Long-term imaging reveals behavioral plasticity during C. elegans dauer exit.
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ABSTRACT: During their lifetime, animals must adapt their behavior to survive in changing environments. This ability requires the nervous system to adjust through dynamic expression of neurotransmitters and receptors but also through growth, spatial reorganization and connectivity while integrating external stimuli. For instance, despite having a fixed neuronal cell lineage, the nematode Caenorhabditis elegans’ nervous system remains plastic throughout its development. Here, we focus on a specific example of nervous system plasticity, the C. elegans dauer exit decision. Under unfavorable conditions, larvae will enter the non-feeding and non-reproductive dauer stage and adapt their behavior to cope with a new environment. Upon improved conditions, this stress resistant developmental stage is actively reversed to resume reproductive development. However, how different environmental stimuli regulate the exit decision mechanism and thereby drive the larva’s behavioral change is unknown. To fill this gap, we developed a new open hardware method for long-term imaging (12h) of C.elegans larvae. We identified dauer-specific behavioral motifs and characterized the behavioral trajectory of dauer exit in different environments to identify key decision points. Combining long-term behavioral imaging with transcriptomics, we find that bacterial ingestion triggers a change in neuropeptide gene expression to establish post-dauer behavior. Taken together, we show how a developing nervous system can robustly integrate environmental changes, activate a developmental switch and adapt the organism’s behavior to a new environment.
Project description:Both plasticity and robustness are pervasive features of developmental programs. The dauer in Caenorhabditis elegans is an alternative to the third larval stage of the nematode and is an example of phenotypic plasticity. The dauer is an arrested, hypometabolic state that undergoes dramatic changes in gene expression compared to conspecifics that continue development, and can be induced by several adverse environments or genetic mutations that act as independent and parallel inputs into the larval developmental program. However, given the different genetic or environmental triggers that can induce dauer, gene expression in dauer larvae could be invariant or vary depending on the larvae’s route into dauer entry; this question has not been examined. Here we use RNA-sequencing to characterize gene expression in dauer larvae induced to arrest development in response to different stimuli. By assessing the variance in the expression levels of all genes and computing the Spearman's rank-order correlation of gene expression within several Gene Ontologies (GO) and gene networks, we find that the expression patterns of most genes, except for those that act in specific defense and metabolic pathways, are strongly correlated between the different dauer larvae, suggestive of transcriptional robustness. We speculate that the transcriptional robustness of core dauer pathways allows for the buffering of variation in the expression of genes involved in their response to the environment, allowing the different dauers to be better suited to survive in and exploit different niches.
Project description:Transcriptional profiling of P. pacificus worms from (1) dauer stage, or (2) dauer-exit at 12 hours stage, compared to mix-stage worms as a common reference. The goal was to determine genes regulated during dauer development and recovery or exit from dauer stage. This data was then compared to data generated for corresponding developmental stages in the C. elegans (see NCBI GEO series GSE30977) , to study evolution of developmental pathways regulating dauer development. Two-condition experiments. Experiment 1 = Dauers vs. Mix-stage worms. 4 biological replicates for each condition, including 2 dye-swaps. Experiment 2 = Dauer-Exit at 12 hour time-point s vs. Mix-stage worms. 3 biological replicates for each condition, including 1 dye-swaps. Total samples from both experiments 1 and 2 = 7.
Project description:Transcriptional profiling of P. pacificus worms from (1) dauer stage, or (2) dauer-exit at 12 hours stage, compared to mix-stage worms as a common reference. The goal was to determine genes regulated during dauer development and recovery or exit from dauer stage. This data was then compared to data generated for corresponding developmental stages in the C. elegans (see NCBI GEO series GSE30977) , to study evolution of developmental pathways regulating dauer development.
Project description:Transcriptional profiling of C. elegans worms from (1) dauer stage, or (2) dauer-exit at 12 hours stage, compared to mix-stage worms as a common reference. The goal was to determine genes regulated during dauer development and recovery or exit from dauer stage. This data was then compared to data generated for corresponding developmental stages in the nematode Pristionchus pacificus (see NCBI GEO series GSE31861) , to study evolution of developmental pathways regulating dauer development.
Project description:Transcriptional profiling of C. elegans worms from (1) dauer stage, or (2) dauer-exit at 12 hours stage, compared to mix-stage worms as a common reference. The goal was to determine genes regulated during dauer development and recovery or exit from dauer stage. This data was then compared to data generated for corresponding developmental stages in the nematode Pristionchus pacificus (separate data-sets on a custom microarray platform designed by us and manufactured by Agilent) , to study evolution of developmental pathways regulating dauer development. Two-condition experiments. Experiment 1 = Dauers vs. Mix-stage worms. 4 biological replicates for each condition, including 2 dye-swaps. Experiment 2 = Dauer-Exit at 12 hour time-point s vs. Mix-stage worms. 4 biological replicates for each condition, including 2 dye-swaps. Total samples from both experiments 1 and 2 = 8.
Project description:This SuperSeries is composed of the following subset Series: GSE30977: C. elegans: Dauers and Dauer-Exit at 12 hour time-point vs. Mix-stage worms GSE31861: P. pacificus : Dauers and Dauer-Exit at 12 hour time-point vs. Mix-stage worms Refer to individual Series
Project description:Molecular profiles of neurons influence information processing, but bridging the gap between genes, circuits and behavior has been very difficult. Furthermore, the behavioral state of an animal continuously changes across development and as a result of sensory experience. How behavioral state influences molecular cell state is poorly understood. Here we present a complete atlas of the Drosophila larval nervous system. We develop polyseq, a python analysis package, and use single molecule RNA-FISH to validate our scRNAseq findings. To investigate how internal state affects cell state, we altered internal state with high-throughput behaviour protocols designed to mimic wasp sting and over activation of the memory system. We found nervous system-wide gene expression changes related to cell state. This work advances our understanding of how genes, neurons, and circuits generate behavior.
Project description:Interorgan signaling events are emerging as key regulators of behavioral plasticity. The foregut and hindgut circuits of the C. elegans enteric nervous system (ENS) control feeding and defecation behavior, respectively. Here we show that epithelial cells in the midgut integrate feeding state information to control these behavioral outputs via releasing distinct neuropeptidergic signals. In favorable conditions, insulin and non-insulin peptides released from midgut epithelia activate foregut and hindgut enteric neurons, respectively, to sustain normal feeding and defecation behavior. During food scarcity, altered insulin signaling from sensory neurons activates the transcription factor DAF-16/FoxO in midgut epithelia, which blocks both peptidergic signaling axes to the ENS via transcriptionally shutting down the intestinal neuropeptide secretion machinery. Our findings demonstrate that midgut epithelial cells act as integrators to relay internal state information to distinct parts of the enteric nervous system to control animal behavior.
Project description:We wanted to analyze the differences in acetyl-H4 content related to inter-individual behavioral variability. We retrieved three groups of samples: The first one was composed by 4 different clusters of zebrafish composed each one by 5 zebrafish larvae. Within each cluster, the behavioral differences across the larvae were minimal, while between the clusters, there were high differences in the behavior. The second one was composed by 4 different clusters of sodium butyrate (NaBu)-treated zebrafish composed each one by 5 larvae. The selection choice was the same as in the first group, but due to their behavioral effect of NaBu, the differences between the clusters were significantly reduced compared to control. The third one was composed by 3 different clusters of 5 zebrafish each randomly selected from the behavioral space. This group is a control of variability not associated to behavior.