Project description:Animals respond to dietary changes by adapting their metabolism to available nutrients through insulin and insulin-like growth factor signalling. Restricting calorie intake generally extends life and health span, but Drosophila fed non-ideal sugars such as galactose are stressed and have shorter life spans. Here, we report that although these flies have shorter life spans, their offspring show significant life extension if switched to a normal sugar (glucose) diet. We define this as TGH or trans-generational hormesis, a beneficial effect that comes from a mild stress. We trace the effects to changes in stress responses in parents, ROS production, effects on lipid metabolism, and changes in chromatin and gene expression. We find that this mechanism is similar to what happens to the long lived Indy mutants on normal food, but surprisingly find that Indy is required for life span extension for galactose fed flies. Indy mutant flies grown on galactose do not live longer as do their siblings grown on glucose, rather overexpression of Indy rescues lifespan for galactose reared flies. We define a process where sugar metabolism can generate epigenetic changes that are inherited by offspring, providing a mechanism for how transgenerational nutrient sensitivities are passed on.
Project description:Animals respond to dietary changes by adapting their metabolism to available nutrients through insulin and insulin-like growth factor signalling. Restricting calorie intake generally extends life and health span, but Drosophila fed non-ideal sugars such as galactose are stressed and have shorter life spans. Here, we report that although these flies have shorter life spans, their offspring show significant life extension if switched to a normal sugar (glucose) diet. We define this as TGH or trans-generational hormesis, a beneficial effect that comes from a mild stress. We trace the effects to changes in stress responses in parents, ROS production, effects on lipid metabolism, and changes in chromatin and gene expression. We find that this mechanism is similar to what happens to the long lived Indy mutants on normal food, but surprisingly find that Indy is required for life span extension for galactose fed flies. Indy mutant flies grown on galactose do not live longer as do their siblings grown on glucose, rather overexpression of Indy rescues lifespan for galactose reared flies. We define a process where sugar metabolism can generate epigenetic changes that are inherited by offspring, providing a mechanism for how transgenerational nutrient sensitivities are passed on.
Project description:Trans-generational epigenetic inheritance (TEI), which functionally intersects RNA with histone modification, recently forced a reinterpretation of the interplay between gene expression and selective pressures. Our groups integrate genetic, genomic, dynamic imaging, biochemistry and proteomic technologies to provide a functional mechanistic understanding of the interplay of TEI and the RNA interference (RNAi) phenomena in the nematode C. elegans. We discovered a family of proteins (the nuclear Argonaute-interacting proteins or NIPs), which controls the strength, inheritance and gene target specificity of nuclear RNAi. Loss of NIP-1 and NIP-2 in the soma leads to an enhancement of nuclear RNAi activities without affecting cytoplasmic RNAi. Loss of NIP-3 in the germline disables TEI and leads to a profoundly impaired response to transposable genomic elements (viral-like sequences). The genome of nip-3 mutants becomes de-stabilized; spontaneous visible mutations arise at high frequency due to an unbridled mobilization of a subset of transposable elements. Surprisingly, silencing of a distinct subset of transposable elements is coincidentally enhanced. Finally, expression imaging revealed an eminent role for the maturing male germline in TEI. This data supports a model wherein NIPs determine the potency and stability of TEI by gating and sorting small RNAs (which provide specificity) towards germline and somatic nuclear RNAi and epigenetic machineries. Our work further implies that this molecular machinery evolved to atone an animal’s epigenetic memory to preserve a species’ integrity in face of genetic pathogens.
Project description:Trans-generational inheritance of a phenotypically neutral epimutation enables descendants to reinstate an ancestral silencing episode
Project description:Piwi interacting (pi)RNAs repress diverse transposable elements in the germ cells of metazoans and are essential for fertility in both invertebrates and vertebrates. The precursors of piRNAs are transcribed from distinct genomic regions, the so-called piRNA clusters; however, how piRNA clusters are differentiated from the rest of the genome is not known. To address this question, we studied piRNA biogenesis in two Drosophila virilis strains that show differential ability to generate piRNAs from several genomic regions. We found that active piRNA biogenesis correlates with high levels of histone 3 lysine 9 trimethylation (H3K9me3) over genomic regions that give rise to piRNAs. Furthermore, piRNA biogenesis in the progeny requires the trans-generational inheritance of an epigenetic signal, presumably in form of homologous piRNAs that are generated in the maternal germline and deposited into the oocyte. The inherited piRNAs enhance piRNA biogenesis by installment of H3K9me3 mark on piRNA clusters and by promoting ping-pong processing of homologous transcripts into mature piRNAs. We submitted the resequencing data together with the functional genomic datasets because it was generated with the sole purpose of supporting those. The SRA accession numbers are SRR1536176 and SRR1536175. ChIP-seq against H3K9me3 and Pol2, Total RNA-seq, in Drosophila virilis Strain9 and Strain160 as well as crosses between them
Project description:Cytosine DNA methylation regulates the expression of eukaryotic genes and transposable elements. Methylation is copied by DNA methyltransferases after DNA replication, which results in faithful transmission of methylation patterns during cell division and, at least in flowering plants, across generations. Trans-generational inheritance is mediated by a small group of cells that includes gametes and their progenitors. However, methylation is usually analyzed in somatic tissues that do not contribute to the next generation, and the mechanisms of trans-generational inheritance are inferred from such studies. To gain a better understanding of how DNA methylation is inherited, we analyzed purified Arabidopsis thaliana sperm and vegetative cells – the cell types that comprise pollen – with mutations in the DRM, CMT2 and CMT3 methyltransferases.