Loss of Prm1 leads to defective chromatin protamination, impaired PRM2 processing, reduced sperm motility and subfertility in male mice [PRM1]
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ABSTRACT: One of the key events during spermiogenesis is the hypercondensation of chromatin by substitution of the majority of histones by protamines. In humans and mice, protamine 1 (PRM1/Prm1) and protamine 2 (PRM2/Prm2), are expressed in a species-specific ratio. Using CRISPR-Cas9-mediated gene editing we generated Prm1-deficient mice and demonstrate, that Prm1+/- mice are subfertile while Prm1-/- are infertile. Prm1-/- and Prm2-/- sperm show high levels of reactive oxygen species (ROS)-mediated DNA damages and increased histone retention. In contrast, Prm1+/- sperm display only moderate DNA damages. The majority of Prm1+/- sperm were CMA3 positive indicating protamine-free DNA. This is not due to increased histone retention in Prm1+/- sperm. Additionally, we found that sperm from Prm1+/- and Prm1-/- mice contain high levels of incompletely processed PRM2. Further, the PRM1:PRM2 ratio is skewed from 1:2 in WT to 1:5 in Prm1+/- animals. Our results reveal that PRM1 is required for proper PRM2 processing to produce the mature PRM2 which, together with PRM1 is able to hypercondense DNA. Hence, the species specific PRM1:PRM2 ratio has to be precisely controlled in order to retain full fertility.
Project description:Protamines are unique sperm-specific proteins that package and protect paternal chromatin until fertilization. A subset of mammalian species expresses two protamines (PRM1 and PRM2), while in others PRM1 is sufficient for sperm chromatin packaging. Alterations of the species-specific ratio between PRM1 and PRM2 are associated with infertility. Unlike PRM1, PRM2 is generated as a precursor protein consisting of a highly conserved N-terminal domain, termed cleaved PRM2 (cP2), which is consecutively trimmed off during chromatin condensation. The carboxyterminal part, called mature PRM2 (mP2), interacts with DNA and together with PRM1, mediates chromatin-hypercondensation. The removal of the cP2 domain is believed to be imperative for proper chromatin condensation, yet, the role of cP2 is not yet understood. We generated mice lacking the cP2 domain while the mP2 is still expressed. We show that the cP2 domain is indispensable for complete sperm chromatin protamination and male mouse fertility. cP2 deficient sperm show incomplete PRM2 incorporation, resulting in a severely altered protamine ratio, retention of transition proteins and aberrant retention of the testis specific histone variant H2A.L.2. During epididymal transit, cP2 deficient sperm seem to undergo ROS mediated degradation leading to complete DNA fragmentation. The cP2 domain therefore seems to be a key aspect in the complex crosstalk between histones, transition proteins and protamines during sperm chromatin condensation. Overall, we present the first step towards understanding the role of the cP2 domain in paternal chromatin packaging and open up avenues for further research.
Project description:MTD project_description Protamines are testis-specific proteins, which replace the majority of histones during spermiogenesis. This results in a hypercondensation of the sperm DNA, finally causing a conformational change from a nucleosomal chromatin structure into a mainly toroid like structure. This is assumed to protect the paternal genome and to contribute to the formation of a hydrodynamic sperm head shape. In mice and humans, two protamines, Protamine 1 (Prm1) and Protamine 2 (Prm2), are expressed. Impaired sperm protamination has been repeatedly correlated with male subfertility in mice and humans. Apart from defects in DNA condensation and impaired DNA integrity, protamine-deficient human and murine sperm show multiple secondary defects, which cannot be explained by the chromosomal function of protamines. These include impaired sperm motility, decreased viability as well as acrsosomal malformations. In this study, we utilized a Prm2-deficient mouse model to investigate the underlying molecular mechanisms of these defects. Since trancription is silenced upon incorporation of protamines, we used LC-MS in combination with label-free quantification to compare the sperm proteome of Prm2-deficient (Prm2-/-) males with the proteome of wildtype (Prm2+/+) and Prm2 heterozygous (Prm2+/-) males. We show that Prm2 deficient mice display a strongly altered proteomic profile compared to controls. Of note, a significant downregulation of proteins SOD1 and PRDX5, which have a well-known function for the detoxification of reactive oxygen species was observed. Thus, together with a series of additional experiments, we could for the first time show that Prm2-deficiency triggers a reactive oxygen species (ROS) mediated sperm destruction cascade during epididymal sperm maturation, finally causing described secondary sperm defects.
Project description:Histone ubiquitination has been suggested to serve as a “tag” for nucleosome removal during histone-to-protamine exchange that is essential for chromatin packaging in round spermatids. Here, we screen for putative E3 ligase and identify that the PHF7, containing both RING finger and PHD domains, is critical for H2A ubiquitination and histone removal. Mechanistically, its PHD domain as a histone code reader can specifically bind H3K4me3/me2 and its RING domain as a histone writer can ubiquinate H2A. PHF7 deficiency results in male infertility in mice by generating Phf7 knockout mice using CRISPR-Cas9 technology. Futhermore, we find impaired histone-to-protamine exchange leads to reduced chromatin compaction in Phf7 knockout sperm. Immunostaining and western blot further confirme abnormal retention of core histones and reduced levels of protamine PRM1 and PRM2 in Phf7 knockout sperm. In order to exclude the possibility that Phf7 regulate the expession of protamine, we sorte the round spermatids from WT and Phf7 knockout females for RNA-seq. The transcriptomes in round spermatids are very similar between WT and Phf7 knockout mice. There are few differentially expressed genes in the two groups and the expression of protamine is also unchanged even if PHF7 deficiency. Therefore we find PHF7 has no effects on gene regulation in histone-to-protamine exchange.
Project description:Protamines are the safeguards of the paternal sperm genome. They replace most of the histones during spermiogenesis, resulting in DNA hypercondensation, thereby protecting its genome from environmental noxa. Impaired protamination has been linked to male infertility in mice and humans in many studies. Apart from impaired DNA integrity, protamine-deficient human and murine sperm show multiple secondary effects, including decreased motility and aberrant head morphology. In this study, we use a Prm2-deficient mouse model in combination with label-free quantitative proteomics to decipher the underlying molecular processes of these effects. We show that loss of the sperm`s antioxidant capacity, indicated by downregulation of key proteins like SOD1 and PRDX5, ultimately initiates an oxidative stress-mediated destruction cascade during epididymal sperm maturation. This is confirmed by an increased level of 8-OHdG in epididymal sperm, a biomarker for oxidative stress-mediated DNA damage. Prm2-deficient testicular sperm are not affected and initiate the proper development of blastocyst stage preimplantation embryos in vitro upon intracytoplasmic sperm injection (ICSI) into oocytes. Our results provide new insight into the role of Prm2 and its downstream molecular effects on sperm function and present an important contribution to the investigation of new treatment regimens for infertile men with impaired protamination.
Project description:Conventional dogma presumes that protamine-mediated DNA compaction in sperm is achieved by electrostatic interactions between DNA and the arginine-rich core of protamines. However, phylogenetic analysis reveals several non-arginine residues conserved within, but not across species. The significance of these residues or post-translational modifications are poorly understood. Here, we investigated the functional role of K49, a rodent-specific lysine residue in mouse protamine 1 (P1) that is acetylated early in spermiogenesis and retained in sperm. In vivo, alanine substitution (P1 K49A) results in loss of programmatic histone retention, decreased sperm motility, decreased male fertility, and in zygotes, premature P1 removal from paternal chromatin, altered DNA replication, and embryonic arrest. In vitro, P1 K49A decreases protamine-DNA binding and alters DNA compaction/decompaction kinetics. Hence, a single amino acid substitution outside the P1 arginine core is sufficient to profoundly alter protein function and developmental outcomes, suggesting that protamine non-arginine residues are essential for reproductive fitness.
Project description:Conventional dogma presumes that protamine-mediated DNA compaction in sperm is achieved by electrostatic interactions between DNA and the arginine-rich core of protamines. However, phylogenetic analysis reveals several non-arginine residues conserved within, but not across species. The significance of these residues or post-translational modifications are poorly understood. Here, we investigated the functional role of K49, a rodent-specific lysine residue in mouse protamine 1 (P1) that is acetylated early in spermiogenesis and retained in sperm. In vivo, alanine substitution (P1 K49A) results in loss of programmatic histone retention, decreased sperm motility, decreased male fertility, and in zygotes, premature P1 removal from paternal chromatin, altered DNA replication, and embryonic arrest. In vitro, P1 K49A decreases protamine-DNA binding and alters DNA compaction/decompaction kinetics. Hence, a single amino acid substitution outside the P1 arginine core is sufficient to profoundly alter protein function and developmental outcomes, suggesting that protamine non-arginine residues are essential for reproductive fitness.
Project description:Conventional dogma presumes that protamine-mediated DNA compaction in sperm is achieved by electrostatic interactions between DNA and the arginine-rich core of protamines. However, phylogenetic analysis reveals several non-arginine residues conserved within, but not across species. The significance of these residues or post-translational modifications are poorly understood. Here, we investigated the functional role of K49, a rodent-specific lysine residue in mouse protamine 1 (P1) that is acetylated early in spermiogenesis and retained in sperm. In vivo, alanine substitution (P1 K49A) results in loss of programmatic histone retention, decreased sperm motility, decreased male fertility, and in zygotes, premature P1 removal from paternal chromatin, altered DNA replication, and embryonic arrest. In vitro, P1 K49A decreases protamine-DNA binding and alters DNA compaction/decompaction kinetics. Hence, a single amino acid substitution outside the P1 arginine core is sufficient to profoundly alter protein function and developmental outcomes, suggesting that protamine non-arginine residues are essential for reproductive fitness.
Project description:DNA methyltransferases (DNMT) and histone deacetylases (HDAC) inhibitors are used as cancer epigenome drugs. However, these epigenetic drugs lack targeting specificity and could risk inducing genome instability and the expression of oncogenes. Therefore, there is a need to develop new therapeutic strategies where specific cancer genes can be targeted for silencing or activation. The CRISPR-dCas9 system represents a promising powerful therapeutic tool because of its simplicity and specificity. Protamine 1 (PRM1) is exclusively expressed in sperm and has a vital role in the tight packaging of DNA, thus inducing transcriptional silencing in sperm cells. We hypothesized that the activation of the PRM1 gene in tumorigenic cells would lead to DNA condensation and reduce the proliferation of these cells. We transfected human embryonic kidney cells 293T with a dCas9-P300 plasmid that adds acetyl groups to the promoter region of PRM1. RNA-Seq analysis of transfected cells revealed high specificity of targeted gene activation. PRM1 expression resulted in a significant decrease in cell proliferation as measured by the BrdU ELISA assay. To confirm that the activation of PRM1 was due to acetyl groups deposited to H3K27, a ChIP-qPCR was performed. The acetylation of the PRM1 promoter region targetted by dCa9-p300 in transfected cells was higher than that of the control cells. Interestingly, the targeted promoter region for acetylation showed reduced DNA methylation. These findings demonstrate the efficacy of epigenome editing in activating PRM1 in non-expressing tumorigenic cells, which can be used as a promising therapeutic strategy in cancer treatment.
Project description:Loss of Prm1 leads to defective chromatin protamination, impaired PRM2 processing, reduced sperm motility and subfertility in male mice [PRM1]
Project description:The wild-type p53-induced phosphatase 1 (WIP1) frustrated mice exhibited defects in reproductive organs. This study aimed to understand how Wip1 deficiency affects the spermatogenesis or maturation. We employed the Wip1-/- mouse model and conducted a gel-free iTRAQ LC-MS/MS based quantitative proteomics analysis of whole epididymis including the sperms and somatic tissue. A total of 8763 proteins were identified, of which 91 were significantly differentially expressed proteins (DEPs) in the Wip1 depleted mice. Four DEPs (PRM2, ODF1, PIWIL1 and KLHL10) were confirmed with western blotting. The DEPs enriched in biological process of reproduction were identified by GO analysis and further confirmed in the mouse phenotype database. Pathway analysis suggested that Smac/Diablo-mediated apoptosis pathway and SERPINA3-mediated inflammatory process might contribute to the atrophy and the marked sperm decrease in epididymis. Network analysis of productivity related DEPs revealed possible interactions that WIP1 might affect the sperm maturation by decreasing the outer dense fiber protein 1 (ODF1) and protamine-2 (PRM2), and increasing the PIWIL1/MIWI through p53. PRM2 was down-regulated and PIWIL1 was up-regulated by immunohistochemistry staining. It was further confirmed that the spermatid deficiency began from the testis observed by HE staining. Therefore, WIP1 disruption caused the deficiency of spermatogenesis potentially through regulating the expression of the above DEPs and pathways.