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Acutely silencing specific neurons informs about their functional roles in circuits and behavior. Existing optogenetic silencers include ion pumps, channels, metabotropic receptors, and tools that damage the neurotransmitter release machinery. While the former hyperpolarize the cell, alter ionic gradients or cellular biochemistry, the latter allow only slow recovery, requiring de novo synthesis. Thus, tools combining fast activation and reversibility are needed. Here, we use light-evoked homo-oligomerization of cryptochrome CRY2 to silence synaptic transmission, by clustering synaptic vesicles (SVs). We benchmark this tool, optoSynC, in Caenorhabditis elegans , zebrafish, and murine hippocampal neurons. optoSynC clusters SVs, observable by electron microscopy. Locomotion silencing occurs with tau on ~7.2 s and recovers with tau off ~6.5 min after light-off. optoSynC can inhibit exocytosis for several hours, at very low light intensities, does not affect ion currents, biochemistry or synaptic proteins, and may further allow manipulating different SV pools and the transfer of SVs between them. Existing optogenetic silencing methods affect membrane potential, biochemistry or protein integrity. Here, the authors demonstrate an approach for silencing synaptic transmission that combines fast activation and reversibility, by using nondisruptive, reversible, light-evoked clustering of synaptic vesicles, which they validate in Caenorhabditis elegans , zebrafish, and murine cell culture.

Excitable cells can be stimulated or inhibited by optogenetics. Since optogenetic actuation regimes are often static, neurons and circuits can quickly adapt, allowing perturbation, but not true control. Hence, we established an optogenetic voltage-clamp (OVC). The voltage-indicator QuasAr2 provides information for fast, closed-loop optical feedback to the bidirectional optogenetic actuator BiPOLES. Voltage-dependent fluorescence is held within tight margins, thus clamping the cell to distinct potentials. We established the OVC in muscles and neurons of Caenorhabditis elegans , and transferred it to rat hippocampal neurons in slice culture. Fluorescence signals were calibrated to electrically measured potentials, and wavelengths to currents, enabling to determine optical I/V-relationships. The OVC reports on homeostatically altered cellular physiology in mutants and on Ca 2+ -channel properties, and can dynamically clamp spiking in C. elegans . Combining non-invasive imaging with control capabilities of electrophysiology, the OVC facilitates high-throughput, contact-less electrophysiology in individual cells and paves the way for true optogenetic control in behaving animals. Optogenetic actuation regimes are often static, which allows perturbation, but not true control of neuronal activity. Here, the authors describe an all-optical method for bidirectional steering of membrane potential, in closed loop, in C. elegans muscles and neurons, and rat hippocampal slice culture. The ‘optogenetic voltage clamp’ uses two microbial rhodopsin actuators and the rhodopsin voltage indicator QuasAr.

The regulation of synaptic transmission is crucial for plasticity, homeostasis and learning. Chemical synaptic transmission is thus modulated to accommodate different activity levels, which also enables homeostatic scaling in pre- and postsynaptic compartments. In nematodes, cAMP signaling enhances cholinergic neuron output, and these neurons use neuropeptide signaling to modulate synaptic vesicle content. To explore if this mechanism is conserved in vertebrates, we studied the involvement of neuropeptides in cholinergic transmission at the neuromuscular junction of larval zebrafish. Optogenetic stimulation by photoactivated adenylyl cyclase (bPAC) resulted in elevated locomotion as measured in behavioural assays. Furthermore, post-synaptic patch-clamp recordings revealed that in bPAC transgenics, the frequency of miniature excitatory postsynaptic currents (mEPSCs) was increased after photostimulation. These results suggested that cAMP-mediated activation of ZF motor neurons leads to increased fusion of SVs, consequently resulting in enhanced neuromuscular activity. We generated mutants lacking the neuropeptide processing enzyme carboxypeptidase E (cpe), and the most abundant neuropeptide precursor in motor neurons, tachykinin (tac1). Both mutants showed exaggerated locomotion after photostimulation. cpe mutants exhibit lower mEPSC frequency during photostimulation and less large-amplitude mEPSCs. In tac1 mutants mEPSC frequency was not affected but amplitudes were significantly smaller. Exaggerated locomotion in the mutants thus reflected upscaling of postsynaptic excitability. cpe and tac1 mutant muscles expressed more nicotinic acetylcholine receptors (nAChR) on their surface. Thus, neuropeptide signaling regulates synaptic transmitter output in zebrafish motor neurons, and muscle cells homeostatically regulate nAChR surface expression, compensating reduced presynaptic input. This mechanism may be widely conserved in the animal kingdom.Competing Interest StatementThe authors have declared no competing interest.

Serial cardiac magnetic resonance imaging (CMR) is the reference standard for evaluating left ventricular function, wall motion, and infarct size in patients with acute myocardial infarction, as well as remodeling during follow-up. The cardiac CMR substudy of the randomized multicenter REPAIR-AMI trial (Reinfusion of Enriched Progenitor cells And Infarct Remodeling in Acute Myocardial Infarction study) aimed at gaining insight into postinfarction left ventricular remodeling processes. Consecutive patients with ST-segment elevation myocardial infarction and primary percutaneous coronary intervention were enrolled (n = 204) and randomly assigned to either stem cell therapy (bone marrow-derived progenitor cells [BMC]) or placebo after bone marrow aspiration. In the magnetic resonance imaging substudy, 54 patients completed serial CMR (baseline, 4 and 12 months, respectively) after enrollment (27 BMC, 27 placebo). Image analysis was performed at a central core laboratory. There were no significant differences between the 2 groups with respect to global ejection fraction (EF), end-diastolic volume (EDV), and end-systolic volume (ESV) at baseline. At 12 months, the treatment effect of BMC infusion on EF amounted to 2.8 absolute percentage points ( P = .26), the progression of EDV at 12 months was less in the BMC group (treatment effect 14 mL, P = .12), and unlike placebo, ESV did not increase (absolute treatment effect 13 mL, P = .08), respectively. In patients with a baseline EF < median (EF ≤ 48.9%), BMC administration was associated with a significantly improved EF (+6.6%, P = .01), reduced EDV increase (treatment effect 29.1 mL, P = .02), and abrogation of ESV increase (treatment effect 29.4 mL, P = .01) after 12 months, respectively. Intracoronary administration of BMC additionally improved left ventricular function in patients with impaired left ventricular function after ST-segment elevation myocardial infarction despite optimal “state-of-the-art” reperfusion and pharmacologic treatment on 1-year follow-up and beneficially interfered with adverse postinfarction left ventricular remodeling.

In this analysis, the authors directly compared the performance of flow cytometry data processing algorithms to manual gating approaches. The results offer information of practical utility about the performance of the algorithms as applied to different data sets and challenges. Traditional methods for flow cytometry (FCM) data processing rely on subjective manual gating. Recently, several groups have developed computational methods for identifying cell populations in multidimensional FCM data. The Flow Cytometry: Critical Assessment of Population Identification Methods (FlowCAP) challenges were established to compare the performance of these methods on two tasks: (i) mammalian cell population identification, to determine whether automated algorithms can reproduce expert manual gating and (ii) sample classification, to determine whether analysis pipelines can identify characteristics that correlate with external variables (such as clinical outcome). This analysis presents the results of the first FlowCAP challenges. Several methods performed well as compared to manual gating or external variables using statistical performance measures, which suggests that automated methods have reached a sufficient level of maturity and accuracy for reliable use in FCM data analysis.

Frontotemporal dementia (FTD) is a clinically and genetically heterogeneous disorder. To which extent genetic aberrations dictate clinical presentation remains elusive. We investigated the spectrum of genetic causes and assessed the genotype-driven differences in biomarker profiles, disease severity and clinical manifestation by recruiting 509 FTD patients from different centers of the German FTLD consortium where individuals were clinically assessed including biomarker analysis. Exome sequencing as well as C9orf72 repeat analysis were performed in all patients. These genetic analyses resulted in a diagnostic yield of 18.1%. Pathogenic variants in C9orf72 (n = 47), GRN (n = 26), MAPT (n = 11), TBK1 (n = 5), FUS (n = 1), TARDBP (n = 1), and CTSF (n = 1) were identified across all clinical subtypes of FTD. TBK1-associated FTD was frequent accounting for 5.4% of solved cases. Detection of a homozygous missense variant verified CTSF as an FTD gene. ABCA7 was identified as a candidate gene for monogenic FTD. The distribution of APOE alleles did not differ significantly between FTD patients and the average population. Male sex was weakly associated with clinical manifestation of the behavioral variant of FTD. Age of onset was lowest in MAPT patients. Further, high CSF neurofilament light chain levels were found to be related to GRN-associated FTD. Our study provides large-scale retrospective clinico-genetic data such as on disease manifestation and progression of FTD. These data will be relevant for counseling patients and their families.

Multi-detector CT reliably permits visualization of coronary arteries, but due to the occurrence of motion artefacts at heart rates >65 bpm caused by a temporal resolution of 165 ms, its utilisation has so far been limited to patients with a preferably low heart rate. We investigated the assessment of image quality on computed tomography of coronary arteries in a large series of patients without additional heart rate control using dual-source computed tomography (DSCT). DSCT (Siemens Somatom Definition, 83-ms temporal resolution) was performed in 165 consecutive patients (mean age 64 ± 11.4 years) after injection of 60–80 ml of contrast. Data sets were reconstructed in 5% intervals of the cardiac cycle and evaluated by two readers in consensus concerning evaluability of the coronary arteries and presence of motion and beam-hardening artefacts using the AHA 16-segment coronary model. Mean heart rate during CT was 65 ± 10.5 bpm; visualisation without artefacts was possible in 98.7% of 2,541 coronary segments. Only two segments were considered unevaluable due to cardiac motion; 30 segments were unassessable due to poor signal-to-noise ratio or coronary calcifications (both n = 15). Data reconstruction at 65-70% of the cardiac cycle provided for the best image quality. For heart rates >85 bpm, a systolic reconstruction at 45% revealed satisfactory results. Compared with earlier CT generations, DSCT provides for non-invasive coronary angiography with diagnostic image quality even at heart rates >65 bpm and thus may broaden the spectrum of patients that can be investigated non-invasively.

A new cardiac syndrome with transient left ventricular dysfunction has been recently reported and is referred to as Tako-Tsubo cardiomyopathy, which is characterized by a transient akinesia of the apex and compensatory basal hyperkinesis. Today, the etiology remains unknown. We report for the first time of a patient with multiple episodes of a transient global left ventricular dysfunction which is reminiscent to apical ballooning.These episodes were always preceded by severe emotional stress proposing a potential common pathomechanism.