Search

Background Dravet syndrome is a severe, genetic epileptic encephalopathy with seizures starting during the first year of life. We present a review of the genetic and clinical picture along with treatment aspects. Material and methods This review is based on a non-systematic literature search in PubMed until April 2011 and the personal experiences of the authors. Results Dravet syndrome should be suspected in children with febrile hemiconvulsions or tonic-clonic seizures in the first year of life. Non-febrile seizures also occur, and other seizure types gradually appear, e.g. myoclonic jerks, atypical absences or focal seizures. In adulthood the clinical picture is less characteristic. The clinical diagnosis is supported by genetic testing; 70-80% of the patients have mutations in the sodium channel subunit gene SCN1A. Seizure control is difficult to achieve, but valproate, benzodiazepines and stiripentol may cause improvement, whereas sodium channel blockers, such as lamotrigine and carbamazepine may aggravate the tendency towards seizures. Interpretation Dravet syndrome appears to be an under-recognised condition among both children and adults with severe epilepsy and learning disability. Clinical information from the first years of life is essential in making the diagnosis. A correct diagnosis at an early age is essential for appropriate treatment and genetic counselling.

Autism spectrum disorders (ASDs) are a heterogeneous group of disorders with a complex genetic etiology. We used high-resolution whole genome array-based comparative genomic hybridization (array-CGH) to screen 223 ASD patients for gene dose alterations associated with susceptibility for autism. Clinically significant copy number variations (CNVs) were identified in 18 individuals (8%), of which 9 cases (4%) had de novo aberrations. In addition, 20 individuals (9%) were shown to have CNVs of unclear clinical relevance. Among these, 13 cases carried rare but inherited CNVs that may increase the risk for developing ASDs, while parental samples were unavailable in the remaining seven cases. Classification of all patients into different phenotypic and inheritance pattern groups indicated the presence of different CNV patterns in different patient groups. Clinically relevant CNVs were more common in syndromic cases compared to non-syndromic cases. Rare inherited CNVs were present in a higher proportion of ASD cases having first- or second-degree relatives with an ASD-related neuropsychiatric phenotype in comparison with cases without reported heredity (P = 0.0096). We conclude that rare CNVs, encompassing potential candidate regions for ASDs, increase the susceptibility for the development of ASDs and related neuropsychiatric disorders giving us further insight into the complex genetics underlying ASDs. © 2010 Wiley-Liss, Inc.

Little is known about the cytogenetic features and molecular mechanisms behind hairy cell leukaemia (HCL), despite the advances in diagnosis and treatment. Therefore, we used high-resolution genome-wide array-based comparative genomic hybridisation (array-CGH) and multiplex ligation-dependent probe amplification (MLPA) to characterise copy number alterations (CNAs) in DNA from 13 cases of HCL. We also summarise CNAs and cytogenetic features in 109 HCL cases comprising our 13 cases and 96 cases from the literature. Genomic array-CGH revealed imbalances in two out of 13 cases in addition to previously described copy number variants (CNVs) found in healthy individuals. In one case, a 700 kb deletion of 20q11.22 was detected encompassing ten characterised genes, among them the TP53INP2, DNCL2A and ITCH genes. In the second case, trisomy 5, and a deletion of 5p15.2 encompassing a non-characterised gene AY328033 was found. Altogether only 20/81 (25%) of all cases studied by CGH or gene dose array revealed CNAs. The most common recurrent deletions and breakpoints were 14q22-32 (33%), 6q25 (16%), 2p12 (10%), 22q11 (10%), 17p11-13 (10%), 7q32-36 (9%), 18q11-13 (7%), 1q32-44 (6%), 8p22-23 (6%) and 7q11 (6%). Trisomy 5 occurred in 15%. In addition, several other recurrent breakpoints were identified. Although a number of genomic imbalances were identified in the HCL samples, the genome appeared remarkably stable.

Forkhead box class O (FoxO) transcription factors are a family of conserved proteins that regulate the cellular responses to various stimuli, such as energy deprivation, stress, and developmental cues. FoxO proteins are important mediators of the insulin signaling pathway, adjusting growth and metabolism to nutrient availability. Insulin signaling acts together with the glucagon-stimulated cAMP signaling pathway to orchestrate the organism response to various nutritional conditions. In this study, we demonstrate that Drosophila melanogaster FoxO (dFoxO) regulates cAMP signaling by directly inducing the expression of an adenylate cyclase gene, ac76e. Interestingly, ac76e is expressed in a highly restricted pattern throughout fly development, limited to the corpus allatum (CA), gastric cecum, and malpighian tubules. dFoxO activation of AC76E in the CA increases starvation resistance and limits growth. Our results unravel a new role for dFoxO, integrating cAMP and insulin signaling to adapt organism growth to the existing nutritional conditions.

Seven cases with an interstitial deletion of the short arm of chromosome 6 involving the 6p22 region have previously been reported. The clinical phenotype of these cases includes developmental delay, brain-, heart-, and kidney defects, eye abnormalities, short neck, craniofacial malformations, hypotonia, as well as clinodactyly or syndactyly. Here, we report a patient with a 7.1 Mb interstitial deletion of chromosome band 6p22.3, detected by genome-wide screening array CGH. The patient is a 4-year-old girl with developmental delay and dysmorphic features including eye abnormalities, short neck, and a ventricular septum defect. The deleted region at 6p22.3 in our patient overlaps with six out of the seven previously reported cases with a 6p22–24 interstitial deletion. This enabled us to further narrow down the critical region for the 6p22 deletion phenotype to 2.2 Mb. Twelve genes are mapped to the overlapping deleted region, among them the gene encoding the ataxin-1 protein, the ATXN1 gene. Mice with homozygous deletions in ATXN1 are phenotypically normal but show cognitive delay. Haploinsufficiency of ATXN1 may therefore contribute to the learning difficulties observed in the patients harboring a 6p22 deletion.

Several studies have suggested that rare copy number variants (CNVs) are an important genetic contributor to autism spectrum disorders. The aims of the study were to use chromosomal microarray to investigate the presence of rare copy number variants in a population-based cohort of well-characterised young children with autism spectrum disorders and to relate the genetic results to neurodevelopmental profiles and medical conditions.We performed chromosomal microarray on samples from 162 children who had been referred to the Stockholm Autism Centre for Young Children in Sweden after being diagnosed with autism spectrum disorder between 20 and 54 months of age.Pathogenic aberrations were detected in 8.6% of the children and variants of uncertain significance were present in another 8.6%. CNVs were more frequent in children with congenital malformations or dysmorphic features as well as in the subgroup with intellectual disability.Our results support the use of chromosomal microarray methods for the first tier genetic analysis of autism spectrum disorder. However, it is likely in the near future that chromosomal microarray methods will probably be replaced by whole-exome and whole-genome sequencing technologies in clinical genetic testing.

In this study, we used deletions at 22q13, which represent a substantial source of human pathology (Phelan/McDermid syndrome), as a model for investigating the molecular mechanisms of terminal deletions that are currently poorly understood. We characterized at the molecular level the genomic rearrangement in 44 unrelated patients with 22q13 monosomy resulting from simple terminal deletions (72%), ring chromosomes (14%), and unbalanced translocations (7%). We also discovered interstitial deletions between 17–74 kb in 9% of the patients. Haploinsufficiency of the SHANK3 gene, confirmed in all rearrangements, is very likely the cause of the major neurological features associated with PMS. SHANK3 mutations can also result in language and/or social interaction disabilities. We determined the breakpoint junctions in 29 cases, providing a realistic snapshot of the variety of mechanisms driving non-recurrent deletion and repair at chromosome ends. De novo telomere synthesis and telomere capture are used to repair terminal deletions; non-homologous end-joining or microhomology-mediated break-induced replication is probably involved in ring 22 formation and translocations; non-homologous end-joining and fork stalling and template switching prevail in cases with interstitial 22q13.3. For the first time, we also demonstrated that distinct stabilizing events of the same terminal deletion can occur in different early embryonic cells, proving that terminal deletions can be repaired by multistep healing events and supporting the recent hypothesis that rare pathogenic germline rearrangements may have mitotic origin. Finally, the progressive clinical deterioration observed throughout the longitudinal medical history of three subjects over forty years supports the hypothesis of a role for SHANK3 haploinsufficiency in neurological deterioration, in addition to its involvement in the neurobehavioral phenotype of PMS., Author Summary Terminal chromosome deletions are among the most commonly observed rearrangements detected by cytogenetics and may result in several well-known genetic syndromes. We used 22q13 deletions to study how these types of chromosome abnormalities arise. Children with Phelan/McDermid syndrome, caused by deletion of the terminal portion of chromosome 22, experience developmental delay, absent or severely delayed speech, and frequent behavioral problems. Lack of one copy of SHANK3, a key gene for the correct development and organization of brain synapses, is very likely the basis of the syndrome's major neurological features. Deletion of additional genes probably causes more complex phenotypes in subjects with larger deletions. We also studied patients who only lack a portion of SHANK3 and demonstrated that small, hard-to-detect deletions of this gene may cause substantial clinical problems. Until now, the 22q distal deletion had been only diagnosed in very young people. We studied a large group of patients of different ages and discovered that all adult patients face progressive cognitive decline. Our study demonstrates that deletion of the terminal portion of chromosome 22, a prototype for terminal deletions in human chromosomes, can occur in several ways. Mosaic deletions of different size can also form in early embryogenesis.

Background One consistent finding in autism spectrum disorders (ASD) is a decreased level of the pineal gland hormone melatonin and it has recently been demonstrated that this decrease to a large extent is due to low activity of the acetylserotonin O-methyltransferase (ASMT), the last enzyme in the melatonin synthesis pathway. Moreover, mutations in the ASMT gene have been identified, including a splice site mutation, that were associated with low ASMT activity and melatonin secretion, suggesting that the low ASMT activity observed in autism is, at least partly, due to variation within the ASMT gene. Methods In the present study, we have investigated all the genes involved in the melatonin pathway by mutation screening of AA-NAT (arylalkylamine N-acetyltransferase), ASMT, MTNR1A, MTNR1B (melatonin receptor 1A and 1B) and GPR50 (G protein-coupled receptor 50), encoding both synthesis enzymes and the three main receptors of melatonin, in 109 patients with autism spectrum disorders (ASD). A cohort of 188 subjects from the general population was used as a comparison group and was genotyped for the variants identified in the patient sample. Results Several rare variants were identified in patients with ASD, including the previously reported splice site mutation in ASMT (IVS5+2T>C). Of the variants affecting protein sequence, only the V124I in the MTNR1B gene was absent in our comparison group. However, mutations were found in upstream regulatory regions in three of the genes investigated, ASMT, MTNR1A, and MTNR1B. Conclusions Our report of another ASD patient carrying the splice site mutation IVS5+2T>C, in ASMT further supports an involvement of this gene in autism. Moreover, our results also suggest that other melatonin related genes might be interesting candidates for further investigation in the search for genes involved in autism spectrum disorders and related neurobehavioral phenotypes. However, further studies of the novel variants identified in this study are warranted to shed light on their potential role in the pathophysiology of these disorders.

The chromosome region 22q11.2 has long been recognized to be susceptible to genomic rearrangement. More recently, this genomic instability has been shown to extend distally (involving LCR22E–H) to the commonly deleted/duplicated region. To date, 21 index cases with ‘distal’ 22q11.2 duplications have been reported. We report on the clinical and molecular characterization of 16 individuals with distal 22q11.2 duplications identified by DNA microarray analysis. Two of the individuals have been partly described previously. The clinical phenotype varied among the patients in this study, although the majority displayed various degrees of developmental delay and speech disturbances. Other clinical features included behavioral problems, hypotonia, and dysmorphic facial features. Notably, none of the patients was diagnosed with a congenital heart defect. We found a high degree of inherited duplications. Additional copy number changes of unclear clinical significance were identified in 5 of our patients, and it is possible that these may contribute to the phenotypic expression in these patients as has been suggested recently in a 2-hit ‘digenic’ model for 16p12.1 deletions. The varied phenotypic expression and incomplete penetrance observed for distal 22q11.2 duplications makes it exceedingly difficult to ascribe pathogenicity for these duplications. Given the observed enrichment of the duplication in patient samples versus healthy controls, it is likely that distal 22q11.2 duplications represent a susceptibility/risk locus for speech and mild developmental delay.

The autism spectrum disorder (ASD) is a heterogenous condition characterized by impaired socialization and communication in association with stereotypic behaviors. ASD is highly heritable and heterogeneous with a complex genetic etiology. Recurrent submicroscopic deletions or duplications have been identified in a subgroup of individuals with ASD using array technology. Adequate genetic testing for these genomic imbalances have not yet been widely implemented in the diagnostic setting due to lack of feasible and cost-effective methods as well as difficulties to interpret the clinical significance of these small copy number variants (CNVs). We developed a multiplex ligation-dependent probe amplification (MLPA) assay to investigate its usefulness for detection of copy number alterations (CNAs) in autistic patients. This test proved to be easy to perform, fast, cost-effective, and suitable for reliable detection of multiple loci in a single reaction. We screened 148 autistic patients for 15 different loci covering 26 genes and found a 15q11-13 interstitial duplication that had escaped detection by conventional karyotyping in 1.3% of the patients. Synthetic probe MLPA allows for a flexible analysis of a continuously increasing number of CNAs associated with autism. Our result show that MLPA assay is an easy and cost-effective method for the identification of selected CNAs in diagnostic laboratories.