Williams Beuren syndrome (WBS) is a multisystemic disorder caused by a hemizygous deletion of 1.5 Mb on chromosome 7q11.23 spanning 28 genes. A few patients with larger and smaller WBS deletion have been reported. They show clinical features that vary between isolated SVAS to the full spectrum of WBS phenotype, associated with epilepsy or autism spectrum behavior. Here we describe four patients with atypical WBS 7q11.23 deletions. Two carry ∼3.5 Mb larger deletion towards the telomere that includes Huntingtin-interacting protein 1 (HIP1) and tyrosine 3-monooxygenase/tryptophan 5-monooxigenase activation protein gamma (YWHAG) genes. Other two carry a shorter deletion of ∼1.2 Mb at centromeric side that excludes the distal WBS genes BAZ1B and FZD9. Along with previously reported cases, genotype–phenotype correlation in the patients described here further suggests that haploinsufficiency of HIP1 and YWHAG might cause the severe neurological and neuropsychological deficits including epilepsy and autistic traits, and that the preservation of BAZ1B and FZD9 genes may be related to mild facial features and moderate neuropsychological deficits. This report highlights the importance to characterize additional patients with 7q11.23 atypical deletions comparing neuropsychological and clinical features between these individuals to shed light on the pathogenic role of genes within and flanking the WBS region.
Williams Beuren syndrome; 7q11.23; haploinsufficiency; qPCR
Klinefelter syndrome (KS) is a common genetic condition that is currently under-diagnosed. The phenotype is broad, with physical, medical and psychosocial features ranging from mild to severe. When a child is diagnosed with KS, the parents may spend months to years searching for a diagnosis. This study used a qualitative methods approach to explore parents' experiences of having a child with KS and receiving a diagnosis. Fifteen semistructured one-to-one in-depth interviews were conducted to explore their experiences and views. The interviews were then transcribed, coded and thematically analysed. The interviews revealed that parents had diverse experiences related to: the timing of the diagnosis of their child and reasons why their child was investigated for KS; the information that was provided at the time of diagnosis; the supports that were available and the concerns that parents held for the future of their child. The conclusions from this study were that parents' experiences of having a child with KS and receiving a diagnosis were complex and multifaceted. This experience was shaped by the timing of when the diagnosis was received, who provided the diagnosis, what information was provided from health-care professionals and that which parents may have encountered on the internet. The long-term experiences for parents were also impacted by the level of support they received. These findings have implications for the process by which KS is recognised by the health-care community and supports available for families.
Klinefelter syndrome; diagnostic odyssey; non-physical features; mothers; fathers
Genome-wide association studies can provide researchers some reference on gene mapping of complex trait, a key point of which is how to improve the power of association test. Recently, two-stage approaches are widely used to genome-wide association analysis. In the first stage, a screening test is used to select markers, and in the second stage, a family-based association test is performed based on a smaller set of the selected markers. Here, we modify an existing two-stage approach and propose a new test statistic for the association analysis. Simulation studies are conducted to compare the type I error rates and powers of the proposed approach with those of the existing two-stage approaches. Simulation results show that the new two-stage approach has greater power than the other two-stage approaches to some extent.
association test; complex disease; FDR; gene mapping; two-stage approach
The use of genetic tests is expanding rapidly. Given limited health-care budgets throughout Europe and few national coverage decisions specifically for genetic tests, decisions about allocating scarce resources to genetic tests are frequently ad hoc and left to lower-level decision makers. This study assesses substantive ethical and economic criteria to prioritize genetic services in a reasonable and fair manner. Principles for allocating health-care resources can be classified into four categories: need-based allocation; maximizing total benefits; treating people equally; and promoting and rewarding social usefulness. In the face of scarcity, the degree of an individual's need for medical intervention is an important criterion. Also, different economic concepts of efficiency are of relevance in the theory and practice of prioritizing genetic tests. Equity concerns are most likely to be relevant in terms of avoiding undesirable inequities, which may also set boundaries to the use of efficiency as a prioritization criterion. The aim of promoting and rewarding social usefulness is unlikely to be relevant to the question of what priority a genetic test should have in clinical practice. Further work is needed to select an appropriate set of criteria; operationalize them; and assign weights before some kind of standardized priority information can be added to information sources for genetic services. Besides the substantive criteria, formal considerations like those pointed out in the framework of accountability for reasonableness need to be considered in decision making.
health-care prioritization; genetic testing; costs and cost analysis; resource allocation; ethics
Paediatric research; whole-genome sequencing; best interests of the child
Trichorhinophalangeal syndrome type I (TRPSI) is a genetic disorder characterized by sparse hair, a bulbous nasal tip, short stature with severe generalized shortening of all phalanges, metacarpal and metatarsal bones and cone-shaped epiphyses. This syndrome is caused by autosomal dominant mutations in the TRPS1 gene. However, because recurrence has been observed in siblings from healthy parents, an autosomal recessive mode of inheritance has also been suggested. We report on a male patient, born to healthy unrelated parents, with TRPSI. Using Sanger sequencing, we identified a mutation in the TRPS1 gene (c.2735 G>A, P.Cys912Tyr). The same mutation was detected as a 10% mosaic mutation by Pyrosequencing in blood-derived DNA from his healthy mother. To our knowledge, this is the first time that somatic mosaicism has been identified in TRPSI. This data combined with the observations of recurrences in siblings from healthy parents modifies the genetic counseling for TRPSI, which should discuss a 5–10 percent recurrence risk for healthy parents with an affected child because of the possibility of germinal mosaicism.
autosomal dominant; autosomal recessive; genetic counseling; mosaicism; trichorhinophalangeal syndrome type 1; TRPS1 gene
Copy number variations associated with abnormal gene dosage have an important role in the genetic etiology of many neurodevelopmental disorders, including intellectual disability (ID) and autism. We hypothesize that the chromosome 2q23.1 region encompassing MBD5 is a dosage-dependent region, wherein deletion or duplication results in altered gene dosage. We previously established the 2q23.1 microdeletion syndrome and report herein 23 individuals with 2q23.1 duplications, thus establishing a complementary duplication syndrome. The observed phenotype includes ID, language impairments, infantile hypotonia and gross motor delay, behavioral problems, autistic features, dysmorphic facial features (pinnae anomalies, arched eyebrows, prominent nose, small chin, thin upper lip), and minor digital anomalies (fifth finger clinodactyly and large broad first toe). The microduplication size varies among all cases and ranges from 68 kb to 53.7 Mb, encompassing a region that includes MBD5, an important factor in methylation patterning and epigenetic regulation. We previously reported that haploinsufficiency of MBD5 is the primary causal factor in 2q23.1 microdeletion syndrome and that mutations in MBD5 are associated with autism. In this study, we demonstrate that MBD5 is the only gene in common among all duplication cases and that overexpression of MBD5 is likely responsible for the core clinical features present in 2q23.1 microduplication syndrome. Phenotypic analyses suggest that 2q23.1 duplication results in a slightly less severe phenotype than the reciprocal deletion. The features associated with a deletion, mutation or duplication of MBD5 and the gene expression changes observed support MBD5 as a dosage-sensitive gene critical for normal development.
MBD5; gene dosage; 2q23.1; autism spectrum disorder; microduplication; microdeletion
Hereditary retinal dystrophies (RD) constitute a group of blinding diseases that are characterized by clinical variability and pronounced genetic heterogeneity. The different forms of RD can be caused by mutations in >100 genes, including >1600 exons. Consequently, next generation sequencing (NGS) technologies are among the most promising approaches to identify mutations in RD. So far, NGS is not routinely used in gene diagnostics. We developed a diagnostic NGS pipeline to identify mutations in 170 genetically and clinically unselected RD patients. NGS was applied to 105 RD-associated genes. Underrepresented regions were examined by Sanger sequencing. The NGS approach was successfully established using cases with known sequence alterations. Depending on the initial clinical diagnosis, we identified likely causative mutations in 55% of retinitis pigmentosa and 80% of Bardet–Biedl or Usher syndrome cases. Seventy-one novel mutations in 40 genes were newly associated with RD. The genes USH2A, EYS, ABCA4, and RHO were more frequently affected than others. Occasionally, cases carried mutations in more than one RD-associated gene. In addition, we found possible dominant de-novo mutations in cases with sporadic RD, which implies consequences for counseling of patients and families. NGS-based mutation analyses are reliable and cost-efficient approaches in gene diagnostics of genetically heterogeneous diseases like RD.
next generation sequencing; hereditary retinal dystrophy; gene diagnostics; genetic modifiers; de-novo mutations
J-wave syndromes have been associated with increased risk of ventricular fibrillation and sudden cardiac death. Previous studies have identified the KCNJ8-S422L variant in heterozygous form in individuals with J-wave syndromes. Its absence in over 1500 controls, coupled with in vitro analysis, have led to the conclusion that S422L is pathogenic. We previously performed whole-genome sequencing in a family quartet of Ashkenazi Jewish decent with no history of J-wave syndrome. Re-examination of these data reveals that both parents are heterozygous for the S422L variant, while the 12-year old son carries two copies – thus representing the first reported case of a S422L homozygote. In order to examine whether the S422L mutation might segregate at appreciable frequencies in specific populations, we genotyped the variant in a panel consisting of 722 individuals from 22 European, Middle Eastern non-Jewish, Ashkenazi Jewish, and non-Ashkenazi Jewish populations. We found that the S422L allele was at a significantly higher frequency in Ashkenazi Jews (∼4%) compared with other populations in our survey, which have frequencies <0.25%. We also performed ECGs in both male members of the family quartet. The homozygous boy demonstrated no clinically significant ECG abnormalities, while the heterozygous father presented with a subtle J-wave point elevation. Our results suggest that either (a) previous studies implicating S422L as pathogenic for J-wave syndromes failed to appropriately account for European population structure and the variant is likely benign, or (b) Ashkenazi Jews may be at significantly increased risk of J-wave syndromes and ultimately sudden cardiac death.
J-wave syndromes; sudden cardiac arrest; idiopathic ventricular fibrillation; early repolarization syndromes; Brugada syndrome
Mutations of genes encoding the subunits of the succinate dehydrogenase (SDH) complex were described in KIT/PDGFRA wild-type GIST separately in different reports. In this study, we simultaneously sequenced the genome of all subunits, SDHA, SDHB, SDHC, and SDHD in a larger series of KIT/PDGFRA wild-type GIST in order to evaluate the frequency of the mutations and explore their biological role. SDHA, SDHB, SDHC, and SDHD were sequenced on the available samples obtained from 34 KIT/PDGFRA wild-type GISTs. Of these, in 10 cases, both tumor and peripheral blood (PB) were available, in 19 cases only tumor, and in 5 cases only PB. Overall, 9 of the 34 patients with KIT/PDGFRA wild-type GIST carried mutations in one of the four subunits of the SDH complex (six patients in SDHA, two in SDHB, one in SDHC). WB and immunohistochemistry analysis showed that patients with KIT/PDGFRA wild-type GIST who harbored SDHA mutations exhibited a significant downregulation of both SDHA and SDHB protein expression, with respect to the other GIST lacking SDH mutations and to KIT/PDGFRA-mutated GIST. Clinically, four out of six patients with SDHA mutations presented with metastatic disease at diagnosis with a very slow, indolent course. Patients with KIT/PDGFRA wild-type GIST may harbor germline and/or de novo mutations of SDH complex with prevalence for mutations within SDHA, which is associated with a downregulation of SDHA and SDHB protein expression. The presence of germline mutations may suggest that these patients should be followed up for the risk of development of other cancers.
SDHA; SDHB; SDHC; SDHD; wild-type GIST; gastrointestinal stromal tumors
Inherited cardiac conditions (ICCs) can lead to sudden cardiac death at any age, yet are often asymptomatic and clinically undetected. Prophylactic interventions are available and cascade testing is recommended to identify family members at risk. When a disease-causing mutation has been identified in a family, pre-symptomatic genetic testing (PSGT) is available. This study explores perceptions of the cascade process, impact of PSGT and attitudes towards direct contact as an alternative to family-mediated dissemination for ICCs. In depth, interviews were conducted with 22 participants eligible for PSGT for Hypertrophic Cardiomyopathy or Long QT syndrome. Data were analysed using an inductive, thematic approach. Risk is perceived to be low pre-test in the absence of symptoms, and participants frequently test with the aim of ruling out risk to self and children. Testing of children is a complex decision; although older participants have concerns about possible adverse effects of genetic testing early in the life course, young participants are pragmatic about their result. The meaning of a positive genetic test result may be difficult to conceptualise in the absence of clinical evidence of disease, and this may deter further dissemination to at-risk family members. A majority of participants see advantages in direct contact from health professionals and support it in principle. Implications for practice include addressing risk perception pre-test, and presenting genetic test information as part of a risk stratification process rather than a binary outcome. Families may require more support or intervention in cascading genetic test information.
HCM; LQTS; genetic; psychosocial; qualitative
Duchenne and Becker muscular dystrophies (DMD/BMD) are the most commonly inherited neuromuscular disease. However, accurate and convenient molecular diagnosis cannot be achieved easily because of the enormous size of the dystrophin gene and complex causative mutation spectrum. Such traditional methods as multiplex ligation-dependent probe amplification plus Sanger sequencing require multiple steps to fulfill the diagnosis of DMD/BMD. Here, we introduce a new single-step method for the genetic analysis of DMD patients and female carriers in real clinical settings and demonstrate the validation of its accuracy. A total of 89 patients, 18 female carriers and 245 non-DMD patients were evaluated using our targeted NGS approaches. Compared with traditional methods, our new method yielded 99.99% specificity and 98.96% sensitivity for copy number variations detection and 100% accuracy for the identification of single-nucleotide variation mutations. Additionally, this method is able to detect partial deletions/duplications, thus offering precise personal DMD gene information for gene therapy. We detected novel partial deletions of exons in nine samples for which the breakpoints were located within exonic regions. The results proved that our new method is suitable for routine clinical practice, with shorter turnaround time, higher accuracy, and better insight into comprehensive genetic information (detailed breakpoints) for ensuing gene therapy.
targeted NGS; genetic diagnosis; Duchenne and Becker muscular dystrophies; statistical analysis for CNVs; breakpoints
The 1100delC mutation in the CHEK2 gene has a carrier frequency of up to 1.5% in individuals from North-West Europe. Women heterozygous for 1100delC have an increased breast cancer risk (odds ratio 2.7). To explore the prevalence and clinical consequences of 1100delC homozygosity in the Netherlands, we genotyped a sporadic breast cancer hospital-based cohort, a group of non-BRCA1/2 breast cancer families, and breast tumors from a tumor tissue bank. Three 1100delC homozygous patients were found in the cohort of 1434 sporadic breast cancer patients, suggesting an increased breast cancer risk for 1100delC homozygotes (odds ratio 3.4, 95% confidence interval 0.4–32.6, P=0.3). Another 1100delC homozygote was found in 592 individuals from 108 non-BRCA1/2 breast cancer families, and two more were found after testing 1706 breast tumors and confirming homozygosity on their wild-type DNA. Follow-up data was available for five homozygous patients, and remarkably, three of them had developed contralateral breast cancer. A possible relationship between 1100delC and lung cancer risk was investigated in 457 unrelated lung cancer patients but could not be confirmed. Due to the small number of 1100delC homozygotes identified, the breast cancer risk estimate associated with this genotype had limited accuracy but is probably higher than the risk in heterozygous females. Screening for CHEK2 1100delC could be beneficial in countries with a relatively high allele frequency.
CHEK2; 1100delC homozygotes; genotype risk; bilateral breast cancer; lung cancer
Insulin-dependent juvenile-onset diabetes may occur in the context of rare syndromic presentations suggesting monogenic inheritance rather than common multifactorial autoimmune type 1 diabetes. Here, we report the case of a Lebanese patient diagnosed with juvenile-onset insulin-dependent diabetes presenting ketoacidosis, early-onset retinopathy with optic atrophy, hearing loss, diabetes insipidus, epilepsy, and normal weight and stature, who later developed insulin resistance. Despite similarities with Wolfram syndrome, we excluded the WFS1 gene as responsible for this disease. Using combined linkage and candidate gene study, we selected ALMS1, responsible for Alström syndrome, as a candidate gene. We identified a novel splice mutation in intron 18 located 3 bp before the intron–exon junction (IVS18-3T>G), resulting in exon 19 skipping and consequent frameshift generating a truncated protein (V3958fs3964X). The clinical presentation of the patient significantly differed from typical Alström syndrome by the absence of truncal obesity and short stature, and by the presence of ketoacidotic insulin-dependent diabetes, optic atrophy and diabetes insipidus. Our observation broadens the clinical spectrum of Alström syndrome and suggests that ALMS1 mutations may be considered in patients who initially present with an acute onset of insulin-dependent diabetes.
diabetes; genetic diagnosis; monogenic disease; Wolfram syndrome; Alström syndrome
Copy number variants (CNVs) have repeatedly been found to cause or predispose to autism spectrum disorders (ASDs). For diagnostic purposes, we screened 194 individuals with ASDs for CNVs using Illumina SNP arrays. In several probands, we also analyzed candidate genes located in inherited deletions to unmask autosomal recessive variants. Three CNVs, a de novo triplication of chromosome 15q11–q12 of paternal origin, a deletion on chromosome 9p24 and a de novo 3q29 deletion, were identified as the cause of the disorder in one individual each. An autosomal recessive cause was considered possible in two patients: a homozygous 1p31.1 deletion encompassing PTGER3 and a deletion of the entire DOCK10 gene associated with a rare hemizygous missense variant. We also identified multiple private or recurrent CNVs, the majority of which were inherited from asymptomatic parents. Although highly penetrant CNVs or variants inherited in an autosomal recessive manner were detected in rare cases, our results mainly support the hypothesis that most CNVs contribute to ASDs in association with other CNVs or point variants located elsewhere in the genome. Identification of these genetic interactions in individuals with ASDs constitutes a formidable challenge.
copy number variants; autism spectrum disorders; 15q11–q12 triplication; autosomal recessive inheritance; genetic interactions
Recent studies have established the role of rare copy number variants (CNVs) in several neurological disorders but the contribution of rare CNVs to cerebral palsy (CP) is not known. Fifty Caucasian families having children with CP were studied using two microarray designs. Potentially pathogenic, rare (<1% population frequency) CNVs were identified, and their frequency determined, by comparing the CNVs found in cases with 8329 adult controls with no known neurological disorders. Ten of the 50 cases (20%) had rare CNVs of potential relevance to CP; there were a total of 14 CNVs, which were observed in <0.1% (<8/8329) of the control population. Eight inherited from an unaffected mother: a 751-kb deletion including FSCB, a 1.5-Mb duplication of 7q21.13, a 534-kb duplication of 15q11.2, a 446-kb duplication including CTNND2, a 219-kb duplication including MCPH1, a 169-kb duplication of 22q13.33, a 64-kb duplication of MC2R, and a 135-bp exonic deletion of SLC06A1. Three inherited from an unaffected father: a 386-kb deletion of 12p12.2-p12.1, a 234-kb duplication of 10q26.13, and a 4-kb exonic deletion of COPS3. The inheritance was unknown for three CNVs: a 157-bp exonic deletion of ACOX1, a 693-kb duplication of 17q25.3, and a 265-kb duplication of DAAM1. This is the first systematic study of CNVs in CP, and although it did not identify de novo mutations, has shown inherited, rare CNVs involving potentially pathogenic genes and pathways requiring further investigation.
copy number; cerebral palsy; microarray