Dismantling silos: The case for an integrated approach to address childhood determinants of lifelong brain health

Early-life environments have an immense influence on long-term health outcomes. We have started to elucidate the mechanisms underlying this association but have made little progress in reducing the disease burden of environmentally mediated neurological and psychiatric illness. Here, we highlight barriers to innovation and how they may be overcome.

Microbial modulation via cross-fostering prevents the effects of pervasive environmental stressors on microglia and social behavior, but not the dopamine system

Environmental toxicant exposure, including air pollution, is increasing worldwide. However, toxicant exposures are not equitably distributed. Rather, low-income and minority communities bear the greatest burden, along with higher levels of psychosocial stress. Both air pollution and maternal stress during pregnancy have been linked to neurodevelopmental disorders such as autism, but biological mechanisms and targets for therapeutic intervention remain poorly understood. We demonstrate that combined prenatal exposure to air pollution (diesel exhaust particles, DEP) and maternal stress (MS) in mice induces social behavior deficits only in male offspring, in line with the male bias in autism. These behavioral deficits are accompanied by changes in microglial morphology and gene expression as well as decreased dopamine receptor expression and dopaminergic fiber input in the nucleus accumbens (NAc). Importantly, the gut-brain axis has been implicated in ASD, and both microglia and the dopamine system are sensitive to the composition of the gut microbiome. In line with this, we find that the composition of the gut microbiome and the structure of the intestinal epithelium are significantly shifted in DEP/MS-exposed males. Excitingly, both the DEP/MS-induced social deficits and microglial alterations in males are prevented by shifting the gut microbiome at birth via a cross-fostering procedure. However, while social deficits in DEP/MS males can be reversed by chemogenetic activation of dopamine neurons in the ventral tegmental area, modulation of the gut microbiome does not impact dopamine endpoints. These findings demonstrate male-specific changes in the gut-brain axis following DEP/MS and suggest that the gut microbiome is an important modulator of both social behavior and microglia.

Tau activation of microglial cGAS-IFN reduces MEF2C-mediated cognitive resilience

Pathological hallmarks of Alzheimer's disease (AD) precede clinical symptoms by years, indicating a period of cognitive resilience before the onset of dementia. Here, we report that activation of cyclic GMP-AMP synthase (cGAS) diminishes cognitive resilience by decreasing the neuronal transcriptional network of myocyte enhancer factor 2c (MEF2C) through type I interferon (IFN-I) signaling. Pathogenic tau activates cGAS and IFN-I responses in microglia, in part mediated by cytosolic leakage of mitochondrial DNA. Genetic ablation of Cgas in mice with tauopathy diminished the microglial IFN-I response, preserved synapse integrity and plasticity and protected against cognitive impairment without affecting the pathogenic tau load. cGAS ablation increased, while activation of IFN-I decreased, the neuronal MEF2C expression network linked to cognitive resilience in AD. Pharmacological inhibition of cGAS in mice with tauopathy enhanced the neuronal MEF2C transcriptional network and restored synaptic integrity, plasticity and memory, supporting the therapeutic potential of targeting the cGAS-IFN-MEF2C axis to improve resilience against AD-related pathological insults.

Loss of sleep when it is needed most - Consequences of persistent developmental sleep disruption: A scoping review of rodent models

Sleep is an essential component of development. Developmental sleep disruption (DSD) impacts brain maturation and has been associated with significant consequences on socio-emotional development. In humans, poor sleep during infancy and adolescence affects neurodevelopmental outcomes and may be a risk factor for the development of autism spectrum disorder (ASD) or other neuropsychiatric illness. Given the wide-reaching and enduring consequences of DSD, identifying underlying mechanisms is critical to best inform interventions with translational capacity. In rodents, studies have identified some mechanisms and neural circuits by which DSD causes later social, emotional, sensorimotor, and cognitive changes. However, these studies spanned methodological differences, including different developmental timepoints for both sleep disruption and testing, different DSD paradigms, and even different rodent species. In this scoping review on DSD in rodents, we synthesize these various studies into a cohesive framework to identify common neural mechanisms underlying DSD-induced dysfunction in brain and behavior. Ultimately, this review serves the goal to inform the generation of novel translational interventions for human developmental disorders featuring sleep disruption.

A Cdk5-derived peptide inhibits Cdk5/p25 activity and improves neurodegenerative phenotypes

Aberrant activity of cyclin-dependent kinase (Cdk5) has been implicated in various neurodegenerative diseases. This deleterious effect is mediated by pathological cleavage of the Cdk5 activator p35 into the truncated product p25, leading to prolonged Cdk5 activation and altered substrate specificity. Elevated p25 levels have been reported in humans and rodents with neurodegeneration, and the benefit of genetically blocking p25 production has been demonstrated previously in rodent and human neurodegenerative models. Here, we report a 12-amino-acid-long peptide fragment derived from Cdk5 (Cdk5i) that is considerably smaller than existing peptide inhibitors of Cdk5 (P5 and CIP) but shows high binding affinity toward the Cdk5/p25 complex, disrupts the interaction of Cdk5 with p25, and lowers Cdk5/p25 kinase activity. When tagged with a fluorophore (FITC) and the cell-penetrating transactivator of transcription (TAT) sequence, the Cdk5i-FT peptide exhibits cell- and brain-penetrant properties and confers protection against neurodegenerative phenotypes associated with Cdk5 hyperactivity in cell and mouse models of neurodegeneration, highlighting Cdk5i's therapeutic potential.

Development and use of an infant resuscitation performance tool (Infa-RePT) to improve team performance

BACKGROUND

Measurement of neonatal team resuscitation performance is critical to identify opportunities for improvement and to target education. An effective tool to measure team performance during infant resuscitations is lacking.

METHODS

We developed an in-hospital infant resuscitation performance tool (Infa-RePT) using the modified Delphi method. We employed a QI framework and targeted interventions, including the use of role responsibility checklists, mock codes, and an educational video. We tracked Infa-RePT scores, mock code team attendance, and confidence surveys. Our specific aim was to improve Infa-RePT score from a baseline of 7.4 to <5 (lower is better) over a 26-month period.

RESULTS

Twenty-five elements reached >80% consensus as essential components to include on the Infa-RePT. Independent observation showed 86% concordance on checklist items. Simulation (n = 26) and unit-based code (n = 10) Infa-RePT scores showed significant improvement after project start from 7.4 to 4.2 (p < 0.01) with special cause variation noted on control chart analysis. No significant difference was observed between simulations and in-unit codes. Staff confidence self-reports improved over the study period.

CONCLUSIONS

Use of a novel scoring tool can help monitor team progress over time and identify areas for improvement. Focused interventions can improve resuscitation team performance.

IMPACT

We developed and used a novel, comprehensive measurement tool for team infant resuscitation performance in both simulation and in-unit settings. Using QI methodology, team performance improved after the enhancement of a mock code simulation program. Review of team performance scores can highlight key areas to target interventions and monitor progress over time.

MEF2 is a key regulator of cognitive potential and confers resilience to neurodegeneration

[Figure: see text].

Mapping the epigenomic and transcriptomic interplay during memory formation and recall in the hippocampal engram ensemble

The epigenome and three-dimensional (3D) genomic architecture are emerging as key factors in the dynamic regulation of different transcriptional programs required for neuronal functions. In this study, we used an activity-dependent tagging system in mice to determine the epigenetic state, 3D genome architecture and transcriptional landscape of engram cells over the lifespan of memory formation and recall. Our findings reveal that memory encoding leads to an epigenetic priming event, marked by increased accessibility of enhancers without the corresponding transcriptional changes. Memory consolidation subsequently results in spatial reorganization of large chromatin segments and promoter-enhancer interactions. Finally, with reactivation, engram neurons use a subset of de novo long-range interactions, where primed enhancers are brought in contact with their respective promoters to upregulate genes involved in local protein translation in synaptic compartments. Collectively, our work elucidates the comprehensive transcriptional and epigenomic landscape across the lifespan of memory formation and recall in the hippocampal engram ensemble.

An Antibacterial β-Lactone Kills Mycobacterium tuberculosis by Disrupting Mycolic Acid Biosynthesis

The spread of antibiotic resistance is a major challenge for the treatment of Mycobacterium tuberculosis infections. In addition, the efficacy of drugs is often limited by the restricted permeability of the mycomembrane. Frontline antibiotics inhibit mycomembrane biosynthesis, leading to rapid cell death. Inspired by this mechanism, we exploited β-lactones as putative mycolic acid mimics to block serine hydrolases involved in their biosynthesis. Among a collection of β-lactones, we found one hit with potent anti-mycobacterial and bactericidal activity. Chemical proteomics using an alkynylated probe identified Pks13 and Ag85 serine hydrolases as major targets. Validation through enzyme assays and customized ¹³ C metabolite profiling showed that both targets are functionally impaired by the β-lactone. Co-administration with front-line antibiotics enhanced the potency against M. tuberculosis by more than 100-fold, thus demonstrating the therapeutic potential of targeting mycomembrane biosynthesis serine hydrolases.

Leveraging Advances in Tuberculosis Diagnosis and Treatment to Address Nontuberculous Mycobacterial Disease

Recent advances in TB diagnosis and treatment must be considered in the basic scientific research of other mycobacterial diseases.

The nontuberculous mycobacteria (NTM), defined as any mycobacterial pathogen other than Mycobacterium tuberculosis or Mycobacterium leprae, are a diverse group of pathogens that collectively cause a substantive but often unappreciated worldwide burden of illness. Although NTMs may cause illness similar to M. tuberculosis, these pathogens generally do not respond to classic tuberculosis (TB) drug regimens, resulting in misdiagnosis and poor treatment, particularly in resource-poor settings. Although a few high-quality epidemiologic surveys have been made on the topic, existing evidence suggests that NTM-associated disease is much more common than previously thought: more common than TB in the industrialized world and likely increasing in prevalence globally. Despite this evidence, these organisms remain markedly understudied, and few international grants support basic science and clinical research. Here we suggest that the considerable efforts in developing new treatments and diagnostics for TB can be harnessed in the fight against NTM-associated illnesses.

Inflammatory signaling in human tuberculosis granulomas is spatially organized

Granulomas are the pathological hallmark of tuberculosis (TB). However, their function and mechanisms of formation remain poorly understood. To understand the role of granulomas in TB, we analyzed the proteomes of granulomas from subjects with tuberculosis in an unbiased fashion. Using laser capture microdissection, mass spectrometry and confocal microscopy, we generated detailed molecular maps of human granulomas. We found that the centers of granulomas possess a pro-inflammatory environment characterized by anti-microbial peptides, ROS and pro-inflammatory eicosanoids. Conversely, the tissue surrounding the caseum possesses a comparatively anti-inflammatory signature. These findings are consistent across a set of six subjects and in rabbits. While the balance between systemic pro- and anti-inflammatory signals is crucial to TB disease outcome, here we find that these signals are physically segregated within each granuloma. The protein and lipid snapshots of human and rabbit lesions analysed here suggest that the pathologic response to TB is shaped by the precise anatomical localization of these inflammatory pathways during the development of the granuloma.

Post-translational regulation via Clp protease is critical for survival of Mycobacterium tuberculosis

Unlike most bacterial species, Mycobacterium tuberculosis depends on the Clp proteolysis system for survival even in in vitro conditions. We hypothesized that Clp is required for the physiologic turnover of mycobacterial proteins whose accumulation is deleterious to bacterial growth and survival. To identify cellular substrates, we employed quantitative proteomics and transcriptomics to identify the set of proteins that accumulated upon the loss of functional Clp protease. Among the set of potential Clp substrates uncovered, we were able to unambiguously identify WhiB1, an essential transcriptional repressor capable of auto-repression, as a substrate of the mycobacterial Clp protease. Dysregulation of WhiB1 turnover had a toxic effect that was not rescued by repression of whiB1 transcription. Thus, under normal growth conditions, Clp protease is the predominant regulatory check on the levels of potentially toxic cellular proteins. Our findings add to the growing evidence of how post-translational regulation plays a critical role in the regulation of bacterial physiology.

Mycobacterium tuberculosis ClpP1 and ClpP2 function together in protein degradation and are required for viability in vitro and during infection

In most bacteria, Clp protease is a conserved, non-essential serine protease that regulates the response to various stresses. Mycobacteria, including Mycobacterium tuberculosis (Mtb) and Mycobacterium smegmatis, unlike most well studied prokaryotes, encode two ClpP homologs, ClpP1 and ClpP2, in a single operon. Here we demonstrate that the two proteins form a mixed complex (ClpP1P2) in mycobacteria. Using two different approaches, promoter replacement, and a novel system of inducible protein degradation, leading to inducible expression of clpP1 and clpP2, we demonstrate that both genes are essential for growth and that a marked depletion of either one results in rapid bacterial death. ClpP1P2 protease appears important in degrading missense and prematurely terminated peptides, as partial depletion of ClpP2 reduced growth specifically in the presence of antibiotics that increase errors in translation. We further show that the ClpP1P2 protease is required for the degradation of proteins tagged with the SsrA motif, a tag co-translationally added to incomplete protein products. Using active site mutants of ClpP1 and ClpP2, we show that the activity of each subunit is required for proteolysis, for normal growth of Mtb in vitro and during infection of mice. These observations suggest that the Clp protease plays an unusual and essential role in Mtb and may serve as an ideal target for antimycobacterial therapy.

Due to the significant and rapid rise in multidrug resistant Mycobacterium tuberculosis (Mtb), there is an urgent need to validate novel drug targets for the treatment of tuberculosis. Here, we show that Clp protease is an ideal potential target. Mtb encodes two ClpP genes, ClpP1 and ClpP2, which associate together to form a single proteolytic complex, referred to as ClpP1P2. Both proteins are required for growth in vitro and in a mouse model of infection. Depletion of either protein results in rapid death of the bacteria. Interestingly, this is rare among bacteria, most of which have only one ClpP gene that is dispensable for normal growth. We also show that Clp protease plays an important quality control role by clearing abnormally produced proteins. As known antimycobacterial therapeutics increase errors in protein synthesis, inhibitors of ClpP1P2 protease in Mtb may prove synergistic with already existing agents.

The active ClpP protease from M. tuberculosis is a complex composed of a heptameric ClpP1 and a ClpP2 ring

Mycobacterium tuberculosis (Mtb) contains two clpP genes, both of which are essential for viability. We expressed and purified Mtb ClpP1 and ClpP2 separately. Although each formed a tetradecameric structure and was processed, they lacked proteolytic activity. We could, however, reconstitute an active, mixed ClpP1P2 complex after identifying N-blocked dipeptides that stimulate dramatically (>1000-fold) ClpP1P2 activity against certain peptides and proteins. These activators function cooperatively to induce the dissociation of ClpP1 and ClpP2 tetradecamers into heptameric rings, which then re-associate to form the active ClpP1P2 2-ring mixed complex. No analogous small molecule-induced enzyme activation mechanism involving dissociation and re-association of multimeric rings has been described. ClpP1P2 possesses chymotrypsin and caspase-like activities, and ClpP1 and ClpP2 differ in cleavage preferences. The regulatory ATPase ClpC1 was purified and shown to increase hydrolysis of proteins by ClpP1P2, but not peptides. ClpC1 did not activate ClpP1 or ClpP2 homotetradecamers and stimulated ClpP1P2 only when both ATP and a dipeptide activator were present. ClpP1P2 activity, its unusual activation mechanism and ClpC1 ATPase represent attractive drug targets to combat tuberculosis.

Serological responses to experimental Norwalk virus infection measured using a quantitative duplex time-resolved fluorescence immunoassay

A quantitative duplex time-resolved fluorescence assay, dissociation-enhanced lanthanide fluorescent immunoassay (DELFIA), was developed to measure Norwalk virus (NV)-specific IgA and IgG antibodies simultaneously. The duplex assay showed superior performance by detecting seroconversion following experimental NV infection at an earlier time point than a reference total immunoglobulin enzyme-linked immunosorbent assay (ELISA).