A novel mosaic NSD1 intragenic deletion in a patient with an atypical phenotype

Sotos syndrome, which is characterized by overgrowth, macrocephaly, distinctive facial features, and developmental delay, arises from mutations and deletions of the NSD1 gene at 5q35.3. Sixteen NSD1 intragenic deletions (including one in a mosaic condition) and one partial duplication have been reported in patients with Sotos syndrome. Here, we describe a boy aged 4 years and 10 months that showed facial dysmorphism (including frontal bossing, widely spaced eyes, deeply set eyes, a wide nasal bridge, anteverted nares, and a wide mouth), normal growth, and a psychomotor delay. High‐resolution array comparative genomic hybridization (CGH) analysis identified a mosaic heterozygous intragenic NSD1 deletion of 38 kb, which included part of intron 2 and the entire exon 3, and led to NSD1 haploinsufficiency. The deletion somatic mosaicism was subsequently confirmed by fluorescence in situ hybridization (FISH) analysis using fosmid clones. This patient presents the most atypical phenotype thus far associated with NSD1 haploinsufficiency. It is possible that this atypical phenotype may have resulted from the somatic mosaicism of the NSD1 defect. Our study confirms the usefulness of array CGH for increasing the detection rate of NSD1 abnormalities and for diagnosing syndromic patients that do not present an easily recognized phenotype. © 2013 Wiley Periodicals, Inc.     

Mutations in NSD1 are responsible for Sotos syndrome, but are not a frequent finding in other overgrowth phenotypes

Recently, deletions encompassing the nuclear receptor binding SET-Domain 1 (NSD1) gene have been described as the major cause of Japanese patients with the Sotos syndrome, whereas point mutations have been identified in the majority of European Sotos syndrome patients. In order to investigate a possible phenotype-genotype correlation and to further define the predictive value of NSD1 mutations, we performed mutational analysis of the NSD1 gene in 20 patients and one familial case with Sotos syndrome, five patients with Weaver syndrome, six patients with unclassified overgrowth/mental retardation, and six patients with macrocephaly/mental retardation. We were able to identify mutations within the NSD1 gene in 18 patients and the familial case with Sotos syndrome (90%). The mutations (six nonsense, eight frame shifts, three splice site, one missense, one in-frame deletion) are expected to result in an impairment of NSD1 function. The best correlation between clinical assessment and molecular results was obtained for the Sotos facial gestalt in conjunction with overgrowth, macrocephaly, and developmental delay. In contrast to the high mutation detection rate in Sotos syndrome, none of the patients with Weaver syndrome, unclassified overgrowth/mental retardation and macrocephaly/mental retardation, harbored NSD1 mutations. We tested for large deletions by FISH analysis but were not able to identify any deletion cases. The results indicate that the great majority of patients with Sotos syndrome are caused by mutations in NSD1. Deletions covering the NSD1 locus were not found in the patients analyzed here.     

Heterogeneity of NSD1 alterations in 116 patients with Sotos syndrome

Sotos syndrome is an overgrowth syndrome characterized by distinctive facial features, learning difficulties, and macrocephaly with frequent pre- and postnatal overgrowth with advanced bone age. Here, we report on our experience in the molecular diagnostic of Sotos syndrome on 116 patients. Using direct sequencing and a quantitative multiplex PCR of short fluorescent fragments (QMPSF)-based assay allowing accurate detection of both total and partial NSD1 deletions, we identified NSD1 abnormalities in 104 patients corresponding to 102 Sotos families (90%). NSD1 point mutations were detected in 80% of the index cases, large deletions removing the NSD1 gene entirely in 14%, and intragenic NSD1 rearrangements in 6%. Among the 69 detected distinct point mutations, 48 were novel. The QMPSF assay detected an exonic duplication and a mosaic partial deletion. QMPSF mapping of the 15 large deletions revealed the heterogeneity of the deletions, which vary in size from 1 to 4.5 Mb. Clinical features of NSD1-positive Sotos patients revealed that the phenotype in patients with nontruncating mutations was less severe that in patients with truncating mutations. This study confirms the heterogeneity of NSD1 alterations in Sotos syndrome and therefore the need to complete sequencing analysis by screening for partial deletions and duplications to ensure an accurate molecular diagnosis of this syndrome.     

Hyperinsulinemic hypoglycemia in seven patients with de novo NSD1 mutations

Sotos syndrome is an overgrowth syndrome characterized by distinctive facial features and intellectual disability caused by haploinsufficiency of the NSD1 gene. Genotype–phenotype correlations have been observed, with major anomalies seen more frequently in patients with 5q35 deletions than those with point mutations in NSD1. Though endocrine features have rarely been described, transient hyperinsulinemic hypoglycemia (HI) of the neonatal period has been reported as an uncommon presentation of Sotos syndrome. Eight cases of 5q35 deletions and one patient with an intragenic NSD1 mutation with transient HI have been reported. Here, we describe seven individuals with HI caused by NSD1 gene mutations with three having persistent hyperinsulinemic hypoglycemia. These patients with persistent HI and Sotos syndrome caused by NSD1 mutations, further dispel the hypothesis that HI is due to the deletion of other genes in the deleted 5q35 region. These patients emphasize that NSD1 haploinsufficiency is sufficient to cause HI, and suggest that Sotos syndrome should be considered in patients presenting with neonatal HI. Lastly, these patients help extend the phenotypic spectrum of Sotos syndrome to include HI as a significant feature.     

Spectrum of NSD1 mutations in Sotos and Weaver syndromes

Interestingly, mental retardation was consistently more severe in patients with NSD1 deletions. Macrocephaly and facial gestalt but not overgrowth and advanced bone age were consistently observed in Sotos syndrome patients. We suggest therefore considering macrocephaly and facial gestalt as mandatory criteria for the diagnosis of Sotos syndrome and overgrowth and advanced bone age as minor criteria.     

Sotos syndrome in two children from India

Sotos syndrome is one of the overgrowth syndromes, and can present with intellectual disability, behavioral problems and tall stature. In some cases, seizures, pectus deformity, cardiac and renal anomalies may be identified. Here we report two Indian children with Sotos syndrome whose initial presentation was macrocephaly and behavioral problems, respectively. The pathogenic variants in NSD1 gene were confirmed by next generation sequencing. The gene variants in the two children, one male and one female; were NSD1: c.2362C>T and NSD1: c.5474dup, respectively, leading to premature termination of protein formation.     

Sotos syndrome

Sotos syndrome is an autosomal dominant condition characterised by a distinctive facial appearance, learning disability and overgrowth resulting in tall stature and macrocephaly. In 2002, Sotos syndrome was shown to be caused by mutations and deletions of NSD1, which encodes a histone methyltransferase implicated in chromatin regulation. More recently, the NSD1 mutational spectrum has been defined, the phenotype of Sotos syndrome clarified and diagnostic and management guidelines developed.     

A syndrome of short stature, microcephaly and speech delay is associated with duplications reciprocal to the common Sotos syndrome deletion

Genomic rearrangements are an increasingly recognized mechanism of human phenotypic variation and susceptibility to disease. Sotos syndrome is characterized by overgrowth, macrocephaly, developmental delay and advanced osseous maturation. Haploinsufficiency of NSD1, caused by inactivating point mutations or deletion copy number variants, is the only known cause of Sotos syndrome. A recurrent 2 Mb deletion has been described with variable frequency in different populations. In this study, we report two individuals of different ethnic and geographical backgrounds, with duplications reciprocal to the common Sotos syndrome deletion. Our findings provide evidence for the existence of a novel syndrome of short stature, microcephaly, delayed bone development, speech delay and mild or absent facial dysmorphism. The phenotype is remarkably opposite to that of Sotos syndrome, suggesting a role for NSD1 in the regulation of somatic growth in humans.     

Marfanoid hypermobility caused by an 862 kb deletion of Xq22.3 in a patient with Sotos syndrome

Sotos syndrome is a rare genetic disorder characterized by overgrowth associated with macrocephaly and delayed psychomotor development. Patients with Sotos syndrome show 5q35 deletions involving NSD1 or its point mutations. We identified the common 5q35 deletion in a patient with atypical Sotos syndrome manifesting extremely severe developmental delay, joint hypermobility, and skin hyperextensibility, which are recognized as Marfanoid hypermobility syndrome. Further analyses were performed to identify the genetic cause of these additional findings. aCGH analysis revealed an additional 862 kb deletion of Xq22.3 in this patient, which was inherited from his healthy mother. The deleted region included five genes, including the nik‐related kinase gene (NRK), which would be a candidate gene for the patient's Marfanoid hypermobility, because it is a member of the glucokinase subfamily that are involved in activating the JNK pathway, and is expressed in developing skeletal musculature. Severe developmental delay seen in the patient may be derived from position effect of the deletion for neighboring interleukin 1 receptor accessory protein‐like 2 gene (IL1RAPL2), which is a candidate gene for X‐linked mental retardation. © 2011 Wiley‐Liss, Inc.     

Mutation analysis of the NSD1 gene in a group of 59 patients with congenital overgrowth

Sotos syndrome is characterized by pre- and post-natal overgrowth, typical craniofacial features, advanced bone age, and developmental delay. Some degree of phenotypic overlap exists with other overgrowth syndromes, in particular with Weaver syndrome. Sotos syndrome is caused by haploinsufficiency of the NSD1 (nuclear receptor SET domain containing gene 1) gene. Microdeletions involving the gene are the major cause of the syndrome in Japanese patients, whereas intragenic mutations are more frequent in non-Japanese patients. NSD1 aberrations have also been described in some patients diagnosed as Weaver syndrome. Some authors have suggested a certain degree of genotype-phenotype correlation, with a milder degree of overgrowth, a more severe mental retardation, and a higher frequency of congenital anomalies in microdeleted patients. Data on larger series are needed to confirm this suggestion. We report here on microdeletion and mutation analysis of NSD1 in 59 patients with congenital overgrowth. Fourteen novel mutations, two previously described and one microdeletion were identified. All patients with a NSD1 mutation had been clinically classified as "classical Sotos," although their phenotype analysis demonstrated that some major criteria, such as overgrowth and macrocephaly, could be absent. All patients with confirmed mutations shared the typical Sotos facial gestalt. A high frequency of congenital heart defects was present in patients with intragenic mutations, supporting the relevance of the NSD1 gene in the pathogenesis of this particular defect.     

Nevo syndrome with an NSD1 deletion: a variant of Sotos syndrome?

A 17-month-old girl with clinical manifestations of Nevo syndrome and NSD1 (nuclear receptor binding SET domain protein 1) deletion is described. Nevo syndrome is a rare overgrowth syndrome showing considerable phenotypic overlap with Sotos syndrome-another, more frequent overgrowth syndrome caused by NSD1 mutations or deletions. About a half of Japanese Sotos syndrome patients carry a 2.2-Mb common deletion encompassing NSD1 and present with frequent brain, cardiovascular, or urinary tract anomalies. The girl we described had the common deletion and showed patent ductus arteriosus, atrial septal defect, vesicoureteral reflux, and bilateral hydronephrosis. It was thus concluded that the clinical manifestations, including the Nevo syndrome phenotype, were caused by the microdeletion.     

Hyperinsulinemic hypoglycemia of infancy in Sotos syndrome

Sotos syndrome (OMIM #117550) is a congenital syndrome characterized by overgrowth with advanced bone age, macrocephaly, and learning difficulties. Endocrine complications of this syndrome have not yet been fully described in previous reports. We here investigated the clinical manifestations of Sotos syndrome in Japanese patients who presented with hyperinsulinemic hypoglycemia of infancy. We recruited patients diagnosed as having Sotos syndrome who presented with the complication of hyperinsulinemia during the neonatal period using a survey of the abstracts of Pediatric Meetings in domestic areas of Japan from 2007 to 2011. As a result, five patients (four females and one male) were recruited to evaluate the clinical presentation of Sotos syndrome by reference to the clinical record of each patient. A 5q35 deletion including the NSD1 gene was detected in all patients. Major anomalies in the central nervous, cardiovascular, and genito‐urinary systems were frequently found. Hypoglycemia occurred between 0.5 and 3 hr after birth and high levels of insulin were initially found within 3 days of birth. The patients were treated with intravenous glucose infusion at a maximum rate of 4.6–11.0 mg/kg/min for 12–49 days. Three of the five patients required nasal tube feeding. One patient received medical treatment with diazoxide. This study shows that patients with Sotos syndrome may present with transient hyperinsulinemic hypoglycemia in the neonatal period. © 2012 Wiley Periodicals, Inc.     

Sotos综合征的研究进展

Sotos综合征(MIM#117550)是一种以儿童期过度生长现象为特征的遗传病,主要表现为巨头畸形、特殊面容、骨龄提前以及不同程度的发育迟缓.目前已有数百名病例报道,具体发病率不详.约75%的病例是由NSD1基因内点突变或5q35微缺失所导致,欧裔患者多由5q35微缺失引起,而约50%日本患者主要由基因内点突变引起,仍有约25%病例未检测出NSDI基因异常,其具体致病机制尚不完全清楚.NSD1基因定位于染色体5q35,此基因编码一种组蛋白甲基化酶,该酶与转录调节过程有关.通过FISH(fluorescent in situ hybridization)分析、MLPA(multiplex ligation-dependent probe amplification)及实时定量荧光PCR反应等技术可以检测NSD1基因整体或部分缺失,直接测序可以检测出NSD1基因点突变.绝大部分NSD1基因异常为新生突变,多数为散发病例,但也发现数例家族性遗传病例.本病鉴别诊断主要为以生长过度为特征的疾病,包括Weaver综合征,Beckwith-Wiedeman综合征,脆性X染色体综合征等.目前本病尚无理想疗法,主要为对症治疗.出生后第一年内儿科随访对于本病临床并发症如脊柱侧弯及热性癫痫发作的治疗和预防监测有重要意义.     

NSD1 duplication in Silver–Russell syndrome (SRS): molecular karyotyping in patients with SRS features

Silver–Russell syndrome (SRS) is a growth retardation syndrome characterized by intrauterine and postnatal growth retardation, relative macrocephaly and protruding forehead, body asymmetry and feeding difficulties. Nearly 50% of cases show a hypomethylation in 11p15.5, in 10% maternal uniparental disomy of chromosome 7 is present. A significant number of patients with SRS features also exhibit chromosomal aberrations. We analyzed 43 individuals referred for SRS genetic testing by molecular karyotyping. Pathogenic variants could be detected in five of them, including a NSD1 duplication in 5q35 and a 14q32 microdeletion. NSD1 deletions are detectable in overgrowth disorders (Sotos syndrome and Beckwith–Wiedemann syndrome), whereas NSD1 duplications are associated with growth retardation. The 14q32 deletion is typically associated with Temple syndrome (TS14), but the identification of a patient in our cohort reflects the clinical overlap between TS14 and SRS. As determination of molecular subtypes is the basis for a directed counseling and therapy, the identification of pathogenic variants in >10% of the total cohort of patients referred for SRS testing and in >16% of characteristic individuals with the characteristic SRS phenotype confirms the need to apply molecular karyotyping in this cohort.     

NSD1 mutations in Sotos syndrome

Sotos syndrome is a genetic disorder characterized by a typical facial appearance, macrocephaly, accelerated growth, developmental delay, and a variable range of associated abnormalities. The NSD1 gene was recently found to be responsible for Sotos syndrome, and more than 150 patients with NSD1 alterations have been identified. A significant ethnic difference is found in the prevalence of different types of mutation, with a high percentage of microdeletions identified in Japanese Sotos syndrome patients and with intragenic mutations in most non-Japanese patients. NSD1 aberrations are rather specific for Sotos syndrome, but have also been detected in patients lacking one or more major criteria of the disorder, namely overgrowth, macrocephaly, and advanced bone age. Thus, new diagnostic criteria should be considered. Studies have reported different frequencies of mutations versus non-mutations in Sotos syndrome, thus indicating allelic or locus hetereogeneity. Although some authors have suggested genotype/phenotype correlations, further studies are needed.     

Left ventricular noncompaction in Sotos syndrome

Sotos syndrome is an autosomal dominant condition characterized by pre- and postnatal overgrowth (tall stature and macrocephaly), a typical facial appearance, advanced bone age, and developmental delay. The syndrome is caused by mutations or deletions of the nuclear receptor binding SET domain protein 1 (NSD1) gene, which encodes a histone methyltransferase implicated in the regulation of chromatin. Left ventricular noncompaction (LVNC), also called left ventricular (LV) hypertrabeculation, is a rare disorder classified as a primary genetic cardiomyopathy by the American Heart Association. This condition is characterized by an altered myocardial wall due to arrest of embryonic compaction of the loose interwoven meshwork that makes up the fetal myocardial primordium. The cardiac manifestations of this cardiomyopathy are variable, ranging from an absence of symptoms to a progressive deterioration in cardiac function, with heart failure, arrhythmias, and systemic thromboemboli. We describe two unrelated patients who had LVNC, as based on echocardiographic findings, and Sotos syndrome, as based on physical features and molecular analysis. To our knowledge, the literature contains no previous reports of concomitant LVNC and Sotos syndrome. In the light of these two cases, we suggest that patients with Sotos syndrome be evaluated for LVNC cardiomyopathy when being screened for heart defects.     

Familial gigantism caused by an NSD1 mutation

A three-generation family with autosomal dominant segregation of a novel NSD1 mutation (6605G --> A, resulting in Cys2202Tyr) is reported. Haploinsufficiency of NSD1 has been identified as the major cause of Sotos syndrome. The overgrowth condition (MIM 117550) is characterized by facial anomalies, macrocephaly, advanced bone age, and learning disabilities. Manifestations in the present family include dramatically increased height, weight, and head circumference together with a long face, large mandible, and large ears, but mental deficiency was absent.     

dHPLC Screening of the NSD1 gene Identifies Nine Novel Mutations – Summary of the first 100 Sotos Syndrome Mutations

Sotos syndrome belongs to the family of overgrowth syndromes and is characterized by large head circumference, craniofacial anomalies, advanced bone age and mental retardation. The syndrome is due to haploinsufficiency of the NSD1 gene, consisting of 23 exons with an open reading frame of 8088bp, which makes mutation screening by direct sequencing quite a laborious and expensive task. We have developed a dHPLC screening protocol for mutation detection in NSD1 and identified 9 novel mutations among 33 patients, thus achieving a mutation detection efficiency comparable to direct sequencing. A real‐time quantitative PCR approach identified two patients with NSD1 deletions. Our mutation screen is compared to other studies and all published mutations and polymorphisms are summarized.     

Sotos综合征的研究进展

Sotos综合征(MIM#117550)是一种以儿童期过度生长现象为特征的遗传病,主要表现为巨头畸形、特殊面容、骨龄提前以及不同程度的发育迟缓.目前已有数百名病例报道,具体发病率不详.约75%的病例是由NSD1基因内点突变或5q35微缺失所导致,欧裔患者多由5q35微缺失引起,而约50%日本患者主要由基因内点突变引起,仍有约25%病例未检测出NSDI基因异常,其具体致病机制尚不完全清楚.NSD1基因定位于染色体5q35,此基因编码一种组蛋白甲基化酶,该酶与转录调节过程有关.通过FISH(fluorescent in situ hybridization)分析、MLPA(multiplex ligation-dependent probe amplification)及实时定量荧光PCR反应等技术可以检测NSD1基因整体或部分缺失,直接测序可以检测出NSD1基因点突变.绝大部分NSD1基因异常为新生突变,多数为散发病例,但也发现数例家族性遗传病例.本病鉴别诊断主要为以生长过度为特征的疾病,包括Weaver综合征,Beckwith-Wiedeman综合征,脆性X染色体综合征等.目前本病尚无理想疗法,主要为对症治疗.出生后第一年内儿科随访对于本病临床并发症如脊柱侧弯及热性癫痫发作的治疗和预防监测有重要意义.