Project description:Case Description:We report the case of a one-year-old girl who was diagnosed with Wiedemann-Steiner Syndrome based on the identification of a novel de novo frameshift mutation in the KMT2A gene by whole exome sequencing and supported by her clinical features. Clinical Findings:KMT2A mutations cause Wiedemann-Steiner Syndrome, a very rare genetic disorder characterized by congenital hypertrichosis, short stature, intellectual disability, and distinct facial features. Treatment and Outcome:Whole exome sequencing identified a novel frameshift variant: c. 4177dupA (p.Ile1393Asnfs * 14) in KMT2A; this change generates an alteration of the specific binding to non-methylated CpG motifs of the DNA to the protein. The genotype and phenotype of the patient were compared with those of earlier reported patients in the literature. Clinical Relevance:In diseases with low frequency, it is necessary to establish a genotype-phenotype correlation that allows the establishment of therapeutic and follow-up goals. The phenotype comparation with other reported cases did not show differences attributable to sex or age among patients with Wiedemann-Steiner Syndrome. Whole exome sequencing allows identifying causality in conditions with high clinical and genetic heterogeneity like hypertrichosis.
Project description:Variants in KMT2A, encoding the histone methyltransferase KMT2A, are a growing cause of intellectual disability (ID). Up to now, the majority of KMT2A variants are non-sense and frameshift variants causing a typical form of Wiedemann-Steiner syndrome. We studied KMT2A gene in a cohort of 200 patients with unexplained syndromic and non-syndromic ID and identified four novel variants, one splice and three missense variants, possibly deleterious. We used primary cells from the patients and molecular approaches to determine the deleterious effects of those variants on KMT2A expression and function. For the putative splice variant c.11322-1G>A, we showed that it led to only one nucleotide deletion and loss of the C-terminal part of the protein. For two studied KMT2A missense variants, c.3460C>T (p.(Arg1154Trp)) and c.8558T>G (p.(Met2853Arg)), located at the cysteine-rich CXXC domain and the transactivation domain of the protein, respectively, we found altered KMT2A target genes expression in patient's fibroblasts compared to controls. Furthermore, we found a disturbed subcellular distribution of KMT2A for the c.3460C>T mutant. Taken together, our results demonstrated the deleterious impact of the splice variant and of the missense variants located at two different functional domains and suggested reduction of KMT2A function as the disease-causing mechanism.
Project description:BACKGROUND:Wiedemann-Steiner syndrome (WDSTS) is a rare genetic disorder characterized by facial gestalt, neurodevelopmental delay, skeletal anomalies and growth retardation, which is caused by variation of KMT2A gene. To date, only 2 Chinese WDSTS patients have been reported. Here, we report the phenotypes and KMT2A gene variations in 14 unrelated Chinese WDSTS patients and investigate the phenotypic differences between the Chinese and French cohorts. METHODS:Next generation sequencing was performed for each patient, and the variants in the KMT2A gene were validated by Sanger sequencing. The phenotypes of 16 Chinese WDSTS patients were summarized and compared to 33 French patients. RESULTS:Genetic sequencing identified 13 deleterious de novo KMT2A variants in 14 patients, including 10 truncating, 2 missenses and 1 splicing variants. Of the 13 variants, 11 are novel and two have been reported previously. One of the patients is mosaic in the KMT2A gene. The variation spectra and phenotypic profiles of the Chinese WDSTS patients showed no difference with patients of other ethnicities; however, differ in the frequencies of several clinical features. We demonstrated that variations in the KMT2A gene can lead to both advanced and delayed bone age. We identified 6 novel phenotypes, which include microcephaly, deep palmar crease, external ear deformity, carpal epiphyseal growth retardation, dyslipidemia, and glossoptosis. In addition, patients harbored missense variants in the CXXC zinc finger domain of KMT2A showed more severe neurophenotypes. CONCLUSION:Our study consists of the largest cohort of Chinese WDSTS patients that continues to expand the WDSTS phenotypic and variation spectrum. Our results support the notion that the CXXC zinc finger domain of KMT2A gene is a hotspot for missense variants associated with more severe neurophenotypes.
Project description:Wiedemann-Steiner Syndrome (WSS) is a rare condition characterised by short stature, hypertrichosis of the elbow, intellectual disability and characteristic facial dysmorphism due to heterozygous loss of function mutations in KMT2A, a gene encoding a histone 3 lysine 4 methyltransferase. Children with WSS are often short and until recently, it had been assumed that short stature is an intrinsic part of the syndrome. GHD has recently been reported as part of the phenotypic spectrum of WSS. We describe the case of an 8-year-old boy with a novel heterozygous variant in KMT2A and features consistent with a diagnosis of WSS who also had growth hormone deficiency (GHD). GHD was diagnosed on dynamic function testing for growth hormone (GH) secretion, low insulin-like growth factor I (IGF-I) levels and pituitary-specific MRI demonstrating anterior pituitary hypoplasia and an ectopic posterior pituitary. Treatment with GH improved height performance with growth trajectory being normalised to the parental height range. Our case highlights the need for GH testing in children with WSS and short stature as treatment with GH improves growth trajectory. Learning points:Growth hormone deficiency might be part of the phenotypic spectrum of Wiedemann-Steiner Syndrome (WSS).Investigation of pituitary function should be undertaken in children with WSS and short stature. A pituitary MR scan should be considered if there is biochemical evidence of growth hormone deficiency (GHD).Recombinant human growth hormone treatment should be considered for treatment of GHD.
Project description:Lysine-specific methyltransferase 2A (KMT2A) is responsible for methylation of histone H3 (K4H3me) and contributes to chromatin remodeling, acting as "writer" of the epigenetic machinery. Mutations in KMT2A were first reported in Wiedemann-Steiner syndrome (WDSTS). More recently, KMT2A variants have been described in probands with a specific clinical diagnosis comprised in the so-called chromatinopathies. Such conditions, including WDSTS, are a group of overlapping disorders caused by mutations in genes coding for the epigenetic machinery. Among them, Rubinstein-Taybi syndrome (RSTS) is mainly caused by heterozygous pathogenic variants in CREBBP or EP300. In this work, we used next generation sequencing (either by custom-made panel or by whole exome) to identify alternative causative genes in individuals with a RSTS-like phenotype negative to CREBBP and EP300 mutational screening. In six patients we identified different novel unreported variants in KMT2A gene. The identified variants are de novo in at least four out of six tested individuals and all of them display some typical RSTS phenotypic features but also WDSTS specific signs. This study reinforces the concept that germline variants affecting the epigenetic machinery lead to a shared molecular effect (alteration of the chromatin state) determining superimposable clinical conditions.
Project description:BACKGROUND:Wiedemann-Steiner Syndrome (WSS) is characterized by short stature, a variety of dysmorphic facial and skeletal features, characteristic hypertrichosis cubiti (excessive hair on the elbows), mild-to-moderate developmental delay and intellectual disability. [MIM#: 605130]. Here we report two unrelated children for whom clinical exome sequencing of parent-proband trios was performed at UCLA, resulting in a molecular diagnosis of WSS and atypical clinical presentation. CASE PRESENTATION:For patient 1, clinical features at 9 years of age included developmental delay, craniofacial abnormalities, and multiple minor anomalies. Patient 2 presented at 1 year of age with developmental delay, microphthalmia, partial 3-4 left hand syndactyly, and craniofacial abnormalities. A de novo missense c.4342T>C variant and a de novo splice site c.4086+G>A variant were identified in the KMT2A gene in patients 1 and 2, respectively. CONCLUSIONS:Based on the clinical and molecular findings, both patients appear to have novel presentations of WSS. As the hallmark hypertrichosis cubiti was not initially appreciated in either case, this syndrome was not suspected during the clinical evaluation. This report expands the phenotypic spectrum of the clinical phenotypes and KMT2A variants associated with WSS.
Project description:De novo loss-of-function (LoF) variants in the KMT2A gene are associated with Wiedemann-Steiner Syndrome (WSS). Recently, de novo KMT2A variants have been identified in sequencing studies of cohorts of individuals with neurodevelopmental disorders (NDDs). However, most of these studies lack the detailed clinical information required to determine whether those individuals have isolated NDDs or WSS (i.e. syndromic NDDs). We performed thorough clinical and neurodevelopmental phenotyping on six individuals with de novo KMT2A variants. From these data, we found that all six patients met clinical criteria for WSS and we further define the neurodevelopmental phenotypes associated with KMT2A variants and WSS. In particular, we identified a subtype of Autism Spectrum Disorder (ASD) in five individuals, characterized by marked rigid, repetitive and inflexible behaviours, emotional dysregulation, externalizing behaviours, but relative social motivation. To further explore the clinical spectrum associated with KMT2A variants, we also conducted a meta-analysis of individuals with KMT2A variants reported in the published literature. We found that de novo LoF or missense variants in KMT2A were significantly more prevalent than predicted by a previously established statistical model of de novo mutation rate for KMT2A. Our genotype-phenotype findings better define the clinical spectrum associated with KMT2A variants and suggest that individuals with de novo LoF and missense variants likely have a clinically unrecognized diagnosis of WSS, rather than isolated NDD or ASD alone. This highlights the importance of a clinical genetic and neurodevelopmental assessment for individuals with such variants in KMT2A.
Project description:BACKGROUND:The KMT2A gene encoded lysine methyltransferase plays an essential role in regulating gene expression during early development and hematopoiesis. To date, 92 different mutations of KMT2A have been curated in the human gene mutation database (HGMD), resulting in Wiedemann-Steiner syndrome (WDSTS) and intellectual disability (ID)/developmental delay (DD). CASE PRESENTATION:In this report, we present a de novo heterozygous deletion mutation [c.74delG; p. (Gly26Alafs*2)] in the KMT2A gene, which was identified by trio-based whole exome sequencing from a 5.5-year-old boy with ID/DD, stereotypic hand movements and blood eosinophilia. Many deleterious germline mutations of KMT2A have been documented to affect development of central nervous system, oral and craniofacial tissues, but not blood eosinophils. CONCLUSIONS:This is the first report of a rare case with ID/DD as well as eosinophilia, resulting from a previously undescribed null mutation of KMT2A. Our findings expand the phenotypical spectrum in affected individuals with KMT2A mutations, and may shed some insight into the role of KMT2A in eosinophil metabolism.
Project description:RATIONALE:Wiedemann-Steiner syndrome (WDSTS, online mendelian inheritance in man 605130) is a rare autosomal dominant disorder characterized by hypertrichosis cubiti. Here, we report a Chinese boy who do not show the characteristic of hypertrichosis cubiti, and was misdiagnosed as blepharophimosis-ptosis-epicanthus inversus syndrome at first. We found a de novo frameshift mutation (p.Glu390Lysfs*10) in the KMT2A gene, which was not reported before. Our study increases the cohort of Chinese WDSTS patients, and expand the WDSTS phenotypic and variation spectrum. PATIENT CONCERNS:The patient demonstrated typical craniofacial features of blepharophimosis-ptosis-epicanthus inversus syndrome, including small palpebral fissures, ptosis, telecanthus, and epicanthus inversus, besides he had congenital heart disease (ventricular septal defects), strabismus, hypotonia, amblyopia, delayed speech and language development, delayed psychomotor development, and amblyopia (HP:0000646) which was not reported before. DIAGNOSIS:FOXL2 gene was cloned and sequenced, however, there was no mutation detected in this patient. The result of Chromosomal microarray analysis was normal. The patient was diagnosed as WDSTS by whole exome sequencing. INTERVENTIONS:The patient received cardiac surgery, frontalis suspension and regular speech and occupational therapy. He also treated with growth hormone (GH). OUTCOMES:The patient's symptoms are improved after cardiac surgery and frontalis suspension, he can express himself well now and had a 10?cm gain in height. LESSONS:As the relationship between genotype and phenotype becomes more and more clear, WES is incredibly powerful tool to diagnose the disease of WDSTS.