Project description:Human activity is altering the environment at a rapid pace, challenging the adaptive capacities of genetic variation within animal populations. Animals also harbor extensive gut microbiomes, which play diverse roles in host health and fitness and may help expanding host capabilities. The unprecedented scale of human usage of xenobiotics and contamination with environmental toxins describes one challenge against which bacteria with their immense biochemical diversity are particularly suited to offer solutions. To explore the paths leading to bacteria-assisted rapid adaptation, we used Caenorhabditis elegans harboring a defined microbiome, and the antibiotic neomycin as a model toxin, harmful for the worm host and neutralized to different extents by microbiome members. Worms exposed to neomycin showed delayed development and decreased survival but were protected when colonized by neomycin-resistant members of the microbiome. Through a combination of 16S gene sequencing, counting of live bacteria and behavioral assays we identified two distinct mechanisms that facilitated adaptation: gut enrichment for a neomycin-modifying strain driven by altered bacterial competition; and host avoidance behavior, which depended on the stress-activated KGB-1/JNK and enabled preference of neomycin-protective bacteria. The straightforwardness of these mechanisms suggests that bacteria-assisted host adaptation may be more common than currently appreciated, protecting animals from novel stressors. However, gut remodeling may also cause dysbiosis, and additional experiments identified fitness trade-offs including increased susceptibility to infection as well as metabolic remodeling. Extending these results to other toxins suggests yet unaccounted-for microbiome-dependent long-term consequences of toxin exposure.
Project description:Competition between promoters within a shared regulatory landscape has been implicated in development and disease, but the determinants of promoter competition remain unclear. Here, we introduce diverse promoters into defined genomic sites within the Sox2 locus and measure how these insertions attenuate endogenous Sox2 expression. We find that the level of reduction in endogenous Sox2 transcription is correlated with the strength of the inserted promoter. Transcription from the inserted promoter is required for competition, with longer transcript resulting in more competition. The inserted active promoter and its associated transcriptional unit function as an insulator, rendering competition position-dependent. Finally, we observe HUSH-mediated silencing of the inserted promoters, which counteracts competition. Together, our work uncovers the rules governing promoter competition, highlights its impact on tuning gene expression levels and genome evolution, and suggests that transcripts of sufficient level and length can mediate insulation independently of CTCF and cohesin.
Project description:We quantitatively examine inputs and outputs of the mouse gut microbiome, using isotope tracing. To determine nutrient preferences across bacteria, we traced into genus-specific bacterial protein sequences. By in vivo isotope tracer feeding, mapped the contribution of different dietary nutrients vs circulating nutrients contribution to different gut bacterial genera.
Project description:Competition between promoters within a shared regulatory landscape has been implicated in development and disease, but the determinants of promoter competition remain unclear. Here, we introduce diverse promoters into defined genomic sites within the Sox2 locus and measure how these insertions attenuate endogenous Sox2 expression. We find that the level of reduction in endogenous Sox2 transcription is correlated with the strength of the inserted promoter. Transcription from the inserted promoter is required for competition, with longer transcript resulting in more competition. The inserted active promoter and its associated transcriptional unit function as an insulator, rendering competition position-dependent. Finally, we observe HUSH-mediated silencing of the inserted promoters, which counteracts competition. Together, our work uncovers the rules governing promoter competition, highlights its impact on tuning gene expression levels and genome evolution, and suggests that transcripts of sufficient level and length can mediate insulation independently of CTCF and cohesin.
Project description:Gut bacterial β-glucuronidases (GUS) promote the toxic side effects of therapeutics by reactivating drugs from their inactive glucuronide conjugates. It is increasingly clear that the interindividual variability of bacterial GUS-producing species in the gut microbiota contributes to differential drug responses. Indeed, the anticancer drug irinotecan exhibits variable clinical toxicity outcomes that have been linked to interindividual differences in the composition of the gut microbiota. However, identification of the specific GUS enzymes responsible for drug metabolism in the context of the complexity of the human fecal microbiota has not been achieved. Here we pinpoint the specific bacterial GUS enzymes that reactivate SN-38, the active metabolite of irinotecan, from complex human fecal microbiota samples with activity-based protein profiling (ABPP). We identify and quantify gut bacterial GUS enzymes from human feces with ABPP-enabled proteomics and then integrate this information with ex vivo kinetics to reveal the specific GUS enzymes responsible for the reactivation of SN-38. The same ABPP approach also reveals the molecular basis for differential gut bacterial GUS inhibition between human fecal samples. Taken together, this work provides an unprecedented pipeline to identify the specific bacterial GUS enzymes responsible for drug-induced GI toxicity from the complexity of human feces, which may serve as highly precise biomarkers of clinical outcomes for irinotecan and other therapeutics.
Project description:Although increasing studies have proved cell competition widely involved in the growth and homeostasis of multicellular organisms is closely linked to tumorigenesis and development, the mechanistic contributions between drug resistance and tumor cell competition remain ill-defined. In this paper, we applied MS of cell competition group to determine the dominant characteristics of lenvatinib resistance and its metabolic differences in cell competition. Our results showed a vital role of HSP90-IDH1 mediated lipid accumulation in maintaining the competitive outcome of HCC drug-resistant cells via regulating lipid metabolism. HSP90-IDH1 axis could be a promising target to overcome HCC drug resistance.
Project description:This study was designed to look for differential gene expression in the annual dicot weed velvetleaf when it is grown in competition with corn relative to when it is grown in monoculture. Keywords: weed/crop competition
Project description:Imbalance in beneficial and harmful bacteria underlies gastrointestinal diseases, such as inflammatory bowel disease. Here, we demonstrated that certain E. coli strains, specifically adherent-invasive E. coli (AIEC), utilize a serine metabolism pathway to outcompete other E. coli strains in the inflamed gut. In contrast, amino acid metabolism has a minimal effect on their competitive fitness in the healthy gut. The availability of luminal serine used for the competition of E. coli is largely dependent on dietary intake, as the inflammation-induced blooms of AIEC are significantly blunted when amino acids, particularly serine, are removed from the diet. Thus, intestinal inflammation regulates the intraspecific competition between Enterobacteriaceae by eliciting their metabolic reprogramming.
Project description:In early mammalian embryogenesis, the selective elimination of suboptimal cells is critical for developmental integrity. Cell competition is a non-autonomous quality control in which “winner” cells eliminate viable but suboptimal “loser” cells based on their relative difference in fitness. Due to its central role in fitness perception, loss of p53 results in the emergence of “supercompetitor” cells, which stand at the apex of cell competition and induce apoptosis in neighboring wild-type (WT) cells. Here, we investigate cell competition dynamics using mosaic 3D mouse gastruloids, an embryonic stem cell (ESC)-based in vitro model of gastrulation, composed of defined numbers of WT and p53-KO cells. In mosaic gastruloids, even low numbers of p53-KO cells robustly outcompete WT cells, and introduction of as few as two p53-KO cells is sufficient to measurably impair neighboring WT cell growth. Cell competition in gastruloids is independent of proliferation rates, nutrient availability, or reactive oxygen species, and not influenced by Nodal and ERK signaling. However, we observe that Wnt and BMP signaling protect from cell competition, which is exclusively driven by intrinsic apoptosis, as indicated by Bcl2-mediated complete rescue of WT cells. During gastruloid development, cell competition is temporally restricted to a window of 48–96 hours after aggregation, mirroring embryonic days E5.5–E7.5 in the mouse. Heterochronic mosaic gastruloid experiments demonstrate that relative differences in pluripotency levels are neither necessary nor sufficient to cause supercompetition, but that cell competition is contingent on both competitors residing within the developmental window permissive to competition. Neither pluripotent mosaic 3D aggregates, nor 3D EpiGastruloids, which model more advanced developmental processes, display any competition, supporting the hypothesis that developmental cell competition is specific to the onset of gastrulation. Our findings offer insights into the mechanisms of cell fitness evaluation in mammalian embryogenesis and establish gastruloids as a powerful 3D model for investigating developmental stage-specific cell competition.