Novel mutations and phenotypes of epilepsy-associated genes in epileptic encephalopathies.

Epileptic encephalopathies are severe epilepsy disorders with strong genetic bases. We performed targeted next-generation sequencing (NGS) in 70 patients with epileptic encephalopathies. The likely pathogenicity of variants in candidate genes was evaluated by American College of Medical Genetics and Genomics (ACMG) scoring taken together with the accepted clinical presentation. Thirty-three candidate variants were detected after population filtration and computational prediction. According to ACMG, 21 candidate variants, including 18 de novo variants, were assessed to be pathogenic/likely pathogenic with clinical concordance. Twelve variants were initially assessed as uncertain significance by ACMG, among which 3 were considered causative and 3 others were considered possibly causative after analysis of clinical concordance. In total, 24 variants were identified as putatively causative, among which 19 were novel findings. SCN1A mutations were identified in 50% of patients with Dravet syndrome. TSC1/TSC2 mutations were detected in 66.7% of patients with tuberous sclerosis. STXBP1 mutations were the main findings in patients with West syndrome. Mutations in SCN2A, KCNT1, KCNQ2 and CLCN4 were identified in patients with epileptic infantile with migrating focal seizures; among them, KCNQ2 and CLCN4 were first identified as potential causative genes. Only one CHD2 mutation was detected in patients with Lennox-Gastaut syndrome. This study highlighted the utility of targeted NGS in genetic diagnoses of epileptic encephalopathies and a comprehensive evaluation of the pathogenicity of variants based on ACMG scoring and assessment of clinical concordance. Epileptic encephalopathies differ in genetic causes, and the genotype-phenotype correlations would provide insights into the underlying pathogenic mechanisms.

Electrophysiological Differences between the Same Pore Region Mutation in SCN1A and SCN3A.

Mutations in the sodium channel gene, SCN1A (NaV1.1), have been linked to a spectrum of epilepsy syndromes, and many of these mutations occur in the pore region of the channel. Electrophysiological characterization has revealed that most SCN1A mutations in the pore region result in complete loss of function. SCN3A mutations have also been identified in patients with epilepsy; however, mutations in this pore region maintain some degree of electrophysiological function. It is thus speculated that compared to SCN3A disruptions, SCN1A mutations have a more pronounced effect on electrophysiological function. In this study, we identified a novel mutation, N302S, in the SCN3A pore region of a child with epilepsy. To investigate if mutations at the pore regions of SCN3A and SCN1A have different impacts on channel function, we studied the electrophysiological properties of N302S in NaV1.3 and its homologous mutation (with the same amino acid substitution) in NaV1.1 (N301S). Functional analysis demonstrated that SCN1A-N301S had no measurable sodium current, indicating a complete loss of function, while SCN3A-N302S slightly reduced channel activity. This observation indicates that the same pore region mutation affects SCN1A more than SCN3A. Our study further revealed a huge difference in electrophysiological function between SCN1A and SCN3A mutations in the pore region; this might explain the more common SCN1A mutations detected in patients with epilepsy and the more severe phenotypes associated with these mutations.

The targeting and functions of miRNA-383 are mediated by FMRP during spermatogenesis.

Our previous studies have shown that microRNA-383 (miR-383) expression is downregulated in the testes of infertile men with maturation arrest (MA). Abnormal testicular miR-383 expression may potentiate the connections between male infertility and testicular germ cell tumors. However, the mechanisms underlying the targeting and functions of miR-383 during spermatogenesis remain unknown. In this study, we found that fragile X mental retardation protein (FMRP) was associated with 88 miRNAs in mouse testis including miR-383. Knockdown of FMRP in NTERA-2 (NT2) (testicular embryonal carcinoma) cells enhanced miR-383-induced suppression of cell proliferation by decreasing the interaction between FMRP and miR-383, and then affecting miR-383 binding to the 3'-untranslated region of its target genes, including interferon regulatory factor-1 (IRF1) and Cyclin D1 both in vivo and in vitro. On the other hand, FMRP levels were also downregulated by overexpression of miR-383 in NT2 cells and GC1 (spermatogonia germ cell line). miR-383 targeted to Cyclin D1 directly, and then inhibited its downstream effectors, including phosphorylated pRb and E2F1, which ultimately resulted in decreased FMRP expression. Reduced miR-383 expression, dysregulated cyclin-dependent kinase 4 expression (one of the downstream genes of miR-383) and increased DNA damage were also observed in the testes of Fmr1 knockout mice and of MA patients with a downregulation of FMRP. A potential feedback loop between FMRP and miR-383 during spermatogenesis is proposed, and FMRP acts as a negative regulator of miR-383 functions. Our data also indicate that dysregulation of the FMRP-miR-383 pathway may partially contribute to human spermatogenic failure with MA.

Novel PRRT2 mutations in paroxysmal dyskinesia patients with variant inheritance and phenotypes.

Paroxysmal dyskinesias (PDs) are a group of episodic movement disorders with marked variability in clinical manifestation and potential association with epilepsy. PRRT2 has been identified as a causative gene for PDs, but the phenotypes and inheritance patterns of PRRT2 mutations need further clarification. In this study, 10 familial and 21 sporadic cases with PDs and PDs-related phenotypes were collected. Genomic DNA was screened for PRRT2 mutations by direct sequencing. Seven PRRT2 mutations were identified in nine (90.0%) familial cases and in six (28.6%) sporadic cases. Five mutations are novel: two missense mutations (c.647C>G/p.Pro216Arg and c.872C>T/p.Ala291Val) and three truncating mutations (c.117delA/p.Val41TyrfsX49, c.510dupT/p.Leu171SerfsX3 and c.579dupA/p.Glu194ArgfsX6). Autosomal dominant inheritance with incomplete penetrance was observed in most of the familial cases. In the sporadic cases, inheritance was heterogeneous including recessive inheritance with compound heterozygous mutations, inherited mutations with incomplete parental penetrance and de novo mutation. Variant phenotypes associated with PRRT2 mutations, found in 36.0% of the affected cases, included febrile convulsions, epilepsy, infantile non-convulsive seizures (INCS) and nocturnal convulsions (NC). All patients with INCS or NC, not reported previously, displayed abnormalities on electroencephalogram (EEG). No EEG abnormalities were recorded in patients with classical infantile convulsions and paroxysmal choreoathetosis (ICCA)/paroxysmal kinesigenic dyskinesia (PKD). Our study further confirms that PRRT2 mutations are the most common cause of familial PDs, displaying both dominant and recessive inheritance. Epilepsy may occasionally occur in ICCA/PKD patients with PRRT2 mutations. Variant phenotypes INCS or NC differ from classical ICCA/PKD clinically and electroencephalographically. They have some similarities with, but not identical to epilepsy, possibly represent an overlap between ICCA/PKD and epilepsy.

Mosaic SCN1A mutations in familial partial epilepsy with antecedent febrile seizures.

SCN1A is the most relevant epilepsy gene. Mutations of SCN1A generate phenotypes ranging from the extremely severe form of Dravet syndrome (DS) to a mild form of generalized epilepsy with febrile seizures plus (GEFS+). Mosaic SCN1A mutations have been identified in rare familial DS. It is suspected that mosaic mutations of SCN1A may cause other types of familial epilepsies with febrile seizures (FS), which are more common clinically. Thus, we screened SCN1A mutations in 13 families with partial epilepsy with antecedent febrile seizures (PEFS+) using denaturing high-performance liquid chromatography and sequencing. The level of mosaicism was further quantified by pyrosequencing. Two missense SCN1A mutations with mosaic origin were identified in two unrelated families, accounting for 15.4% (2/13) of the PEFS+ families tested. One of the mosaic carriers with ~25.0% mutation of c.5768A>G/p.Q1923R had experienced simple FS; another with ~12.5% mutation of c.4847T>C/p.I1616T was asymptomatic. Their heterozygous children had PEFS+. Recurrent transmission occurred in both families, as noted in most of the families with germline mosaicism reported previously. The two mosaic mutations identified in this study are less destructive missense, compared with the more destructive truncating and splice-site mutations identified in the majority of previous studies. This is the first report of mosaic SCN1A mutations in families with probands that do not exhibit DS, but manifest only a milder phenotype. Therefore, such families with mild cases should be approached with caution in genetic counseling and the possibility of mosaicism origin associated with high recurrence risk should be excluded.

Altered expression of voltage-gated potassium channel 4.2 and voltage-gated potassium channel 4-interacting protein, and changes in intracellular calcium levels following lithium-pilocarpine-induced status epilepticus.

The A-type voltage-gated potassium channels (Kv4) have been proved to play a major role as modulators of somatodendritic excitability. Recent studies indicate that neuronal hyperactivity in epilepsy is associated with changes in Kv4. However, the precise regulation of Kv4 in the development of epilepsy and its underlying mechanism remain unclear. In this study, we investigated whether the expression of the Kv4.2 channel and of its major modulator, voltage-dependent potassium channel-interacting protein (KChIP1), is altered following lithium-pilocarpine induced status epilepticus (SE) and the chronic-epilepsy phase in the rat model. We found that Kv4.2 and KChIP1 expression was transiently up-regulated following SE, whereas it was down-regulated during the chronic phase: this was most prominent in the CA1 and CA3 regions. The time-course analysis of the protein expression level showed that the peak Kv4.2 up-regulation was between 6 and 24 h after SE, whereas KChIP1 expression was increased earlier and for a shorter period. The temporospatial changes in Kv4.2 were very similar to those of its major modulator KChIP1. We compared the difference in 4-aminopyridine (4-AP)-induced intracellular calcium ([Ca(2+)]i) elevation between model and control brain slices. The results showed that the [Ca(2+)]i elevation induced by the Kv4 channel blocker 4-AP was aggravated and prolonged in the model slice after SE. The functional relevance of these changes in Ca(2+) homeostasis and Kv4.2 and KChIP1 expression may be associated with intrinsic neuronal excitability regulation and epileptogenesis.

Upregulation of dihydropyrimidinase-related protein 2, spectrin alpha II chain, heat shock cognate protein 70 pseudogene 1 and tropomodulin 2 after focal cerebral ischemia in rats--a proteomics approach.

In recent years, there are an increasing number of proteomics studies that investigated the alterations in the protein expression relevant to human diseases but none for stroke. We, therefore, attempted such a study in a paradigm of focal cerebral ischemia in rat. Rats were subjected to cerebral ischemia by unilateral occlusion of the middle cerebral artery. Global protein analysis was performed after 24h on the lesioned and sham-control cerebral cortex using two-dimensional gel electrophoresis. Protein spots with more than a 3-fold change in intensity were identified by mass spectrometry. Middle cerebral artery occlusion (MCAO) caused infarct volume of 18-22% predominantly in the cortex of the lesioned hemisphere. Two-dimensional gel electrophoresis resolved about 1500 protein spots of which only 12 were significantly upregulated by 3-46-fold. Three spots were identified to be dihydropyrimidinase-related protein 2 (DRP-2, also known as collapsin response mediator protein 2 (CRMP-2) or turned on after division, 64 kD protein (TOAD-64)). The spots varied in pI values only and this may reflect different phosphorylation status of the same protein. Two spots were identified as spectrin alpha II chain (rat fragment, also known as alpha-fodrin or non-erythroid alpha chain, SPNA-2); and one spot each for heat shock cognate protein 70 pseudogene 1 (HSC70-ps1, also known as heat shock protein 8 pseudogene 1), and tropomodulin 2 (Tmod2). The upregulation of protein expression was corroborated by observed upregulation of mRNA expression. The remaining five spots were not identified satisfactorily. As DRP-2, spectrin, and Tmod2 are involved in axonal and neurite growth as well as synaptic plasticity and maturation, the presently observed upregulation of the expression of these proteins may indicate active neuroregeneration and repair at 24h after the induction of cerebral ischemia.

Liposomal delivery of alpha-Interferon to murine bladder tumor cells via transferrin receptor-mediated endocytosis.

The role of transferrin receptor-mediated endocytosis in promoting murine bladder tumor cell (MBT2) uptake of liposomes and the antiproliferative effect of liposome-entrapped alpha-interferon (alpha-IFN) against MBT2 were investigated. Liposomes (0.11 microm) were prepared using phosphatidylcholine and phosphatidylserine in a molar ratio of 7:3, with or without surface conjugation of transferrin-polylysine (TFPL). The uptake of plain liposomes (without TFPL) by MBT2 was less than 5% after incubation for 48 h. In contrast, cell uptake of TFPL-liposomes was markedly enhanced by TFPL in a dose-dependent manner and reached plateau levels in 24 h. This increase was partially blocked by the addition of free transferrin, suggesting that the uptake process involves transferrin receptor-mediated endocytosis. The antiproliferative activity of alpha-IFN (100-200 U/well), delivered via plain liposomes, measured against blank liposome control, was in the range of 25-35%, which was similar to that of free alpha-IFN. In comparison, inhibition of cell proliferation by same concentrations of alpha-IFN delivered by TFPL-liposomes was 90-100%. These results show a strong correlation between antiproliferative activity and the uptake of liposomes by the tumor cells, indicating that TFPL-liposomes promote intracellular delivery of alpha-IFN and enhance the effect of alpha-IFN against MBT2 cell growth. The potential cytotoxicity of drug-free liposomes was also investigated. Liposomes containing various concentrations of TFPL showed significant dose- and time-dependent antiproliferative activity against MBT2. This effect maybe attributed to lipidosis and/or the destruction of intracellular cycle of iron transport.

Simultaneous determination of tryptophan, 5-hydroxytryptophan, 5-hydroxytryptamine, 5-hydroxyindoleacetic acid, 4-hydroxy-3-methoxyphenylacetic acid and 3-methoxy-4-hydroxyphenylglycol in human cerebrospinal fluid.

Serotonin (5-hydroxytryptamine) metabolism may be influenced by its precursor tryptophan. A method utilizing reversed-phase high-performance liquid chromatography and electrochemical and ultraviolet detection with a mobile phase composed of acetate buffer and methanol has been developed for determination of tryptophan, its metabolites 5-hydroxytryptophan, serotonin, 5-hydroxyindoleacetic acid, as well as 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid) and 3-methoxy-4-hydroxyphenylglycol in human cerebrospinal fluid (CSF). The electrochemical potential is set at 0.6 V in order to reduce the background current. Since tryptophan is not electroactive at this potential, it is detected by ultraviolet absorbance. The present method is simple, rapid, specific and accurate as compared with a previously reported method. No sample pretreatment is necessary and it takes ca. 20 min to run a sample. The concentrations of the compounds measured in CSF are similar to those obtained by HPLC in previous reports, although there are still arguments about the true level of serotonin in CSF.

[Altered monoamine metabolism in children with epilepsy].

Tryptophan (Trp), 5-HTP, 5-HT, 5-HIAA, HVA, and MHPG in CSF and total Trp(T-Trp), free Trp(F-Trp) and serotonin in serum were determined in 80 children with epilepsy and also in a control group. It was found that Trp, 5-HT, 5-HIAA in CSF and F-Trp in blood decreased in children with epilepsy. But the decrease of F-Trp was not the main cause of decreased 5-HT metabolism, because the no positive correlations among the four substances were found. Each of them returned to normal levels after the treatment with phenytoin or valproate. 5-HT concentration was negatively correlated with the frequency of the epilepsy episodes. 5-HIAA and HVA levels were relatively higher in the epileptics with brain damage as with compared with those who had no brain damage. The MHPG level was higher in the patients simple partial seizures. Complex partial epileptics and those patients receiving antiepileptic drugs had a lower serum T-Trp level. T-Trp was negatively correlated with the serum valproate concentration. Both T-Trp and F-Trp levels decreased in the patients treated with phenytoin.