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.     

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.     

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.     

Ganglioglioma in a Sotos syndrome patient with an NSD1 deletion

Sotos syndrome, a disorder with macrocephaly, mental delay, and facial anomalies, has been noted to have an increased risk of neoplasia. Here, we report a patient with a microdeletion in nuclear receptor SET-domain-containing protein (NSD1) and a previously undescribed intracranial ganglioglioma.     

Analysis of the NSD1 promoter region in patients with a Sotos syndrome phenotype

Sotos syndrome (SoS, OMIM#117550) is an overgrowth disorder characterized by excessive growth—especially in the first years of childhood—distinctive craniofacial features, and various degrees of mental retardation. Haploinsufficiency of the nuclear receptor binding SET domain containing protein 1 (NSD1) gene, due to either intragenic mutations or whole-gene microdeletions, is found in the majority of patients with SoS. However, in approximately 10–40% of patients with a typical SoS phenotype, no abnormalities are detected. In this study, hemizygous hypermethylation or genomic sequence abnormalities of the promoter region of NSD1 were hypothesized to be the underlying cause in patients with a SoS phenotype, but without confirmed NSD1 alterations. In 18 patients, including one patient with a reported hepatocellular carcinoma, the promoter region of NSD1 was analyzed. However, no hypermethylation or sequence abnormalities in the promoter region could be detected. It therefore seems unlikely that such abnormalities of NSD1 are a major culprit in patients with phenotypical SoS. Additional methods are necessary for detection of other genetic or epigenetic causes of SoS.     

NSD1 analysis for Sotos syndrome: insights and perspectives from the clinical laboratory.

PURPOSE: Sotos syndrome is a genetic disorder characterized primarily by overgrowth, developmental delay, and a characteristic facial gestalt. Defects in the NSD1 gene are present in approximately 80% of patients with Sotos syndrome. The goal of this study was to determine the incidence of NSD1 abnormalities in patients referred to a clinical laboratory for testing and to identify clinical criteria that distinguish between patients with and without NSD1 abnormalities. METHODS: Deletion or mutation analysis of the NSD1 gene was performed on 435 patients referred to our clinical genetics laboratory. Detailed clinical information was obtained on 86 patients with and without NSD1 abnormalities, and a clinical checklist was developed to help distinguish between these two groups of patients. RESULTS: Abnormalities of the NSD1 gene were identified in 55 patients, including 9 deletions and 46 mutations. Thus, in the clinical laboratory setting, deletions were found in 2% and mutations in 21% of samples analyzed, because not all patients had both tests. Thirty-three previously unreported mutations in the NSD1 gene were identified. Clinical features typically associated with Sotos syndrome were not found to be significantly different between individuals with and without NSD1 abnormalities. The clinical checklist developed included poor feeding, increased body mass index, and enlarged cerebral ventricles, in addition to the typical clinical features of Sotos syndrome, and was able to distinguish between the two groups with 80% sensitivity and 70% specificity. CONCLUSIONS: The dramatic decrease in the frequency of finding NSD1 abnormalities in the clinical laboratory is likely because of the heterogeneity of the patient population. Our experience from a diagnostic laboratory can help guide clinicians in deciding for whom NSD1 genetic analysis is indicated.     

Identification of novel WFS1 mutations in Italian children with Wolfram syndrome

Six unrelated Italian children with Wolfram syndrome (WS) were analyzed for mutations in the WFS1. Four novel mutations (1387delCTCT, S443I, 1519del16, and IVS6+16g->a) were identified. In addition, we found two new, probably neutral changes (A684V and R708C). Other previously described variants were a heterozygous I333V in three alleles and the H611R in two. The 1519del16 mutation was carried by two patients whereas the CTCT deletion occurred in three subjects from two apparently unrelated families with WS. The current study expands the spectrum of mutations in WFS1 and represents the first molecular characterization of Italian WS patients.     

Identification of novel mutations in WFS1 and genotype-phenotype correlation in Wolfram syndrome

Mutations in the WFS1 gene have been reported in Wolfram syndrome (WS), an autosomal recessive disorder defined by early onset of diabetes mellitus (DM) and progressive optic atrophy. Because of the low prevalence of this syndrome and the recent identification of the WFS1 gene, few data are available concerning the relationships between clinical and molecular aspects of the disease. Here, we describe 12 patients from 11 families with WS. We report on eight novel (A214fsX285, L293fsX303, P346L, I427S, V503fsX517, R558C, S605fsX711, P838L) and seven previously reported mutations. We also looked for genotype-phenotype correlation both in patients included in this study and 19 additional WS patients that were previously reported. Subsequently, we performed a systematic review and meta-analysis of five published clinical and molecular studies of WFS1 for genotype-phenotype correlation, combined with our current French patient group for a total of 96 patients. The presence of two inactivating mutations was shown to predispose to an earlier age of onset of both DM and optic atrophy. Moreover, the clinical expression of WS was more complete and occurred earlier in patients harboring no missense mutation.     

Craniofacial and oral features of Sotos syndrome: differences in patients with submicroscopic deletion and mutation of NSD1 gene

Sotos syndrome is a well-known overgrowth syndrome caused by haploinsufficiency of NSD1 gene located at 5q35. There are two types of mutations that cause NSD1 haploinsufficiency: mutations within the NSD1 gene (mutation type) and a 5q35 submicroscopic deletion encompassing the entire NSD1 gene (deletion type). We investigated detailed craniofacial, dental, and oral findings in five patients with deletion type, and three patients with mutation type Sotos syndrome. All eight patients had a high palate, excessive tooth wear, crowding, and all but one patient had hypodontia and deep bite. Hypodontia was exclusively observed in the second premolars, and there were no differences between the deletion and mutation types in the number of missing teeth. Another feature frequently seen in common with both types was maxillary recession. Findings seen more frequently and more pronounced in deletion-type than in mutation-type included mandibular recession, scissors or posterior cross bite, and small dental arch with labioclination of the maxillary central incisors. It is noteworthy that although either scissors bite or cross bite was present in all of the deletion-type patients, neither of these was observed in mutation-type patients. Other features seen in a few patients include enamel hypoplasia (two deletion patients), and ectopic tooth eruption (one deletion and one mutation patients). Our study suggests that Sotos syndrome patients should be observed closely for possible dental and oral complications especially for malocculusion in the deletion-type patients.     

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.     

Identification of 9 novel FBN1 mutations in German patients with Marfan syndrome

We report 9 new mutations in German patients presenting with classical Marfan syndrome. All mutations occur in exons with calcium‐binding (cb) epidermal growth factor‐like (EGF) domains. Five mutations are missense involving exons 12, 27, 30, 44, and 52 with the resultant substitution of cysteine by phenylalanine (C504F), cysteine by tyrosine (C1129Y), tyrosine by cysteine (Y1261C), cysteine by serine (C1833S), and cysteine by tyrosine (C2142Y), respectively. The other four mutations are single base deletions in exons 39, 43, 48, and 58, at nucleotide A4826, C5311, T6018, and A7291, respectively, each resulting in frameshift with premature termination. Four mutations were detected in sporadic cases and are likely to be de novo. Hum Mutat 14:181, 1999. © 1999 Wiley‐Liss, Inc.     

Identification of novel mutations in patients with Shwachman-Diamond syndrome

Shwachman-Diamond syndrome (SDS) is a rare autosomal recessive disease, mainly characterized by exocrine pancreatic insufficiency, hematological dysfunction and skeletal abnormalities. The SDS disease locus was mapped to chromosome 7q11 and disease-associated mutations were reported in the Shwachman-Bodian-Diamond syndrome (SBDS) gene. SBDS is a member of a highly conserved protein family with putative orthologs in diverse species including archaea and eukaryotes. It is widely expressed in many tissues and its function is still unknown. In the present study we analyzed the genotype of 15 unrelated Italian SDS patients. After sequencing the whole coding region we were able to complete all genotypes of the SDS patients tested. A total of eleven distinct mutations were identified. The most frequent mutations are due to gene conversion events between SBDS and its unprocessed pseudogene, named SBDSP. We described four new gene conversions involving exon 2 and three novel mutations that are not a result of gene conversion events. In two out of the fifteen cases, the family analysis evidenced an apparently unexpected inheritance of SDS alleles between parents and affected children. In the first case we found a new large gene conversion event, that caused the failure of the amplification of the father's allele and in the second what could be explained as a de novo gene conversion. Both cases have important implications for genetic counseling and molecular genetic analysis. In a disorder caused by gene conversions of variable extension these findings emphasize the necessity of testing patient's parents and the significance of the choice of primers.