Environmental programming of neuronal gene expression by endogenous RNAi pathways

Syracuse University, Syracuse NY

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Abstract

The mechanisms by which fetal and childhood experiences influence adult disease phenotypes are poorly understood. Increasing evidence suggests that the genome is ?programmed? by environmental stimuli early in development via changes in epigenetic states in the brain and other tissues, and that this programming affects predisposition to altered behaviors in adulthood. However, the molecular pathways by which environmental cues experienced in utero or during childhood result in long-lasting effects are still unclear. C. elegans nematodes provide an experimentally amenable animal model system in which to explore the mechanisms of developmental programming. Previous results have shown that adult worms retain a cellular memory of their developmental history reflected in changes in gene expression, genome-wide chromatin state, behaviors, and life history traits. A subset of these altered adult phenotypes is regulated in part by endogenous RNAi pathways. One of the targets of developmental programming is the TRPV channel gene osm-9, which is essential for chemosensation, osmosensation, and noceiceptive behaviors in C. elegans. The osm-9 gene is down-regulated specifically in a sensory neuron type in animals that experienced early-life stress, which results in altered sensory behaviors in adults. The overall goal of this proposal is to characterize the molecular mechanisms by which environmental experiences program adult gene expression in C. elegans neurons and the resulting behavioral phenotypes as a model for developmental programming. The Specific Aims are to: 1) Investigate the roles of RNAi and chromatin remodeling pathways in the developmental programming of osm-9. Experiments proposed in this aim will examine the recruitment and interaction of RNAi and chromatin remodeling proteins at the osm-9 locus as a result of environmental stress early in development, and identify additional proteins binding to the osm-9 promoter using a yeast one-hybrid screen. 2) Examine changes in small RNA and mRNA abundance as a result of early-life stress at the resolution of a single neuron type. Individual neurons will be isolated via fluorescence cell sorting, and small RNAs and mRNAs will be cloned and sequenced on the Illumina platform. 3) Determine the behavioral consequences of the developmental programming of osm-9. Hermaphrodites and males that down-regulate osm-9 due to early-life stress fail to avoid stressful environments as adults. Experiments proposed in this aim will test whether this altered behavior promotes outcrossing among animals that experienced environmental stress to increase genetic diversity within the population. It is expected that the studies proposed in this grant will further understanding of the molecular mechanisms that regulate developmental programming in neurons and the resulting behavioral consequences as a result of early-life stress. Given the high degree of conservation of gene regulatory pathways across species, results from this work will also inform related investigations in higher organisms including humans.