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Novel approaches to uncover the molecular etiology of neurodevelopmental disorders (NDD) are highly needed. Even using a powerful tool such as whole exome sequencing (WES), the diagnostic process may still prove long and arduous due to the high clinical and genetic heterogeneity of these conditions. The main strategies to improve the diagnostic rate are based on family segregation, re-evaluation of the clinical features by reverse-phenotyping, re-analysis of unsolved NGS-based cases and epigenetic functional studies. In this article, we described three selected cases from a cohort of patients with NDD in which trio WES was applied, in order to underline the typical challenges encountered during the diagnostic process: (1) an ultra-rare condition caused by a missense variant in MEIS2, identified through the updated Solve-RD re-analysis; (2) a patient with Noonan-like features in which the NGS analysis revealed a novel variant in NIPBL causing Cornelia de Lange syndrome; and (3) a case with de novo variants in genes involved in the chromatin-remodeling complex, for which the study of the epigenetic signature excluded a pathogenic role. In this perspective, we aimed to (i) provide an example of the relevance of the genetic re-analysis of all unsolved cases through network projects on rare diseases; (ii) point out the role and the uncertainties of the reverse phenotyping in the interpretation of the genetic results; and (iii) describe the use of methylation signatures in neurodevelopmental syndromes for the validation of the variants of uncertain significance.

Kleefstra syndrome (KS) is a rare autosomic dominant genetic disorder caused by euchromatic histone methyltransferase 1 (EHMT1) alterations. Patients mainly present with moderate to severe intellectual disability, a severe delay in/or absence of speech, autism spectrum disorder, childhood hypotonia, neuropsychiatric anomalies, and distinctive dysmorphic features. Here, we report the cases of a male and a female, two younger siblings of three, with asymptomatic parents. An EHMT1 new mutation was identified. Both presented with a typical core phenotype. Some specific features were noted, such as macrocephaly (previously reported) and enuresis (not yet described). Parental analysis identified the mutation in the mosaic state in the father. Reverse phenotyping enabled us to highlight the pauci phenotype features of inguinal hernia, azoospermia, and possible behavioral disorders. This allowed us to adapt his follow-up and genetic counseling for the family. Our three reported cases provide a new description of KS with an intragenic EHMT1 mutation, whereas in the literature most reported cases have EHMT1 deletions. Moreover, in the areas of next-generation sequencing and trio techniques with parental segregation, it is important to remain cautious about disregarding variants based on an autosomal recessive hypothesis.

Kleefstra syndrome (KS) is a genetic syndrome caused by a haploinsufficiency of the EHMT1 gene and characterized by intellectual disability, language disorders, childhood hypotonia and distinct facial features. Only a few cases of first episode of psychosis in KS have already been reported. We describe a young female patient with KS who presented a first episode of psychosis. In a context of an initial diagnosis wavering and a lack of recommendations, this clinical observation illustrates the importance of psychiatric comorbidities and their diagnostic and therapeutic complexity in KS; with a need for multidisciplinary management considering its specific aspects and vulnerabilities.

Spine deformities could be considered a possible manifestation of the childhood hypotonia, typical feature of Kleefstra Syndrome (KS). There is a paucity of literature describing posterior spinal fusion in the Kleefstra syndrome patient. For patients who develop severe scoliotic curve, bracing is often ineffective and surgery is recommended. We report the first corrective surgery for scoliosis in one patient with KS. We describe a case of 13-year-old female with severe developmental scoliosis in KS. Preoperative examination showed a thoracolumbar scoliosis with left convex thoracic curve (T3-T9, 97°) and right convex thoracolumbar curve (T9-L3, 88°). Posterior correction, pedicle screw fixation and bone graft fusion T3-L5 was performed. Postoperatively, the thoracic curve was corrected to 33° while the thoracolumbar one to 26° and better standing posture was obtained. Six month follow-up images showed no loosening of the hardware. The patient is still in our follow-up program. Scoliosis seems to be a rare evenience of the severe hypotonia of patients with KS. We report the first case of scoliosis in KS treated successfully with surgery. Corrective surgery for spinal deformity, such as scoliosis, could help in posture and improve the quality of life especially in complicated patients such as syndromic ones.

Kleefstra syndrome is a genetic disorder that may involve different parts of the body, but its main characteristics are intellectual disability and childhood hypotonia. We report a 10-year-old mentally retarded male patient who presented with seizure. His medical history revealed recurrent upper respiratory infections, neurodevelopmental delay, and epilepsy. It was also found that he had had a hospitalization in the neonatal intensive care unit for five days due to tachypnea, low APGAR score, and meconium aspiration syndrome. His brain MRI had shown some degree of distension of the lateral cerebral ventricles with the basal cistern. The electromyography and the nerve conduction velocity were however normal. He was diagnosed with Kleefstra syndrome by the loss of the EHMT1 gene. He is now under treatment by piracetam and work-therapy. This is the second case report of this syndrome in Iran. This case presentation aims to improve the diagnosis of Kleefstra syndrome patients, as a rare syndrome with non-characteristic manifestations.

Kleefstra syndrome is a rare autosomal dominant genetic disorder caused by haploinsufficiency of the EHMT1 (Euchromatic Histone MethylTransferase 1). Patients with Kleefstra syndrome have following most common symptoms: moderate or severe intellectual deficiency, absence of speech, significant diffuse muscular hypotonia, micro-brachycephaly, congenital defects of heart, kidneys, genitourinary tract and recognizable dysmorphic features of face. The article presents 2 similar clinical cases of Kleefstra syndrome in combination with epilepsy. Both patients, along with a typical clinical picture of the underlying disease, have serial epileptic spasms with an onset after first year of life, modified hypsarrhythmia with tendency to synchronization on the electroencephalogram, pharmacoresistant epilepsy. This indicates that Kleefstra syndrome can include epilepsy as one of symptoms of the disease.

Schizophrenia is a complex genetic disorder involving many common variants with modest effects and rare mutations with high penetrance. Rare mutations associated with schizophrenia are highly heterogeneous and private for affected individuals and families. Identifying such mutations can help establish the molecular diagnosis, elucidate the pathogenesis, and provide helpful genetic counseling for affected patients and families. We performed a whole-exome sequencing analysis to search for rare pathogenic mutations co-segregating with schizophrenia transmitted in a dominant inheritance in a two-generation multiplex family. We identified a rare missense mutation H1574R (Histidine1574Arginine, rs199796552) of KMT2C (lysine methyltransferase 2C) co-segregating with affected members in this family. The mutation is a novel deleterious mutation of KMT2C, not reported before in the literature. The KMT2C encodes a histone 3 lysine 4 (H3K4)-specific methyltransferase and involves epigenetic regulation of brain gene expression. Mutations of KMT2C have been found in neurodevelopmental disorders, such as Kleefstra syndrome, intellectual disability, and autism spectrum disorders. Our finding suggests that schizophrenia might be one of the clinical phenotype spectra of KMT2C mutations, and KMT2C might be a novel risk gene for schizophrenia. Nevertheless, the co-segregation of this mutation with schizophrenia in this family might also be due to chance; functional assays of this mutation are needed to address this issue.

Background Over 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. Methods In 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. Results As 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. Conclusion The 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.

Summary Haploinsufficiency of EHMT1, which encodes histone H3 lysine 9 (H3K9) methyltransferase G9a-like protein (GLP), causes Kleefstra syndrome (KS), a complex disorder of developmental delay and intellectual disability. Here, we examined whether postnatal supply of GLP can reverse the neurological phenotypes seen in Ehmt1Δ/+ mice as a KS model. Ubiquitous GLP supply from the juvenile stage ameliorated behavioral abnormalities in Ehmt1Δ/+ mice. Postnatal neuron-specific GLP supply was not sufficient for the improvement of abnormal behaviors but still reversed the reduction of H3K9me2 and spine number in Ehmt1Δ/+ mice. Interestingly, some inflammatory genes, including IL-1β (Il1b), were upregulated and activated microglial cells increased in the Ehmt1Δ/+ brain, and such phenotypes were also reversed by neuron-specific postnatal GLP supply. Il1b inactivation canceled the microglial and spine number phenotypes in the Ehmt1Δ/+ mice. Thus, H3K9me2 and some neurological phenotypes are reversible, but behavioral abnormalities are more difficult to improve depending on the timing of GLP supply., Graphical abstract, Highlights • Activated microglias increase in a Ehmt1Δ/+ mouse model of Kleefstra syndrome • Diminished H3K9me2 in Ehmt1Δ/+ mouse neurons is reversed by post-natal GLP supply • GLP supply from the juvenile stage can improve abnormal behaviors of Ehmt1Δ/+ mice • Il1b KO cancelles the microglial and spine number phenotypes in the Ehmt1Δ/+ mice, Pathophysiology; Behavioral neuroscience; Molecular neuroscience; Developmental neuroscience

SummaryGenetic evidence indicates disrupted epigenetic regulation as a major risk factor for psychiatric disorders, but the molecular mechanisms that drive this association are undetermined. EHMT1 is an epigenetic repressor that is causal for Kleefstra Syndrome (KS), a neurodevelopmental disorder (NDD) leading to ID, and is associated with schizophrenia. Here, we show that reduced EHMT1 activity decreases NRSF/REST protein leading to abnormal neuronal gene expression and progression of neurodevelopment in human iPSC. We further show that EHMT1 regulates NRSF/REST indirectly via repression of miRNA leading to aberrant neuronal gene regulation and neurodevelopment timing. Expression of a NRSF/REST mRNA that lacks the miRNA-binding sites restores neuronal gene regulation to EHMT1 deficient cells. Importantly, the EHMT1-regulated miRNA gene set with elevated expression is enriched for NRSF/REST regulators with an association for ID and schizophrenia. This reveals a molecular interaction between H3K9 dimethylation and NSRF/REST contributing to the aetiology of psychiatric disorders.

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.

AIMS The aim of this retrospective study was to determine the detection rate of the pathogenic copy number variants (CNVs) in a cohort of 33 foetuses - 32 with CHD (congenital heart defects) and 1 with kidney defect, after exclusion of common aneuploidies (trisomy 13, 18, 21, and monosomy X) by karyotyping, Multiplex ligation - dependent probe amplification (MLPA) and chromosomal microarray analysis (CMA). We also assess the effectivity of MLPA as a method of the first tier for quick and inexpensive detection of mutations, causing congenital malformations in foetuses. METHODS MLPA with probe mixes P070, P036 - Telomere 3 and 5, P245 - microdeletions, P250 - DiGeorge syndrome, and P311 - CHD (Congenital heart defects) was performed in 33 samples of amniotic fluid and chorionic villi. CMA was performed in 10 relevant cases. RESULTS Pathogenic CNVs were found in 5 samples: microdeletions in region 22q11.2 (≈2 Mb) in two foetuses, one distal microdeletion of the 22q11.2 region containing genes LZTR1, CRKL, AIFM3 and SNAP29 (≈416 kb) in the foetus with bilateral renal agenesis, 8p23.1 (3.8 Mb) microdeletion syndrome and microdeletion in area 9q34.3 (1.7 Mb, Kleefstra syndrome). MLPA as an initial screening method revealed unambiguously pathogenic CNVs in 15.2 % of samples. CONCLUSION Our study suggests that MLPA and CMA are a reliable and high-resolution technology and should be used as the first-tier test for prenatal diagnosis of congenital heart disease. Determination of the cause of the abnormality is crucial for genetic counselling and further management of the pregnancy.

Usually overlooked by physicians, olfactory abnormalities are not uncommon. Olfactory malformations have recently been reported in an emerging group of genetic disorders called Mendelian Disorders of the Epigenetic Machinery (MDEM). This study aims to determine the prevalence of olfactory malformations in a heterogeneous group of subjects with MDEM. We reviewed the clinical data of 35 patients, 20 females and 15 males, with a mean age of 9.52 years (SD 4.99). All patients had a MDEM and an already available high-resolution brain MRI scan. Two experienced neuroradiologists reviewed the MR images, noting abnormalities and classifying olfactory malformations. Main findings included Corpus Callosum, Cerebellar vermis, and olfactory defects. The latter were found in 11/35 cases (31.4%), of which 7/11 had Rubinstein-Taybi syndrome (RSTS), 2/11 had CHARGE syndrome, 1/11 had Kleefstra syndrome (KLFS), and 1/11 had Weaver syndrome (WVS). The irregularities mainly concerned the olfactory bulbs and were bilateral in 9/11 patients. With over 30% of our sample having an olfactory malformation, this study reveals a possible new diagnostic marker for MDEM and links the epigenetic machinery to the development of the olfactory bulbs.

Purpose Guidelines by professional organizations for assessing variant pathogenicity include the recommendation to utilize biologically relevant transcripts, however there is variability in transcript selection by laboratories. Methods We describe three patients whose genomic results were incorrect, because alternative transcripts and tissue expression patterns were not considered by the commercial laboratories. Results In individual 1, a pathogenic coding variant in a brain-expressed isoform of CKDL5 was missed twice on sequencing, because the variant was intronic in the transcripts considered in analysis. In individual 2, a microdeletion affecting KMT2C was not reported on microarray, since deletions of proximal exons in this gene are seen in healthy individuals; however this individual had a more distal deletion involving the brain-expressed KMT2C isoform, giving her a diagnosis of Kleefstra syndrome. Individual 3 was reported to have a pathogenic variant in exon 10 of OFD1 on exome, but had no typical features of the OFD1-related disorders. Since exon 10 is spliced from the more biologically relevant transcripts of OFD1, it was determined that he did not have an OFD1 disorder. Conclusion These examples illustrate the importance of considering alternative transcripts as a potential confounder when genetic results are negative or discordant with the phenotype.

The type 2 lysine methyltransferases KMT2C and KMT2D are large, enzymatically active scaffold proteins that form the core of nuclear regulatory structures known as KMT2C/D COMPASS complexes (complex of proteins associating with Set1). These evolutionarily conserved proteins regulate DNA promoter and enhancer elements, modulating the activity of diverse cell types critical for embryonic morphogenesis, central nervous system development, and post-natal survival. KMT2C/D COMPASS complexes and their binding partners enhance active gene expression of specific loci via the targeted modification of histone-3 tail residues, in general promoting active euchromatic conformations. Over the last 20 years, mutations in five key COMPASS complex genes have been linked to three human congenital syndromes: Kabuki syndrome (type 1 [KMT2D] and 2 [KDM6A]), Rubinstein-Taybi syndrome (type 1 [CBP] and 2 [EP300]), and Kleefstra syndrome type 2 (KMT2C). Here, we review the composition and biochemical function of the KMT2 complexes. The specific cellular and embryonic roles of the KMT2C/D COMPASS complex are highlight with a focus on clinically relevant mechanisms sensitive to haploinsufficiency. The phenotypic similarities and differences between the members of this new family of disorders are outlined and emerging therapeutic strategies are detailed.

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.

International audience; Kleefstra syndrome is a disorder caused by a mutation in the EHMT1 gene characterized in humans by general developmental delay, mild to severe intellectual disability and autism. Here, we characterized cumulative memory in the Ehmt1 +/− mouse model using the Object Space Task. We combined conventional behavioral analysis with automated analysis by deep-learning networks, a session-based computational learning model, and a trial-based classifier. Ehmt1 +/− mice showed more anxiety-like features and generally explored objects less, but the difference decreased over time. Interestingly, when analyzing memory-specific exploration, Ehmt1 +/− show increased expression of cumulative memory, but a deficit in a more simple, control memory condition. Using our automatic classifier to differentiate between genotypes, we found that cumulative memory features are better suited for classification than general exploration differences. Thus, detailed behavioral classification with the Object Space Task produced a more detailed behavioral phenotype of the Ehmt1 +/− mouse model.

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 (IPAH), heritable (HPAH), or associated (APAH) 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 3 patients with 9q34.3 microdeletions with CHD and PH along with review of 5 similar cases reported in the literature and discuss the potential association of PH with Kleefstra syndrome.

Kleefstra syndrome (KS) is a rare genetic condition resulting from either 9q34.3 microdeletions or mutations in the EHMT1 gene located in the same genomic region. To date, approximately 100 patients have been reported, thereby allowing the core phenotype of KS to be defined as developmental delay/intellectual disability, generalized hypotonia, neuropsychiatric anomalies, and a distinctive facial appearance. Here, to further expand the knowledge on genotype and phenotype of this condition, we report 2 novel cases: one patient carrying a 46-kb 9q34.3 deletion and showing macrocephaly never described in KS, and a second patient carrying a classic 9q34.3 deletion, presenting with a previously unreported skeletal feature (postaxial polydactyly of the right foot) and an unusual brain anomaly (olfactory bulb hypoplasia) observed via magnetic resonance imaging. Further, we provide a review of the current literature regarding KS and compare these 2 patients with those previously described, thereby confirming that the genotype-phenotype correlation in KS remains difficult to determine.

Kleefstra syndrome (KS) is characterized by developmental delay, intellectual disability, hypotonia and distinct facial features. Additional clinical features include congenital heart defects, cerebral abnormalities, urogenital defects and weight gain. The syndrome is caused by a microdeletion in chromosomal region 9q34.3 (in 85% of cases) or by a mutation in the EHMT1 gene coding for euchromatin histone methyltransferase 1. The prenatal phenotype has not yet been characterized. Herein, we sought to define this phenotype on the basis of a new case report and literature review.

Background Kleefstra syndrome type 1 (KS1, OMIM# 610253 ) is a rare autosomal-dominant Mendelian disorder due to heterozygous mutations in the EHMT1 gene or heterozygous deletion of genomic segment of 9q34.3(9qdel). Neurodevelopmental disorder (NDD), intellectual disability (ID) and childhood-onset hypotonia are the well-known phenotypes of KS1. However, these findings were all investigated based on western patients with KS1. Methods KS1 patients were diagnosed by genetic tests. The clinical data was collected and the phenotypes were standardized by compared with patients that previously reported. In silico, conservational and protein structural analysis were performed to assessment the missense variants. Results Ten patients from unrelated families were diagnosed as KS1, who all had NDD and seven of them had global developmental delay (GDD) with significant personal-social disabilities. Among the ten patients, only one (1/10) patient showed neonatal or infantile obesity. The other nine patients were heterozygous variations, including three missense mutations (p.Glu235Gly, p.Asp903Gly, and p.Leu943Pro), three frameshifting mutations (p.Asn1106Lysfs*71, p.Asn1055Tyrfs*121, and p.Lys288Argfs*20), one nonsense mutation (p.Arg246*), one slice site mutation (c.3540+2T > C) and one 9q34.3 deletion in gene of EHMT1. Furthermore, missense mutations showed potential pathogenicity analyzed by in silico. Conclusion We demonstrated that the clinical features in Chinese patients with KS1 were due to EHMT1 defects. We also reported seven novel variants which enriched the mutation spectrum and provided a good understanding of the pathogenesis of KS1.

Background Kleefstra syndrome (KS) is associated with developmental delay, autism, intellectual disability, psychosis, and regression. Research has not been conducted to assess the impact of KS on parents. Objective/hypothesis A mixed-method study was conducted to assess the impact on parental well-being by evaluating parents’ well-being, identifying factors of parental experience predicting well-being, and exploring the parental experience. Methods Parents completed an online survey containing the PedsQL™ Family Impact Module (FIM) and a questionnaire created by the researchers. One-Way T-Test compared parents of children with KS to parents of children with Prader-Willi syndrome (PWS). Multiple linear regression used parents’ total scale scores on PedsQL™ FIM to identify factors influencing parental well-being. Constant comparative analysis used open-ended responses to explore the parental experience of having a child with KS. Results Parents of children with KS had statistically lower scores in daily activity and social functioning, but statistically higher scores in communication and emotional functioning compared to parents of children with PWS. However, the power was below 0.80, meaning additional research needs to be completed to confirm these findings. The linear multiple regression was not significant. Most importantly, the themes of establishing the diagnosis, importance of knowledge, sense of community, KS and relationships with others, how life changed, and what the future will hold, characterized the parental experience. Conclusions Knowledge and support were important to parents who had a child recently diagnosed with KS. Therefore, parents should be provided resources about KS and support groups at diagnosis.

Kleefstra syndrome (KS) (Mendelian Inheritance in Man (MIM) no. 610253), also known as 9q34 deletion syndrome, is an autosomal dominant disorder caused by haploinsufficiency of euchromatic histone methyltransferase-1 (EHMT1). The clinical phenotype of KS includes moderate to severe intellectual disability with absent speech, hypotonia, brachycephaly, congenital heart defects, and dysmorphic facial features with hypertelorism, synophrys, macroglossia, protruding tongue, and prognathism. Only a few cases of de novo missense mutations in EHMT1 giving rise to KS have been described. However, some EHMT1 variants have been described in individuals presenting with autism spectrum disorder or mild intellectual disability, suggesting that the phenotypic spectrum resulting from EHMT1 alterations may be quite broad. In this report, we describe two unrelated patients with complex medical histories consistent with KS in whom next generation sequencing identified the same novel c.2426C>T (p.P809L) missense variant in EHMT1. To examine the functional significance of this novel variant, we performed molecular dynamics simulations of the wild type and p.P809L variant, which predicted that the latter would have a propensity to misfold, leading to abnormal histone mark binding. Recombinant EHMT1 p.P809L was also studied using far UV circular dichroism spectroscopy and intrinsic protein fluorescence. These functional studies confirmed the model-based hypotheses and provided evidence for protein misfolding and aberrant target recognition as the underlying pathogenic mechanism for this novel KS-associated variant. This is the first report to suggest that missense variants in EHMT1 that lead to protein misfolding and disrupted histone mark binding can lead to KS.

Background Kleefstra Syndrome (KS) (MIM# 610253) is an autosomal dominant disorder caused by haploinsufficiency of euchromatic histone methyltransferase-1 (EHMT1, GLP). EHMT1 (MIM# 607001) encodes a histone methyltransferase that heterodimerizes with EHMT2 (also known as G9a, MIM# 604599), which together are responsible for mono- and dimethylation of H3 lysine 9 (H3K9me1 and -me2), resulting in transcriptional repression of target genes. Methods This report describes an 18-year-old woman with intellectual disability, severely limited speech, hypotonia, microcephaly, and facial dysmorphisms, who was found to have a novel de novo single-base frameshift deletion in EHMT1. Results Functional studies using patient fibroblasts showed decreased H3K9me2 compared to wild-type control cells, thus providing a rapid confirmatory test that complements molecular studies. Conclusion Whole exome sequencing revealed a novel frameshift deletion in EHMT1 after a lengthy diagnostic odyssey in this patient. Functional testing using this patient's fibroblasts provides proof-of-concept for the analysis of variants of uncertain significance that are predicted to impact EHMT1 enzymatic activity.

Contains fulltext : 173890.pdf (Publisher’s version ) (Closed access) Detailed neurobehavioural profiles are of major value for specific clinical management, but have remained underexposed in the population with intellectual disabilities (ID). This was traditionally classified based on IQ level only. Rapid advances in genetics enable etiology based stratification in the majority of patients, which reduces clinical heterogeneity. This paper illustrates that specific profiles can be obtained for rare syndromes with ID. Our main aim was to study (mal)adaptive functioning in Kleefstra Syndrome (KS) by comparing and contrasting our findings to three other subgroups: Koolen-de Vries Syndrome, GATAD2B-related syndrome, and a mixed control group of individuals with ID. In total, we studied 58 individuals (28 males, 30 females) with ID; 24 were diagnosed with KS, 13 with Koolen-de Vries Syndrome, 6 with the GATAD2B-related syndrome, and 15 individuals with undefined neurodevelopmental disorders. All individuals were examined with a Vineland Adaptive Behavior Scale, mini PAS-ADD interview, and an Autism Diagnostic Observation Schedule to obtain measures of adaptive and maladaptive functioning. Each of the three distinctive genetic disorders showed its own specific profile of adaptive and maladaptive functioning, while being contrasted mutually. However, when data of the subgroups altogether are contrasted to the data of KS, such differences could not be demonstrated. Based on our findings, specific management recommendations were discussed for each of the three syndromes. It is strongly suggested to consider the genetic origin in individuals with congenital neurodevelopmental disorders for individual based psychiatric and behavioral management. 10 p.

Background Kleefstra syndrome (KS) is a rare autosomal dominant developmental disability, caused by microdeletions or intragenic mutations within the epigenetic regulator gene EHMT1 (euchromatic histone lysine N-methyltransferase 1). In addition to common features of autism, young adult regressive behaviors have been reported. However, the genetic downstream effects of the reported deletions or mutations on KS phenotype have not yet been completely explored. While genetic backgrounds affecting drug metabolism can have a profound effect on therapeutic interventions, pharmacogenomic variations are seldom considered in directing psychotropic therapies. Methods In this report, we used next-generation sequencing (exome sequencing and high-throughput RNA sequencing) in a patient and his parents to identify causative genetic variants followed by pharmacogenomics-guided clinical decision-making for making positive changes toward his treatment strategies. The patient had an early autism diagnosis and showed significant regressive behaviors and physical aberrations at age 23. Results Exome sequencing identified a novel, de novo splice site variant NM_024757.4: c.2750-1G>T in EHMT1, a candidate gene for Kleefstra syndrome, in the patient that results in exon skipping and downstream frameshift and termination. Gene expression results from the patient showed, when compared to his parents, there was a significant decreased expression of several reported gene variants associated with autism risk. Further, using a pharmacogenomics genotyping panel, we discovered that the patient had the CYP2D6 nonfunctioning variant genotype *4/*4 that results in very low metabolic activity on a number of psychotropic drugs, including fluvoxamine which he was prescribed. As reported here, a change in psychotropic drugs and intense behavior therapies resulted in a significant reversal of the regressive behaviors and physical aberrations. Conclusion These results demonstrate an individualized approach that integrated genetic information and behavior therapies, resulting in a dramatic improvement in regressive behaviors associated with KS.

Kleefstra syndrome is a disorder caused by a mutation in theEHMT1gene characterized in humans by general developmental delay, mild to severe intellectual disability and autism. Here, we characterized semantic- and episodic-like memory in theEhmt1+/-mouse model using the Object Space Task. We combined conventional behavioral analysis with automated analysis by deep-learning networks, a session-based computational learning model and a trial-based classifier.Ehmt1+/-mice showed more anxiety-like features and generally explored objects less, but the difference decreased over time. Interestingly, when analyzing memory-specific exploration,Ehmt1+/-show increased expression of semantic-like memory, but a deficit in episodic-like memory. A similar dissociation of semantic and episodic memory performance has been previously reported in humans with autism. Using our automatic classifier to differentiate between genotypes, we found that semantic-like memory features are better suited for classification than general exploration differences. Thus, detailed behavioral classification with the Object Space Task produced a more detailed behavioral phenotype of theEhmt1+/-mouse model.One Sentence SummaryEhmt1+/-mice show decreased exploration and episodic-like memory but increased semantic-like memory In the Object Space Task. (143 of 150)

The type 2 lysine methyltransferases KMT2C and KMT2D are large, enzymatically active scaffold proteins that form the core of nuclear regulatory structures known as KMT2C/D COMPASS complexes (complex of proteins associating with Set1). These evolutionarily conserved proteins regulate DNA promoter and enhancer elements, modulating the activity of diverse cell types critical for embryonic morphogenesis, central nervous system development, and post-natal survival. KMT2C/D COMPASS complexes and their binding partners enhance active gene expression of specific loci via the targeted modification of histone-3 tail residues, in general promoting active euchromatic conformations. Over the last 20 years, mutations in five key COMPASS complex genes have been linked to three human congenital syndromes: Kabuki syndrome (type 1 [KMT2D] and 2 [KDM6A]), Rubinstein-Taybi syndrome (type 1 [CBP] and 2 [EP300]), and Kleefstra syndrome type 2 (KMT2C). Here, we review the composition and biochemical function of the KMT2 complexes. The specific cellular and embryonic roles of the KMT2C/D COMPASS complex are highlight with a focus on clinically relevant mechanisms sensitive to haploinsufficiency. The phenotypic similarities and differences between the members of this new family of disorders are outlined and emerging therapeutic strategies are detailed.

Both copy number losses and gains occur within subtelomeric 9q34 region without common breakpoints. The microdeletions cause Kleefstra syndrome (KS), whose responsible gene is EHMT1. A 9q34 duplication syndrome (9q34 DS) had been reported in literature, but it has never been characterized by a detailed molecular analysis of the gene content and endpoints. To the best of our knowledge, we report on the first patient carrying the smallest 9q34.3 duplication containing EHMT1 as the only relevant gene. We compared him with 21 reported patients described here as carrying 9q34.3 duplications encompassing the entire gene and extending within ~ 3 Mb. By surveying the available clinical and molecular cytogenetic data, we were able to discover that similar neurodevelopmental disorders (NDDs) were shared by patient carriers of even very differently sized duplications. Moreover, some facial features of the 9q34 DS were more represented than those of KS. However, an accurate in silico analysis of the genes mapped in all the duplications allowed us to support EHMT1 as being sufficient to cause a NDD phenotype. Wider patient cohorts are needed to ascertain whether the rearrangements have full causative role or simply confer the susceptibility to NDDs and possibly to identify the cognitive and behavioral profile associated with the increased dosage of EHMT1.

International audience; Objectives Congenital heart defects (CHDs) may be isolated or associated with other malformations. The use of chromosome microarray (CMA) can increase the genetic diagnostic yield for CHDs by between 4% and 10%. The objective of this study was to evaluate the value of CMA after the prenatal diagnosis of an isolated CHD. Methods In a retrospective, nationwide study performed in France, we collected data on all cases of isolated CHD that had been explored using CMAs in 2015. Results A total of 239 fetuses were included and 33 copy number variations (CNVs) were reported; 19 were considered to be pathogenic, six were variants of unknown significance, and eight were benign variants. The anomaly detection rate was 10.4% overall but ranged from 0% to 16.7% as a function of the isolated CHD in question. The known CNVs were 22q11.21 deletions (n = 10), 22q11.21 duplications (n = 2), 8p23 deletions (n = 2), an Alagille syndrome (n = 1), and a Kleefstra syndrome (n = 1). Conclusion The additional diagnostic yield was clinically significant (3.1%), even when anomalies in the 22q11.21 region were not taken into account. Hence, patients with a suspected isolated CHD and a normal karyotype must be screened for chromosome anomalies other than 22q11.21 duplications and deletions.

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.

Stress responses are crucial processes that require activation of genetic programs that protect from the stressor. Stress responses are also energy consuming and can thus be deleterious to the organism. The mechanisms coordinating energy consumption during stress response in multicellular organisms are not well understood. Here, we show that loss of the epigenetic regulator G9a in Drosophila causes a shift in the transcriptional and metabolic responses to oxidative stress (OS) that leads to decreased survival time upon feeding the xenobiotic paraquat. During OS exposure, G9a mutants show overactivation of stress response genes, rapid depletion of glycogen, and inability to access lipid energy stores. The OS survival deficiency of G9a mutants can be rescued by a high-sugar diet. Control flies also show improved OS survival when fed a high-sugar diet, suggesting that energy availability is generally a limiting factor for OS tolerance. Directly limiting access to glycogen stores by knocking down glycogen phosphorylase recapitulates the OS-induced survival defects of G9a mutants. We propose that G9a mutants are sensitive to stress because they experience a net reduction in available energy due to (1) rapid glycogen use, (2) an inability to access lipid energy stores, and (3) an overinduced transcriptional response to stress that further exacerbates energy demands. This suggests that G9a acts as a critical regulatory hub between the transcriptional and metabolic responses to OS. Our findings, together with recent studies that established a role for G9a in hypoxia resistance in cancer cell lines, suggest that G9a is of wide importance in controlling the cellular and organismal response to multiple types of stress., Author summary Stress responses require proper activation of genetic programs to protect the organism from the stressor. However, the mechanisms controlling energy consumption during stress responses are not well understood. Here, we investigate the role of epigenetic modifier G9a in regulating metabolism and gene transcription during oxidative stress responses in Drosophila. Flies lacking G9a show a shift in the metabolic and transcriptional responses to oxidative stress, leading to decreased stress tolerance despite intact oxidative stress defense mechanisms. During oxidative stress exposure, G9a mutants show overactivation of stress response and many other genes, rapid depletion of glycogen energy stores, and an inability to access lipid energy stores. The increased susceptibility of G9a mutant flies to oxidative stress can be rescued simply by providing extra sugar. This suggests that G9a mutants are sensitive to stress because of reduced access to immediately available energy. Wild-type flies also become more tolerant to oxidative stress when they are fed extra sugar, whereas blocking energy access by genetically reducing a key metabolic enzyme leads to oxidative stress sensitivity. Though the genetic response to oxidative stress has long been appreciated, our study emphasizes the importance of energy metabolism for stress tolerance and identifies the histone methyltransferase G9a as an important player regulating both.

Kleefstra syndrome (KS) is a neurodevelopmental disorder caused by mutations in the histone methyltransferase EHMT1. 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. Neuronal networks of patient-derived cells exhibit network bursting with a reduced rate, longer duration, and increased temporal irregularity compared to control networks. We show that these changes are mediated by upregulation of NMDA receptor (NMDAR) subunit 1 correlating with reduced deposition of the repressive H3K9me2 mark, the catalytic product of EHMT1, at the GRIN1 promoter. In mice EHMT1 deficiency leads to similar neuronal network impairments with increased NMDAR function. Finally, we rescue the KS patient-derived neuronal network phenotypes by pharmacological inhibition of NMDARs. Summarized, we demonstrate a direct link between EHMT1 deficiency and NMDAR hyperfunction in human neurons, providing a potential basis for more targeted therapeutic approaches for KS., Kleefstra syndrome is a neurodevelopmental disorder associated with hapoinsufficiency of the histone methyltransferase EHMT1. Here the authors show using induced pluripotent cells-derived neurons from patients that network dysfunction occurs and is due to dysfunction of the NMDA receptor.

Kleefstra syndrome (chromosome 9q34.3 deletion) is a rare genetic disorder with less than 110 patients reported till date. We report a 4-month-old Caucasian girl with Kleefstra syndrome and Shone’s complex, an association which has not been previously reported. Surgical planning for patients with Kleefstra syndrome and complex CHD can pose challenges due to an uncertain natural history and a risk of post-operative pulmonary hypertension.

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.

Neuronal gene transcription through epigenetic modifications plays an important role in the etiology of intellectual disability (ID) and autism spectrum disorders (ASD). Haploinsufficiency of the Euchromatin Histone Methyltransferase 1 (EHMT1) gene causes Kleefstra syndrome, a neurodevelopmental disorder with the clinical features of both ID and ASD. Interestingly, patients with loss-of-function mutations in the functionally distinct epigenetic regulators MBD5, MLL3 or SMARCB1 also share the same core features, referred to as the Kleefstra syndrome spectrum (KSS). Currently, little is known about how variants in these different chromatin remodelers lead to the phenotypic convergence in KSS. To decipher the pathophysiology underlying KSS we here directly compared the effect of loss of function of four distinct KSS genes in developing rodent neuronal networks, using a combination of transcriptional analysis, immunocytochemistry, single-cell recordings and micro-electrode arrays. KSS gene-deficient neuronal networks all showed impaired neural network activity, resulting in hyperactive networks with altered network organization. At the single-cell level, we found genotype-specific changes in intrinsic excitability and in excitatory-inhibitory balance, all leading to increased excitability. These findings we could also recapitulate in a mouse model for Kleefstra syndrome. Transcriptional analysis further revealed distinct regulatory mechanisms. Nevertheless, KSS-target genes share similar functions in regulating neuronal excitability and synaptic function, several of which are associated with ID and ASD. Our results show that KSS genes mainly converge at the level of neuronal network development, providing new insights into the pathophysiology of KSS and to other phenotypically congruent disorders involving ID and autism.

Neurodevelopmental disorders (NDDs) are a collection of heterogeneous syndromes involving disruption of early neurobiological development. While the identification of disease genes has great benefits for diagnostic and prognostic purposes, for the vast majority of these genes there is little knowledge about neurobiological mechanisms that they control at the cellular and network level. Recent studies demonstrate that NDDs are "diseases of the synapse". Synaptic malfunction can severely affect network connectivity and dynamic. Understanding the neural circuit basis of NDDs is therefore imperial for a better understanding of these disorders. Kleefstra syndrome (KS) is a NDD characterized by moderate to severe intellectual disability, childhood hypotonia, and facial dysmorphism associated with genes deficiency. Here, we studied how KS genes-deficiency affects neuronal network maturation using dissociated neuronal cultures (i.e. from rodent or KS patient induced pluripotent stem cells). Using micro-electrode arrays technology we characterized the electrophysiological activity of control and KS genes-deficient neuronal networks. We showed that KS genes-deficient neuronal networks exhibited different pattern of synchronous activity compared to control condition. In particular, KS genes-deficiency induced an inappropriate network organization and irregular pattern of activity, indicating that KS genes are required for proper network formation. The neuronal network phenotype found here, provides for relevant future directions in the elucidation of pathophysiology in KS.

Regulators of chromatin dynamics and transcription are increasingly implicated in the aetiology of neurodevelopmental disorders (NDDs). Haploinsufficiency of EHMT1, encoding a histone methyl-transferase, is associated with several NDDs, including Kleefstra syndrome, developmental delay and autism spectrum disorder. Using a mouse model of Ehmt1 haploinsufficiency (Ehmt1D6Cre/+), we examined a number of brain and behavioural endophenotypes of relevance to NDDs. Specifically, we show that Ehmt1D6Cre/+ mice have deficits in information processing, evidenced by abnormal sensory-motor gating, a complete absence of object recognition memory and a reduced magnitude of auditory evoked potentials in both paired-pulse inhibition and mismatch negativity (MMN). The electrophysiological experiments show that differences in magnitude response to auditory stimulus were associated with marked reductions in total and evoked beta- and gamma-band oscillatory activity, as well as significant reductions in phase synchronisation. The pattern of electrophysiological deficits in Ehmt1D6Cre/+ matches those seen in control mice following administration of the selective NMDA-R antagonist, ketamine. This, coupled with reduction of Grin1 mRNA expression in Ehmt1D6Cre/+ hippocampus, suggests that Ehmt1 haploinsufficiency may lead to disruption in NMDA-R. Taken together, these data indicate that reduced Ehmt1 dosage during forebrain development leads to abnormal circuitry formation, which in turn results in profound information processing deficits. Such information processing deficits are likely paramount to our understanding of the cognitive and neurological dysfunctions shared across the NDDs associated with EHMT1 haploinsufficiency.

Background: Genetic 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.Methods: Three 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.Results: All 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.Conclusion: Individuals 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.

The nuclear receptor constitutive androstane receptor (CAR; NR1I3) controls the inducible expression of many enzymes and transporters involved in drug metabolism and transport, energy metabolism and toxicity. Single nucleotide variants of CAR are quite rare and usually associated with changes in pharmacokinetics of therapeutic drugs. Recently, a non-synonymous variant (F243S in the wild-type CAR) has been linked to the Kleefstra syndrome (MIM 610253) affecting neurological development. We identified another, previously unknown CAR variant (I281T) in a patient suffering from Kleefstra-like symptoms. Detailed reporter gene assays and molecular modelling indicated that the I281T mutation decreases the ability of CAR to recruit co-activators, likely by interfering with the assembly of functional CAR/retinoid X receptor (RXR) heterodimers. Although the I281T variant does not seem to cause the features of the patient, the present study adds to our knowledge about CAR function.

Kleefstra syndrome is a genetic condition characterized by intellectual disability, childhood hypotonia, and facial dysmorphisms. Genital anomalies such as micropenis, cryptorchidism, and hypospadias have been reported in 30-40% of males diagnosed with the disease. However, endocrinological investigations have been limited. We describe a case of an adolescent male with Kleefstra syndrome due to a pathogenic variant in the EHMT1 gene whose workup for isolated micropenis is suggestive of a partial hypogonadotropic hypogonadism. A possible endocrine mechanism of the genital anomaly associated with Kleefstra syndrome is discussed.

Contains fulltext : 193230.pdf (Publisher’s version ) (Open Access) Kleefstra syndrome, a disease with intellectual disability, autism spectrum disorders and other developmental defects is caused in humans by haploinsufficiency of EHMT1. Although EHMT1 and its paralog EHMT2 were shown to be histone methyltransferases responsible for deposition of the di-methylated H3K9 (H3K9me2), the exact nature of epigenetic dysfunctions in Kleefstra syndrome remains unknown. Here, we found that the epigenome of Ehmt1+/- adult mouse brain displays a marked increase of H3K9me2/3 which correlates with impaired expression of protocadherins, master regulators of neuronal diversity. Increased H3K9me3 was present already at birth, indicating that aberrant methylation patterns are established during embryogenesis. Interestingly, we found that Ehmt2+/- mice do not present neither the marked increase of H3K9me2/3 nor the cognitive deficits found in Ehmt1+/- mice, indicating an evolutionary diversification of functions. Our finding of increased H3K9me3 in Ehmt1+/- mice is the first one supporting the notion that EHMT1 can quench the deposition of tri-methylation by other Histone methyltransferases, ultimately leading to impaired neurocognitive functioning. Our insights into the epigenetic pathophysiology of Kleefstra syndrome may offer guidance for future developments of therapeutic strategies for this disease.

Kleefstra syndrome (KS) (9q34 deletion syndrome) is a rare autosomal dominant disorder characterized by intellectual disability, frequently coupled with a spectrum of complex physical and clinical manifestations. As the euchromatic histone methyltransferase-1 gene (EHMT1, GLP, or KMT1D) within the 9q34 region is deleted or mutated in most of the individuals with KS, its absence or defect in one allele is speculated to cause the major symptoms of the syndrome. Most of the EHMT1 mutations are frameshift or nonsense mutations, but two individuals with KS were reported to possess EHMT1 missense mutations. These two mutations have been predicted to cause a defective enzymatic function, but precise biochemical validation was not conducted. Therefore, we validated these two mutations by performing in vitro histone methyltransferase (HMT) activity assay and found that C1073Y and R1197W mutations severely affected the HMT activity. Additionally, the same amino-acid substitutions in mouse GLP induced impairment of in vivo GLP function. Furthermore, these two EHMT1 mutants showed defective heterocomplex formation with G9a (partner HMT) which is essential for their in vivo HMT function. Conclusively, our biochemical characterization clearly demonstrates that the previously reported two missense mutations of EHMT1 deteriorate HMT activity and GLP function, which presumably cause KS.

Kleefstra Syndrome is characterized by severe mental retardation, brachycephaly, microcephaly, epileptic seizures, distinct facial features, and infantile weak muscle tone and heart defects. Deletion of EHMT1 is the main player in 75% of cases. Because of blurriness in genotype-phenotype correlation through clinical and molecular features of both 9q34.3 microdeletion patients and those with an intragenic EHMT1 mutation in Kleefstra Syndrome, genetic characterization of patients with clinical symptoms of such spectrum is desirable. We report the first Kleefstra Syndrome patient in Iran characterized through genetic approaches. Our report could improve KS diagnosis in Iran and prepare PND and PGs options for involved families.

Rearrangements of the distal region of 9p are important chromosome imbalances in human beings. Trisomy 9p is the fourth most frequent chromosome anomaly and is a clinically recognizable syndrome. Kleefstra syndrome, previously named 9q subtelomeric deletion syndrome, is either caused by a submicroscopic deletion in 9q34.3 or an intragenic mutation of EHMT1. We report a Mexican male patient with abnormal development, dysmorphism, systemic anomalies and a complex chromosomal rearrangement (CCR). GTG-banding revealed a 46,XY,add(9)(q34.3) karyotype, whereas array analysis resulted in arr[hg19] 9p24.3p23(203,861-11,842,172)×3, 9q34.3(138,959,881-139,753,294)×3, 9q34.3(139,784,913-141,020,389)×1. Array and karyotype analyses were normal in both parents. Partial duplication of 9p is one of the most commonly detected autosomal structural abnormalities in liveborn infants. A microdeletion in 9q34.3 corresponds to Kleefstra syndrome, whereas a microduplication in 9q34.3 shows a great clinical variability. Here, we present a CCR in a patient with multiple congenital anomalies who represents the first case with partial 9p trisomy, partial 9q trisomy and partial 9q monosomy.

Background Kleefstra syndrome arises from haploinsufficiency of EHMT1 caused by either microdeletions at 9q34.3 or intragenic mutations. Patients with Kleefstra syndrome have multisystem involvement including intellectual disability, hypotonia, and characteristic facial features. Methods We report on the severe neonatal presentation of the first case of Kleefstra syndrome associated with hypoplastic left heart syndrome and multicystic renal disease in a patient with a 9q34.3 microdeletion. Results Array-CGH analysis revealed a 2.1 Mb deletion at 9q34.3, including EHMT1 and NOTCH1. Conclusion Kleefstra syndrome is a multisystem disorder with a high frequency of congenital heart disease and less frequently, renal defects. Mortality has rarely been documented, particularly in infancy. Based on the present case and the extant literature, a routine echocardiogram and renal ultrasound should be ordered in all cases of Kleefstra syndrome. The cardiac changes seen in this patient could be the result of the haploinsufficiency of EHMT1, NOTCH1, or their combined effect. Birth Defects Research (Part A), 2014. © 2014 Wiley Periodicals, Inc. Birth Defects Research (Part A) 100:985–990, 2014. © 2014 Wiley Periodicals, Inc.

A decade after the designation of MED13L as a gene and its link to intellectual disability (ID) and dextro-looped transposition of great arteries in 2003, we previously described a recognizable syndrome due to MED13L haploinsufficiency. Subsequent reports of 22 further patients diagnosed by genome-wide testing further delineated the syndrome with expansion of the phenotypic spectrum and showed reduced penetrance for congenital heart defects. We now report two novel patients identified by whole exome sequencing, one with a de novo MED13L truncating mutation and the other with a de novo missense mutation. The first patient indicates some facial resemblance to Kleefstra syndrome as a novel differential diagnosis, and the second patient shows, for the first time, recurrence of a MED13L missense mutation (p.(Asp860Gly)). Notably, our in silico modelling predicted this missense mutation to decrease the stability of an alpha-helix and thereby affecting the MED13L secondary structure, while the majority of published missense mutations remain variants of uncertain significance. Review of the reported patients with MED13L haploinsufficiency indicates moderate to severe ID and facial anomalies in all patients, as well as severe speech delay and muscular hypotonia in the majority. Further common signs include abnormal MRI findings of myelination defects and abnormal corpus callosum, ataxia and coordination problems, autistic features, seizures/abnormal EEG, or congenital heart defects, present in about 20-50% of the patients. With reference to facial anomalies, the majority of patients were reported to show broad/prominent forehead, low set ears, bitemporal narrowing, upslanting palpebral fissures, depressed/flat nasal bridge, bulbous nose, and abnormal chin, but macroglossia and horizontal eyebrows were also observed in ∼30%. The latter are especially important in the differential diagnosis of 1p36 deletion and Kleefstra syndromes, while the more common facial gestalt shows some resemblance to 22q11.2 deletion syndrome. Despite the fact that MED13L was found to be one of the most common ID genes in the Deciphering Developmental Disorders Study, further detailed patient descriptions are needed to explore the full clinical spectrum, potential genotype-phenotype correlations, as well as the role of missense mutations and potential mutational hotspots along the gene.