PolyADP-ribosylation is required for pronuclear fusion during postfertilization in mice

A Molecular Perspective and Role of NAD+ in Ovarian Aging

The decline in female fecundity is linked to advancing chronological age. The ovarian reserve diminishes in quantity and quality as women age, impacting reproductive efficiency and the aging process in the rest of the body. NAD+ is an essential coenzyme in cellular energy production, metabolism, cell signaling, and survival. It is involved in aging and is linked to various age-related conditions. Hallmarks associated with aging, diseases, and metabolic dysfunctions can significantly affect fertility by disturbing the delicate relationship between energy metabolism and female reproduction. Enzymes such as sirtuins, PARPs, and CD38 play essential roles in NAD+ biology, which actively consume NAD+ in their enzymatic activities. In recent years, NAD+ has gained much attention for its role in aging and age-related diseases like cancer, Alzheimer's, cardiovascular diseases, and neurodegenerative disorders, highlighting its involvement in various pathophysiological processes. However, its impact on female reproduction is not well understood. This review aims to bridge this knowledge gap by comprehensively exploring the complex interplay between NAD+ biology and female reproductive aging and providing valuable information that could help develop plans to improve women's reproductive health and prevent fertility issues.

PARP12 is required to repress the replication of a Mac1 mutant coronavirus in a cell- and tissue-specific manner

ADP-ribosyltransferases (ARTs) mediate the transfer of ADP-ribose from NAD+ to protein or nucleic acid substrates. This modification can be removed by several different types of proteins, including macrodomains. Several ARTs, also known as PARPs, are stimulated by interferon indicating ADP-ribosylation is an important aspect of the innate immune response. All coronaviruses (CoVs) encode for a highly conserved macrodomain (Mac1) that is critical for CoVs to replicate and cause disease, indicating that ADP-ribosylation can effectively control coronavirus infection. Our siRNA screen indicated that PARP12 might inhibit the replication of a murine hepatitis virus (MHV) Mac1 mutant virus in bone-marrow-derived macrophages (BMDMs). To conclusively demonstrate that PARP12 is a key mediator of the antiviral response to CoVs both in cell culture and in vivo, we produced PARP12-/-mice and tested the ability of MHV A59 (hepatotropic/neurotropic) and JHM (neurotropic) Mac1 mutant viruses to replicate and cause disease in these mice. Notably, in the absence of PARP12, Mac1 mutant replication was increased in BMDMs and mice. In addition, liver pathology was also increased in A59-infected mice. However, the PARP12 knockout did not restore Mac1 mutant virus replication to WT virus levels in all cell or tissue types and did not significantly increase the lethality of Mac1 mutant viruses. These results demonstrate that while PARP12 inhibits MHV Mac1 mutant virus infection, additional PARPs or innate immune factors must contribute to the extreme attenuation of this virus in mice. IMPORTANCE Over the last decade, the importance of ADP-ribosyltransferases (ARTs), also known as PARPs, in the antiviral response has gained increased significance as several were shown to either restrict virus replication or impact innate immune responses. However, there are few studies showing ART-mediated inhibition of virus replication or pathogenesis in animal models. We found that the CoV macrodomain (Mac1) was required to prevent ART-mediated inhibition of virus replication in cell culture. Using knockout mice, we found that PARP12, an interferon-stimulated ART, was required to repress the replication of a Mac1 mutant CoV both in cell culture and in mice, demonstrating that PARP12 represses coronavirus replication. However, the deletion of PARP12 did not fully rescue Mac1 mutant virus replication or pathogenesis, indicating that multiple PARPs function to counter coronavirus infection.

PARP12 is required to repress the replication of a Mac1 mutant coronavirus in a cell and tissue specific manner

ADP-ribosyltransferases (ARTs) mediate the transfer of ADP-ribose from NAD + to protein or nucleic acid substrates. This modification can be removed by several different types of proteins, including macrodomains. Several ARTs, also known as PARPs, are stimulated by interferon, indicating ADP-ribosylation is an important aspect of the innate immune response. All coronaviruses (CoVs) encode for a highly conserved macrodomain (Mac1) that is critical for CoVs to replicate and cause disease, indicating that ADP-ribosylation can effectively control coronavirus infection. Our siRNA screen indicated that PARP12 might inhibit the replication of a MHV Mac1 mutant virus in bone-marrow derived macrophages (BMDMs). To conclusively demonstrate that PARP12 is a key mediator of the antiviral response to CoVs both in cell culture and in vivo , we produced PARP12 -/- mice and tested the ability of MHV A59 (hepatotropic/neurotropic) and JHM (neurotropic) Mac1 mutant viruses to replicate and cause disease in these mice. Notably, in the absence of PARP12, Mac1 mutant replication was increased in BMDMs and in mice. In addition, liver pathology was also increased in A59 infected mice. However, the PARP12 knockout did not restore Mac1 mutant virus replication to WT virus levels in all cell or tissue types and did not significantly increase the lethality of Mac1 mutant viruses. These results demonstrate that while PARP12 inhibits MHV Mac1 mutant virus infection, additional PARPs or innate immune factors must contribute to the extreme attenuation of this virus in mice.

IMPORTANCE

Over the last decade, the importance of ADP-ribosyltransferases (ARTs), also known as PARPs, in the antiviral response has gained increased significance as several were shown to either restrict virus replication or impact innate immune responses. However, there are few studies showing ART-mediated inhibition of virus replication or pathogenesis in animal models. We found that the CoV macrodomain (Mac1) was required to prevent ART-mediated inhibition of virus replication in cell culture. Here, using knockout mice, we found that PARP12, an interferon-stimulated ART, was required to repress the replication of a Mac1 mutant CoV both in cell culture and in mice, demonstrating that PARP12 represses coronavirus replication. However, the deletion of PARP12 did not fully rescue Mac1 mutant virus replication or pathogenesis, indicating that multiple PARPs function to counter coronavirus infection.

NAD+, Sirtuins and PARPs: enhancing oocyte developmental competence

Oocyte quality is the limiting factor in female fertility. It is well known that maternal nutrition plays a role in reproductive function, and manipulating nutrition to improve fertility in livestock has been common practice in the past, particularly with respect to negative energy balance in cattle. A deficiency in nicotinamide adenine dinucleotide (NAD⁺) production has been associated with increased incidences of miscarriage and congenital defects in humans and mice, while elevating NAD⁺ through dietary supplements in aged subjects improved oocyte quality and embryo development. NAD⁺ is consumed by Sirtuins and poly-ADP-ribose polymerases (PARPs) within the cell and thus need constant replenishment in order to maintain various cellular functions. Sirtuins and PARPs play important roles in oocyte maturation and embryo development, and their activation may prove beneficial to in vitro embryo production and livestock breeding programs. This review examines the roles of NAD⁺, Sirtuins and PARPs in aspects of fertility, providing insights into the potential use of NAD⁺-elevating treatments in livestock breeding and embryo production programs.

Protective Effect of Minocycline Hydrochloride on the Mouse Embryonic Development Against Suboptimal Environment

Numerous studies have reported how inner cell mass (ICM) and trophectoderm (TE) was determined during the process of early mouse embryonic development from zygotes into organized blastocysts, however, multiple mysteries still remain. It is noteworthy that pluripotent stem cells (PSCs), which are derived from embryos at different developmental stages, have identical developmental potential and molecular characteristics to their counterpart embryos. Advances of PSCs research may provide us a distinctive perspective of deciphering embryonic development mechanism. Minocycline hydrochloride (MiH), a critical component for maintaining medium of novel type of extended pluripotent stem cells, which possesses developmental potential similar to both ICM and TE, can be substituted with genetic disruption of Parp1 in our previous study. Though Parp1-deficient mouse ESCs are more susceptible to differentiate into trophoblast derivatives, what role of MiH plays in mouse preimplantation embryonic development is still a subject of concern. Here, by incubating mouse zygotes in a medium containing MiH till 100 h after fertilization, we found that MiH could slow down embryonic developmental kinetics during cleavage stage without impairing blastocyst formation potential. Olaparib and Talazoparib, two FDA approved PARP1 inhibitors, exhibited similar effects on mouse embryos, indicating the aforementioned effects of MiH were through inhibiting of PARP1. Besides, we showed an embryonic protective role of MiH against suboptimal environment including long term exposure to external environment and H2O2 treatment, which could mimic inevitable manipulation during embryo culture procedures in clinical IVF laboratory. To our knowledge, it is not only for the first time to study MiH in the field of embryo development, but also for the first time to propose MiH as a protective supplement for embryo culture, giving the way to more studies on exploring the multiple molecular mechanisms on embryonic development that might be useful in assisted reproductive technology.

Post-Translational Modifications in Oocyte Maturation and Embryo Development

Mammalian oocyte maturation and embryo development are unique biological processes regulated by various modifications. Since de novo mRNA transcription is absent during oocyte meiosis, protein-level regulation, especially post-translational modification (PTM), is crucial. It is known that PTM plays key roles in diverse cellular events such as DNA damage response, chromosome condensation, and cytoskeletal organization during oocyte maturation and embryo development. However, most previous reviews on PTM in oocytes and embryos have only focused on studies of Xenopus laevis or Caenorhabditis elegans eggs. In this review, we will discuss the latest discoveries regarding PTM in mammalian oocytes maturation and embryo development, focusing on phosphorylation, ubiquitination, SUMOylation and Poly(ADP-ribosyl)ation (PARylation). Phosphorylation functions in chromosome condensation and spindle alignment by regulating histone H3, mitogen-activated protein kinases, and some other pathways during mammalian oocyte maturation. Ubiquitination is a three-step enzymatic cascade that facilitates the degradation of proteins, and numerous E3 ubiquitin ligases are involved in modifying substrates and thus regulating oocyte maturation, oocyte-sperm binding, and early embryo development. Through the reversible addition and removal of SUMO (small ubiquitin-related modifier) on lysine residues, SUMOylation affects the cell cycle and DNA damage response in oocytes. As an emerging PTM, PARlation has been shown to not only participate in DNA damage repair, but also mediate asymmetric division of oocyte meiosis. Each of these PTMs and external environments is versatile and contributes to distinct phases during oocyte maturation and embryo development.

Poly (ADP-ribose) polymerase inhibitor exposure reduces ovarian reserve followed by dysfunction in granulosa cells

The use of poly (ADP-ribose) polymerase (PARP) inhibitors is expected to increase, but their effect on fertility is still unclear. The aim of this study was to investigate the effect of PARP inhibitors on ovarian function. In an in vitro study, cultures of ovaries and granulosa cells (GCs) exposed to the PARP inhibitor olaparib were evaluated by real-time RT-PCR, histological study, and hormone assays. In an in vivo study, mice were administered olaparib orally and evaluated via in vitro fertilization (IVF), follicle count, immunohistochemical staining, and real-time RT-PCR. In vitro, the gene expression of GC markers decreased in the olaparib-treated group. Olaparib also negatively affected estradiol production and the expression of GC markers in cultured GCs, with abnormal morphology of GCs observed in the treated group. The follicle number indicated depletion of follicles due to atretic changes in the treatment group, both in vitro and in vivo. Also, olaparib reduced the number of retrieved oocytes and the fertilization rate of IVF, but they recovered after 3 weeks of cessation. Our results indicate that olaparib is toxic to ovaries.

Features of DNA Repair in the Early Stages of Mammalian Embryonic Development

Cell repair machinery is responsible for protecting the genome from endogenous and exogenous effects that induce DNA damage. Mutations that occur in somatic cells lead to dysfunction in certain tissues or organs, while a violation of genomic integrity during the embryonic period often leads to death. A mammalian embryo’s ability to respond to damaged DNA and repair it, as well as its sensitivity to specific lesions, is still not well understood. In this review, we combine disparate data on repair processes in the early stages of preimplantation development in mammalian embryos.

The effect of poly(ADP-ribosyl)ation inhibition on the porcine cumulus-oocyte complex during in vitro maturation

Poly(ADP-ribosyl)ation (PARylation) plays important roles in DNA repair, apoptosis, transcriptional regulation, and cell death, and occurs via the activity of poly(ADP-ribose) polymerases (PARPs). Previous studies have shown that PARylation affects mouse and porcine pre-implantation development and participates in mechanisms of autophagy. However, there have not yet been reported the role of PARylation during in vitro maturation (IVM) of porcine oocytes. Thus, we investigated the effect of PARylation inhibition on this process; cumulus-oocyte complexes (COCs) were cultured with 3-aminobenzamide (3-ABA, PARP inhibitor) during porcine IVM. Full cumulus expansion was significantly reduced (10.34 ± 1.23 [3-ABA] vs. 48.17 ± 2.03% [control]), but nuclear maturation rates were not changed in the 3-ABA treatment group. Especially, we observed that cumulus cells were little expanded after 22 h in 3-ABA treated COCs. The mRNA expression levels of oocyte maturation- and cumulus expansion-related genes were evaluated at 22 and 44 h. GDF9, BMP15, COX-2, and PTX3 expression were upregulated at 44 h, whereas the levels of HAS2 and TNFAIP6 were downregulated in the 3-ABA treated group. Furthermore, 3-ABA treatment significantly decreased the developmental rate (28.24 ± 1.06 vs. 40.24 ± 3.03%) and total cell number (41.12 ± 2.10 vs. 50.38 ± 2.27), but increased the total apoptotic index (6.44 ± 0.81 vs. 3.08 ± 0.51) in parthenogenetically activated embryos. In conclusion, these results showed that PARylation regulates cumulus expansion through the regulation of gene expression and affects developmental competence and quality in parthenogenetic embryos.

Microinjection free delivery of miRNA inhibitor into zygotes

The development of gene delivery systems into embryos is challenging due to technical difficulties, delivery efficiency and toxicity. Here, we developed an organic compound (VisuFect)-mediated gene delivery system for zygotes. The VisuFect, which is hydrophilic and Cy5.5-labeled, was conjugated with poly(A) oligo (VFA). The VFA into CHO cells showed clathrin-mediated internalization and no toxicity. The VFA successfully penetrated through the zona pellucida of fertilized eggs of various species including pigs, zebrafish, drosophilas and mice. The experiment with VisuFect-mediated delivery of the miR34c inhibitor showed similar results with direct microinjection of the miR34c inhibitor by suppressing the development of zygotes up to the blastocyst stage. Noticeable features of the VisuFect will provide great benefits for further studies on gene function in sperms and embryos.

Poly(ADP-ribosylation) regulates chromatin organization through histone H3 modification and DNA methylation of the first cell cycle of mouse embryos

We examined the roles of poly(ADP-ribosylation) in chromatin remodeling during the first cell cycle of mouse embryos. Drug-based inhibition of poly(ADP-ribosylation) by a PARP inhibitor, PJ-34, revealed up-regulation of dimethylation of histone H3 at lysine 4 in male pronuclei and down-regulation of dimethylation of histone H3 at lysine 9 (H3K9) and lysine 27 (H3K27). Association of poly(ADP-ribosylation) with histone modification was suggested to be supported by the interaction of Suz12, a histone methyltransferase in the polycomb complex, with Parp1. PARP activity was suggested to be required for a proper localization and maintenance of Suz12 on chromosomes. Notably, DNA methylation level of female pronuclei in one-cell embryos was robustly decreased by PJ-34. Electron microscopic analysis showed a frequent appearance of unusual electron-dense areas within the female pronuclei, implying the disorganized and hypercondensed chromatin ultrastructure. These results show that poly(ADP-ribosylation) is important for the integrity of non-equivalent epigenetic dynamics of pronuclei during the first cell cycle of mouse embryos.

The activation of DNA damage detection and repair responses in cleavage-stage rat embryos by a damaged paternal genome

Male germ cell DNA damage, after exposure to radiation, exogenous chemicals, or chemotherapeutic agents, is a major cause of male infertility. DNA-damaged spermatozoa can fertilize oocytes; this is of concern because there is limited information on the capacity of early embryos to repair a damaged male genome or on the fate of these embryos if repair is inadequate. We hypothesized that the early activation of DNA damage response in the early embryo is a critical determinant of its fate. The objective of this study was to assess the DNA damage response and mitochondrial function as a measure of the energy supply for DNA repair and general health in cleavage-stage embryos sired by males chronically exposed to an anticancer alkylating agent, cyclophosphamide. Male rats were treated with saline or cyclophosphamide (6 mg/kg/day) for 4 weeks and mated to naturally cycling females. Pronuclear two- and eight-cell embryos were collected for immunofluorescence analysis of mitochondrial function and biomarkers of the DNA damage response: γH2AX foci, 53BP1 reactivity, and poly(ADP-ribose) polymer formation. Mitochondrial activities did not differ between embryos sired by control- and cyclophosphamide-exposed males. At the two-cell stage, there was no treatment-related increase in DNA double-strand breaks; by the eight-cell stage, a significant increase was noted, as indicated by increased medium and large γH2AX foci. This was accompanied by a dampened DNA repair response, detected as a decrease in the nuclear intensity of poly(ADP-ribose) polymers. The micronuclei formed in cyclophosphamide-sired embryos contained large γH2AX foci and enhanced poly(ADP-ribose) polymer and 53BP1 reactivity compared with their nuclear counterparts. Thus, paternal cyclophosphamide exposure activated a DNA damage response in cleavage-stage embryos. Furthermore, this damage response may be useful in assessing embryo quality and developmental competence.

Role of poly(ADP-ribose) glycohydrolase in the regulation of cell fate in response to benzo(a)pyrene

Poly(ADP-ribosyl)ation is a crucial regulator of cell fate in response to genotoxic stress. Poly(ADP-ribosyl)ation plays important roles in multiple cellular processes, including DNA repair, chromosomal stability, chromatin function, apoptosis, and transcriptional regulation. Poly(ADP-ribose) (PAR) degradation is carried out mainly by poly(ADP-ribose) glycohydrolase (PARG) enzymes. Benzo(a)pyrene (BaP) is a known human carcinogen. Previous studies in our laboratory demonstrated that exposure to BaP caused a concentration-dependent DNA damage in human bronchial epithelial (16HBE) cells. The role of PARG in the regulation of DNA damage induced by BaP is still unclear. To gain insight into the function of PARG and PAR in response to BaP, we used lentiviral gene silencing to generate 16HBE cell lines with stably suppressed PARG, and determined parameters of cell death and cell cycle following BaP exposure. We found that PARG was partially dependent on PAR synthesis, PARG depletion led to PAR accumulation. BaP-induced cell death was regulated by PARG, the absence of which was beneficial for undamaged cells. Our results further suggested that PARG probably has influence on ATM/p53 pathway and metabolic activation of BaP. Experimental evidences provided from this study suggest significant preventive properties of PAR accumulation in the toxicity caused by BaP.