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Sperm-inherited H3K27me3 epialleles are transmitted transgenerationally in cis

ABSTRACT: The role that gamete-inherited chromatin states serve in regulating gene expression across generations is poorly understood. To interrogate how histone marks inherited on parental genomes influence gene expression in offspring, we profiled different tissue contexts in worms that inherited the sperm genome lacking the repressive mark H3K27me3. We found that worms that inherited the sperm genome lacking H3K27me3 upregulated genes in all tissues profiled, which included hermaphrodite and male germlines and mixed soma. We found that most upregulated genes were upregulated specifically from sperm alleles and in a tissue-specific manner, highlighting the importance of cellular context in determining which genes are sensitive to upregulation when H3K27me3 repression is absent. To determine whether chromatin states can impact gene expression transgenerationally, i.e. across 3 generations, we profiled gene expression and chromatin states in the germlines of worms that inherited the sperm genome lacking H3K27me3 (F1 generation) and in the germlines of their offspring (F2 generation). We found that genes upregulated in F1 germlines maintained the H3K27me3(-) state of sperm alleles and that the upregulated and H3K27me3(-) state of sperm alleles was maintained in the germlines of their offspring (F2 generation). These findings demonstrate that histone marks can serve as a transgenerational carrier.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE205113 | GEO | 2022/05/31

REPOSITORIES: GEO

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Project description:RNA-seq transcriptome analysis of C. elegans germlines that inherited only paternal chromosomes (non-Mendelian inheritance, 'red-head worms') and the germlines of their offspring ('offspring of red-head worms') vs. germlines that inherited both maternal and paternal chromosomes (Mendelian inheritance, HBR1280 control). Given that epigenetic marking of sperm chromosomes is faithfully transmitted through embryo cell divisions, and that sperm epigenetic marking is important in offspring, we tested if sperm epigenetic marking alone is sufficient for proper development of the germline in offspring. We utilized a mutant that, during the first embryonic division, delivers the sperm genome to the daughter cell that generates the germline and the oocyte genome to the other daughter cell (Besseling & Bringmann, 2016). This mutant over-expresses GPR-1, a protein involved in regulation of kinetochore pulling forces. GPR-1 over-expression results in excessive pulling forces, causing the paternal and maternal pronuclei to inappropriately move to opposite poles of the 1-cell embryo instead of merging in the center of the embryo. In this mutant background, ~60% of offspring undergo atypical chromosome segregation, generating mosaic embryos whose germlines are derived entirely from sperm chromosomes (Besseling & Bringmann, 2016). To track the parental genomes, differentially tagged histone transgenes were used: a GFP-tagged histone H2B encoded in the sperm genome, and a TdTomato-tagged histone H2B encoded in the oocyte genome. The mosaic embryos whose germline inherited only sperm chromosomes (‘red-head' worms) develop into fertile adults with a normal brood size, similar to control worms, in which the germline inherited both sperm and oocyte chromosomes. RNA-seq analysis demonstrated that the germline transcriptome of ‘red-head’ worms and their offspring show few (<80 genes) and minor changes compared to control worms. These findings demonstrate that epigenetic information provided by sperm can guide proper germ cell development.

Project description:Background: DNA methylation (DNAme) erasure and reacquisition occurs during prenatal male germ cell development; some further remodelling takes place after birth during spermatogenesis. Environmental insults during germline epigenetic reprogramming may affect DNAme, presenting a potential mechanism for transmission of environmental exposures across multiple generations. Objectives: We investigated how germ cell DNAme is impacted by lifetime exposures to diets containing either low or high, clinically relevant, levels of the methyl donor folic acid and whether resulting DNAme alterations were inherited in germ cells of male offspring of subsequent generations. Materials and Methods: Female mice were placed on a 7-fold folic acid deficient (7FD) and 10- or 20-fold supplemented (10FS and 20FS) diets before and during pregnancy. Resulting F1 litters were weaned on the respective diets. F2 and F3 males received control diets. Genome-wide DNAme was assessed in F1 spermatogonia, and in F1, F2 and F3 sperm. Results: In F1 germ cells, a greater number of differentially methylated cytosines (DMCs) was observed in spermatogonia as compared with F1 sperm for all folic acid diets. DMCs were lower in number in F2 versus F1 sperm, while an unexpected increase was found in F3 sperm. DMCs were predominantly hypomethylated, with genes in neurodevelopmental pathways commonly affected in F1, F2 and F3 male germ cells. While no DMCs were found to be inherited inter- or transgenerationally, we observed over-representation of repetitive elements, particularly young LINEs. Discussion and Conclusion: These results suggest that the prenatal window is the time most susceptible to folate-induced alterations in sperm DNAme in male germ cells. Altered methylation of specific sites in F1 sperm was not present in later generations. However, the finding of hypomethylated young LINE1 elements in sperm from F1 to F3 males provides insight into potential mechanisms of epigenetic inheritance of the effects of folate deficiency and supplementation.

Project description:Purpose: Paternal life experiences impact offspring health via germline, and epigenetic inheritance provides a potential mechanism. However, global reprogramming during offspring embryogenesis and gametogenesis represents the largest hurdle to conceptualize it. Yet, detailed characterization of how sperm epigenetic alterations carrying “environmental memory” can evade offspring embryonic reprogramming remains elusive. Methods: we profiled the sperm DNA methylation patterns of three consecutive generations (F0, F1 and F2) in both control and stress groups by using whole-genome bisulfite sequencing (WGBS). A total of 18 sperm samples were analyzed, including three biological replicates for each generation under each treatment. In addition, small RNA sequencing was carried out on paternal sperm samples to investigate whether long-term psychological stress affected the enrichment of certain sncRNAs and to identify whether they participated in mediating the occurrence and paternal inheritance of the stress-induced DMRs Rsults: Using an optimized data analysis workflow, we obtained approximately 800 million clean reads per sample (build mm10) with strand-specific coverage ~21×, and the data covered ~96.00% of the total 21,867,837 reference CpG dinucleotides. A total of 24,427, 7,975, and 5,173 differentially methylated regions (DMRs) between control and stress groups were found in the F0, F1, and F2 generations, respectively. Inter- and transgenerational inheritance of paternal DMRs were at frequencies approximately 11.36% and 0.48%, respectively. These DMRs related to genes with functional implications for psychological stress response, and tissue inheritance of these DMRs passed paternal disorders epigenetically to offspring. More importantly, these DMRs evaded offspring embryonic reprogramming through erasure and subsequent reestablishment, but not via un-erasure way. Nonetheless, their reestablishment proportions in the primitive streak (E7.5) stage were altered. Furthermore, sncRNA-seq revealed that stress-induced tsRNA, miRNA and rsRNA dysregulation in paternal sperm might play important roles in DMRs occurrence and paternal inheritance.

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Sperm-inherited H3K27me3 epialleles are transmitted transgenerationally in cis

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