Project description:Life experiences trigger transgenerational small RNA-based responses in C. elegans nematodes1. Dedicated machinery ensures that heritable effects would re-set, typically after a few generations2,3. Here we show that isogenic individuals differ dramatically in the persistence of transgenerational responses. By examining lineages composed of >20,000 worms we reveal 3 inheritance rules: (1) Once a response is initiated, each isogenic mother stochastically assumes an “inheritance state”, establishing a commitment that determines the fate of the inheritance. (2) The response that each mother transfers is uniform in each generation of her descendants. (3) The likelihood that an RNAi response would transmit to the progeny increases the more generations the response lasts, according to a “hot hand” principle. Mechanistically, the different parental “inheritance states” correspond to global changes in the expression levels of endogenous small RNAs, immune response genes, and targets of the conserved transcription factor HSF-1. We show that these rules predict the descendants’ developmental rate and resistance to stress.
Project description:Some epigenetic modifications are inherited from one generation to the next, providing a potential mechanism for the inheritance of environmentally acquired traits. Transgenerational inheritance of RNA interference phenotypes in C. elegans provides an excellent model to study this phenomenon, and whilst studies have implicated both chromatin modifications and small RNA pathways in heritable silencing their relative contributions remain unclear. Here we demonstrate that the histone methyltransferases SET-25 and SET-32 are required for the establishment of a transgenerational silencing signal, but not for long-term maintenance of this signal between subsequent generations suggesting that transgenerational epigenetic inheritance is a multi-step process, with distinct genetic requirements for establishment and maintenance of heritable silencing. Furthermore, small RNA sequencing reveals that the abundance of secondary siRNA (thought to be the effector molecules of heritable silencing) does not correlate with silencing phenotypes. Together, our results suggest that the current mechanistic models of epigenetic inheritance are incomplete.
Project description:Transgenerational inheritance is challenging basic concepts of heredity and achieving control over such responses is of great interest. In C. elegans nematodes, small RNAs are transmitted across generations to establish a transgenerational memory trace of ancestral environments. Inheritance of small RNAs is regulated by dedicated machinery and can be tuned by outside cues. Carryover of aberrant heritable small RNA responses was shown to be maladaptive and to induce sterility in certain cases. Here we show that various types of stress (starvation, high temperatures, and hyperosmotic conditions) but not non-stressful changes in cultivation, lead to resetting of small RNA inheritance. We found that stress leads to a genome-wide reduction in heritable small RNA levels and that mutants defective in different stress pathways exhibit irregular RNAi inheritance dynamics. Moreover, we discovered that resetting of heritable RNAi is orchestrated by MAPK pathway factors, the transcription factor SKN-1, and the MET-2 methyltransferase. Termination of small RNA inheritance, and the fact that this process depends on stress, could protect from run-on of environment-irrelevant heritable gene regulation.
Project description:Transgenerational inheritance of acquired traits/characteristics from ancestors is believed to play important roles in evolution, as well as health problems/symptoms not due to “classical genetic inheritance”. However, the central enigma, such as how the acquired transgenerational characteristics are developed, and how the acquired traits are transmitted from generations to generations of offspring, largely remained veiled. In this study, we used C elegans as a model system and provide evidence that the dynamic of H3K27me3 as a hallmark and regulator for the gut-mediated transgenerational inheritance of acquired traits. Further, we demonstrate that yolk proteins guide the establishment of the acquired epigenetic imprints in soma, as well as determines the transgenerational inheritance of epigenetic imprints and subsequent acquired behavior in offspring by maternal provision. Taken together, our findings support that yolk proteins both function as a systemic “non-nuclear factor” for establishing the somatic epigenetic imprints and as a “cargo” to transmit acquired epigenetic information to the subsequent generations through oocytes.
Project description:Chromatin modifiers regulate lifespan in several organisms, raising the question of whether changes in chromatin states in the parental generation could be incompletely reprogrammed in the next generation and thereby affect the lifespan of descendents. The histone H3 lysine 4 trimethylation (H3K4me3) complex composed of ASH-2, WDR-5, and the histone methyltransferase SET-2 regulates C. elegans lifespan. Here we show that deficiencies in the H3K4me3 chromatin modifiers ASH-2, WDR-5, or SET-2 in the parental generation extend the lifespan of descendents up until the third generation. The transgenerational inheritance of lifespan extension by members of the ASH-2 complex is dependent on the H3K4me3 demethylase RBR-2, and requires the presence of a functioning germline in the descendents. Transgenerational inheritance of lifespan is specific for the H3K4me3 methylation complex and is associated with epigenetic changes in gene expression. Thus, manipulation of specific chromatin modifiers only in parents can induce an epigenetic memory of longevity in descendents. There are 35 samples in total. We found that genetically WT descendents from mutants of the H3K4me3 modifying complex had extended longevity up until the F4 generation. Their lifespan returned to WT levels in the F5 generation. We performed microarrays to examine what gene expression differences there were between N2(WT) worms, +/+ (from wdr-5 mutant) worms, and wdr-5/wdr-5 in the F4 and the F5 generation. We analyzed L3 samples from the first and second days of egg laying in triplicate each. Samples consist of ~1000 worms each.
Project description:Chromatin modifiers regulate lifespan in several organisms, raising the question of whether changes in chromatin states in the parental generation could be incompletely reprogrammed in the next generation and thereby affect the lifespan of descendents. The histone H3 lysine 4 trimethylation (H3K4me3) complex composed of ASH-2, WDR-5, and the histone methyltransferase SET-2 regulates C. elegans lifespan. Here we show that deficiencies in the H3K4me3 chromatin modifiers ASH-2, WDR-5, or SET-2 in the parental generation extend the lifespan of descendents up until the third generation. The transgenerational inheritance of lifespan extension by members of the ASH-2 complex is dependent on the H3K4me3 demethylase RBR-2, and requires the presence of a functioning germline in the descendents. Transgenerational inheritance of lifespan is specific for the H3K4me3 methylation complex and is associated with epigenetic changes in gene expression. Thus, manipulation of specific chromatin modifiers only in parents can induce an epigenetic memory of longevity in descendents.
Project description:Environmentally induced epigenetic transgenerational inheritance of adult onset disease involves a variety of phenotypic changes suggesting a general alteration in genome activity. Investigation of eleven different tissue transcriptomes in male and female F3 generation vinclozolin versus control lineage rats demonstrated all tissues examined had unique transgenerational transcriptomes. Common cellular pathways and processes were identified among the tissues. A bionetwork analysis identified gene modules with coordinated gene expression and each had unique gene networks regulating tissue specific gene expression and function. A large number of statistically significant over-represented clusters of differentially expressed genes were identified and termed M-bM-^@M-^\Epigenetic Control RegionsM-bM-^@M-^]. Combined observations demonstrate that all tissues derived from the epigenetically altered germ line develop transgenerational transcriptomes unique to the tissue, but common epigenetic control regions in the genome appear to in part coordinately regulate these tissue specific transcriptomes. This systems biology approach provides insight into the molecular mechanisms involved in the epigenetic transgenerational inheritance of a variety of adult onset disease phenotypes. We used microarrays to determine genes expressed differentially in rats 11 male or female smatic tissues -male heart, kidney, liver, testis, prostate, seminal vesicles; female heart, kidney, liver, ovary, uterus - due to Vinclozolin treatments of their grand-grandmothers. For each of 11 male or female smatic tissues, RNA samples from 2 treatment groups - control (Con) and vinclozolin (Vin) - were compared to each other. Each treatment groups contained 3 biological replica. RNA for each replica was pooled from 2 individual animals.
Project description:Environmental compounds can promote epigenetic transgenerational inheritance of adult-onset disease in subsequent generations following ancestral exposure during fetal gonadal sex determination. The current study examined the ability of dioxin (2,3,7,8-tetrachlorodibenzo[p]dioxin, TCDD) to promote epigenetic transgenerational inheritance of disease and DNA methylation epimutations in sperm. Gestating F0 generation females were exposed to dioxin during fetal day 8 to 14 and adult-onset disease was evaluated in F1 and F3 generation rats. The incidences of total disease and multiple disease increased in F1 and F3 generations. Prostate disease, ovarian primordial follicle loss and polycystic ovary disease were increased in F1 generation dioxin lineage. Kidney disease in males, pubertal abnormalities in females, ovarian primordial follicle loss and polycystic ovary disease were increased in F3 generation dioxin lineage animals. Analysis of the F3 generation sperm epigenome identified 50 differentially DNA methylated regions (DMR) in gene promoters. These DMR provide potential epigenetic biomarkers for transgenerational disease and ancestral environmental exposures. Observations demonstrate dioxin exposure of a gestating female promotes epigenetic transgenerational inheritance of adult onset disease and sperm epimutations. Methylated sperm DNA was isolated from rats ancestrally exposed to dioxin (Hip). Three independent samples from the treatment group were obtained. Differential DNA methylation between treatment groups was determined using Nimblegen microarrays. Treated samples were paired with control samples and hybridized together on arrays (Hip1/Cip1, Hip2/Cip2, and Hip3/Cip3), resulting in three arrays for the treatment.