Partial deletions of the gene encoding the neuronal splicing regulator RBFOX1 have been reported in a range of neurodevelopmental diseases, including idiopathic generalized epilepsy. The RBFOX1 protein and its homologues (RBFOX2 and RBFOX3) regulate alternative splicing of many neuronal transcripts involved in the homeostatic control of neuronal excitability. In this study, we explored if structural microdeletions and exonic sequence variations in RBFOX1, RBFOX2, RBFOX3 confer susceptibility to rolandic epilepsy (RE), a common idiopathic focal childhood epilepsy. By high-density SNP array screening of 289 unrelated RE patients, we identified two hemizygous deletions, a 365 kb deletion affecting two untranslated 5′-terminal exons of RBFOX1 and a 43 kb deletion spanning exon 3 of RBFOX3. Exome sequencing of 242 RE patients revealed two novel probably deleterious variants in RBFOX1, a frameshift mutation (p.A233Vfs*74) and a hexanucleotide deletion (p.A299_A300del), and a novel nonsense mutation in RBFOX3 (p.Y287*). Although the three variants were inherited from unaffected parents, they were present in all family members exhibiting the RE trait clinically or electroencephalographically with only one exception. In contrast, no deleterious mutations of RBFOX1 and RBFOX3 were found in the exomes of 6503 non-RE subjects deposited in the Exome Variant Server database. The observed RBFOX3 exon 3 deletion and nonsense mutation suggest that RBFOX3 represents a novel risk factor for RE, indicating that exon deletions and truncating mutations of RBFOX1 and RBFOX3 contribute to the genetic variance of partial and generalized idiopathic epilepsy syndromes.
MicroRNAs (miRNAs) are small non-coding RNAs that regulate various biological processes. Cell-free miRNAs measured in blood plasma have emerged as specific and sensitive markers of physiological processes and disease. In this study, we investigated whether circulating miRNAs can serve as biomarkers for the detection of autologous blood transfusion, a major doping technique that is still undetectable. Plasma miRNA levels were analyzed using high-throughput quantitative real-time PCR. Plasma samples were obtained before and at several time points after autologous blood transfusion (blood bag storage time 42 days) in 10 healthy subjects and 10 controls without transfusion. Other serum markers of erythropoiesis were determined in the same samples. Our results revealed a distinct change in the pattern of circulating miRNAs. Ten miRNAs were upregulated in transfusion samples compared with control samples. Among these, miR-30b, miR-30c, and miR-26b increased significantly and showed a 3.9-, 4.0-, and 3.0-fold change, respectively. The origin of these miRNAs was related to pulmonary and liver tissues. Erythropoietin (EPO) concentration decreased after blood reinfusion. A combination of miRNAs and EPO measurement in a mathematical model enhanced the efficiency of autologous transfusion detection through miRNA analysis. Therefore, our results lay the foundation for the development of miRNAs as novel blood-based biomarkers to detect autologous transfusion.
Emerging evidence suggests that excessive exposure to traffic-derived air pollution during pregnancy may increase the vulnerability to neurodevelopmental alterations that underlie a broad array of neuropsychiatric disorders. We present a mouse model for prenatal exposure to urban freeway nanoparticulate matter (nPM). In prior studies, we developed a model for adult rodent exposure to re-aerosolized urban nPM which caused inflammatory brain responses with altered neuronal glutamatergic functions. nPMs are collected continuously for one month from a local freeway and stored as an aqueous suspension, prior to re-aerosolization for exposure of mice under controlled dose and duration. This paradigm was used for a pilot study of prenatal nPM impact on neonatal neurons and adult behaviors. Adult C57BL/6J female mice were exposed to re-aerosolized nPM (350 µg/m3) or control filtered ambient air for 10 weeks (3×5 hour exposures per week), encompassing gestation and oocyte maturation prior to mating. Prenatal nPM did not alter litter size, pup weight, or postnatal growth. Neonatal cerebral cortex neurons at 24 hours in vitro showed impaired differentiation, with 50% reduction of stage 3 neurons with long neurites and correspondingly more undifferentiated neurons at Stages 0 and 1. Neuron number after 24 hours of culture was not altered by prenatal nPM exposure. Addition of exogenous nPM (2 µg/ml) to the cultures impaired pyramidal neuron Stage 3 differentiation by 60%. Adult males showed increased depression-like responses in the tail-suspension test, but not anxiety-related behaviors. These pilot data suggest that prenatal exposure to nPM can alter neuronal differentiation with gender-specific behavioral sequelae that may be relevant to human prenatal exposure to urban vehicular aerosols.
ClC-2 is a voltage-dependent chloride channel that activates slowly at voltages negative to the chloride reversal potential. Adenosine triphosphate (ATP) and other nucleotides have been shown to bind to carboxy-terminal cystathionine-ß-synthase (CBS) domains of ClC-2, but the functional consequences of binding are not sufficiently understood. We here studied the effect of nucleotides on channel gating using single-channel and whole-cell patch clamp recordings on transfected mammalian cells. ATP slowed down macroscopic activation and deactivation time courses in a dose-dependent manner. Removal of the complete carboxy-terminus abolishes the effect of ATP, suggesting that CBS domains are necessary for ATP regulation of ClC-2 gating. Single-channel recordings identified long-lasting closed states of ATP-bound channels as basis of this gating deceleration. ClC-2 channel dimers exhibit two largely independent protopores that are opened and closed individually as well as by a common gating process. A seven-state model of common gating with altered voltage dependencies of opening and closing transitions for ATP-bound states correctly describes the effects of ATP on macroscopic and microscopic ClC-2 currents. To test for a potential pathophysiological impact of ClC-2 regulation by ATP, we studied ClC-2 channels carrying naturally occurring sequence variants found in patients with idiopathic generalized epilepsy, G715E, R577Q, and R653T. All naturally occurring sequence variants accelerate common gating in the presence but not in the absence of ATP. We propose that ClC-2 uses ATP as a co-factor to slow down common gating for sufficient electrical stability of neurons under physiological conditions.
Electronic supplementary material
The online version of this article (doi:10.1007/s00424-013-1286-0) contains supplementary material, which is available to authorized users.
Chloride channel; Single-channel recording; Channel gating; Epilepsy
Sphericity of erythrocytes can be estimated from analysis of FSC signal distribution in flow cytometry. Previously, Pearson’s coefficient of dissymmetry (PCD) and spherical index (SphI) were applied to determine erythrocyte sphericity from the FSC histogram. The aim of the present study is to illustrate the application of kurtosis as an indicator of erythrocyte sphericity in flow cytometry in a broad range of FSC distributions. Moreover, the possibility of longitudinal evaluation of erythrocyte sphericity is studied. Change of erythrocyte sphericity of 10 healthy subjects was induced by variation of buffer osmolarity to validate applicability of sphericity measures. Agreement between the sphericity indicators was then studied in samples from 20 healthy donors taken at three time points, which were processed through density gradient centrifugation and incubated with FITC-labelled antibodies to induce a broad variation of erythrocyte form (1086 samples). SphI, PCD and kurtosis of FSC distribution were calculated. Correlation of the respective measures, standard error of measurement (SEM) and r ratio (intra- to interindividual variance) were determined to illustrate agreement between the sphericity indicators. In the first study part, all sphericity indicators illustrated change of erythrocyte shape as induced by osmolarity variation. In the second part, correlation between kurtosis and SphI was −0.97 and correlation between kurtosis and PCD was 0.58 (p<0.05). In isotype control samples, correlation between kurtosis and SphI was −0.98 and correlation between kurtosis and PCD was 0.48 (p<0.05). In these samples, mean kurtosis was −0.80 (SEM 0.03), mean SphI was 2.19 (SEM 0.04) and mean PCD was −0.31 (SEM 0.02). r ratios of all measures of sphericity were <0.6. Our results show that kurtosis is closely correlated with SphI in a broad range of erythrocyte FSC distributions. Moreover, all measures of sphericity feature r ratios <0.6, highlighting that erythrocyte sphericity appears as a feasible parameter for individual longitudinal data monitoring.
15q13.3 microdeletions are the most common genetic findings in Idiopathic Generalized Epilepsies identified to date, present in up to 1% of patients. In addition, 15q13.3 microdeletions have been described in patients with epilepsy as part of a complex neurodevelopmental phenotype. We analyzed a cohort of 570 patients with various pediatric epilepsies for 15q13.3 microdeletions. Screening was performed using quantitative polymerase chain reaction, deletions were confirmed by array comparative genomic hybridization. We carried out detailed phenotyping of deletion carriers. In total, we identified four pediatric patients with 15q13.3 microdeletions including one previously described patient. 2/4 deletions were de novo, 1 deletion was inherited from an unaffected parent, and in one patient, inheritance is unknown. All four patients had absence epilepsy with various degrees of intellectual disability. We suggest that absence epilepsy accompanied by intellectual disability may represent a common phenotype of the 15q13.3 microdeletion in pediatric epilepsy patients.
Intellectual disability; IGE
Mutations in the FKBP10 gene were first described in patients with Osteogenesis imperfecta type III. Two follow up reports found FKBP10 mutations to be associated with Bruck syndrome type 1, a rare disorder characterized by congenital contractures and bone fragility. This raised the question if the patients in the first report indeed had isolated Osteogenesis imperfecta or if Bruck syndrome would have been the better diagnosis.
The patients described here are affected by severe autosomal recessive Osteogenesis imperfecta without contractures.
Homozygosity mapping identified FKBP10 as a candidate gene, and sequencing revealed a base pair exchange that causes a C-terminal premature stop codon in this gene.
Our study demonstrates that FKBP10 mutations not only cause Bruck syndrome or Osteogenesis imperfecta type III but can result in a severe type of isolated Osteogenesis imperfecta type IV with prenatal onset. Furthermore, it adds dentinogenesis imperfecta to the spectrum of clinical symptoms associated with FKBP10 mutations.
Microdeletion at chromosomal position 15q13.3 has been described in intellectual disability, autism spectrum disorders, schizophrenia and recently in idiopathic generalized epilepsy (IGE). Using independent IGE cohorts, we first aimed to confirm the association of 15q13.3 deletions and IGE. We then set out to determine the relative occurrence of sporadic and familial cases and to examine the likelihood of having seizures for individuals with the microdeletion in familial cases. The 15q13.3 microdeletion was identified in 7 of 539 (1.3%) unrelated cases of IGE using quantitative PCR or SNP arrays and confirmed by array comparative genomic hybridization analysis using probes specific to the 15q13.3 region. The inheritance of this lesion was tracked using family studies. Of the seven microdeletions identified in probands, three were de novo, two were transmitted from an unaffected parent and in two cases the parents were unavailable. Non-penetrance of the microdeletion was identified in 4/7 pedigrees and three pedigrees included other family members with IGE who lacked the 15q13.3 deletion. The odds ratio is 68 (95% confidence interval 29–181), indicating a pathogenic lesion predisposing to epilepsy with complex inheritance and incomplete penetrance for the IGE component of the phenotype in multiplex families.
Childhood absence epilepsy (CAE) is an idiopathic generalised epilepsy (IGE) characterised by typical absence seizures manifested by transitory loss of awareness with 2.5–4 Hz spike-wave complexes on ictal EEG. A genetic component to the aetiology is well recognised but the mechanism of inheritance and the genes involved are yet to be fully established.
A genome wide single nucleotide polymorphism (SNP)-based high density linkage scan was carried out using 41 nuclear pedigrees with at least two affected members. Multipoint parametric and non-parametric linkage analyses were performed using MERLIN 1.1.1 and a susceptibility locus was identified on chromosome 3p23-p14 (Zmean = 3.9, p < 0.0001; HLOD = 3.3, α = 0.7). The linked region harbours the functional candidate genes TRAK1 and CACNA2D2. Fine-mapping using a tagSNP approach demonstrated disease association with variants in TRAK1.
Childhood absence epilepsy; Linkage; Association; Chromosome 3; TRAK1
Background: Executive control of attention in schizophrenia has recently been assessed by means of the Attention Network Test (ANT). In the past, for tasks assessing executive attention, findings in schizophrenia have been contradictory, among others suggesting a lack of increased stimulus interference effects. Attention and executive functioning are substantially influenced by candidate genes of schizophrenia, including the functional single-nucleotide polymorphism catechol-o-methyltransferase (COMT) Val108/158Met, with task-dependent, specific effects of Met allele load on cognitive function. Therefore, we aimed at investigating executive attention in schizophrenic patients (SZP) as compared with healthy controls (HC), and to assess the specific impact of COMT Val108/158Met on executive attention, using ANT. Methods: We applied ANT to 63 SZP and 40 HC. We calculated a general linear model to investigate the influence of affection status and the COMT Val108/158Met genotype on executive attention as assessed by the ANT. Results: Multivariate analysis of variance revealed a significant effect of group on executive attention. SZP exhibited smaller conflict effects in the ANT. Met allele load significantly modulated executive attention efficiency, with homozygous Met individuals showing low overall reaction time but increased effects conflicting stimulus information in executive attention. Conclusions: Our data suggest a disease-related dissociation of executive attention with reduced conflict effects in SZP. Furthermore, they support the hypothesis of differential tonic-phasic dopamine activation and specific dopamine level effects in different cognitive tasks, which helps interpreting contradictory findings of Met allele load on cognitive performance. Disease status seems to modulate the impact of COMT Val108/158Met on cognitive performance.
schizophrenia; endophenotype; genetics; attention; dopamine
Hyperpolarization-activated cyclic nucleotide-gated (HCN1-4) channels play an important role in the regulation of neuronal rhythmicity. In the present study we describe the mutation analysis of HCN1 and HCN2 in 84 unrelated patients with idiopathic generalized epilepsy (IGE). Several functional variants were identified including the amino acid substitution R527Q in HCN2 exon 5. HCN2 channels containing the R527Q variant demonstrated a trend towards a decreased slope of the conductance-voltage relation. We also identified a variant in the splice donor site of HCN2 exon 5 that results in the formation of a cryptic splice donor. In HCN1, the amino acid substitution A881T was identified in one sporadic IGE patient but was not observed in 510 controls. Seven variants were examined further in a case-control association study consisting of a larger cohort of IGE patients. Further studies are warranted to more clearly establish the contribution of HCN1 and HCN2 dysfunction to the genetic variance of common IGE syndromes.
Hyperpolarization-activated cyclic nucleotide-gated channel; HCN1; HCN2; idiopathic generalized epilepsy; IGE; mutation analysis
Childhood absence epilepsy (CAE) is an idiopathic generalised epilepsy characterised by absence seizures manifested by transitory loss of awareness with 2.5-4Hz spike-wave complexes on ictal EEG. A genetic component to aetiology is established but the mechanism of inheritance and the genes involved are not fully defined. Available evidence suggests that genes encoding brain expressed voltage-gated calcium channels, including CACNG3 on chromosome 16p12-p13.1, may represent susceptibility loci for CAE. The aim of this work was to further evaluate CACNG3 as a susceptibility locus by linkage and association analysis. Assuming locus heterogeneity, a significant HLOD score (HLOD=3.54, α=0.62) was obtained for markers encompassing CACNG3 in 65 nuclear families with a proband with CAE. The maximum NPL score was 2.87 (p<0.002). Re-sequencing of the coding exons in 59 patients did not identify any putative causal variants. A linkage disequilibrium (LD) map of CACNG3 was constructed using 23 single nucleotide polymorphisms (SNPs). Transmission disequilibrium was sought using individual SNPs and SNP-based haplotypes with the pedigree disequilibrium test in 217 CAE trios and the 65 nuclear pedigrees.
Evidence for transmission disequilibrium (p≤0.01) was found for SNPs within a ∼35kb region of high LD encompassing the 5′UTR, exon 1 and part of intron 1 of CACNG3. Re-sequencing of this interval was undertaken in 24 affected individuals. Seventy-two variants were identified: 45 upstream; two 5′UTR; and 25 intronic SNPs. No coding sequence variants were identified, although four variants are predicted to affect exonic splicing.
This evidence supports CACNG3 as a susceptibility locus in a subset of CAE patients.
Absence epilepsy; linkage; association; CACNG3; genetics; splice variants
The vesicular monoamine transporter 1 gene (VMAT1/SLC18A1) maps to the shared bipolar disorder (BPD) / schizophrenia (SZ) susceptibility locus on chromosome 8p21. Vesicular monoamine transporters are involved in transport of monoamine neurotransmitters which have been postulated to play a relevant role in the etiology of BPD and/or SZ. Variations in the VMAT1 gene might affect transporter function and/or expression and might be involved in the etiology of BPD and/or SZ. Genotypes of 585 patients with BPD type I and 563 control subjects were obtained for three missense SNPs (Thr4Pro, Thr98Ser, Thr136Ile) and 4 non-coding SNPs (rs988713, rs2279709, rs3735835, rs1497020). All cases and controls were of European descent. Allele frequencies differed significantly for the potential functional polymorphism Thr136Ser between BPD patients and controls (p = 0.003; df = 1; OR = 1.34; 95% CI: 1.11 – 1.62). Polymorphisms in the promoter region (rs988713: p = 0.005, df = 1; OR = 1.31; 95% CI: 1.09 – 1.59) and intron 8 (rs2279709: p = 0.039, df = 1; OR = 0.84; 95% CI: 0.71 – 0.99) were also associated with disease. Expression analysis confirmed that VMAT1 is expressed in human brain at the mRNA and protein level. Results suggest that variations in the VMAT1 gene may confer susceptibility to BPD in patients of European descent. Additional studies are necessary to confirm this effect and to elucidate the role of VMAT1 in CNS physiology.
We demonstrate that common genetic polymorphisms contribute to the increasing heterogeneity of cognitive functioning in old age. We assess two common Val/Met polymorphisms, one affecting the Catechol-O-Methyltransferase (COMT) enzyme, which degrades dopamine (DA) in prefrontal cortex (PFC), and the other influencing the brain-derived neurotrophic factor (BDNF) protein. In two tasks (Wisconsin Card Sorting and spatial working memory), we find that effects of COMT genotype on cognitive performance are magnified in old age and modulated by BDNF genotype. Older COMT Val homozygotes showed particularly low levels of performance if they were also BDNF Met carriers. The age-associated magnification of COMT gene effects provides novel information on the inverted U-shaped relation linking dopaminergic neuromodulation in PFC to cognitive performance. The modulation of COMT effects by BDNF extends recent evidence of close interactions between frontal and medial-temporal circuitries in executive functioning and working memory.
genes; dopamine; executive functions; prefrontal cortex; aging
15q13.3 microdeletions are the most common genetic findings identified in idiopathic generalized epilepsies to date, and they are present in up to 1% of patients. In addition, 15q13.3 microdeletions have been described in patients with epilepsy as part of a complex neurodevelopmental phenotype. We analyzed a cohort of 570 patients with various pediatric epilepsies for 15q13.3 microdeletions. Screening was performed using quantitative polymerase chain reaction; deletions were confirmed by array comparative genomic hybridization (CGH). We carried out detailed phenotyping of deletion carriers. In total, we identified four pediatric patients with 15q13.3 microdeletions, including one previously described patient. Two of four deletions were de novo, one deletion was inherited from an unaffected parent, and for one patient the inheritance is unknown. All four patients had absence epilepsy with various degrees of intellectual disability. We suggest that absence epilepsy accompanied by intellectual disability may represent a common phenotype of the 15q13.3 microdeletion in pediatric patients with epilepsy.
Intellectual disability; Idiopathic generalized epilepsy