Project description:We report the application of bulk RNA-sequencing-based technology for high-throughput profiling to examine the individual and combinatorial effects of the liver circadian clock and gut microbes on the liver transcriptome over 24-hours. Principle Component Analysis demonstrated that functionality of the liver circadian clock is the primary driver of the hepatic transcriptome profile, and presence of microbes is the secondary driver. We identified a range of significantly oscillating transcripts within each experimental group using empirical_JTK_CYCLE, and revealed an overall increase in oscillating transcripts with both the loss of cuntional liver clock and gut microbes. Network analysis via Spearman correlation revealed that a broken liver clock results in increased connections and correlated transcripts only in the presence of gut microbes. Finally, we show by differential expression and gene set enrichment analysis that several key metabolic pathways, particularly carbohydrate and lipid metabolism, were significantly downregulated when the liver clock is broken, regardless of microbial status. This study demonstrates the complex contributions of the liver circadian clock and gut microbes in transcriptome programming, both over time and overall.
Project description:Gut-brain connections monitor the intestinal tissue and its microbial and dietary content1, regulating both intestinal physiological functions such as nutrient absorption and motility2,3, and brain–wired feeding behaviour2. It is therefore plausible that circuits exist to detect gut microbes and relay this information to central nervous system (CNS) areas that, in turn, regulate gut physiology4. We characterized the influence of the microbiota on enteric–associated neurons (EAN) by combining gnotobiotic mouse models with transcriptomics, circuit–tracing methods, and functional manipulation. We found that the gut microbiome modulates gut–extrinsic sympathetic neurons; while microbiota depletion led to increased cFos expression, colonization of germ-free mice with short-chain fatty acid–producing bacteria suppressed cFos expression in the gut sympathetic ganglia. Chemogenetic manipulations, translational profiling, and anterograde tracing identified a subset of distal intestine-projecting vagal neurons positioned to play an afferent role in microbiota–mediated modulation of gut sympathetic neurons. Retrograde polysynaptic neuronal tracing from the intestinal wall identified brainstem sensory nuclei activated during microbial depletion, as well as efferent sympathetic premotor glutamatergic neurons that regulate gastrointestinal transit. These results reveal microbiota–dependent control of gut extrinsic sympathetic activation through a gut-brain circuit.
Project description:Here, we explore the impact of rearing zebrafish embryos in the absence of microbes on early neural development as well as investigate whether any potential changes can be rescued with treatment of metabolites derived from the zebrafish gut microbiota. RNA was extracted from a pool of five heads for each treatment at long-pec stage (2 days post fertilization) and sequenced at a depth of 80-100 million reads per sample. We identified 361 genes significantly down regulated in GF embryos compared to conventionally raised embryos via RNA-Seq analysis. Of these, 42 were rescued with the treatment of zebrafish gut-derived metabolites to GF embryos. Gene ontology analysis revealed that these genes are involved in prominent neurodevelopmental pathways including transcriptional regulation and Wnt signalling.