The Testing Imperative: Why the US Ending the Human Immunodeficiency Virus (HIV) Epidemic Program Needs to Renew Efforts to Expand HIV Testing in Clinical and Community-Based Settings.

Data from several modeling studies demonstrate that large-scale increases in human immunodeficiency virus (HIV) testing across settings with a high burden of HIV may produce the largest incidence reductions to support the US Ending the HIV Epidemic (EHE) initiative's goal of reducing new HIV infections 90% by 2030. Despite US Centers for Disease Control and Prevention's recommendations for routine HIV screening within clinical settings and at least yearly screening for individuals most at risk of acquiring HIV, fewer than half of US adults report ever receiving an HIV test. Furthermore, total domestic funding for HIV prevention has remained unchanged between 2013 and 2019. The authors describe the evidence supporting the value of expanded HIV testing, identify challenges in implementation, and present recommendations to address these barriers through approaches at local and federal levels to reach EHE targets.

Lateral septum modulates cortical state to tune responsivity to threat stimuli.

Sudden unexpected environmental changes capture attention and, when perceived as potentially dangerous, evoke defensive behavioral states. Perturbations of the lateral septum (LS) can produce extreme hyperdefensiveness even to innocuous stimuli, but how this structure influences stimulus-evoked defensive responses and threat perception remains unclear. Here, we show that Crhr2-expressing neurons in mouse LS exhibit phasic activation upon detection of threatening but not rewarding stimuli. Threat-stimulus-driven activity predicts the probability but not vigor or type of defensive behavior evoked. Although necessary for and sufficient to potentiate stimulus-triggered defensive responses, LSCrhr2 neurons do not promote specific behaviors. Rather, their stimulation elicits negative valence and physiological arousal. Moreover, LSCrhr2 activity tracks brain state fluctuations and drives cortical activation and rapid awakening in the absence of threat. Together, our findings suggest that LS directs bottom-up modulation of cortical function to evoke preparatory defensive internal states and selectively enhance responsivity to threat-related stimuli.

Projected Impact of Expanded Long-Acting Injectable PrEP Use Among Men Who Have Sex With Men on Local HIV Epidemics.

BACKGROUND: Pre-exposure prophylaxis (PrEP) is a key component in helping to reduce HIV incidence in the United States. Long-acting injectable (LAI) PrEP is a new alternative to oral PrEP; its potential to affect local HIV epidemics remains unclear. METHODS: The Johns Hopkins HIV Economic Epidemiological model (JHEEM) is a dynamic model of HIV transmission in 32 US urban areas. We used JHEEM to project the HIV incidence among men who have sex with men (MSM) from 2020 to 2030 under a range of interventions aimed at increasing PrEP use. RESULTS: In the absence of any intervention (ie, current levels of oral PrEP and HIV care engagement), we projected a 19% reduction (95% credible interval, CrI 1% to 36%) in HIV incidence among MSM from 2020 to 2030 across all 32 cities. Adding 10% LAI PrEP uptake (above a base case of all oral PrEP) reduced the incidence by 36% (95% CrI 23% to 50%) by year 2030. This effect varied between cities, ranging from 22% in Atlanta to 51% in San Francisco. At 25% additional LAI PrEP uptake, this incidence reduction increased to 54% (95% CrI 45% to 64%). Reductions in incidence after introducing LAI PrEP were driven primarily by increased uptake and sustained usage rather than increased efficacy. CONCLUSIONS: LAI PrEP has the potential to substantially reduce HIV incidence among MSM, particularly if it increases PrEP uptake and continued use beyond existing levels. Because potential effects vary by city, the effectiveness of expanding PrEP use is dependent on local dynamics.

Whole-Brain Wiring Diagram of Oxytocin System in Adult Mice.

Oxytocin (Oxt) neurons regulate diverse physiological responses via direct connections with different neural circuits. However, the lack of comprehensive input-output wiring diagrams of Oxt neurons and their quantitative relationship with Oxt receptor (Oxtr) expression presents challenges to understanding circuit-specific Oxt functions. Here, we establish a whole-brain distribution and anatomic connectivity map of Oxt neurons, and their relationship with Oxtr expression using high-resolution 3D mapping methods in adult male and female mice. We use a flatmap to describe Oxt neuronal expression in four hypothalamic domains including under-characterized Oxt neurons in the tuberal nucleus (TU). Oxt neurons in the paraventricular hypothalamus (PVH) broadly project to nine functional circuits that control cognition, brain state, and somatic visceral response. In contrast, Oxt neurons in the supraoptic (SO) and accessory (AN) nuclei have limited central projection to a small subset of the nine circuits. Surprisingly, quantitative comparison between Oxt output and Oxtr expression showed no significant correlation across the whole brain, suggesting abundant indirect Oxt signaling in Oxtr-expressing areas. Unlike output, Oxt neurons in both the PVH and SO receive similar monosynaptic inputs from a subset of the nine circuits mainly in the thalamic, hypothalamic, and cerebral nuclei areas. Our results suggest that PVH-Oxt neurons serve as a central modulator to integrate external and internal information via largely reciprocal connection with the nine circuits while the SO-Oxt neurons act mainly as unidirectional Oxt hormonal output. In summary, our Oxt wiring diagram provides anatomic insights about distinct behavioral functions of Oxt signaling in the brain.SIGNIFICANCE STATEMENT Oxytocin (Oxt) neurons regulate diverse physiological functions from prosocial behavior to pain sensation via central projection in the brain. Thus, understanding detailed anatomic connectivity of Oxt neurons can provide insight on circuit-specific roles of Oxt signaling in regulating different physiological functions. Here, we use high-resolution mapping methods to describe the 3D distribution, monosynaptic input and long-range output of Oxt neurons, and their relationship with Oxt receptor (Oxtr) expression across the entire mouse brain. We found Oxt connections with nine functional circuits controlling cognition, brain state, and somatic visceral response. Furthermore, we identified a quantitatively unmatched Oxt-Oxtr relationship, suggesting broad indirect Oxt signaling. Together, our comprehensive Oxt wiring diagram advances our understanding of circuit-specific roles of Oxt neurons.

Achieving a "step change" in the tuberculosis epidemic through comprehensive community-wide intervention: a model-based analysis.

BACKGROUND: Global progress towards reducing tuberculosis (TB) incidence and mortality has consistently lagged behind the World Health Organization targets leading to a perception that large reductions in TB burden cannot be achieved. However, several recent and historical trials suggest that intervention efforts that are comprehensive and intensive can have a substantial epidemiological impact. We aimed to quantify the potential epidemiological impact of an intensive but realistic, community-wide campaign utilizing existing tools and designed to achieve a "step change" in the TB burden. METHODS: We developed a compartmental model that resembled TB transmission and epidemiology of a mid-sized city in India, the country with the greatest absolute TB burden worldwide. We modeled the impact of a one-time, community-wide screening campaign, with treatment for TB disease and preventive therapy for latent TB infection (LTBI). This one-time intervention was followed by the strengthening of the tuberculosis-related health system, potentially facilitated by leveraging the one-time campaign. We estimated the tuberculosis cases and deaths that could be averted over 10 years using this comprehensive approach and assessed the contributions of individual components of the intervention. RESULTS: A campaign that successfully screened 70% of the adult population for active and latent tuberculosis and subsequently reduced diagnostic and treatment delays and unsuccessful treatment outcomes by 50% was projected to avert 7800 (95% range 5450-10,200) cases and 1710 (1290-2180) tuberculosis-related deaths per 1 million population over 10 years. Of the total averted deaths, 33.5% (28.2-38.3) were attributable to the inclusion of preventive therapy and 52.9% (48.4-56.9) to health system strengthening. CONCLUSIONS: A one-time, community-wide mass campaign, comprehensively designed to detect, treat, and prevent tuberculosis with currently existing tools can have a meaningful and long-lasting epidemiological impact. Successful treatment of LTBI is critical to achieving this result. Health system strengthening is essential to any effort to transform the TB response.

What Will It Take to End HIV in the United States? : A Comprehensive, Local-Level Modeling Study.

BACKGROUND: The Ending the HIV Epidemic (EHE) initiative aims to reduce incident HIV infections by 90% over a span of 10 years. The intensity of interventions needed to achieve this for local epidemics is unclear. OBJECTIVE: To estimate the effect of HIV interventions at the city level. DESIGN: A compartmental model of city-level HIV transmission stratified by age, race, sex, and HIV risk factor was developed and calibrated. SETTING: 32 priority metropolitan statistical areas (MSAs). PATIENTS: Simulated populations in each MSA. INTERVENTION: Combinations of HIV testing and preexposure prophylaxis (PrEP) coverage among those at risk for HIV, plus viral suppression in persons with diagnosed HIV infection. MEASUREMENTS: The primary outcome was the projected reduction in incident cases from 2020 to 2030. RESULTS: Absent intervention, HIV incidence was projected to decrease by 19% across all 32 MSAs. Modest increases in testing (1.25-fold per year), PrEP coverage (5 percentage points), and viral suppression (10 percentage points) across the population could achieve reductions of 34% to 67% by 2030. Twenty-five percent PrEP coverage, testing twice a year on average, and 90% viral suppression among young Black and Hispanic men who have sex with men (MSM) achieved similar reductions (13% to 68%). Including all MSM and persons who inject drugs could reduce incidence by 48% to 90%. Thirteen of 32 MSAs could achieve greater than 90% reductions in HIV incidence with large-scale interventions that include heterosexuals. A web application with location-specific results is publicly available (www.jheem.org). LIMITATION: The COVID-19 pandemic was not represented. CONCLUSION: Large reductions in HIV incidence are achievable with substantial investment, but the EHE goals will be difficult to achieve in most locations. An interactive model that can help policymakers maximize the effect in their local environments is presented. PRIMARY FUNDING SOURCE: National Institutes of Health.

Stimulus salience determines defensive behaviors elicited by aversively conditioned serial compound auditory stimuli.

Assessing the imminence of threatening events using environmental cues enables proactive engagement of appropriate avoidance responses. The neural processes employed to anticipate event occurrence depend upon which cue properties are used to formulate predictions. In serial compound stimulus (SCS) conditioning in mice, repeated presentations of sequential tone (CS1) and white noise (CS2) auditory stimuli immediately prior to an aversive event (US) produces freezing and flight responses to CS1 and CS2, respectively (Fadok et al., 2017). Recent work reported that these responses reflect learned temporal relationships of CS1 and CS2 to the US (Dong et al., 2019). However, we find that frequency and sound pressure levels, not temporal proximity to the US, are the key factors underlying SCS-driven conditioned responses. Moreover, white noise elicits greater physiological and behavioral responses than tones even prior to conditioning. Thus, stimulus salience is the primary determinant of behavior in the SCS paradigm, and represents a potential confound in experiments utilizing multiple sensory stimuli.

If you notice the skies above you becoming darker, your first thought might be to seek shelter. Experience will have taught you that darkening skies are often a sign of an approaching storm. Learning to recognise changes that occur prior to an unpleasant event can help us avoid danger. But this is not the only strategy people can use to predict when something bad is about to happen. Another option is to use the intensity, or salience, of sensory information. Soldiers fighting on the front line, for example, might rely on the loudness of enemy voices or vehicles to judge how close an advancing enemy is. This information will help them decide when to retreat. Different brain processes are active when individuals use each of these two strategies to predict when an upcoming event will occur. One approach to study these processes is to use a technique called "SCS conditioning". This involves exposing mice to two sounds, followed by a mild electric shock administered to the feet. The first sound is a pure tone; the second is a burst of white noise. After repeated trials, mice begin to show distinct responses to the two sounds. They freeze in response to the tone but run away upon hearing the white noise. These responses parallel behaviors seen in the wild. When mice detect a distant predator, they freeze to avoid detection. But if the predator comes too close for the mice to avoid being spotted, they instead try to flee. Some have argued that in the SCS task, mice learn that the white noise predicts an imminent shock. The mice therefore flee as soon as they hear it. By contrast, they learn that the tone predicts a delayed shock and therefore choose to freeze instead. However, by tweaking the SCS procedure, Hersman et al. now show that even if the white noise occurs before the tone, it is still more likely than the tone to trigger an escape response. In fact, mice are more reactive to white noise than tones even if the sounds are never paired with shocks. This suggests that mice find white noise naturally more noticeable than tones. Moreover, Hersman et al. show that tones can also trigger escape responses if they are sufficiently intense. Together these results suggest that mice use the intensity of the stimuli ­ rather than the length of time between each stimulus and the shock ­ to decide whether to freeze or flee. People with anxiety disorders often show exaggerated responses to things that do not pose a genuine threat. At present the pathways in the brain that are responsible for these excessive reactions are unclear. The results of Hersman et al. will aid research into the brain circuits that detect, assess and respond to threats. Understanding these circuits could in the future lead to better treatments for anxiety disorders.

Angiotensin (1-7) does not interact directly with MAS1, but can potently antagonize signaling from the AT1 receptor.

Angiotensin (1-7) has been reported to be a ligand for the GPCR MAS1. Small molecule MAS1 modulators have also been recently characterized. Aside from convincing evidence for MAS1 activation of Gq signaling, little is known about MAS1 mediated signaling pathways initiated by these ligands, especially Ang (1-7). We performed a comprehensive characterization of recombinant MAS1 signaling induced by Ang (1-7) and small molecule ligands through numerous G protein-dependent and independent pathways, and in a signaling pathway agnostic approach. We find that small molecule ligands modulate numerous G protein-dependent and independent pathways through MAS1, including Gq and Gi pathways, GTPγS binding, ß-arrestin recruitment, Erk1/2 and Akt phosphorylation, arachidonic acid release, and receptor internalization. Moreover, in dynamic mass redistribution (DMR) assays that provide a pathway-agnostic readout of cellular responses, small molecule agonists produced robust responses. In contrast, Ang (1-7) failed to induce or block signaling in any of these assay platforms. We detected specific binding of radiolabeled Ang (1-7) to rat aortic endothelial cell (RAEC) membranes, but not to recombinant MAS1. Biphasic, concentration-dependent biased signaling responses to Ang II were detected in RAEC. These phases were associated with vastly different DMR characteristics and this likely provides a molecular basis for previously observed concentration-dependent divergent physiological actions of Ang II. Both phases of Ang II signaling in RAECs were potently inhibited by Ang (1-7), providing a plausible molecular mechanism for Ang (1-7) as counter regulator of the Ang II- AT1 axis, responsible at least in part for Ang (1-7) physiological activities.

Embelin and its derivatives unravel the signaling, proinflammatory and antiatherogenic properties of GPR84 receptor.

GPR84 is an orphan G-protein coupled receptor, expressed on monocytes, macrophages and neutrophils and is significantly upregulated by inflammatory stimuli. The physiological role of GPR84 remains largely unknown. Medium chain fatty acids (MCFA) activate the receptor and have been proposed to be its endogenous ligands, although the high concentrations of MCFAs required for receptor activation generally exceed normal physiological levels. We identified the natural product embelin as a highly potent and selective surrogate GPR84 agonist (originally disclosed in patent application WO2007027661A2, 2007) and synthesized close structural analogs with widely varying receptor activities. These tools were used to perform a comprehensive study of GPR84 signaling and function in recombinant cells and in primary human macrophages and neutrophils. Activation of recombinant GPR84 by embelin in HEK293 cells results in Gi/o as well as G12/13-Rho signaling. In human macrophages, GPR84 initiates PTX sensitive Erk1/2 and Akt phosphorylation, PI-3 kinase activation, calcium flux, and release of prostaglandin E2. In addition, GPR84 signaling in macrophages elicits Gi Gßγ-mediated augmentation of intracellular cAMP, rather than the decrease expected from Giα engagement. GPR84 activation drives human neutrophil chemotaxis and primes them for amplification of oxidative burst induced by FMLP and C5A. Loss of GPR84 is associated with attenuated LPS-induced release of proinflammatory mediators IL-6, KC-GROα, VEGF, MIP-2 and NGAL from peritoneal exudates. While initiating numerous proinflammatory activities in macrophages and neutrophils, GPR84 also possesses GPR109A-like antiatherosclerotic properties in macrophages. Macrophage receptor activation leads to upregulation of cholesterol transporters ABCA1 and ABCG1 and stimulates reverse cholesterol transport. These data suggest that GPR84 may be a target of therapeutic value and that distinct modes of receptor modulation (inhibition vs. stimulation) may be required for inflammatory and atherosclerotic indications.

Transient inhibition of the ERK pathway prevents cerebellar developmental defects and improves long-term motor functions in murine models of neurofibromatosis type 1.

Individuals with neurofibromatosis type 1 (NF1) frequently exhibit cognitive and motor impairments and characteristics of autism. The cerebellum plays a critical role in motor control, cognition, and social interaction, suggesting that cerebellar defects likely contribute to NF1-associated neurodevelopmental disorders. Here we show that Nf1 inactivation during early, but not late stages of cerebellar development, disrupts neuronal lamination, which is partially caused by overproduction of glia and subsequent disruption of the Bergmann glia (BG) scaffold. Specific Nf1 inactivation in glutamatergic neuronal precursors causes premature differentiation of granule cell (GC) precursors and ectopic production of unipolar brush cells (UBCs), indirectly disrupting neuronal migration. Transient MEK inhibition during a neonatal window prevents cerebellar developmental defects and improves long-term motor performance of Nf1-deficient mice. This study reveals essential roles of Nf1 in GC/UBC migration by generating correct numbers of glia and controlling GC/UBC fate-specification/differentiation, identifying a therapeutic prevention strategy for multiple NF1-associcated developmental abnormalities.

Discovery of APD334: Design of a Clinical Stage Functional Antagonist of the Sphingosine-1-phosphate-1 Receptor.

APD334 was discovered as part of our internal effort to identify potent, centrally available, functional antagonists of the S1P1 receptor for use as next generation therapeutics for treating multiple sclerosis (MS) and other autoimmune diseases. APD334 is a potent functional antagonist of S1P1 and has a favorable PK/PD profile, producing robust lymphocyte lowering at relatively low plasma concentrations in several preclinical species. This new agent was efficacious in a mouse experimental autoimmune encephalomyelitis (EAE) model of MS and a rat collagen induced arthritis (CIA) model and was found to have appreciable central exposure.

(7-Benzyloxy-2,3-dihydro-1H-pyrrolo[1,2-a]indol-1-yl)acetic Acids as S1P1 Functional Antagonists.

S1P1 is a validated target for treatment of autoimmune disease, and functional antagonists with superior safety and pharmacokinetic properties are being sought as second generation therapeutics. We describe the discovery and optimization of (7-benzyloxy-2,3-dihydro-1H-pyrrolo[1,2-a]indol-1-yl)acetic acids as potent, centrally available, direct acting S1P1 functional antagonists, with favorable pharmacokinetic and safety properties.

Central amygdala PKC-δ(+) neurons mediate the influence of multiple anorexigenic signals.

Feeding can be inhibited by multiple cues, including those associated with satiety, sickness or unpalatable food. How such anorexigenic signals inhibit feeding at the neural circuit level is not completely understood. Although some inhibitory circuits have been identified, it is not yet clear whether distinct anorexigenic influences are processed in a convergent or parallel manner. The amygdala central nucleus (CEA) has been implicated in feeding control, but its role is controversial. The lateral subdivision of CEA (CEl) contains a subpopulation of GABAergic neurons that are marked by protein kinase C-δ (PKC-δ). We found that CEl PKC-δ(+) neurons in mice were activated by diverse anorexigenic signals in vivo, were required for the inhibition of feeding by such signals and strongly suppressed food intake when activated. They received presynaptic inputs from anatomically distributed neurons activated by different anorexigenic agents. Our data suggest that CEl PKC-δ(+) neurons constitute an important node that mediates the influence of multiple anorexigenic signals.

Scalable control of mounting and attack by Esr1+ neurons in the ventromedial hypothalamus.

Social behaviours, such as aggression or mating, proceed through a series of appetitive and consummatory phases that are associated with increasing levels of arousal. How such escalation is encoded in the brain, and linked to behavioural action selection, remains an unsolved problem in neuroscience. The ventrolateral subdivision of the murine ventromedial hypothalamus (VMHvl) contains neurons whose activity increases during male-male and male-female social encounters. Non-cell-type-specific optogenetic activation of this region elicited attack behaviour, but not mounting. We have identified a subset of VMHvl neurons marked by the oestrogen receptor 1 (Esr1), and investigated their role in male social behaviour. Optogenetic manipulations indicated that Esr1(+) (but not Esr1(-)) neurons are sufficient to initiate attack, and that their activity is continuously required during ongoing agonistic behaviour. Surprisingly, weaker optogenetic activation of these neurons promoted mounting behaviour, rather than attack, towards both males and females, as well as sniffing and close investigation. Increasing photostimulation intensity could promote a transition from close investigation and mounting to attack, within a single social encounter. Importantly, time-resolved optogenetic inhibition experiments revealed requirements for Esr1(+) neurons in both the appetitive (investigative) and the consummatory phases of social interactions. Combined optogenetic activation and calcium imaging experiments in vitro, as well as c-Fos analysis in vivo, indicated that increasing photostimulation intensity increases both the number of active neurons and the average level of activity per neuron. These data suggest that Esr1(+) neurons in VMHvl control the progression of a social encounter from its appetitive through its consummatory phases, in a scalable manner that reflects the number or type of active neurons in the population.

Control of stress-induced persistent anxiety by an extra-amygdala septohypothalamic circuit.

The extended amygdala has dominated research on the neural circuitry of fear and anxiety, but the septohippocampal axis also plays an important role. The lateral septum (LS) is thought to suppress fear and anxiety through its outputs to the hypothalamus. However, this structure has not yet been dissected using modern tools. The type 2 CRF receptor (Crfr2) marks a subset of LS neurons whose functional connectivity we have investigated using optogenetics. Crfr2(+) cells include GABAergic projection neurons that connect with the anterior hypothalamus. Surprisingly, we find that these LS outputs enhance stress-induced behavioral measures of anxiety. Furthermore, transient activation of Crfr2(+) neurons promotes, while inhibition suppresses, persistent anxious behaviors. LS Crfr2(+) outputs also positively regulate circulating corticosteroid levels. These data identify a subset of LS projection neurons that promote, rather than suppress, stress-induced behavioral and endocrinological dimensions of persistent anxiety states and provide a cellular point of entry to LS circuitry.

Kinetics of 5-HT2B receptor signaling: profound agonist-dependent effects on signaling onset and duration.

The kinetics of drug-receptor interactions can profoundly influence in vivo and in vitro pharmacology. In vitro, the potencies of slowly associating agonists may be underestimated in assays capturing transient signaling events. When divergent receptor-mediated signaling pathways are evaluated using combinations of equilibrium and transient assays, potency differences driven by kinetics may be erroneously interpreted as biased signaling. In vivo, drugs with slow dissociation rates may display prolonged physiologic effects inconsistent with their pharmacokinetic profiles. We evaluated a panel of 5-hydroxytryptamine2B (5-HT2B) receptor agonists in kinetic radioligand binding assays and in transient, calcium flux assays, and inositol phosphate accumulation assays; two functional readouts emanating from Gαq-mediated activation of phospholipase C. In binding studies, ergot derivatives demonstrated slow receptor association and dissociation rates, resulting in significantly reduced potency in calcium assays relative to inositol phosphate accumulation assays. Ergot potencies for activation of extracellular signal-regulated kinases 1 and 2 were also highly time-dependent. A number of ergots produced wash-resistant 5-HT2B signaling that persisted for many hours without appreciable loss of potency, which was not explained simply by slow receptor-dissociation kinetics. Mechanistic studies indicated that persistent signaling originated from internalized or sequestered receptors. This study provides a mechanistic basis for the long durations of action in vivo and wash-resistant effects in ex vivo tissue models often observed for ergots. The 5-HT2B agonist activity of a number of ergot-derived therapeutics has been implicated in development of cardiac valvulopathy in man. The novel, sustained nature of ergot signaling reported here may represent an additional mechanism contributing to the valvulopathic potential of these compounds.

Differential tissue and ligand-dependent signaling of GPR109A receptor: implications for anti-atherosclerotic therapeutic potential.

Until recently, the anti-atherosclerotic effects of niacin were attributed primarily to its lipid modification properties mediated by adipocyte G-protein coupled receptor GPR109A, though recent studies have raised significant doubts about this mechanism. In fact, in rodents it has recently been demonstrated that niacin inhibits progression of atherosclerosis through actions on immune cells, particularly via macrophage-expressed GPR109A, independent of lipid-modifying properties. Here, we studied GPR109A signal transduction in human Langerhans cells, macrophages and adipocytes. We find that the consequences of receptor activation are profoundly influenced by cellular context and that ligand-biased signaling significantly impacts functionally relevant signaling. In Langerhans cells, niacin initiates GPR109A-mediated signaling pathways (Erk1/2 and Ca(2+)) responsible for the release of vasodilatory prostanoids, while the synthetic GPR109A agonist MK-0354 fails to elicit any signaling, providing a mechanistic basis for the latter compound's inability to cause flushing. While GPR109A mediates inhibition of cAMP in adipocytes, in macrophages GPR109A signaling via Gßγ subunits results in paradoxical augmentation of intracellular cAMP levels. Also, in macrophages niacin and GPR109A full agonists induce Erk1/2 and Ca(2+) signaling, release of prostanoids, upregulation of cholesterol transporters ABCA1 and ABCG1 and stimulation of reverse cholesterol transport in GPR109A dependent manner. A mechanism is presented in which signals from the autocrine action of released prostanoids and Gi protein mediated cAMP augmentation are integrated leading to modulation of reverse cholesterol transport regulatory components. These studies provide key insights into mechanisms by which GPR109A may influence cholesterol efflux in macrophages; a process that may be at least partially responsible for niacin's anti-atherosclerotic activity. MK-0354 does not induce niacin-like GPR109A signaling in macrophages, suggesting that biased agonists devoid of the flushing side-effect may also lack properties required for macrophage-mediated anti-atherosclerotic effects.

Genetic lineage tracing defines distinct neurogenic and gliogenic stages of ventral telencephalic radial glial development.

BACKGROUND: Radial glia comprise a molecularly defined neural progenitor population but their role in neurogenesis has remained contested due to the lack of a single universally accepted genetic tool for tracing their progeny and the inability to distinguish functionally distinct developmental stages. RESULTS: By direct comparisons of Cre/loxP lineage tracing results obtained using three different radial glial promoters (Blbp, Glast, and hGFAP), we show that most neurons in the brain are derived from radial glia. Further, we show that hGFAP promoter induction occurs in ventral telencephalic radial glia only after they have largely completed neurogenesis. CONCLUSION: These data establish the major neurogenic role of radial glia in the developing central nervous system and genetically distinguish an early neurogenic Blbp+Glast+hGFAP- stage from a later gliogenic Blbp+Glast+hGFAP+ stage in the ventral telencephalon.

The folate metabolic enzyme ALDH1L1 is restricted to the midline of the early CNS, suggesting a role in human neural tube defects.

Folate supplementation prevents up to 70% of human neural tube defects (NTDs), although the precise cellular and metabolic sites of action remain undefined. One possibility is that folate modulates the function of metabolic enzymes expressed in cellular populations involved in neural tube closure. Here we show that the folate metabolic enzyme ALDH1L1 is cell-specifically expressed in PAX3-negative radial glia at the midline of the neural tube during early murine embryogenesis. Midline restriction is not a general property of this branch of folate metabolism, as MTHFD1 displays broad and apparently ubiquitous expression throughout the neural tube. Consistent with previous work showing antiproliferative effects in vitro, ALDH1L1 upregulation during central nervous system (CNS) development correlates with reduced proliferation and most midline ALDH1L1(+) cells are quiescent. These data provide the first evidence for localized differences in folate metabolism within the early neural tube and suggest that folate might modulate proliferation via effects on midline Aldh1l1(+) cells. To begin addressing its role in neurulation, we analyzed a microdeletion mouse strain lacking Aldh1l1 and observed neither increased failure of neural tube closure nor detectable proliferation defects. Although these results indicate that loss-of-function Aldh1l1 mutations do not impair these processes in mice, the specific midline expression of ALDH1L1 and its ability to dominantly suppress proliferation in a folate responsive manner may suggest that mutations contributing to disease are gain-of-function, rather than loss-of-function. Moreover, a role for loss-of-function mutations in human NTDs remains possible, as Mthfr null mice do not develop NTDs even though MTHFR mutations increase human NTD risk.