SNAP23 is required for constitutive and regulated exocytosis in mouse oocytes†

The light chain of tetanus toxin bound to arginine-rich cell-penetrating peptide inhibits cortical reaction in mouse oocytes

Introduction: Cortical reaction is a secretory process that occurs after a spermatozoon fuses with the oocyte, avoiding the fusion of additional sperm. During this exocytic event, the cortical granule membrane fuses with the oocyte plasma membrane. We have identified several molecular components involved in this process and confirmed that SNARE proteins regulate membrane fusion during cortical reaction in mouse oocytes. In those studies, we microinjected different nonpermeable reagents to demonstrate the participation of a specific protein in the cortical reaction. However, the microinjection technique has several limitations. In this work, we aimed to assess the potential of cell-penetrating peptides (CPP) as biotechnological tools for delivering molecules into oocytes, and to evaluate the functionality of the permeable tetanus toxin (bound to CPP sequence) during cortical reaction. Methods: Arginine-rich cell-penetrating peptides have demonstrated the optimal internalization of small molecules in mammalian cells. Two arginine-rich CPP were used in the present study. One, labeled with 5-carboxyfluorescein, to characterize the factors that can modulate its internalization, and the other, the permeable light chain of tetanus toxin, that cleaves the SNAREs VAMP1 and VAMP3 expressed in mouse oocytes. Results: Results showed that fluorescent CPP was internalized into the oocyte cytoplasm and that internalization was dependent on the concentration, time, temperature, and maturation stage of the oocyte. Using our functional assay to study cortical reaction, the light chain of tetanus toxin bound to arginine-rich cell-penetrating peptide inhibited cortical granules exocytosis. Discussion: Results obtained from the use of permeable peptides demonstrate that this CPP is a promising biotechnological tool to study functional macromolecules in mouse oocytes.

Intracellular fraction of zona pellucida protein 3 is required for the oocyte-to-embryo transition in mice

In oocyte biology, the zona pellucida has long been known to operate three extracellular functions downstream of the secretory pathway, namely, encasing the oocytes in ovarian follicles, mediating sperm-oocyte interaction, and preventing premature embryo contact with oviductal epithelium. The present study uncovers a fourth function that is fundamentally distinct from the other three, being critical for embryonic cell survival in mice. Intriguingly, the three proteins of the mouse zona pellucida (ZP1, ZP2, ZP3) were found abundantly present also inside the embryo 4 days after fertilization, as shown by mass spectrometry, immunoblotting, and immunofluorescence. Contrary to current understanding of the roles of ZP proteins, ZP3 was associated more with the cytoskeleton than with secretory vesicles in the subcortical region of metaphase II oocytes and zygotes, and was excluded from regions of cell-cell contact in cleavage-stage embryos. Trim-away-mediated knockdown of ZP3 in fertilized oocytes hampered the first zygotic cleavage, while ZP3 overexpression supported blastocyst formation. Transcriptome analysis of ZP3-knockdown embryos pointed at defects of cytoplasmic translation in the context of embryonic genome activation. This conclusion was supported by reduced protein synthesis in the ZP3-knockdown and by the lack of cleavage arrest when Trim-away was postponed from the one-cell to the late two-cell stage. These data place constraints on the notion that zona proteins only operate in the extracellular space, revealing also a role during the oocyte-to-embryo transition. Ultimately, these data recruit ZP3 into the family of maternal factors that contribute to developmental competence of mouse oocytes.

Puberty Suppression Followed by Testosterone Therapy Does Not Impair Reproductive Potential in Female Mice

More adolescents are coming out as transgender each year and are put on puberty blockers to suppress natal puberty, which is then followed by cross-hormone treatment to achieve puberty of the desired gender. Studies to examine the effects of puberty suppression and virilizing therapy on future reproductive potential among transgender males are lacking. This study used a translational murine in vitro fertilization model to examine the effects of female puberty suppression with depot leuprolide acetate (LA), followed by virilizing therapy with testosterone cypionate (T), on embryologic and pregnancy outcomes. LA effectively inhibited puberty when mice were treated beginning at 3 weeks of age. LA treatment was associated with higher mouse weight but lower ovarian weight. LA-treated mice ovulated developmentally competent eggs in response to gonadotropin administration, albeit at a higher dose than controls. Ovaries from mice treated with LA and T produced oocytes that had morphologically normal meiotic spindles after in vitro maturation and responded to gonadotropin stimulation. Eggs from mice treated with LA and T were fertilizable and produced developmentally competent embryos that led to births of fertile pups. These results suggest that fertility may not be impaired after puberty suppression and cross-hormone therapy for transgender males.

Beyond canonical PROTAC: biological targeted protein degradation (bioTPD)

Targeted protein degradation (TPD) is an emerging therapeutic strategy with the potential to modulate disease-associated proteins that have previously been considered undruggable, by employing the host destruction machinery. The exploration and discovery of cellular degradation pathways, including but not limited to proteasomes and lysosome pathways as well as their degraders, is an area of active research. Since the concept of proteolysis-targeting chimeras (PROTACs) was introduced in 2001, the paradigm of TPD has been greatly expanded and moved from academia to industry for clinical translation, with small-molecule TPD being particularly represented. As an indispensable part of TPD, biological TPD (bioTPD) technologies including peptide-, fusion protein-, antibody-, nucleic acid-based bioTPD and others have also emerged and undergone significant advancement in recent years, demonstrating unique and promising activities beyond those of conventional small-molecule TPD. In this review, we provide an overview of recent advances in bioTPD technologies, summarize their compositional features and potential applications, and briefly discuss their drawbacks. Moreover, we present some strategies to improve the delivery efficacy of bioTPD, addressing their challenges in further clinical development.

Actin limits egg aneuploidies associated with female reproductive aging

Aging-related centromeric cohesion loss underlies premature separation of sister chromatids and egg aneuploidy in reproductively older females. Here, we show that F-actin maintains chromatid association after cohesion deterioration in aged eggs. F-actin disruption in aged mouse eggs exacerbated untimely dissociation of sister chromatids, while its removal in young eggs induced extensive chromatid separation events generally only seen in advanced reproductive ages. In young eggs containing experimentally reduced cohesion, F-actin removal accelerated premature splitting and scattering of sister chromatids in a microtubule dynamics-dependent manner, suggesting that actin counteracts chromatid-pulling spindle forces. Consistently, F-actin stabilization restricted scattering of unpaired chromatids generated by complete degradation of centromeric cohesion proteins. We conclude that actin mitigates egg aneuploidies arising from age-related cohesion depletion by limiting microtubule-driven separation and dispersion of sister chromatids. This is supported by our finding that spindle-associated F-actin structures are disrupted in eggs of reproductively older females.

Targeted protein degradation by Trim-Away using cell resealing coupled with microscopic image-based quantitative analysis

"Trim-Away" technology enables rapid degradation of endogenous proteins without prior modification of protein-coding genes or mRNAs through delivery of antibodies that target proteins of interest. Although this approach can be readily applied to almost any cytosolic protein, strategies for cytosolic antibody delivery have been limited to microinjection or electroporation, which require skill-dependent operation or specialized equipment. Thus, the development of antibody delivery methods that are convenient, scalable, and preferably do not require detachment of adherent cells is required to extend the versatility of the Trim-Away method. Here, we developed a cell resealing technique optimized for Trim-Away degradation, which uses the pore-forming toxin streptolysin O (SLO) to permeabilize the cell membrane and delivered the antibodies of interest into HEK293T, HeLa, and HK-2 cell lines. We demonstrated the ability of Trim-Away protein degradation using IKKα and mTOR as targets, and we showed the availability of the developed system in antibody screening for the Trim-Away method. Furthermore, we effectively coupled Trim-Away with cyclic immunofluorescence and microscopic image-based analysis, which enables single-cell multiplexed imaging analysis. Taking advantage of this new analysis strategy, we were able to compensate for low signal-to-noise due to cell-to-cell variation, which occurs in the Trim-Away method because of the heterogenous contents of the introduced antibody, target protein, and TRIM21 in individual cells. Therefore, the reported cell resealing technique coupled with microscopic image analysis enables Trim-Away users to elucidate target protein function and the effects of target protein degradation on various cellular functions in a more quantitative and precise manner.

Targeted protein degradation in mammalian cells: A Promising Avenue toward Future

In the eukaryotic cellular milieu, proteins are continuously synthesized and degraded effectively via endogenous protein degradation machineries such as the ubiquitin–proteasome and lysosome pathways. By reengineering and repurposing these natural protein regulatory mechanisms, the targeted protein degradation (TPD) strategies are presenting biologists with powerful tools to manipulate the abundance of proteins of interest directly, precisely, and reversibly at the post-translational level. In recent years, TPD is gaining massive attention and is recognized as a paradigm shift both in basic research, application-oriented synthetic biology, and pioneering clinical work. In this review, we summarize the updated information, especially the engineering efforts and developmental route, of current state-of-the-art TPD technology such as Trim-Away, LYTACs, and AUTACs. Besides, the general design principle, benefits, problems, and opportunities to be addressed were further analyzed, with the aim of providing guidelines for exploration, discovery, and further application of novel TPD tools in the future.

Elevated RIF1 participates in the epigenetic abnormalities of zygotes by regulating histone modifications on MuERV-L in obese mice

BACKGROUND

Maternal obesity impairs embryonic developmental potential and significantly increases the risks of metabolic disorders in offspring. However, the epigenetic transmission mechanism of maternal metabolic abnormalities is still poorly understood.

METHODS

We established an obesity model in female mice by high-fat diet (HFD) feeding. The effects of the HFD on the developmental potential of oocytes and embryos, the metabolic phenotype, and epigenetic modifications were investigated. The efficacy of metformin administration was assessed. Finally, the regulatory pathway of epigenetic remodeling during zygotic genome activation (ZGA) was explored.

RESULTS

Maternal HFD consumption significantly impaired glucose tolerance and increased the risk of metabolic disorders in F0 and F1 mice. Maternal HFD consumption also decreased embryonic developmental potential, increased reactive oxygen species (ROS) and γH2AX levels, and reduced the mitochondrial membrane potential (MMP) within oocytes, causing high levels of oxidative stress damage and DNA damage. Starting with this clue, we observed significantly increased RIF1 levels and shortened telomeres in obese mice. Moreover, significant abnormal DNA methylation and histone modification remodeling were observed during ZGA in obese mice, which may be coregulated by RIF1 and the ZGA marker gene MuERV-L. Metformin treatment reduced RIF1 levels, and partially improved ZGA activation status by rescuing epigenetic modification remodeling in oocytes and preimplantation embryos of obese mice. RIF1 knockdown experiments employing Trim-Away methods showed that RIF1 degradation altered the H3K4me3 and H3K9me3 enrichment and then triggered the MuERV-L transcriptional activation. Moreover, ChIP-seq data analysis of RIF1 knockouts also showed that RIF1 mediates the transcriptional regulation of MuERV-L by changing the enrichment of H3K4me3 and H3K9me3 rather than by altered DNA methylation.

CONCLUSION

Elevated RIF1 in oocytes caused by maternal obesity may mediate abnormal embryonic epigenetic remodeling and increase metabolic risk in offspring by regulating histone modifications on MuERV-L, which can be partially rescued by metformin treatment.

Targeted protein degradation using intracellular antibodies and its application to neurodegenerative disease

Antibodies mediate the majority of their effects in the extracellular domain, or in intracellular compartments isolated from the cytosol. Under a growing list of circumstances, however, antibodies are found to gain access to the cytoplasm. Cytosolic immune complexes are bound by the atypical antibody receptor TRIM21, which mediates the rapid degradation of the immune complexes at the proteasome. These discoveries have informed the development of TRIM-Away, a technique to selectively deplete proteins using delivery of antibodies into cells. A range of related approaches that elicit selective protein degradation using intracellular constructs linking antibody fragments to degradative effector functions have also been developed. These methods hold promise for inducing the degradation of proteins as both research tools and as a novel therapeutic approach. Protein aggregates are a pathophysiological feature of neurodegenerative diseases and are considered to have a causal role in pathology. Immunotherapy is emerging as a promising route towards their selective targeting, and a role of antibodies in the cytosol has been demonstrated in cell-based assays. This review will explore the mechanisms by which therapeutic antibodies engage and eliminate intracellularly aggregated proteins. We will discuss how future developments in intracellular antibody technology may enhance the therapeutic potential of such antibody-derived therapies.

Knockin' on Egg's Door: Maternal Control of Egg Activation That Influences Cortical Granule Exocytosis in Animal Species

Fertilization by multiple sperm leads to lethal chromosomal number abnormalities, failed embryo development, and miscarriage. In some vertebrate and invertebrate eggs, the so-called cortical reaction contributes to their activation and prevents polyspermy during fertilization. This process involves biogenesis, redistribution, and subsequent accumulation of cortical granules (CGs) at the female gamete cortex during oogenesis. CGs are oocyte- and egg-specific secretory vesicles whose content is discharged during fertilization to block polyspermy. Here, we summarize the molecular mechanisms controlling critical aspects of CG biology prior to and after the gametes interaction. This allows to block polyspermy and provide protection to the developing embryo. We also examine how CGs form and are spatially redistributed during oogenesis. During egg activation, CG exocytosis (CGE) and content release are triggered by increases in intracellular calcium and relies on the function of maternally-loaded proteins. We also discuss how mutations in these factors impact CG dynamics, providing unprecedented models to investigate the genetic program executing fertilization. We further explore the phylogenetic distribution of maternal proteins and signaling pathways contributing to CGE and egg activation. We conclude that many important biological questions and genotype–phenotype relationships during fertilization remain unresolved, and therefore, novel molecular players of CG biology need to be discovered. Future functional and image-based studies are expected to elucidate the identity of genetic candidates and components of the molecular machinery involved in the egg activation. This, will open new therapeutic avenues for treating infertility in humans.

The COP9 signalosome subunit 3 is necessary for early embryo survival by way of a stable protein deposit in mouse oocytes

Investigations of genes required in early mammalian development are complicated by protein deposits of maternal products, which continue to operate after the gene locus has been disrupted. This leads to delayed phenotypic manifestations and underestimation of the number of genes known to be needed during the embryonic phase of cellular totipotency. Here we expose a critical role of the gene Cops3 by showing that it protects genome integrity during the 2-cell stage of mouse development, in contrast to the previous functional assignment at postimplantation. This new role is mediated by a substantial deposit of protein (94th percentile of the proteome), divided between an exceptionally stable cortical rim, which is prevalent in oocytes, and an ancillary deposit in the embryonic nuclei. Since protein abundance and stability defeat prospects of DNA- or RNA-based gene inactivation in oocytes, we harnessed a classical method next to an emerging method for protein inactivation: antigen masking (for functional inhibition) versus TRIM21-mediated proteasomal degradation, also known as 'Trim away' (for physical removal). Both resulted in 2-cell embryo lethality, unlike the embryos receiving anti-green fluorescent protein. Comparisons between COPS3 protein-targeted and non-targeted embryos revealed large-scale transcriptome differences, which were most evident for genes associated with biological functions critical for RNA metabolism and for the preservation of genome integrity. The gene expression abnormalities associated with COPS3 inactivation were confirmed in situ by the occurrence of DNA endoreduplication and DNA strand breaks in 2-cell embryos. These results recruit Cops3 to the small family of genes that are necessary for early embryo survival. Overall, assigning genes with roles in embryogenesis may be less safe than assumed, if the protein products of these genes accumulate in oocytes: the inactivation of a gene at the protein level can expose an earlier phenotype than that identified by genetic techniques such as conventional gene silencing.

Nanogel-facilitated Protein Intracellular Specific Degradation through Trim-Away

Recently discovered "Trim-Away" mechanism opens a new window for fast and selective degradation of endogenous proteins. However, the in vivo and clinical application of this approach is stuck by the requirement of special skills and equipment needed for the intracellular delivery of antibodies. Hereby, an antibody conjugated polymer nanogel system, Nano-ERASER, for intracellular delivery and release of antibody, and degradation of a specific endogenous protein has been developed. After being delivered into cells, the antibody is released and forms complex with its target protein, and subsequently binds to the Fc receptor of TRIM21. The resulted complex of target protein/antibody/TRIM21 is then degraded by the proteasome. The efficacy of Nano-ERASER has been validated by depleting GFP protein in a GFP expressing cell line. Furthermore, Nano-ERASER successfully degrades COPZ1, a vital protein for cancer cells, and kills those cells while sparing normal cells. Benefit from its convenience and targeted delivery merit, Nano-ERASER technique is promising in providing a reliable tool for endogenous protein function study as well as paves the way for novel antibody-based Trim-Away therapeutic modalities for cancer and other diseases.

VAMPs sensitive to tetanus toxin are required for cortical granule exocytosis in mouse oocytes

Fusion of cortical granules with oocyte plasma membrane is one of the most significant secretory events to prevent polyspermy during oocyte activation. Cortical granule exocytosis (CGE) is distinct from most other exocytosis because cortical granules are not renewed after secretion. However, it is thought to be mediated by SNARE complex, which mediates membrane fusion in other exocytoses. SNAREs proteins are divided into Q (glutamine)- and R (arginine)-SNAREs. Q-SNAREs include Syntaxins and SNAP25 family, and R-SNAREs include VAMPs family. In mouse oocytes, Syntaxin4 and SNAP23 have been involved in CGE; nevertheless, it is unknown if VAMP is required. Here, we demonstrated by RT-PCR and immunoblotting that VAMP1 and VAMP3 are expressed in mouse oocyte, and they localized in the cortical region of this cell. Using a functional assay to quantify CGE, we showed that tetanus toxin -which specifically cleavages VAMP1, VAMP2 or VAMP3- inhibited CGE suggesting that at least one VAMP was necessary. Function blocking assays demonstrated that only the microinjection of anti-VAMP1 or anti-VAMP3 antibodies abolished CGE in activated oocytes. These findings demonstrate that R-SNAREs sensitive to tetanus toxin, VAMP1 and VAMP3 -but not VAMP2-, are required for CGE and demonstrate that CGE is mediated by the SNARE complex.

SNAP23 is essential for platelet and mast cell development and required in connective tissue mast cells for anaphylaxis

Degranulation, a fundamental effector response from mast cells (MCs) and platelets, is an example of regulated exocytosis. This process is mediated by SNARE proteins and their regulators. We have previously shown that several of these proteins are essential for exocytosis in MCs and platelets. Here, we assessed the role of the SNARE protein SNAP23 using conditional knockout mice, in which SNAP23 was selectively deleted from either the megakaryocyte/platelet or connective tissue MC lineages. We found that removal of SNAP23 in platelets results in severe defects in degranulation of all three platelet secretory granule types, i.e., alpha, dense, and lysosomal granules. The mutation also induces thrombocytopenia, abnormal platelet morphology and activation, and reduction in the number of alpha granules. Therefore, the degranulation defect might not be secondary to an intrinsic failure of the machinery mediating regulated exocytosis in platelets. When we removed SNAP23 expression in MCs, there was a complete developmental failure in vitro and in vivo. The developmental defects in platelets and MCs and the abnormal translocation of membrane proteins to the surface of platelets indicate that SNAP23 is also involved in constitutive exocytosis in these cells. The MC conditional deletant animals lacked connective tissue MCs, but their mucosal MCs were normal and expanded in response to an antigenic stimulus. We used this mouse to show that connective tissue MCs are required and mucosal MCs are not sufficient for an anaphylactic response.

Short-term testosterone use in female mice does not impair fertilizability of eggs: implications for the fertility care of transgender males

STUDY QUESTION

Does testosterone use in females affect reproductive potential, particularly with regard to the production of fertilizable gametes?

SUMMARY ANSWER

Testosterone (T) injections given to post-pubertal female mice caused virilization and although the ovaries were smaller than controls they were still responsive and produced fertilizable eggs when superovulated.

WHAT IS KNOWN ALREADY

Studies to examine the effects of testosterone on reproductive potential in transgender males are lacking. Recently, a model was developed that simulates many aspects of testosterone use in transgender males in order to look at reproductive effects of testosterone in female mice. This study found masculinizing effects on the mice but did not find significant deficits on the number of ovarian follicles; however, effects of testosterone use on ovarian stimulation and fertilizability of oocytes were not investigated.

STUDY DESIGN, SIZE, DURATION

A total of 66, 6-week-old Hsd:NSA (CF-1) female mice and six Hsd:ICR (CD-1) male mice were used for this study. Mice were injected s.c. with 400 µg T or sesame oil once a week for 6 weeks and were either killed 1 week after the sixth injection (active exposure group), or 6-7 weeks after the final T injection (washout group).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Both active exposure and washout groups were further subdivided into three groups: unstimulated, equine CG (eCG)-stimulated or eCG/hCG-stimulated. eCG-stimulated mice were killed 44-48 h after eCG injection. eCG/hCG-stimulated mice were injected with eCG, followed 48 h later with hCG. Mice were killed ∼13-18 h after the hCG injection. Data collected included daily vaginal cytology, terminal testosterone levels, ovary weights and histology, number of oocytes/eggs collected in each group, and cleavage to the two-cell stage following IVF.

MAIN RESULTS AND THE ROLE OF CHANCE

Testosterone-treated mice had testosterone levels elevated to the level of male mice and ceased cycling. Ovaries were significantly smaller in testosterone-treated mice, but they contained normal cohorts of follicles and responded to gonadotrophin stimulation by ovulating similar numbers of eggs as controls, that fertilized and cleaved in vitro.

LIMITATIONS, REASONS FOR CAUTION

Mice were treated for only 6 weeks, whereas many transgender men use testosterone for many years before considering biological children, and developmental competence was not assessed. Importantly, a mouse system may not perfectly simulate human reproductive physiology.

WIDER IMPLICATIONS OF THE FINDINGS

The current standard of care for transgender men who desire biological children is to cease testosterone therapy prior to ovarian stimulation, but the necessity for stopping testosterone is not known. Our model demonstrates that it is possible for testosterone-suppressed ovaries to respond to gonadotrophic stimulation by producing and ovulating fertilizable eggs, thereby obviating the need for testosterone cessation prior to ovarian stimulation. In time, these results may provide insights for future clinical trials of fertility treatment options for transgender men.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Reproductive Endocrinology and Infertility fellowship program through UConn Health Graduate Medical Education (to C.B.B.). The authors have no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Pleiotropic effects of alpha-SNAP M105I mutation on oocyte biology: ultrastructural and cellular changes that adversely affect female fertility in mice

After sperm-oocyte fusion, cortical granules (CGs) located in oocyte cortex undergo exocytosis and their content is released into the perivitelline space to avoid polyspermy. Thus, cortical granule exocytosis (CGE) is a key process for fertilization success. We have demonstrated that alpha-SNAP -and its functional partner NSF- mediate fusion of CGs with the plasma membrane in mouse oocytes. Here, we examined at cellular and ultrastructural level oocytes from hyh (hydrocephalus with hop gait) mice, which present a missense mutation in the Napa gene that results in the substitution of methionine for isoleucine at position 105 (M105I) of alpha-SNAP. Mutated alpha-SNAP was mislocalized in hyh oocytes while NSF expression increased during oocyte maturation. Staining of CGs showed that 9.8% of hyh oocytes had abnormal localization of CGs and oval shape. Functional tests showed that CGE was impaired in hyh oocytes. Interestingly, in vitro fertilization assays showed a decreased fertilization rate for hyh oocytes. Furthermore, fertilized hyh oocytes presented an increased polyspermy rate compared to wild type ones. At ultrastructural level, hyh oocytes showed small mitochondria and a striking accumulation and secretion of degradative structures. Our findings demonstrate the negative effects of alpha-SNAP M105 mutation on oocyte biology and further confirm the relevance of alpha-SNAP in female fertility.

Loss of CENPF leads to developmental failure in mouse embryos

Aneuploidy caused by abnormal chromosome segregation during early embryo development leads to embryonic death or congenital malformation. Centromere protein F (CENPF) is a member of centromere protein family that regulates chromosome segregation during mitosis. However, its necessity in early embryo development has not been fully investigated. In this study, expression and function of CENPF was investigated in mouse early embryogenesis. Detection of CENPF expression and localization revealed a cytoplasm, spindle and nuclear membrane related dynamic pattern throughout mitotic progression. Farnesyltransferase inhibitor (FTI) was employed to inhibit CENPF farnesylation in zygotes. The results showed that CENPF degradation was inhibited and its specific localization on nuclear membranes in morula and blastocyst vanished after FTI treatment. Also, CAAX motif mutation leads to failure of CENPF-C630 localization in morula and blastocyst. These results indicate that farnesylation plays a key role during CENPF degradation and localization in early embryos. To further assess CENPF function in parthenogenetic or fertilized embryos development, morpholino (MO) and Trim-Away were used to disturb CENPF function. CENPF knockdown in Metaphase II (MII) oocytes, zygotes or embryos with MO approach resulted in failure to develop into morulae and blastocysts, revealing its indispensable role in both parthenogenetic and fertilized embryos. Disturbing of CENPF with Trim-Away approach in zygotes resulted in impaired development of 2-cell and 4-cell, but did not affect the morula and blastocyst formation because of the recovered expression of CENPF. Taken together, our data suggest CENPF plays an important role during early embryonic development in mice. Abbreviation: CENPF: centromere protein F; MO: morpholino; FTI: Farnesyltransferase inhibitor; CENPE: centromere protein E; IVF: in vitro fertilization; MII: metaphase II; SAC: spindle assembly checkpoint; Mad1: mitotic arrest deficient 1; BUB1: budding uninhibited by benzimidazole 1; BUBR1: BUB1 mitotic checkpoint serine/threonine kinase B; Cdc20: cell division cycle 20.

TRIM21-From Intracellular Immunity to Therapy

Tripartite motif containing-21 (TRIM21) is a cytosolic ubiquitin ligase and antibody receptor that provides a last line of defense against invading viruses. It does so by acting as a sensor that intercepts antibody-coated viruses that have evaded extracellular neutralization and breached the cell membrane. Upon engagement of the Fc of antibodies bound to viruses, TRIM21 triggers a coordinated effector and signaling response that prevents viral replication while at the same time inducing an anti-viral cellular state. This dual effector function is tightly regulated by auto-ubiquitination and phosphorylation. Therapeutically, TRIM21 has been shown to be detrimental in adenovirus based gene therapy, while it may be favorably utilized to prevent tau aggregation in neurodegenerative disorders. In addition, TRIM21 may synergize with the complement system to block viral replication as well as transgene expression. TRIM21 can also be utilized as a research tool to deplete specific proteins in cells and zebrafish embryos. Here, we review our current biological understanding of TRIM21 in light of its versatile functions.