Modulation of Trust in Borderline Personality Disorder by Script-Based Imaginal Exposure to Betrayal.

Interpersonal and trust-related difficulties are central features of borderline personality disorder (BPD). In this study, we applied script-driven betrayal imagery to evoke mistrustful behavior in a social reinforcement learning task. In 21 BPD and 20 healthy control (HC) participants, we compared this approach to the standard confederate paradigm used in research studies. The script-driven imagery evoked a transient increase in negative affect and also decreased trusting behavior to a similar degree in both groups. Across conditions, we also replicated previously reported between-group differences in negative affect (increased in BPD) and task behavior (more sensitive to social cues in BPD). These results support the validity of script-driven imagery as an alternative social task stimulus. This script-driven imagery approach is appealing for clinical research studies on reinforcement learning because it eliminates deception, scales easily, and evokes disorder-specific states of social difficulty.

Assessing Equity in Mental Health Outreach Services to People Experiencing Unsheltered Homelessness.

OBJECTIVE: The study aimed to evaluate differences in age, gender, race, and ethnicity between a population served by a street psychiatry team and the local community of people experiencing unsheltered homelessness in order to identify intersectional inequities in care. METHODS: We tested for bivariate associations between patient affiliation and age, gender, race, and ethnicity using a Welch two sample t-test for the continuous term (age) and Pearson's chi-squared test with Yates' continuity correction for the categorical terms (gender, race, and ethnicity). RESULTS: The CMHC Street Psychiatry Team served a population (N = 200) that was significantly older (p<.001) and composed of proportionally fewer women (p = .010) and people of color (p<.001) than the local population experiencing unsheltered homelessness (N = 944). CONCLUSIONS: This process of critical evaluation identified disparities in service provision which prompted re-evaluation of services to target efforts to those most at risk of marginalization.

NIMBus: a negative binomial regression based Integrative Method for mutation Burden Analysis.

BACKGROUND: Identifying frequently mutated regions is a key approach to discover DNA elements influencing cancer progression. However, it is challenging to identify these burdened regions due to mutation rate heterogeneity across the genome and across different individuals. Moreover, it is known that this heterogeneity partially stems from genomic confounding factors, such as replication timing and chromatin organization. The increasing availability of cancer whole genome sequences and functional genomics data from the Encyclopedia of DNA Elements (ENCODE) may help address these issues. RESULTS: We developed a negative binomial regression-based Integrative Method for mutation Burden analysiS (NIMBus). Our approach addresses the over-dispersion of mutation count statistics by (1) using a Gamma-Poisson mixture model to capture the mutation-rate heterogeneity across different individuals and (2) estimating regional background mutation rates by regressing the varying local mutation counts against genomic features extracted from ENCODE. We applied NIMBus to whole-genome cancer sequences from the PanCancer Analysis of Whole Genomes project (PCAWG) and other cohorts. It successfully identified well-known coding and noncoding drivers, such as TP53 and the TERT promoter. To further characterize the burdening of non-coding regions, we used NIMBus to screen transcription factor binding sites in promoter regions that intersect DNase I hypersensitive sites (DHSs). This analysis identified mutational hotspots that potentially disrupt gene regulatory networks in cancer. We also compare this method to other mutation burden analysis methods. CONCLUSION: NIMBus is a powerful tool to identify mutational hotspots. The NIMBus software and results are available as an online resource at github.gersteinlab.org/nimbus.

Dscam Proteins Direct Dendritic Targeting through Adhesion.

Cell recognition molecules are key regulators of neural circuit assembly. The Dscam family of recognition molecules in Drosophila has been shown to regulate interactions between neurons through homophilic repulsion. This is exemplified by Dscam1 and Dscam2, which together repel dendrites of lamina neurons, L1 and L2, in the visual system. By contrast, here we show that Dscam2 directs dendritic targeting of another lamina neuron, L4, through homophilic adhesion. Through live imaging and genetic mosaics to dissect interactions between specific cells, we show that Dscam2 is required in L4 and its target cells for correct dendritic targeting. In a genetic screen, we identified Dscam4 as another regulator of L4 targeting which acts with Dscam2 in the same pathway to regulate this process. This ensures tiling of the lamina neuropil through heterotypic interactions. Thus, different combinations of Dscam proteins act through distinct mechanisms in closely related neurons to pattern neural circuits.

Metabolic regulation of protein N-alpha-acetylation by Bcl-xL promotes cell survival.

Previous experiments suggest a connection between the N-alpha-acetylation of proteins and sensitivity of cells to apoptotic signals. Here, we describe a biochemical assay to detect the acetylation status of proteins and demonstrate that protein N-alpha-acetylation is regulated by the availability of acetyl-CoA. Because the antiapoptotic protein Bcl-xL is known to influence mitochondrial metabolism, we reasoned that Bcl-xL may provide a link between protein N-alpha-acetylation and apoptosis. Indeed, Bcl-xL overexpression leads to a reduction in levels of acetyl-CoA and N-alpha-acetylated proteins in the cell. This effect is independent of Bax and Bak, the known binding partners of Bcl-xL. Increasing cellular levels of acetyl-CoA by addition of acetate or citrate restores protein N-alpha-acetylation in Bcl-xL-expressing cells and confers sensitivity to apoptotic stimuli. We propose that acetyl-CoA serves as a signaling molecule that couples apoptotic sensitivity to metabolism by regulating protein N-alpha-acetylation.

The Jekyll and Hyde functions of caspases.

Apoptosis is an ancient form of regulated cell death that functions under pathological and nonpathological contexts in all metazoans. More than a decade of intense research has led to extensive characterization of the core molecular mechanisms for apoptotic cell death. This includes the identification of a family of cysteine proteases, caspases, which are critical for the execution of apoptosis. Whereas completion of the proteolytic caspase cascade leads to elimination of a cell by apoptosis, caspase activation, when finely tuned, directs alternative cellular functions independent of cell death. Exciting recent developments have focused on uncovering nonapoptotic roles of caspases ranging from immune regulation to spermatogenesis, in highly specialized cellular frameworks.

A genome-wide RNAi screen reveals multiple regulators of caspase activation.

Apoptosis is an evolutionally conserved cellular suicide mechanism that can be activated in response to a variety of stressful stimuli. Increasing evidence suggests that apoptotic regulation relies on specialized cell death signaling pathways and also integrates diverse signals from additional regulatory circuits, including those of cellular homeostasis. We present a genome-wide RNA interference screen to systematically identify regulators of apoptosis induced by DNA damage in Drosophila melanogaster cells. We identify 47 double- stranded RNA that target a functionally diverse set of genes, including several with a known function in promoting cell death. Further characterization uncovers 10 genes that influence caspase activation upon the removal of Drosophila inhibitor of apoptosis 1. This set includes the Drosophila initiator caspase Dronc and, surprisingly, several metabolic regulators, a candidate tumor suppressor, Charlatan, and an N-acetyltransferase, ARD1. Importantly, several of these genes show functional conservation in regulating apoptosis in mammalian cells. Our data suggest a previously unappreciated fundamental connection between various cellular processes and caspase-dependent cell death.

Prion pathogenesis is independent of caspase-12.

The pathogenic mechanism(s) underlying neurodegenerative diseases associated with protein misfolding is unclear. Several studies have implicated ER stress pathways in neurodegenerative conditions, including prion disease, amyotrophic lateral sclerosis, Alzheimer's disease and many others. The ER stress response and upregulation of ER stress-responsive chaperones is observed in the brains of patients affected with Creutzfeldt-Jacob disease and in mouse models of prion diseases. In particular, the processing of caspase-12, an ER-localized caspase, correlates with neuronal cell death in prion disease. However, the contribution of caspase-12 to neurodegeneration has not been directly addressed in vivo. We confirm that ER stress is induced and that caspase-12 is proteolytically processed in a murine model of infectious prion disease. To address the causality of caspase-12 in mediating infectious prion pathogenesis, we inoculated mice deficient in caspase-12 with prions. The survival, behavior, pathology and accumulation of proteinase K-resistant PrP are indistinguishable between caspase-12 knockout and control mice, suggesting that caspase-12 is not necessary for mediating the neurotoxic effects of prion protein misfolding.

Innate recognition of bacteria by a macrophage cytosolic surveillance pathway.

Host recognition of bacterial pathogens is a critical component of the immune response. Intracellular bacterial pathogens are able to evade the humoral immune system by residing within the host cell. Here we show the existence of an innate host surveillance mechanism in macrophages that specifically distinguishes bacteria in the cytosol from bacteria in the vacuole. Recognition of Gram-positive and Gram-negative bacterial products by this surveillance system results in transcription of the ifnb gene. The activation of cytosol-specific signaling is associated with translocation of NF-kappaB into the nucleus and phosphorylation of the p38 mitogen-activated protein (MAP) kinase. Activation of the p38 kinase is required for the induction of gene expression by the cytosolic surveillance pathway. Our studies suggest that infection by intracellular bacterial pathogens results in an immune response distinct from that of infection by extracellular bacterial pathogens.