Brain expression profiles of two SCN1A antisense RNAs in children and adolescents with epilepsy

Objective

Heterozygous mutations within the voltage-gated sodium channel α subunit (SCN1A) are responsible for the majority of cases of Dravet syndrome (DS), a severe developmental and epileptic encephalopathy. Development of novel therapeutic approaches is mandatory in order to directly target the molecular consequences of the genetic defect. The aim of the present study was to investigate whether cis-acting long non-coding RNAs (lncRNAs) of SCN1A are expressed in brain specimens of children and adolescent with epilepsy as these molecules comprise possible targets for precision-based therapy approaches.

Methods

We investigated SCN1A mRNA expression and expression of two SCN1A related antisense RNAs in brain tissues in different age groups of pediatric non-Dravet patients who underwent surgery for drug resistant epilepsy. The effect of different antisense oligonucleotides (ASOs) directed against SCN1A specific antisense RNAs on SCN1A expression was tested.

Results

The SCN1A related antisense RNAs SCN1A-dsAS (downstream antisense, RefSeq identifier: NR_110598) and SCN1A-usAS (upstream AS, SCN1A-AS, RefSeq identifier: NR_110260) were widely expressed in the brain of pediatric patients. Expression patterns revealed a negative correlation of SCN1A-dsAS and a positive correlation of lncRNA SCN1A-usAS with SCN1A mRNA expression. Transfection of SK-N-AS cells with an ASO targeted against SCN1A-dsAS was associated with a significant enhancement of SCN1A mRNA expression and reduction in SCN1A-dsAS transcripts.

Conclusion

These findings support the role of SCN1A-dsAS in the suppression of SCN1A mRNA generation. Considering the haploinsufficiency in genetic SCN1A related DS, SCN1A-dsAS is an interesting target candidate for the development of ASOs (AntagoNATs) based precision medicine therapeutic approaches aiming to enhance SCN1A expression in DS.

Peak and baseline concentrations of fondaparinux during prophylactic therapy

Fondaparinux is widely approved for prophylaxis and treatment of venous thromboembolic events (VTE). However, its longer half-life time compared to heparins limits its peri-procedural use.

Aim: To investigate 3h peak and 24h baseline concentrations of fondaparinux when administered for prophylaxis (1 x 2.5 mg qd). Secondary outcome measures: incidences of VTE, bleedings, HIT, allergic skin reactions, 30 days mortality.

Patients, methods: Between 02/2010 and 03/2011, 3h peak and 24h baseline levels of fondaparinux were measured with a chromogenic anti-FXa method in 75 consecutive patients. Medical data were obtained from patients' records.

Results: The 5% and 95% percentile of the 3h peak level were 0.20 μg/ml and 0.83 μg/ml (median: 0.53 μg/ml), and of the 24h baseline level 0.08 μg/ml and 0.53 μg/ml (median 0.21 μg/ml), respectively. An inverse correlation was found between fondaparinux levels and GFRs (rho=-0.617 (3h); rho=-0.648 (24h); p=0.01). Shorter (≤5 days) or longer (≥8 days) duration of prior fondaparinux exposure showed no significantly different 3h peak/24h baseline levels (p>0.6). One progressive thrombosis occurred but no major bleedings, HIT, allergic skin reactions or fatalities.

Conclusions: After fondaparinux exposure, >75% of the patients still had relevant prophylactic 24h baseline levels. This did not coincide with a high rate of bleeding events. Due to the low patient number in this study undergoing surgery or interventions, it remains to be investigated whether or at which concentrations the bleeding risk is increased when baseline levels are within prophylactic ranges.

Masking of transmembrane-based retention signals controls ER export of gamma-secretase

gamma-Secretase is critically involved in the Notch pathway and in Alzheimer's disease. The four subunits of gamma-secretase assemble in the endoplasmic reticulum (ER) and unassembled subunits are retained/retrieved to the ER by specific signals. We here describe a novel ER-retention/retrieval signal in the transmembrane domain (TMD) 4 of presenilin 1, a subunit of gamma-secretase. TMD4 also is essential for complex formation, conferring a dual role for this domain. Likewise, TMD1 of Pen2 is bifunctional as well. It carries an ER-retention/retrieval signal and is important for complex assembly by binding to TMD4. The two TMDs directly interact with each other and mask their respective ER-retention/retrieval signals, allowing surface transport of reporter proteins. Our data suggest a model how assembly of Pen2 into the nascent gamma-secretase complex could mask TMD-based ER-retention/retrieval signals to allow plasma membrane transport of fully assembled gamma-secretase.

A monoclonal antibody prevents aggregation of the NBD1 domain of the cystic fibrosis transmembrane conductance regulator

The homozygous deletion of the phenylalanine at position 508 (DeltaPhe508) in the first nucleotide-binding domain (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) is the most common CF-causing genetic defect. It has been proposed that the propensity of NBD1 to aggregate may lead to a lower display of the CFTR chloride channel to the cell membrane and to the disease, thus opening an avenue for the pharmacological development of CFTR folding correctors. Here, we show that a human monoclonal antibody fragment specific to the folded conformation of NBD1 inhibits the aggregation of NBD1 in vitro. However, in contrast to the previously published observations, we proved experimentally that NBD1 of wild-type and DeltaPhe508 version of CFTR display comparable propensities to aggregate in vitro and that the corresponding full-length CFTR protein reaches the cell membrane with comparable efficiency in mammalian cell expression systems. On the basis of our results, the 'folding defect' hypothesis seems unlikely to represent the causal mechanism for the pathogenesis of CF. A solid understanding of how the DeltaPhe508 deletion leads to the disease represents an absolute requirement for the development of effective drugs against CF.

Endoplasmic reticulum retention of the gamma-secretase complex component Pen2 by Rer1

gamma-Secretase is involved in the production of amyloid beta-peptide, which is the principal component of amyloid plaques in the brains of patients with Alzheimer disease. gamma-Secretase is a complex composed of presenilin (PS), nicastrin, anterior pharynx-defective phenotype 1 (Aph1) and PS enhancer 2 (Pen2). We previously proposed a mechanism of complex assembly by which unassembled subunits are retained in the endoplasmic reticulum (ER) and only the fully assembled complex is exported from the ER. We have now identified Retention in endoplasmic reticulum 1 (Rer1) as a protein that is involved in the retention/retrieval of unassembled Pen2 to the ER. Direct binding of unassembled Pen2 to Rer1 is mediated by the first transmembrane domain of Pen2, and a conserved asparagine in this domain is required. Downregulation of Rer1 leads to increased surface localization of Pen2, whereas overexpression of Rer1 stabilizes unassembled Pen2. To our knowledge, Rer1 is the first identified interaction partner of mammalian transmembrane-based retention/retrieval signals.

Thrombolyse der A. basilaris: Ergebnisse im Saarland über einen Zeitraum von 5 Jahren

Acute thrombosis of the basilar artery has a fatal outcome if left untreated. The relatively good prognosis with intra-arterial thrombolysis makes it the therapy of choice for acute basilar thrombosis. In the Saarland stroke registry, we analyzed 47 patients with angiographically proven basilar artery thrombosis within the last 5 years. We observed a better outcome in patients with good income, with recanalization, and a short time between onset of symptoms and start of thrombolysis. The complications, such as intracerebral bleedings, occurred only in the group treated with rt-PA. Intra-arterial thrombolysis with urokinase or rt-PA is a relatively safe therapy, but should be performed in neuroradiological centers. With progressing symptoms the therapeutic window can be stretched up to 12 h, but coma lasting for more than 4 h is related to a bad outcome.