Dominant-negative effects of KCNQ2 mutations are associated with epileptic encephalopathy.

OBJECTIVE: Mutations in KCNQ2 and KCNQ3, encoding the voltage-gated potassium channels KV 7.2 and KV 7.3, are known to cause benign familial neonatal seizures mainly by haploinsufficiency. Here, we set out to determine the disease mechanism of 7 de novo missense KCNQ2 mutations that were recently described in patients with a severe epileptic encephalopathy including pharmacoresistant seizures and pronounced intellectual disability. METHODS: Mutations were inserted into the KCNQ2 cDNA. Potassium currents were recorded using 2-microelectrode voltage clamping, and surface expression was analyzed by a biotinylation assay in cRNA-injected Xenopus laevis oocytes. RESULTS: We observed a clear loss of function for all mutations. Strikingly, 5 of 7 mutations exhibited a drastic dominant-negative effect on wild-type KV 7.2 or KV 7.3 subunits, either by globally reducing current amplitudes (3 pore mutations) or by a depolarizing shift of the activation curve (2 voltage sensor mutations) decreasing potassium currents at the subthreshold level at which these channels are known to critically influence neuronal firing. One mutation significantly reduced surface expression. Application of retigabine, a recently marketed KV 7 channel opener, partially reversed these effects for the majority of analyzed mutations. INTERPRETATION: The development of severe epilepsy and cognitive decline in children carrying 5 of the 7 studied KCNQ2 mutations can be related to a dominant-negative reduction of the resulting potassium current at subthreshold membrane potentials. Other factors such as genetic modifiers have to be postulated for the remaining 2 mutations. Retigabine or similar drugs may be used as a personalized therapy for this severe disease.

Causal interpretation of correlational studies - Analysis of medical news on the website of the official journal for German physicians.

BACKGROUND: Media frequently draws inappropriate causal statements from observational studies. We analyzed the reporting of study results in the Medical News section of the German medical journal Deutsches Ärzteblatt (DÄ). METHODS: Study design: Retrospective quantitative content analysis of randomly selected news reports and related original journal articles and press releases. A medical news report was selected if headlines comprised at least two linked variables. Two raters independently categorized the headline and text of each news report, conclusions of the abstract and full text of the related journal article, and the press release. The assessment instrument comprised five categories from 'neutral' to 'unconditionally causal'. Outcome measures: degree of matching between 1) news headlines and conclusions of the journal article, 2) headlines and text of news reports, 3) text and conclusions, and 4) headlines and press releases. We analyzed whether news headlines rated as unconditionally causal based on randomized controlled trials (RCTs). RESULTS: One-thousand eighty-seven medical news reports were published between April 2015 and May 2016. The final random sample comprised 176 news reports and 100 related press releases. Degree of matching: 1) 45% (79/176) for news headlines and journal article conclusions, 2) 55% (97/176) for headlines and text, 3) 53% (93/176) for text and conclusions, and 4) 41% (41/100) for headlines and press releases. Exaggerations were found in 45% (80/176) of the headlines compared to the conclusions of the related journal article. Sixty-five of 137 unconditionally causal statements of the news headlines were phrased more weakly in the subsequent news text body. Only 52 of 137 headlines (38%) categorized as unconditionally causal reported RCTs. CONCLUSION: Reporting of medical news in the DÄ medical journal is misleading. Most headlines that imply causal associations were not based on RCTs. Medical journalists should follow standards of reporting scientific study results.

Zebrafish bioassay-guided microfractionation identifies anticonvulsant steroid glycosides from the Philippine medicinal plant Solanum torvum.

Medicinal plants used for the treatment of epilepsy are potentially a valuable source of novel antiepileptic small molecules. To identify anticonvulsant secondary metabolites, we performed an in vivo, zebrafish-based screen of medicinal plants used in Southeast Asia for the treatment of seizures. Solanum torvum Sw. (Solanaceae) was identified as having significant anticonvulsant activity in zebrafish larvae with seizures induced by the GABAA antagonist pentylenetetrazol (PTZ). This finding correlates well with the ethnomedical use of this plant in the Philippines, where a water decoction of S. torvum leaves is used to treat epileptic seizures. HPLC microfractionation of the bioactive crude extract, in combination with the in vivo zebrafish seizure assay, enabled the rapid localization of several bioactive compounds that were partially identified online by UHPLC-TOF-MS as steroid glycosides. Targeted isolation of the active constituents from the methanolic extract enabled the complete de novo structure identification of the six main bioactive compounds that were also present in the traditional preparation. To partially mimic the in vivo metabolism of these triterpene glycosides, their common aglycone was generated by acid hydrolysis. The isolated molecules exhibited significant anticonvulsant activity in zebrafish seizure assays. These results underscore the potential of zebrafish bioassay-guided microfractionation to rapidly identify novel bioactive small molecules of natural origin.