Drug addiction and obesity share the core feature that those afflicted by the disorders express a desire to limit drug or food consumption yet persist despite negative consequences. Emerging evidence suggests that the compulsivity that defines these disorders may arise, to some degree at least, from common underlying neurobiological mechanisms. In particular, both disorders are associated with diminished striatal dopamine D2 receptor (D2R) availability, likely reflecting their decreased maturation and surface expression. In striatum, D2Rs are expressed by approximately half of the principal medium spiny projection neurons (MSNs), the striatopallidal neurons of the so-called 'indirect' pathway. D2Rs are also expressed presynaptically on dopamine terminals and on cholinergic interneurons. This heterogeneity of D2R expression has hindered attempts, largely using traditional pharmacological approaches, to understand their contribution to compulsive drug or food intake. The emergence of genetic technologies to target discrete populations of neurons, coupled to optogenetic and chemicogenetic tools to manipulate their activity, have provided a means to dissect striatopallidal and cholinergic contributions to compulsivity. Here, we review recent evidence supporting an important role for striatal D2R signaling in compulsive drug use and food intake. We pay particular attention to striatopallidal projection neurons and their role in compulsive responding for food and drugs. Finally, we identify opportunities for future obesity research using known mechanisms of addiction as a heuristic, and leveraging new tools to manipulate activity of specific populations of striatal neurons to understand their contributions to addiction and obesity.

Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease with a strong genetic component. African-Americans (AA) are at increased risk of SLE, but the genetic basis of this risk is largely unknown. To identify causal variants in SLE loci in AA, we performed admixture mapping followed by fine mapping in AA and European-Americans (EA). Through genome-wide admixture mapping in AA, we identified a strong SLE susceptibility locus at 2q22-24 (LOD=6.28), and the admixture signal is associated with the European ancestry (ancestry risk ratio  1.5). Large-scale genotypic analysis on 19,726 individuals of African and European ancestry revealed three independently associated variants in the IFIH1 gene: an intronic variant, rs13023380 [P(meta) = 5.20×10(-14); odds ratio, 95% confidence interval = 0.82 (0.78-0.87)], and two missense variants, rs1990760 (Ala946Thr) [P(meta) = 3.08×10(-7); 0.88 (0.84-0.93)] and rs10930046 (Arg460His) [P(dom) = 1.16×10(-8); 0.70 (0.62-0.79)]. Both missense variants produced dramatic phenotypic changes in apoptosis and inflammation-related gene expression. We experimentally validated function of the intronic SNP by DNA electrophoresis, protein identification, and in vitro protein binding assays. DNA carrying the intronic risk allele rs13023380 showed reduced binding efficiency to a cellular protein complex including nucleolin and lupus autoantigen Ku70/80, and showed reduced transcriptional activity in vivo. Thus, in SLE patients, genetic susceptibility could create a biochemical imbalance that dysregulates nucleolin, Ku70/80, or other nucleic acid regulatory proteins. This could promote antibody hypermutation and auto-antibody generation, further destabilizing the cellular network. Together with molecular modeling, our results establish a distinct role for IFIH1 in apoptosis, inflammation, and autoantibody production, and explain the molecular basis of these three risk alleles for SLE pathogenesis.

Calmodulin (CaM) is a universal regulatory protein that communicates the presence of calcium to its molecular targets and correspondingly modulates their function. This key signaling protein is important for controlling the activity of hundreds of membrane channels and transporters. However, understanding of the structural mechanisms driving CaM regulation of full-length membrane proteins has remained elusive. In this study, we determined the pseudoatomic structure of full-length mammalian aquaporin-0 (AQP0, Bos taurus) in complex with CaM, using EM to elucidate how this signaling protein modulates water-channel function. Molecular dynamics and functional mutation studies reveal how CaM binding inhibits AQP0 water permeability by allosterically closing the cytoplasmic gate of AQP0. Our mechanistic model provides new insight, only possible in the context of the fully assembled channel, into how CaM regulates multimeric channels by facilitating cooperativity between adjacent subunits.

We describe an intensity-based glutamate-sensing fluorescent reporter (iGluSnFR) with signal-to-noise ratio and kinetics appropriate for in vivo imaging. We engineered iGluSnFR in vitro to maximize its fluorescence change, and we validated its utility for visualizing glutamate release by neurons and astrocytes in increasingly intact neurological systems. In hippocampal culture, iGluSnFR detected single field stimulus-evoked glutamate release events. In pyramidal neurons in acute brain slices, glutamate uncaging at single spines showed that iGluSnFR responds robustly and specifically to glutamate in situ, and responses correlate with voltage changes. In mouse retina, iGluSnFR-expressing neurons showed intact light-evoked excitatory currents, and the sensor revealed tonic glutamate signaling in response to light stimuli. In worms, glutamate signals preceded and predicted postsynaptic calcium transients. In zebrafish, iGluSnFR revealed spatial organization of direction-selective synaptic activity in the optic tectum. Finally, in mouse forelimb motor cortex, iGluSnFR expression in layer V pyramidal neurons revealed task-dependent single-spine activity during running.

Tracing of neuron morphology is an essential technique in computational neuroscience. However, despite a number of existing methods, few open-source techniques are completely or sufficiently automated and at the same time are able to generate robust results for real 3D microscopy images.

In Caenorhabditis elegans, satiety quiescence mimics behavioral aspects of satiety and postprandial sleep in mammals. On the basis of calcium-imaging, genetics, and behavioral studies, here we report that a pair of amphid neurons, ASI, is activated by nutrition and regulates worms’ behavioral states specifically promoting satiety quiescence; ASI inhibits the switch from quiescence to dwelling (a browsing state) and accelerates the switch from dwelling to quiescence. The canonical TGFβ pathway, whose ligand is released from ASI, regulates satiety quiescence. The mutants of a ligand, a receptor and SMADs in the TGFβ pathway all eat more and show less quiescence than wild-type. The TGFβ receptor in downstream neurons RIM and RIC is sufficient for worms to exhibit satiety quiescence, suggesting neuronal connection from ASI to RIM and RIC is essential for feeding regulation through the TGFβ pathway. ASI also regulates satiety quiescence partly through cGMP signaling; restoring cGMP signaling in ASI rescues the satiety quiescence defect of cGMP signaling mutants. From these results, we propose that TGFβ and cGMP pathways in ASI connect nutritional status to promotion of satiety quiescence, a sleep-like behavioral state.

The most established method of reconstructing neural circuits from animals involves slicing tissue very thin, then taking mosaics of electron microscope (EM) images. To trace neurons across different images and through different sections, these images must be accurately aligned, both with the others in the same section and to the sections above and below. Unfortunately, sectioning and imaging are not ideal processes - some of the problems that make alignment difficult include lens distortion, tissue shrinkage during imaging, tears and folds in the sectioned tissue, and dust and other artifacts. In addition the data sets are large (hundreds of thousands of images) and each image must be aligned with many neighbors, so the process must be automated and reliable. This paper discusses methods of dealing with these problems, with numeric results describing the accuracy of the resulting alignments.

A quantitative description of animal social behaviour is informative for behavioural biologists and clinicians developing drugs to treat social disorders. Social interaction in a group of animals has been difficult to measure because behaviour develops over long periods of time and requires tedious manual scoring, which is subjective and often non-reproducible. Computer-vision systems with the ability to measure complex social behaviour automatically would have a transformative impact on biology. Here, we present a method for tracking group-housed mice individually as they freely interact over multiple days. Each mouse is bleach-marked with a unique fur pattern. The patterns are automatically learned by the tracking software and used to infer identities. Trajectories are analysed to measure behaviour as it develops over days, beyond the range of acute experiments. We demonstrate how our system may be used to study the development of place preferences, associations and social relationships by tracking four mice continuously for five days. Our system enables accurate and reproducible characterisation of wild-type mouse social behaviour and paves the way for high-throughput long-term observation of the effects of genetic, pharmacological and environmental manipulations.

Synaptic loss is the cardinal feature linking neuropathology to cognitive decline in Alzheimer’s disease (AD). However, the mechanism of synaptic damage remains incompletely understood. Here, using FRET-based glutamate sensor imaging, we show that amyloid-β peptide (Aβ) engages α7 nicotinic acetylcholine receptors to induce release of astrocytic glutamate, which in turn activates extrasynaptic NMDA receptors (eNMDARs) on neurons. In hippocampal autapses, this eNMDAR activity is followed by reduction in evoked and miniature excitatory postsynaptic currents (mEPSCs). Decreased mEPSC frequency may reflect early synaptic injury because of concurrent eNMDAR-mediated NO production, tau phosphorylation, and caspase-3 activation, each of which is implicated in spine loss. In hippocampal slices, oligomeric Aβ induces eNMDAR-mediated synaptic depression. In AD-transgenic mice compared with wild type, whole-cell recordings revealed excessive tonic eNMDAR activity accompanied by eNMDAR-sensitive loss of mEPSCs. Importantly, the improved NMDAR antagonist NitroMemantine, which selectively inhibits extrasynaptic over physiological synaptic NMDAR activity, protects synapses from Aβ-induced damage both in vitro and in vivo.

Neuronal computation involves the integration of synaptic inputs that are often distributed over expansive dendritic trees, suggesting the need for compensatory mechanisms that enable spatially disparate synapses to influence neuronal output. In hippocampal CA1 pyramidal neurons, such mechanisms have indeed been reported, which normalize either the ability of distributed synapses to drive action potential initiation in the axon or their ability to drive dendritic spiking locally. Here we report that these mechanisms can coexist, through an elegant combination of distance-dependent regulation of synapse number and synaptic expression of AMPA and NMDA receptors. Together, these complementary gradients allow individual dendrites in both the apical and basal dendritic trees of hippocampal neurons to operate as facile computational subunits capable of supporting both global integration in the soma/axon and local integration in the dendrite.