Prenatal Diagnosis of Fryns Syndrome through Identification of Two Novel Splice Variants in the PIGN Gene-A Case Series.

Fryns syndrome (FS) is a multiple congenital anomaly syndrome with different multisystemic malformations. These include congenital diaphragmatic hernia, pulmonary hypoplasia, and craniofacial dysmorphic features in combination with malformations of the central nervous system such as agenesis of the corpus callosum, cerebellar hypoplasia, and enlarged ventricles. We present a non-consanguineous northern European family with two recurrent cases of FS: a boy with multiple congenital malformations who died at the age of 2.5 months and a female fetus with a complex developmental disorder with similar features in a following pregnancy. Quad whole exome analysis revealed two likely splicing-affecting disease-causing mutations in the PIGN gene: a synonymous mutation c.2619G>A, p.(Leu873=) in the last nucleotide of exon 29 and a 30 bp-deletion c.996_1023+2del (NM_176787.5) protruding into intron 12, with both mutations in trans configuration in the affected patients. Exon skipping resulting from these two variants was confirmed via RNA sequencing. Our molecular and clinical findings identified compound heterozygosity for two novel splice-affecting variants as the underlying pathomechanism for the development of FS in two patients.

De novo variants in GABRA4 are associated with a neurological phenotype including developmental delay, behavioral abnormalities and epilepsy.

Nine out of 19 genes encoding GABAA receptor subunits have been linked to monogenic syndromes characterized by seizures and developmental disorders. Previously, we reported the de novo variant p.(Thr300Ile) in GABRA4 in a patient with epilepsy and neurodevelopmental abnormalities. However, no new cases have been reported since then. Through an international collaboration, we collected molecular and phenotype data of individuals carrying de novo variants in GABRA4. Patients and their parents were investigated either by exome or genome sequencing, followed by targeted Sanger sequencing in some cases. All variants within the transmembrane domain, including the previously reported p.(Thr300Ile) variant, were characterized in silico and analyzed by molecular dynamics (MD) simulation studies. We identified three novel de novo missense variants in GABRA4 (NM_000809.4): c.797 C > T, p.(Pro266Leu), c.899 C > A, p.(Thr300Asn), and c.634 G > A, p.(Val212Ile). The p.(Thr300Asn) variant impacts the same codon as the previously reported variant p.(Thr300Ile) and likely arose post-zygotically as evidenced by sequencing oral mucosal cells. Overlapping phenotypes among affected individuals included developmental delay (4/4), epileptiform EEG abnormalities (3/4), attention deficits (3/4), seizures (2/4), autistic features (2/4) and structural brain abnormalities (2/4). MD simulations of the three variants within the transmembrane domain of the receptor indicate that sub-microsecond scale dynamics differ between wild-type and mutated subunits. Taken together, our findings further corroborate an association between GABRA4 and a neurological phenotype including variable neurodevelopmental, behavioral and epileptic abnormalities.

Properties of stable ensembles of Euclidean random matrices.

We study the spectrum of a system of coupled disordered harmonic oscillators in the thermodynamic limit. This Euclidean random matrix ensemble has been suggested as a model for the low temperature vibrational properties of glass. Exact numerical diagonalization is performed in three and two spatial dimensions, which is accompanied by a detailed finite size analysis. It reveals a low-frequency regime of sound waves that are damped by Rayleigh scattering. At large frequencies localized modes exist. In between, the central peak in the vibrational density of states is well described by Wigner's semicircle law for not too large disorder, as is expected for simple random matrix systems. We compare our results with predictions from two recent self-consistent field theories.

A sensitive non-enzymatic dual-conductive biosensor for continuous glucose monitoring.

BACKGROUND: Diabetes and diabetic wound management have always been urgent issues for global healthcare. In the demand for blood glucose monitoring and wound management, phenylboronic acid (PBA)-based glucose biosensors are effective assistance due to their excellent glucose specificity, high sensitivity, and response stability. Nevertheless, PBA-based glucose biosensors still have challenges in terms of wide linearity and large deformation requirements. Therefore, it is necessary to develop PBA-based glucose biosensors with satisfactory mechanical properties, high response sensitivity, excellent stability, and wide linearity. RESULTS: In this work, a glucose-responsive PBA-based biosensor was successfully synthesized for the first time. The sensor materials exhibited excellent mechanical properties with an elongation at break reached up to 1000%, and the healing efficiency was over 90% within 30 min at 45 °C. Furthermore, the biosensor exhibited exceptional electromechanical responsiveness, stability, high sensitivity, and wide linearity due to the specificity of phenylboronic acid to glucose and the construction of a special HCNT/PEDOT:PSS dual conductive structure. In addition, the assembled biosensor displayed remarkable glucose, pH and temperature responses, exhibiting a linear response to glucose concentration range from 0.20 mM to 2.0 mM, with a sensitivity coefficient of 47.11 mA mM-1 and regression coefficient of 0.942. Moreover, the sensor materials showed satisfactory cytocompatibility, hemocompatibility, and antibacterial properties against Escherichia coli and Staphylococcus aureus. SIGNIFICANCE: For the first time, a dual conductive structural glucose biosensor based on PBA-based copolymer was synthesized. In addition to excellent glucose sensitivity and response stability, the biosensor has a wide linearity range, excellent self-healing property, and satisfactory mechanical performance. As a promising substitute for non-enzymatic glucose biosensors, this new material with special structure and characteristics would also be beneficial to wound management in diabetic patients.

Navigating the complex landscape of benzodiazepine- and Z-drug diversity: insights from comprehensive FDA adverse event reporting system analysis and beyond.

Introduction: Medications which target benzodiazepine (BZD) binding sites of GABAA receptors (GABAARs) have been in widespread use since the nineteen-sixties. They carry labels as anxiolytics, hypnotics or antiepileptics. All benzodiazepines and several nonbenzodiazepine Z-drugs share high affinity binding sites on certain subtypes of GABAA receptors, from which they can be displaced by the clinically used antagonist flumazenil. Additional binding sites exist and overlap in part with sites used by some general anaesthetics and barbiturates. Despite substantial preclinical efforts, it remains unclear which receptor subtypes and ligand features mediate individual drug effects. There is a paucity of literature comparing clinically observed adverse effect liabilities across substances in methodologically coherent ways. Methods: In order to examine heterogeneity in clinical outcome, we screened the publicly available U.S. FDA adverse event reporting system (FAERS) database for reports of individual compounds and analyzed them for each sex individually with the use of disproportionality analysis. The complementary use of physico-chemical descriptors provides a molecular basis for the analysis of clinical observations of wanted and unwanted drug effects. Results and Discussion: We found a multifaceted FAERS picture, and suggest that more thorough clinical and pharmacoepidemiologic investigations of the heterogenous side effect profiles for benzodiazepines and Z-drugs are needed. This may lead to more differentiated safety profiles and prescription practice for particular compounds, which in turn could potentially ease side effect burden in everyday clinical practice considerably. From both preclinical literature and pharmacovigilance data, there is converging evidence that this very large class of psychoactive molecules displays a broad range of distinctive unwanted effect profiles - too broad to be explained by the four canonical, so-called "diazepam-sensitive high-affinity interaction sites". The substance-specific signatures of compound effects may partly be mediated by phenomena such as occupancy of additional binding sites, and/or synergistic interactions with endogenous substances like steroids and endocannabinoids. These in turn drive the wanted and unwanted effects and sex differences of individual compounds.

MOF@Polydopamine-incorporated membrane with high permeability and mechanical property for efficient fouling-resistant and oil/water separation.

Metal organic frameworks (MOFs) have demonstrated great potential for their favorable impacts on the performance of water treatment membranes. Herein, the novel nanoparticles based on both nanoporous MOFs and organic PDA layer was exploited as a novel dopant for the fabrication of PES ultrafiltration (UF) membranes. The PDA was synthesized via oxidative self-polymerization under alkaline conditions and formed adhesive coatings on dispersed MOF. The properties of resulting membranes on the porosity, membrane morphology, hydrophilicity, permeability and anti-fouling performance were adequately investigated. The membranes incorporated with MOF@PDA exhibited exceptionally high permeability (209.02 L m-2·h-1), which is approximately 6 times higher than that of the pure PES membrane, and high BSA rejection (99.12%). Notably, the mechanical property and hydrophilicity of the PES membrane were both enhanced by MOF@PDA, and it has been demonstrated that greater hydrophilicity prevents fouling under practical conditions, which results in significant improvements in flux recovery ratio (FRR) (82%). In addition, the modified PES membranes were used to purify the oil/water emulsion, and the results indicates that the membranes have high permeability and rejection of oil/water emulsion, showing its great promise in practical oily sewage remediation.

Vibrational Phenomena in Glasses at Low Temperatures Captured by Field Theory of Disordered Harmonic Oscillators.

We investigate the vibrational properties of topologically disordered materials by analytically studying particles that harmonically oscillate around random positions. Exploiting classical field theory in the thermodynamic limit at T=0, we build up a self-consistent model by analyzing the Hessian utilizing Euclidean random matrix theory. In accordance with earlier findings [T. S. Grigera et al.J. Stat. Mech. (2011) P02015.JSMTC61742-546810.1088/1742-5468/2011/02/P02015], we take nonplanar diagrams into account to correctly address multiple local scattering events. By doing so, we end up with a first principles theory that can predict the main anomalies of athermal disordered materials, including the boson peak, sound softening, and Rayleigh damping of sound. In the vibrational density of states, the sound modes lead to Debye's law for small frequencies. Additionally, an excess appears in the density of states starting as ω^{4} in the low frequency limit, which is attributed to (quasi-) localized modes.

GABAA receptor-mediated seizure liabilities: a mixed-methods screening approach.

GABAA receptors, members of the pentameric ligand-gated ion channel superfamily, are widely expressed in the central nervous system and mediate a broad range of pharmaco-toxicological effects including bidirectional changes to seizure threshold. Thus, detection of GABAA receptor-mediated seizure liabilities is a big, partly unmet need in early preclinical drug development. This is in part due to the plethora of allosteric binding sites that are present on different subtypes of GABAA receptors and the critical lack of screening methods that detect interactions with any of these sites. To improve in silico screening methods, we assembled an inventory of allosteric binding sites based on structural data. Pharmacophore models representing several of the binding sites were constructed. These models from the NeuroDeRisk IL Profiler were used for in silico screening of a compiled collection of drugs with known GABAA receptor interactions to generate testable hypotheses. Amoxapine was one of the hits identified and subjected to an array of in vitro assays to examine molecular and cellular effects on neuronal excitability and in vivo locomotor pattern changes in zebrafish larvae. An additional level of analysis for our compound collection is provided by pharmacovigilance alerts using FAERS data. Inspired by the Adverse Outcome Pathway framework, we postulate several candidate pathways leading from specific binding sites to acute seizure induction. The whole workflow can be utilized for any compound collection and should inform about GABAA receptor-mediated seizure risks more comprehensively compared to standard displacement screens, as it rests chiefly on functional data.

Amphiphilic Grafted Polymers Based on Citric Acid and Aniline Used to Enhance the Antifouling and Permeability Properties of PES Membranes.

Water treatment technology based on ultrafiltration (UF) faces the problem of severe membrane fouling due to its inherent hydrophobicity. The use of amphiphilic polymers that possess both hydrophobic and hydrophilic chain segments can be advantageous for the hydrophilic modification of UF membranes due to their excellent combination in the membrane matrix. In the present study, we examined a novel amphiphilic CA-g-AN material, constructed by grafting citric acid (CA) to aniline (AN), as a modified material to improve the hydrophilicity of a PES membrane. This material was more compatible with the polymer membrane matrix than a pure hydrophilic modified material. The polyethersulfone (PES) membranes modified by amphiphilic CA-g-AN demonstrated a higher water flux (290.13 L·m-2·h-1), which was more than eight times higher than that of the pure PES membrane. Furthermore, the flux recovery ratio (FRR) of the modified membrane could reach 83.24% and the value of the water contact angle (WCA) was 76.43°, demonstrating the enhanced hydrophilicity and antifouling ability of the modified membranes. With this study, we aimed to develop a new amphiphilic polymer to improve the antifouling property and permeability of polymer-based UF membranes to remove organic pollutants from water.

Cys-loop receptors on cannabinoids: All high?

Endocannabinoids (eCBS) are endogenously derived lipid signaling molecules that serve as tissue hormones and interact with multiple targets, mostly within the endocannabinoid system (ECS). The ECS is a highly conserved regulatory system involved in homeostatic regulation, organ formation, and immunomodulation of chordates. The term "cannabinoid" evolved from the distinctive class of plant compounds found in Cannabis sativa, an ancient herb, due to their action on CB1 and CB2 receptors. CB1/2 receptors are the primary targets for eCBs, but their effects are not limited to the ECS. Due to the high interest and extensive research on the ECS, knowledge on its constituents and physiological role is substantial and still growing. Crosstalk and multiple targeting of molecules are common features of endogenous and plant compounds. Cannabimimetic molecules can be divided according to their origin, natural or synthetic, including phytocannabinoids (pCB's) or synthetic cannabinoids (sCB's). The endocannabinoid system (ECS) consists of receptors, transporters, enzymes, and signaling molecules. In this review, we focus on the effects of cannabinoids on Cys-loop receptors. Cys-loop receptors belong to the class of membrane-bound pentameric ligand gated ion channels, each family comprising multiple subunits. Mammalians possess GABA type A receptors (GABAAR), glycine receptors (GlyR), serotonin receptors type 3 (5-HT3R), and nicotinic acetylcholine receptors (nAChR). Several studies have shown different modulatory effects of CBs on multiple members of the Cys-loop receptor family. We highlight the existing knowledge, especially on subunits and protein domains with conserved binding sites for CBs and their possible pharmacological and physiological role in epilepsy and in chronic pain. We further discuss the potential for cannabinoids as first line treatments in epilepsy, chronic pain and other neuropsychiatric conditions, indicated by their polypharmacology and therapeutic profile.

Novel alpha6 preferring GABA-A receptor ligands based on loreclezole.

The family of GABA-A receptors contains nineteen mammalian subunits from which pentameric, GABA gated anion channels are assembled. The subunit encoded by the GABRA6 gene is highly expressed in the cerebellum and the receptors to which it contributes have recently been demonstrated to be a promising candidate as a novel drug target. Here we examined a series of loreclezole derivatives for potentially selective action at α6ß3γ2 receptors with the help of computational methods and functional testing with the two-electrode voltage clamp technique. The synthetic routes to some previously published ligands were improved, and a new derivative was synthesized based on computational docking results. This new loreclezole derivative, [3-(2-chloro-4-methylphenyl)-3-methylbutanenitrile (40)], was shown to display stronger modulatory action in concatenated α6ß3γ2 receptors compared to their α1ß3γ2 counterpart. The hypothetical bound state structure provides valuable guidance for future design of selective therapeutics.

An integrated multiomic approach as an excellent tool for the diagnosis of metabolic diseases: our first 3720 patients.

To present our experience using a multiomic approach, which integrates genetic and biochemical testing as a first-line diagnostic tool for patients with inherited metabolic disorders (IMDs). A cohort of 3720 patients from 62 countries was tested using a panel including 206 genes with single nucleotide and copy number variant (SNV/CNV) detection, followed by semi-automatic variant filtering and reflex biochemical testing (25 assays). In 1389 patients (37%), a genetic diagnosis was achieved. Within this cohort, the highest diagnostic yield was obtained for patients from Asia (57.5%, mainly from Pakistan). Overall, 701 pathogenic/likely pathogenic unique SNVs and 40 CNVs were identified. In 620 patients, the result of the biochemical tests guided variant classification and reporting. Top five diagnosed diseases were: Gaucher disease, Niemann-Pick disease type A/B, phenylketonuria, mucopolysaccharidosis type I, and Wilson disease. We show that integrated genetic and biochemical testing facilitated the decision on clinical relevance of the variants and led to a high diagnostic yield (37%), which is comparable to exome/genome sequencing. More importantly, up to 43% of these patients (n = 610) could benefit from medical treatments (e.g., enzyme replacement therapy). This multiomic approach constitutes a unique and highly effective tool for the genetic diagnosis of IMDs.

Molecular Mingling: Multimodal Predictions of Ligand Promiscuity in Pentameric Ligand-Gated Ion Channels.

Background: Human pentameric ligand-gated ion channels (pLGICs) comprise nicotinic acetylcholine receptors (nAChRs), 5-hydroxytryptamine type 3 receptors (5-HT3Rs), zinc-activated channels (ZAC), γ-aminobutyric acid type A receptors (GABAARs) and glycine receptors (GlyRs). They are recognized therapeutic targets of some of the most prescribed drugs like general anesthetics, anxiolytics, smoking cessation aids, antiemetics and many more. Currently, approximately 100 experimental structures of pLGICs with ligands bound exist in the protein data bank (PDB). These atomic-level 3D structures enable the generation of a comprehensive binding site inventory for the superfamily and the in silico prediction of binding site properties. Methods: A panel of high throughput in silico methods including pharmacophore screening, conformation analysis and descriptor calculation was applied to a selection of allosteric binding sites for which in vitro screens are lacking. Variant abundance near binding site forming regions and computational docking complement the approach. Results: The structural data reflects known and novel binding sites, some of which may be unique to individual receptors, while others are broadly conserved. The membrane spanning domain, comprising four highly conserved segments, contains ligand interaction sites for which in vitro assays suitable for high throughput screenings are critically lacking. This is also the case for structurally more variable novel sites in the extracellular domain. Our computational results suggest that the phytocannabinoid Δ9-tetrahydrocannabinol (Δ9-THC) can utilize multiple pockets which are likely to exist on most superfamily members. Conclusion: With this study, we explore the potential for polypharmacology among pLGICs. Our data suggest that ligands can display two forms of promiscuity to an extent greater than what has been realized: 1) Ligands can interact with homologous sites in many members of the superfamily, which bears toxicological relevance. 2) Multiple pockets in distinct localizations of individual receptor subtypes share common ligands, which counteracts efforts to develop selective agents. Moreover, conformational states need to be considered for in silico drug screening, as certain binding sites display considerable flexibility. In total, this work contributes to a better understanding of polypharmacology across pLGICs and provides a basis for improved structure guided in silico drug development and drug derisking.

A de novo missense variant in GABRA4 alters receptor function in an epileptic and neurodevelopmental phenotype.

Variants in γ-aminobutyric acid A (GABAA ) receptor genes cause different forms of epilepsy and neurodevelopmental disorders. To date, GABRA4, encoding the α4-subunit, has not been associated with a monogenic condition. However, preclinical evidence points toward seizure susceptibility. Here, we report a de novo missense variant in GABRA4 (c.899C>T, p.Thr300Ile) in an individual with early-onset drug-resistant epilepsy and neurodevelopmental abnormalities. An electrophysiological characterization of the variant, which is located in the pore-forming domain, shows accelerated desensitization and a lack of seizure-protective neurosteroid function. In conclusion, our findings strongly suggest an association between de novo variation in GABRA4 and a neurodevelopmental disorder with epilepsy.

Tricyclic antipsychotics and antidepressants can inhibit α5-containing GABAA receptors by two distinct mechanisms.

BACKGROUND AND PURPOSE: Many psychotherapeutic drugs, including clozapine, display polypharmacology and act on GABAA receptors. Patients with schizophrenia show alterations in function, structure and molecular composition of the hippocampus, and a recent study demonstrated aberrant levels of hippocampal α5 subunit-containing GABAA receptors. The purpose of this study is to investigate the effects of tricyclic compounds on α5 subunit-containing receptor subtypes. EXPERIMENTAL APPROACH: Functional studies of effects by seven antipsychotic and antidepressant medications were performed in several GABAA receptor subtypes by two-electrode voltage-clamp electrophysiology using Xenopus laevis oocytes. Computational structural analysis was employed to design mutated constructs of the α5 subunit, probing a novel binding site. Radioligand displacement data complemented the functional and mutational findings. KEY RESULTS: The antipsychotic drugs clozapine and chlorpromazine exerted functional inhibition on multiple GABAA receptor subtypes, including those containing α5-subunits. Based on a chlorpromazine binding site observed in a GABA-gated bacterial homologue, we identified a novel site in α5 GABAA receptor subunits and demonstrate differential usage of this and the orthosteric sites by these ligands. CONCLUSION AND IMPLICATIONS: Despite high molecular and functional similarities among the tested ligands, they reduce GABA currents by differential usage of allosteric and orthosteric sites. The chlorpromazine site we describe here is a new potential target for optimizing antipsychotic medications with beneficial polypharmacology. Further studies in defined subtypes are needed to substantiate mechanistic links between the therapeutic effects of clozapine and its action on certain GABAA receptor subtypes.

Successful application of genome sequencing in a diagnostic setting: 1007 index cases from a clinically heterogeneous cohort.

Despite clear technical superiority of genome sequencing (GS) over other diagnostic methods such as exome sequencing (ES), few studies are available regarding the advantages of its clinical application. We analyzed 1007 consecutive index cases for whom GS was performed in a diagnostic setting over a 2-year period. We reported pathogenic and likely pathogenic (P/LP) variants that explain the patients' phenotype in 212 of the 1007 cases (21.1%). In 245 additional cases (24.3%), a variant of unknown significance (VUS) related to the phenotype was reported. We especially investigated patients which had had ES with no genetic diagnosis (n = 358). For this group, GS diagnostic yield was 14.5% (52 patients with P/LP out of 358). GS should be especially indicated for ES-negative cases since up to 29.6% of them  could benefit from GS testing (14.5% with P/LP, n = 52 and 15.1% with VUS, n = 54). Genetic diagnoses in most of the ES-negative/GS-positive cases were determined by technical superiority of GS, i.e., access to noncoding regions and more uniform coverage. Importantly, we reported 79 noncoding variants, of which, 41 variants were classified as P/LP. Interpretation of noncoding variants remains challenging, and in many cases, complementary methods based on direct enzyme assessment, biomarker testing and RNA analysis are needed for variant classification and diagnosis. We present the largest cohort of patients with GS performed in a clinical setting to date. The results of this study should direct the decision for GS as standard second-line, or even first-line stand-alone test.

Stress correlation function and linear response of Brownian particles.

We determine the non-local stress autocorrelation tensor in an homogeneous and isotropic system of interacting Brownian particles starting from the Smoluchowski equation of the configurational probability density. In order to relate stresses to particle displacements as appropriate in viscoelastic states, we go beyond the usual hydrodynamic description obtained in the Zwanzig-Mori projection-operator formalism by introducing the proper irreducible dynamics following Cichocki and Hess, and Kawasaki. Differently from these authors, we include transverse contributions as well. This recovers the expression for the stress autocorrelation including the elastic terms in solid states as found for Newtonian and Langevin systems, in case that those are evaluated in the overdamped limit. Finally, we argue that the found memory function reduces to the shear and bulk viscosity in the hydrodynamic limit of smooth and slow fluctuations and derive the corresponding hydrodynamic equations.

Rapid Large-Scale COVID-19 Testing During Shortages.

The Coronavirus disease 2019 (COVID-19) pandemic caused by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) has resulted in economic and social lockdowns in most countries all over the globe. Early identification of infected individuals is regarded as one of the most important prerequisites for fighting the pandemic and for returning to a 'New Normal'. Large-scale testing is therefore crucial, but is facing several challenges including shortage of sample collection tools and of molecular biological reagents, and the need for safe electronic communication of medical reports. We present the successful establishment of a holistic SARS-CoV-2 testing platform that covers proband registration, sample collection and shipment, sample testing, and report issuing. The RT-PCR-based virus detection, being central to the platform, was extensively validated: sensitivity and specificity were defined as 96.8% and 100%, respectively; intra-run and inter-run precision were <3%. A novel type of sample swab and an in-house-developed RNA extraction system were shown to perform as good as commercially available products. The resulting flexibility guarantees independence from the current bottlenecks in SARS-CoV-2 testing. Based on our technology, we offered testing at local, national, and global levels. In the present study, we report the results from approx. 18,000 SARS-CoV-2 tests in almost 10,000 individuals from a low-frequency SARS-CoV-2 pandemic area in a homogenous geographical region in north-eastern Germany for a period of 10 weeks (21 March to 31 May 2020). Among the probands, five SARS-CoV-2 positive cases were identified. Comparative analysis of corresponding virus genomes revealed a diverse origin from three of the five currently recognized SARS-CoV-2 phylogenetic clades. Our study exemplifies how preventive SARS-CoV-2 testing can be set up in a rapid and flexible manner. The application of our test has enabled a safe maintenance/resume of critical local infrastructure, e.g., nursing homes where more than 5000 elderlies and caretakers got tested. The strategy outlined by the present study may serve as a blueprint for the implementation of large-scale preventive SARS-CoV-2 testing elsewhere.

GABAA Receptor Ligands Often Interact with Binding Sites in the Transmembrane Domain and in the Extracellular Domain-Can the Promiscuity Code Be Cracked?

Many allosteric binding sites that modulate gamma aminobutyric acid (GABA) effects have been described in heteropentameric GABA type A (GABAA) receptors, among them sites for benzodiazepines, pyrazoloquinolinones and etomidate. Diazepam not only binds at the high affinity extracellular "canonical" site, but also at sites in the transmembrane domain. Many ligands of the benzodiazepine binding site interact also with homologous sites in the extracellular domain, among them the pyrazoloquinolinones that exert modulation at extracellular α+/ß- sites. Additional interaction of this chemotype with the sites for etomidate has also been described. We have recently described a new indole-based scaffold with pharmacophore features highly similar to pyrazoloquinolinones as a novel class of GABAA receptor modulators. Contrary to what the pharmacophore overlap suggests, the ligand presented here behaves very differently from the identically substituted pyrazoloquinolinone. Structural evidence demonstrates that small changes in pharmacophore features can induce radical changes in ligand binding properties. Analysis of published data reveals that many chemotypes display a strong tendency to interact promiscuously with binding sites in the transmembrane domain and others in the extracellular domain of the same receptor. Further structural investigations of this phenomenon should enable a more targeted path to less promiscuous ligands, potentially reducing side effect liabilities.

Determination of the Pathological Features of NPC1 Variants in a Cellular Complementation Test.

Niemann-Pick Type C (NP-C) is a rare disorder of lipid metabolism caused by mutations within the NPC1 and NPC2 genes. NP-C is a neurovisceral disease leading to a heterogeneous, multisystemic spectrum of symptoms in those affected. Until now, there is no investigative tool to demonstrate the significance of single variants within the NPC genes. Hence, the aim of the study was to establish a test that allows for an objective assessment of the pathological potential of NPC1 gene variants. Chinese hamster ovary cells defective in the NPC1 gene accumulate cholesterol in lysosomal storage organelles. The cells were transfected with NPC1-GFP plasmid vectors carrying distinct sequence variants. Filipin staining was used to test for complementation of the phenotype. The known variant p.Ile1061Thr showed a significantly impaired cholesterol clearance after 12 and 24 h compared to the wild type. Among the investigated variants, p.Ser954Leu and p.Glu1273Lys showed decelerated cholesterol clearance as well. The remaining variants p.Gln60His, p.Val494Met, and p.Ile787Val showed a cholesterol clearance indistinguishable from wild type. Further, p.Ile1061Thr acquired an enhanced clearance ability upon 25-hydroxycholesterol treatment. We conclude that the variants that caused an abnormal clearance phenotype are highly likely to be of clinical relevance. Moreover, we present a system that can be utilized to screen for new drugs.