The Effects of Social Status on Dopaminergic Regulation of Neural Circuit Activation and Behavior

Social hierarchies can be observed within communities across many species and allow for proper allocation of resources. When forming social hierarchies, animals that display the most aggressive behaviors generally emerge as dominant, while less aggressive animals are relegated to a subordinate role. The aim of this study is to address the neural bases of social regulation using zebrafish (Danio rerio) as a model organism. When paired, zebrafish form dominance hierarchies that consist of socially dominant and subordinate fish. To better understand the effects of social dominance on nervous system function we investigated the influence of social experience on the escape and swim behaviors. Using a non-invasive technique of recording field potentials, we monitored escape and swimming behavior between fish of known social status. We showed that social status affects neural activation underlying swimming and escape behaviors. Subordinates favor escape over swim, while dominants favor swim over escape. We hypothesized that a neuromodulator associated with social regulation and aggression, dopamine (DA), may influence the activation of the two underlying neural circuits responsible for these behaviors in a social status-dependent manner. To test this hypothesis, we initially looked at whether the supply of DA influenced differences in swimming and escape behavior. We augmented levels of DA through injection and observed no significant changes in the escape or swimming behavior of dominants or subordinates. Next, we determined if the interpretation of DA, via DA receptors, influenced the status-dependent behavioral differences. We manipulated the activation of DA receptors through injection of DA specific agonists and antagonists. First, antagonizing the dopamine 1 receptor (D1) decreased dominant swimming frequency and increased escape probability, while having no effect on either behavior in subordinates. Activating the D1 receptor caused no changes in escape probability or swimming frequency in either social phenotype. Second, neither application of dopamine 2 receptor (D2) agonist nor antagonist significantly altered escape probability in either social phenotype; however, blocking the D2 receptor reduced dominant swimming frequency. Finally, antagonizing the dopamine 3 receptor (D3) lowered subordinates' probability of escape with no change in swimming frequency, while showing no effect on dominant behavior. Activating the D3 receptor had no effect on dominant or subordinate escape behavior, but decreased dominant swimming. Taken together, these results suggest that the social status-dependent differences in escape and swimming behaviors of zebrafish may be influenced by dopamine receptor activation

Amyloid Plaques Beyond Aβ: A Survey of the Diverse Modulators of Amyloid Aggregation

Aggregation of the amyloid-β (Aβ) peptide is strongly correlated with Alzheimer’s disease (AD). Recent research has improved our understanding of the kinetics of amyloid fibril assembly and revealed new details regarding different stages in plaque formation. Presently, interest is turning toward studying this process in a holistic context, focusing on cellular components which interact with the Aβ peptide at various junctures during aggregation, from monomer to cross-β amyloid fibrils. However, even in isolation, a multitude of factors including protein purity, pH, salt content, and agitation affect Aβ fibril formation and deposition, often producing complicated and conflicting results. The failure of numerous inhibitors in clinical trials for AD suggests that a detailed examination of the complex interactions that occur during plaque formation, including binding of carbohydrates, lipids, nucleic acids, and metal ions, is important for understanding the diversity of manifestations of the disease. Unraveling how a variety of key macromolecular modulators interact with the Aβ peptide and change its aggregation properties may provide opportunities for developing therapies. Since no protein acts in isolation, the interplay of these diverse molecules may differentiate disease onset, progression, and severity, and thus are worth careful consideration

Comprehensive Cancer-Predisposition Gene Testing in an Adult Multiple Primary Tumor Series Shows a Broad Range of Deleterious Variants and Atypical Tumor Phenotypes.

Multiple primary tumors (MPTs) affect a substantial proportion of cancer survivors and can result from various causes, including inherited predisposition. Currently, germline genetic testing of MPT-affected individuals for variants in cancer-predisposition genes (CPGs) is mostly targeted by tumor type. We ascertained pre-assessed MPT individuals (with at least two primary tumors by age 60 years or at least three by 70 years) from genetics centers and performed whole-genome sequencing (WGS) on 460 individuals from 440 families. Despite previous negative genetic assessment and molecular investigations, pathogenic variants in moderate- and high-risk CPGs were detected in 67/440 (15.2%) probands. WGS detected variants that would not be (or were not) detected by targeted resequencing strategies, including low-frequency structural variants (6/440 [1.4%] probands). In most individuals with a germline variant assessed as pathogenic or likely pathogenic (P/LP), at least one of their tumor types was characteristic of variants in the relevant CPG. However, in 29 probands (42.2% of those with a P/LP variant), the tumor phenotype appeared discordant. The frequency of individuals with truncating or splice-site CPG variants and at least one discordant tumor type was significantly higher than in a control population (χ2 = 43.642; p ≤ 0.0001). 2/67 (3%) probands with P/LP variants had evidence of multiple inherited neoplasia allele syndrome (MINAS) with deleterious variants in two CPGs. Together with variant detection rates from a previous series of similarly ascertained MPT-affected individuals, the present results suggest that first-line comprehensive CPG analysis in an MPT cohort referred to clinical genetics services would detect a deleterious variant in about a third of individuals.JW is supported by a Cancer Research UK Cambridge Cancer Centre Clinical Research Training Fellowship. Funding for the NIHR BioResource – Rare diseases project was provided by the National Institute for Health Research (NIHR, grant number RG65966). ERM acknowledges support from the European Research Council (Advanced Researcher Award), NIHR (Senior Investigator Award and Cambridge NIHR Biomedical Research Centre), Cancer Research UK Cambridge Cancer Centre and Medical Research Council Infrastructure Award. The University of Cambridge has received salary support in respect of EM from the NHS in the East of England through the Clinical Academic Reserve. The views expressed are those of the authors and not necessarily those of the NHS or Department of Health. DGE is an NIHR Senior Investigator and is supported by the all Manchester NIHR Biomedical Research Centre

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

GWAS meta-analysis of intrahepatic cholestasis of pregnancy implicates multiple hepatic genes and regulatory elements

Intrahepatic cholestasis of pregnancy (ICP) is a pregnancy-specific liver disorder affecting 0.5–2% of pregnancies. The majority of cases present in the third trimester with pruritus, elevated serum bile acids and abnormal serum liver tests. ICP is associated with an increased risk of adverse outcomes, including spontaneous preterm birth and stillbirth. Whilst rare mutations affecting hepatobiliary transporters contribute to the aetiology of ICP, the role of common genetic variation in ICP has not been systematically characterised to date. Here, we perform genome-wide association studies (GWAS) and meta-analyses for ICP across three studies including 1138 cases and 153,642 controls. Eleven loci achieve genome-wide significance and have been further investigated and fine-mapped using functional genomics approaches. Our results pinpoint common sequence variation in liver-enriched genes and liver-specific cis-regulatory elements as contributing mechanisms to ICP susceptibility

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

THE EFFECT OF SOCIAL EXPERIENCE ON THE SYNERGISTIC NEUROMODULATION OF MOTOR CIRCUITS

Forming social groups is a critical adaptive strategy for the survival of many animal species, where conflict between members can result in dominance relationships. Dominance relationships are often formed through aggressive interactions and influence the cognitive and physiological properties of individuals in a status-dependent manner. The aim of this dissertation is to discern how zebrafish utilize aggression and visual cues to reinforce a stable dominance relationship, and what effect stable dominance has on the neurobiological processes underlying motor behavior, with a focus on dopamine signaling. Dopamine has been implicated in aggression, social regulation, and modulation of motor circuits, making it a central point of study regarding the relationship between social dominance and motor behavior. Using behavioral, pharmacological, and genetic approaches, I have found that (1) in addition to physical aggression, zebrafish alter their stripe coloration intensity to reinforce dominance, (2) stable dominance alters dopamine signaling through decreased expression of the dopamine transporter and the dopamine receptor type-1b, (3) changes in dopamine signaling manifest in altered escape and swimming locomotor behavior, and (4) dopamine acts synergistically with other neurotransmitters to regulate status-dependent motor circuit activation. Results from this dissertation have provided evidence for how stable dominance impacts modulation of motor circuits, revealing how changes in relative excitability of multiple neuromodulatory inputs provide a mechanism for the nervous system to adapt to changes in social conditions and allow animals to select a socially appropriate behavioral response

The Effects of Social Status on Dopaminergic Regulation of Neural Circuit Activation and Behavior

Social hierarchies can be observed within communities across many species and allow for proper allocation of resources. When forming social hierarchies , animals that display the most aggressive behaviors generally emerge as dominant , while less aggressive animals are relegated to a subordinate role. The aim of this study is to address the neural bases of social regulation using zebrafish (Danio rerio) as a model organism. When paired , zebrafish form dominance hierarchies that consist of socially dominant and subordinate fish. To better understand the effects of social dominance on nervous system function we investigated the influence of social experience on the escape and swim behaviors. Using a non-invasive technique of recording field potentials , we monitored escape and swimming behavior between fish of known social status. We showed that social status affects neural activation underlying swimming and escape behaviors. Subordinates favor escape over swim , while dominants favor swim over escape. We hypothesized that a neuromodulator associated with social regulation and aggression , dopamine (DA) , may influence the activation of the two underlying neural circuits responsible for these behaviors in a social status-dependent manner. To test this hypothesis , we initially looked at whether the supply of DA influenced differences in swimming and escape behavior. We augmented levels of DA through injection and observed no significant changes in the escape or swimming behavior of dominants or subordinates. Next , we determined if the interpretation of DA , via DA receptors , influenced the status-dependent behavioral differences. We manipulated the activation of DA receptors through injection of DA specific agonists and antagonists. First , antagonizing the dopamine 1 receptor (D1) decreased dominant swimming frequency and increased escape probability , while having no effect on either behavior in subordinates. Activating the D1 receptor caused no changes in escape probability or swimming frequency in either social phenotype. Second , neither application of dopamine 2 receptor (D2) agonist nor antagonist significantly altered escape probability in either social phenotype; however , blocking the D2 receptor reduced dominant swimming frequency. Finally , antagonizing the dopamine 3 receptor (D3) lowered subordinates' probability of escape with no change in swimming frequency , while showing no effect on dominant behavior. Activating the D3 receptor had no effect on dominant or subordinate escape behavior , but decreased dominant swimming. Taken together , these results suggest that the social status-dependent differences in escape and swimming behaviors of zebrafish may be influenced by dopamine receptor activation

Effects of Social Experience on the Habituation Rate of Zebrafish Startle Escape Response: Empirical and Computational Analyses

While the effects of social experience on nervous system function have been extensively investigated in both vertebrate and invertebrate systems, our understanding of how social status differentially affects learning remains limited. In the context of habituation, a well-characterized form of non-associative learning, we investigated how the learning processes differ between socially dominant and subordinate in zebrafish (Danio rerio). We found that social status and frequency of stimulus inputs influence the habituation rate of short latency C-start escape response that is initiated by the Mauthner neuron (M-cell). Socially dominant animals exhibited higher habituation rates compared to socially subordinate animals at a moderate stimulus frequency, but low stimulus frequency eliminated this difference of habituation rates between the two social phenotypes. Moreover, habituation rates of both dominants and subordinates were higher at a moderate stimulus frequency compared to those at a low stimulus frequency. We investigated a potential mechanism underlying these status-dependent differences by constructing a simplified neurocomputational model of the M-cell escape circuit. The computational study showed that the change in total net excitability of the model M-cell was able to replicate the experimental results. At moderate stimulus frequency, the model M-cell with lower total net excitability, that mimicked a dominant-like phenotype, exhibited higher habituation rates. On the other hand, the model with higher total net excitability, that mimicked the subordinate-like phenotype, exhibited lower habituation rates. The relationship between habituation rates and characteristics (frequency and amplitude) of the repeated stimulus were also investigated. We found that habituation rates are decreasing functions of amplitude and increasing functions of frequency while these rates depend on social status (higher for dominants and lower for subordinate). Our results show that social status affects habituative learning in zebrafish, which could be mediated by a summative neuromodulatory input to the M-cell escape circuit, which enables animals to readily learn to adapt to changes in their social environment

Repurposing CRISPR-Cas13 systems for robust mRNA trans-splicing

Abstract Type VI CRISPR enzymes have been developed as programmable RNA-guided Cas proteins for eukaryotic RNA editing. Notably, Cas13 has been utilized for site-targeted single base edits, demethylation, RNA cleavage or knockdown and alternative splicing. However, the ability to edit large stretches of mRNA transcripts remains a significant challenge. Here, we demonstrate that CRISPR-Cas13 systems can be repurposed to assist trans-splicing of exogenous RNA fragments into an endogenous pre-mRNA transcript, a method termed CRISPR Assisted mRNA Fragment Trans-splicing (CRAFT). Using split reporter-based assays, we evaluate orthogonal Cas13 systems, optimize guide RNA length and screen for optimal trans-splicing site(s) across a range of intronic targets. We achieve markedly improved editing of large 5’ and 3’ segments in different endogenous mRNAs across various mammalian cell types compared to other spliceosome-mediated trans-splicing methods. CRAFT can serve as a versatile platform for attachment of protein tags, studying the impact of multiple mutations/single nucleotide polymorphisms, modification of untranslated regions (UTRs) or replacing large segments of mRNA transcripts