Sperm histone H3 lysine 4 trimethylation is altered in a genetic mouse model of transgenerational epigenetic inheritance
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ABSTRACT: Advancing the molecular knowledge surrounding fertility and inheritance has become critical given the halving of sperm counts in the last 40 years, and the rise in complex disease which cannot be explained by genetics alone. The connection between both these trends may lie in alterations to the sperm epigenome and occur through environmental exposures. Changes to the sperm epigenome are also associated with health risks across generations such as metabolic disorders and cancer. Thus it is imperative to identify the epigenetic modifications that escape reprogramming during spermatogenesis. Here, we aimed to identify the chromatin signature(s) associated with transgenerational phenotypes in our genetic mouse model of epigenetic inheritance that overexpresses the histone demethylase KDM1A in their germ cells. We used sperm-specific chromatin immunoprecipitation followed by in depth sequencing (ChIP-seq), and computational analysis to identify whether differential enrichment of histone H3 lysine 4 trimethylation (H3K4me3), and histone H3 lysine 27 trimethylation (H3K27me3) serve as mechanisms for transgenerational epigenetic inheritance through the paternal germline. Our analysis on the sperm of KDM1A transgenic males revealed specific changes in H3K4me3 enrichment that occurred independently from non-bivalent H3K4me3/H3K27me3 regions. Many regions with altered H3K4me3 enrichment in sperm were identified on the paternal allele of the pre-implantation embryo. These findings suggest that sperm H3K4me3 functions in the transmission of non-genetic phenotypes transgenerationally.
Project description:Parental environmental exposures can strongly influence descendant risks for adult disease. Metabolic disorders arise from the intersection of environmental and genetic risk factors, with epigenetic inheritance being at the center of the familial cycle of transgenerational disease. How paternal high-fat diet changes the sperm chromatin leading to the acquisition of metabolic disease in offspring remains controversial and ill-defined. Using a genetic model of epigenetic inheritance, we investigated the role of histone H3 lysine 4 methylation (H3K4me3) in the paternal transmission of metabolic dysfunction. We show that obesity-induced alterations in sperm H3K4me3 associated with offspring phenotypes and corresponded to embryonic and placental chromatin profiles and gene expression. Transgenerational susceptibility to metabolic disease was only observed when grandsires had a pre-existing genetic predisposition to metabolic dysfunction that was associated with enhanced alterations to sperm H3K4me3. This non-DNA based knowledge of inheritance has the potential to improve our understanding of how environment shapes heritability and may lead to novel routes for the prevention of disease.
Project description:A father’s lifetime experiences can be transmitted to his offspring to affect health and development. The mechanisms underlying paternal epigenetic transmission are unclear. Unlike somatic cells, there are few nucleosomes in sperm and their function in epigenetic inheritance is unknown. We generated transgenic mice in which overexpression of the histone H3 lysine 4 (H3K4) demethylase LSD1/KDM1A during spermatogenesis reduced H3K4 dimethylation in sperm. KDM1A overexpression in one generation severely impaired development and survivability of offspring. These defects persisted transgenerationally in the absence of KDM1A germ line expression and were associated with altered RNA profiles in sperm and offspring. We show that epigenetic inheritance of aberrant development can be initiated by histone demethylase activity in developing sperm, without changes to DNA methylation at CpG-rich regions.
Project description:A father’s lifetime experiences can be transmitted to his offspring to affect health and development. The mechanisms underlying paternal epigenetic transmission are unclear. Unlike somatic cells, there are few nucleosomes in sperm and their function in epigenetic inheritance is unknown. We generated transgenic mice in which overexpression of the histone H3 lysine 4 (H3K4) demethylase LSD1/KDM1A during spermatogenesis reduced H3K4 dimethylation in sperm. KDM1A overexpression in one generation severely impaired development and survivability of offspring. These defects persisted transgenerationally in the absence of KDM1A germ line expression and were associated with altered RNA profiles in sperm and offspring. We show that epigenetic inheritance of aberrant development can be initiated by histone demethylase activity in developing sperm, without changes to DNA methylation at CpG-rich regions.
Project description:Epigenetic mechanisms including DNA methylation, non-coding RNAs and histone modifications control gene expression. Studies suggest that a father's lifetime experiences can be transmitted to his offspring to affect development and health. The mechanisms underlying such epigenetic inheritance are unknown. A potential route for paternal transmission is the unique chromatin composition of spermatozoa. Unlike somatic cells and oocytes, most nucleosomes in sperm are replaced with protamine nucleoproteins. The role of residual nucleosomes, residing at gene regulatory sequences, for epigenetic control of embryonic development is unknown. Here we generated a transgenic mouse model in which over-expression of the histone H3 lysine 4 (H3K4) demethylase LSD1/KDM1A during spermatogenesis alters H3K4 methylation in sperm. Strikingly, KDM1A over-expression in one generation causes severe embryonic defects in non-transgenic descendants spanning three subsequent generations. We show for the first time that correct histone methylation homeostasis during spermatogenesis is critical for offspring development and survival over multiple generations. Identification of H3K4me2 and nucleosome occupancies in sperm of wildtype mice, KDM1A transgenic mice and their non-transgenic littermates.
Project description:Transgenerational epigenetic inheritance (TEI) describes the transmission of gene-regulatory information across generations without altering DNA sequences. TEI allows priming of offspring towards changing environmental conditions and plays a role in the maintenance of gene silencing of selfish genetic elements like transposons. Small regulatory RNAs are well known to act in TEI, and can be transmitted via the male. Such inheritance via sperm requires dedicated mechanisms, as much of the cellular content is extruded during spermatogenesis. We identify a phase separation-based mechanism, which couples the paternal inheritance of a specific small RNA-bound silencing factor via S-palmitoylation to the transport of membranous organelles. Our findings uncover a thus far unknown paternal TEI mechanism, and describe a novel mode of transport of phase-separated condensates.
Project description:Epigenetic information can be inherited through the mammalian germline, and represents a plausible transgenerational carrier of environmental information. To test whether transgenerational inheritance of environmental information occurs in mammals, we carried out an expression profiling screen for genes in mice that responded to paternal diet. As part of this analysis, we chracterise the changes in sperm cytosine methylation in response to different diets. Characterizing the RNA exression changes in livers of offspring mice in response to the paternal diet, comparing between low-protein diet and control-diet. Examination the effect of 3 different paternal diets, control diet, Caloric Restriction and low-protein diet, on sperm cytosine methylation.
Project description:Epigenetic information can be inherited through the mammalian germline, and represents a plausible transgenerational carrier of environmental information. To test whether transgenerational inheritance of environmental information occurs in mammals, we carried out an expression profiling screen for genes in mice that responded to paternal diet. Characterising the change in RNA expression in sperm in response to different paternal diets.
Project description:Epigenetic information can be inherited through the mammalian germline, and represents a plausible transgenerational carrier of environmental information. To test whether transgenerational inheritance of environmental information occurs in mammals, we carried out an expression profiling screen for genes in mice that responded to paternal diet. Characterising the change in RNA expression in sperm in response to different paternal diets. Examination of the effect of different diets, control diet, low-protein diet and caloric-restriction diet, on the RNA expression in the sperm. 8 samples: 3 are control diets and 2 are low protein diets 1 caloric restriction diet, and 2 samples from Epidydimal tissue.
Project description:Epigenetic mechanisms including DNA methylation, non-coding RNAs and histone modifications control gene expression. Studies suggest that a father's lifetime experiences can be transmitted to his offspring to affect development and health. The mechanisms underlying such epigenetic inheritance are unknown. A potential route for paternal transmission is the unique chromatin composition of spermatozoa. Unlike somatic cells and oocytes, most nucleosomes in sperm are replaced with protamine nucleoproteins. The role of residual nucleosomes, residing at gene regulatory sequences, for epigenetic control of embryonic development is unknown. Here we generated a transgenic mouse model in which over-expression of the histone H3 lysine 4 (H3K4) demethylase LSD1/KDM1A during spermatogenesis alters H3K4 methylation in sperm. Strikingly, KDM1A over-expression in one generation causes severe embryonic defects in non-transgenic descendants spanning three subsequent generations. We show for the first time that correct histone methylation homeostasis during spermatogenesis is critical for offspring development and survival over multiple generations.
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.