Project description:How artificial environmental cues are biologically integrated and transgenerationally inherited is still poorly understood. Here, we investigate the mechanisms of inheritance of reproductive outcomes elicited by the model environmental chemical Bisphenol A (BPA) in C. elegans. We show that BPA exposure causes the derepression of an epigenetically silenced transgene in the germline for 5 generations, regardless of ancestral response. ChIP-seq, histone modifications quantitation, and immunofluorescence assays revealed that this effect is associated with a reduction of the repressive marks H3K9me3 and H3K27me3 in whole worms and in germline nuclei in the F3 as well as with reproductive dysfunctions including germline apoptosis and embryonic lethality. Furthermore, targeting of the Jumonji demethylases JMJD-2 and JMJD-3/UTX-1 restores H3K9me3 and H3K27me3 levels, respectively, and fully alleviates the BPA-induced transgenerational effects. Together, our results demonstrate the central role of repressive histone modifications in the inheritance of reproductive defects elicited by a common environmental chemical exposure.
Project description:Adaptation to environmental stresses is crucial for survival. Transgenerational epigenetic inheritance allows organisms to respond to irregular conditions, alert their naïve descendants that stresses could still be present, and for distant descendants to eventually return to a basal state after several generations without the stress. However, it is still unclear whether organisms adapt on a transgenerational scale after repeated generational exposures to the same environmental stress. We recently found that C. elegans exposed to hypoxia in the parental (P0) generation: increased longevity in the P0 generation, caused an intergenerational reduction in lipids, and elicited a transgenerational reduction in fertility (P0-F2) that was dependent on small RNAs that were transmitted from parents to their naïve children. Here, we find that exposure of subsequent generations of C. elegans to hypoxia caused a transgenerational adaptation such that C. elegans that had repeated generational exposure to hypoxia failed to display hypoxia induced phenotypes. We show that upon two repeated generational exposures to hypoxia, C. elegans no longer display an increase in lifespan, and after four repeated generational exposures to hypoxia, C. elegans no longer display a decrease in reproduction. Transgenerational adaptation of the reproduction phenotype is dependent on the putative H3K27 trimethytransferase PRC2 complex and we identified critical genes that adapted on a transgenerational timeframe to repeated hypoxia exposure. Our findings reveal that transgenerational adaptation occurs and suggest that H3K27me3 is a critical modification for adapting to repeated generational stresses.
Project description:How artificial environmental cues are biologically integrated and transgenerationally inherited is still poorly understood. Here, we investigate the mechanisms of inheritance of reproductive outcomes elicited by the model environmental chemical Bisphenol A (BPA) in C. elegans. We show that BPA exposure causes the derepression of an epigenetically silenced transgene in the germline for 5 generations, regardless of ancestral response. ChIP-seq, histone modifications quantitation, and immunofluorescence assays revealed that this effect is associated with a reduction of the repressive marks H3K9me3 and H3K27me3 in whole worms and in germline nuclei in the F3 as well as with reproductive dysfunctions including germline apoptosis and embryonic lethality. Furthermore, targeting of the Jumonji demethylases JMJD-2 and JMJD-3/UTX-1 restores H3K9me3 and H3K27me3 levels, respectively, and fully alleviates the BPA-induced transgenerational effects. Together, our results demonstrate the central role of repressive histone modifications in the inheritance of reproductive defects elicited by a common environmental chemical exposure.
Project description:Exposure to TCDD early in development produces reproductive abnormalities and decreased reproductive capacity in males in subsequent generations. We used WGBS to investigate differential methylation in testicular tissue and identified distinct multigenerational and transgenerational methylation changes due to legacy TCDD exposure in males.
Project description:Environmental stress-induced transgenerational epigenetic effects have been observed in various model organisms and human. The capacity and mechanism of such phenomena, particularly in animals, are poorly understood. In C. elegans, siRNA mediates transgenerational gene silencing through the germline nuclear RNAi pathway. At the organismal level, this pathway plays a transgenerational role in maintaining the germline immortality when C. elegans is under a mild heat stress. However, the underlying molecular mechanism is unknown. In this study, we performed a 12-generation temperature-shift experiment (15˚C->23˚C->15˚C) using the wild type (N2) and a mutant strain that lacks the germline-specific nuclear AGO protein HRDE-1/WAGO-9. We found that the temperature-sensitive mortal germline (Mrt) phenotype of the hrde-1 mutant is reversible, indicating a transgenerational cumulative but also reversible nature of the underlying molecular cause. By taking the whole-genome RNA and chromatin profiling approaches, we revealed an epigenetic role of HRDE-1 in repressing heat stress-induced transcriptional activation of over 280 genes, predominantly in or near LTR retrotransposons. Strikingly, for some of these elements, the heat stress-induced transcription becomes progressively activated in the hrde-1 mutant over several generations under heat stress. Furthermore, the effect of heat stress-induced transcription activation is heritable for at least two generations after the heat stress. Interestingly, the siRNA expression of these genes tend to be heat-inducible in the wild type animals, but not in the hrde-1 mutant, suggesting a role of siRNAs in repressing heat-inducible elements. Our study revealed a novel phenomenon of transgenerational feed-forward transcriptional activation, which is normally repressed in the wild type C. elegans by the germline nuclear RNAi pathway. It also provides a new paradigm to study epigenetic circuitry that connects the environment and gene regulation in the germline.