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Amyloids are a class of protein with unique self-aggregation properties, and their aberrant accumulation can lead to cellular dysfunctions associated with neurodegenerative diseases. While genetic and environmental factors can influence amyloid formation, molecular triggers and/or facilitators are not well defined. Growing evidence suggests that non-identical amyloid proteins may accelerate reciprocal amyloid aggregation in a prion-like fashion. While humans encode ~30 amyloidogenic proteins, the gut microbiome also produces functional amyloids. For example, curli are cell surface amyloid proteins abundantly expressed by certain gut bacteria. In mice overexpressing the human amyloid α-synuclein (αSyn), we reveal that colonization with curli-producing Escherichia coli promotes αSyn pathology in the gut and the brain. Curli expression is required for E. coli to exacerbate αSyn-induced behavioral deficits, including intestinal and motor impairments. Purified curli subunits accelerate αSyn aggregation in biochemical assays, while oral treatment of mice with a gut-restricted amyloid inhibitor prevents curli-mediated acceleration of pathology and behavioral abnormalities. We propose that exposure to microbial amyloids in the gastrointestinal tract can accelerate αSyn aggregation and disease in the gut and the brain.

The intestinal microbiota influence neurodevelopment, modulate behavior, and contribute to neurological disorders. However, a functional link between gut bacteria and neurodegenerative diseases remains unexplored. Synucleinopathies are characterized by aggregation of the protein α-synuclein (αSyn), often resulting in motor dysfunction as exemplified by Parkinson's disease (PD). Using mice that overexpress αSyn, we report herein that gut microbiota are required for motor deficits, microglia activation, and αSyn pathology. Antibiotic treatment ameliorates, while microbial re-colonization promotes, pathophysiology in adult animals, suggesting that postnatal signaling between the gut and the brain modulates disease. Indeed, oral administration of specific microbial metabolites to germ-free mice promotes neuroinflammation and motor symptoms. Remarkably, colonization of αSyn-overexpressing mice with microbiota from PD-affected patients enhances physical impairments compared to microbiota transplants from healthy human donors. These findings reveal that gut bacteria regulate movement disorders in mice and suggest that alterations in the human microbiome represent a risk factor for PD.

Neurodevelopment is a complex process governed by both intrinsic and extrinsic signals. While historically studied by researching the brain, inputs from the periphery impact many neurological conditions. Indeed, emerging data suggest communication between the gut and the brain in anxiety, depression, cognition, and autism spectrum disorder (ASD). The development of a healthy, functional brain depends on key pre- and post-natal events that integrate environmental cues, such as molecular signals from the gut. These cues largely originate from the microbiome, the consortium of symbiotic bacteria that reside within all animals. Research over the past few years reveals that the gut microbiome plays a role in basic neurogenerative processes such as the formation of the blood-brain barrier, myelination, neurogenesis, and microglia maturation and also modulates many aspects of animal behavior. Herein, we discuss the biological intersection of neurodevelopment and the microbiome and explore the hypothesis that gut bacteria are integral contributors to development and function of the nervous system and to the balance between mental health and disease.

CRISPR/Cas (clustered regularly interspaced palindromic repeats/CRISPR-associated) systems are a bacterial defence against invading foreign nucleic acids derived from bacteriophages or exogenous plasmids (1-4). These systems use an array of small [...]

Background: Regulatory interactions between the gut and the brain are essential for energy homeostasis across systems. Current evidence indicates high‐fat, high‐carbohydrate diets (HFHC) impact Alzheimer's disease (AD) pathophysiology, however, the mechanisms underlying this association are poorly understood. We hypothesize that (1) Tumor Necrosis Factor (TNF) mediates metabolic inflammation in an obesogenic environment with impacts across the gut‐brain axis and (2) that HFHC interacts with an AD‐relevant genetic background to promote metabolic and immune dysregulation that accelerates pathological and behavioral dysfunction in an animal model of AD. Method: To investigate the effects of chronic systemic inflammation on AD‐associated pathology, 2‐month old female 5xFAD mice were fed HFHC or a control diets (CD) for 8 weeks. One month following dietary intervention, the brain‐permeant soluble TNF inhibitor XPro1595 or a brain‐impermeant pan (sol and membrane‐bound) TNF inhibitor Etanercept (Enbrel, Amgen‐Wyeth) or vehicle (saline) were dosed twice weekly for 4 weeks. Behavioral test were performed to assess cognitive parameters. Plasma, brain and gut were collected for evaluation of insulin impairment, metabolic and immune parameters. Cortical tissues were subjected to RNAseq analysis to determine gene pathways modified by interactions between diet, genotype, and TNF inhibition. Result: HFHC promoted metabolic syndrome features associated with increases in adiposity, body weight, and plasma glucose, cholesterol, leptin, and insulin. TNF inhibition did not rescue diet‐induced insulin increases, however XPro specifically reduced plasma glucose, while Enbrel increased HOMA‐IR in HFHC‐fed mice. HFHC diet increased circulating IL‐6, CXCL1, CXCL2 and CCL2 and TNF neutralization with either drug decreased IL‐6 in HFHC‐fed groups. In the colon, HFHC diet decreased CCL3 and TNF blockade increased colonic IL‐15 in HFHC‐fed mice. Ongoing behavioral assessment, cortical transcriptional analysis, and hippocampal protein profiles of insulin signaling and inflammatory markers will determine additional effects of TNF and HFHC in the 5XFAD animal model of AD. Conclusion: Collectively, these results suggest that TNF modulates systemic metabolic and inflammatory pathways induced by HFHC consumption and associated with neurodegeneration and neuroinflammation. Blocking soluble TNF decreases hyperglycemia triggered during diet‐induce obesity. Future studies focusing on the impact of TNF on energy homeostasis and inflammation will provide targets for new therapeutics against neurological disease. [ABSTRACT FROM AUTHOR]

Nature 497, 254-257 (2013); doi:10.1038/nature12048 In this Letter, we described two small RNAs (scaRNA and tracrRNA) within the Francisella novicida CRISPR/Cas locus that are necessary for repression of an endogenous [...]

The Cas9 endonuclease is the central component of the Type II CRISPR/Cas system, a prokaryotic adaptive restriction system against invading nucleic acids, such as those originating from bacteriophages and plasmids. Recently, this RNA-directed DNA endonuclease has been harnessed to target DNA sequences of interest. Here, we review the development of Cas9 as an important tool to not only edit the genomes of a number of different prokaryotic and eukaryotic species, but also as an efficient system for site-specific transcriptional repression or activation. Additionally, a specific Cas9 protein has been observed to target an RNA substrate, suggesting that Cas9 may have the ability to be programmed to target RNA as well. Cas proteins from other CRISPR/Cas subtypes may also be exploited in this regard. Thus, CRISPR/Cas systems represent an effective and versatile biotechnological tool, which will have significant impact on future advancements in genome engineering. [ABSTRACT FROM AUTHOR]

Innate recognition systems, including the Toll-like receptors ( TLRs), play a critical role in activating host defences and proinflammatory pathways in response to infection. Pathogens have developed strategies to subvert TLRs in order to survive and replicate within the host. The model intracellular pathogen, Francisella novicida, modulates host defences to promote survival and replication in macrophages. TLR2, which recognizes bacterial lipoproteins ( BLPs), is critical for activating host defences and proinflammatory cytokine production in response to Francisella infection. Here we show that the F. novicida protein FTN_0757 acts to repress BLP production, dampening TLR2 activation. The Δ FTN_0757 mutant strain induced robust TLR2-dependent cytokine production in macrophages compared with wild-type bacteria, and produced increased amounts of BLPs. The deletion of one BLP ( FTN_1103) from Δ FTN_0757 decreased the total BLP concentration to near wild-type level sand correlated with a decrease in the inductionof TLR2 signalling. The overproduction of BLPs also contributed to the in vivo attenuation of the Δ FTN_0757 mutant, which was significantly rescued when FTN_1103 was deleted. Taken together, these data reveal a novel mechanism of immune evasion by the downregulation of BLP expression to subvert TLR2 activation, which is likely used by numerous other intracellular bacterial pathogens. [ABSTRACT FROM AUTHOR]

Background: Insulin resistance (IR) and systemic inflammation are risk factors for Alzheimer's disease (AD); however, the molecular and signaling mechanisms underlying this relationship are not well understood. Elevated plasma cytokine levels are associated with increased risk for both AD and IR. The cytokine tumor necrosis factor (TNF) is a major driver of inflammation and is implicated in IR and neurodegeneration. Here, we hypothesize that soluble TNF (solTNF) drives metabolic and immune alterations in the CNS and periphery that promote IR, thereby increasing the risk for AD pathologies. Method: To investigate this hypothesis, 2‐month old female 5xFAD mice were fed a high‐fat high‐carbohydrate diet (HFHC) or a control diet (CD) for 8 weeks. After 1 month, the brain‐permeant solTNF inhibitor XPro1595 or a brain‐impermeant pan (sol and membrane‐bound) TNF inhibitor Etanercept or saline were dosed twice weekly for 4 weeks. Plasma, adipose tissue, and gut were collected for evaluation of IR, metabolic and immune parameters. Molecular markers of insulin signaling, oxidative stress, mitochondrial impairment and inflammation were assessed in relevant brain regions (hippocampus, hypothalamus and cortex). Result: Our preliminary data demonstrate that HFHC‐fed 5XFAD mice exhibit increased body weight gain compared to CD groups. Ectopic lipid deposition, as measured by gonadal fat pad and liver volumes, was significantly increased, concurrent to anatomical indicators of intestinal inflammation, including shortened small intestine and colon. HFHC diet promoted systemic inflammation, as measured by increases in the classical pro‐inflammatory cytokines IL‐6 and TNF. Further, plasma LCN2, a downstream TNF inflammatory molecule associated with insulin insensitivity, hippocampal alterations, and previously observed to be increased in AD patients, was also significantly increased. Ongoing assessments of mRNA and protein expression of insulin signaling and inflammation in the hippocampus and cortex will determine additional effects of TNF in central insulin impairment and AD pathogenesis and will be presented and integrated into the overall findings. Conclusion: Together, these data suggest HFHC diet disrupts peripheral immune and metabolic parameters in the 5XFAD animal model of AD‐like pathology, thereby triggering neuroinflammation and insulin insensitivity, conditions which have been implicated in significantly increasing the risk for development of AD in humans. [ABSTRACT FROM AUTHOR]