders including ID and autism may be related to deficits in activity-dependent wiring of brain circuits during development. Although Kleefstra syndrome has been associated with dendritic and synaptic defects in mice and Drosophila, little is known about the role of EHMT1 in the development of cortical neuronal networks. Here we used micro-electrode arrays and whole-cell patch-clamp recordings to investigate the impact of EHMT1 deficiency at the network and single cell level. We show that EHMT1 deficiency impaired neural network activity during the transition from uncorrelated background action potential firing to synchronized network bursting. Spontaneous bursting and excitatory synaptic currents were transiently reduced, whereas miniature excitatory postsynaptic currents were not affected. Finally, we show that loss of function of EHMT1 ultimately resulted in less regular network bursting patterns later in development. These data suggest that the developmental impairments observed in EHMT1-deficient networks may result in a temporal misalignment between activity-dependent developmental processes thereby contributing to the pathophysiology of Kleefstra syndrome.

G9a-mediated histone methylation regulates cadmium-induced male fertility damage in pubertal mice.

Increasing evidence suggests that cadmium (Cd) is associated with male fertility damage. However, the effects of histone modification on Cd-induced male fertility damage remain obscure. This study aims to evaluate the roles of histone methylation mediated by euchromatin histone methyltransferase (EHMT2/G9a) in regulating Cd-induced male fertility damage. We exposed 4-week-old male C57BL/6J mice to Cd by intraperitoneal injection at 2mg/kg for 1, 3 and 5days. Our data showed that Cd exposure decreased the numbers of impregnated females and litter sizes, which was concomitant with sperm count reduction, histological changes in the cauda epididymal ducts and seminiferous epithelium, and testicular cell apoptosis as evaluated by terminal dUTP nick-end labeling (TUNEL) assay and immunoblotting with increased levels of cleaved caspase 3, PARP and Bax and a decreased level of Bcl-2. Cd-induced male fertility damage was accompanied by enhanced G9a activity followed by increased histone H3 lysine 9 monomethylation (H3K9me1) and dimethylation (H3K9me2) in testes. Furthermore, inhibition of G9a by BIX-01294 normalized H3K9me1 and H3K9me2 to basal levels and prevented Cd-induced male fertility damage and testicular cell apoptosis. Our present study revealed that G9a-mediated histone methylation plays a critical role in Cd-induced male fertility damage and testicular cell apoptosis.

Reversible white matter lesions associated with mutant EHMT1 and Kleefstra syndrome.

Kleefstra syndrome (KS; OMIM #610253), formerly known as the 9q subtelomeric deletion syndrome, is an autosomal dominant cause of intellectual disability (ID) characterized by hypotonia and facial dysmorphisms.(1,2) The cause of KS is attributed to haploinsufficiency of the euchromatin histone methyltransferase 1 (EHMT1) gene (OMIM *607001) located at chromosome 9q34.3 (i.e., distal long arm of chromosome 9), either by microdeletion or point mutation. EHMT1 encodes a histone H3 methyltransferase at position Lys-9 (H3K9).(1-3).