Type 1 diabetes affects zona pellucida and genome methylation in oocytes and granulosa cells

Diabetes affects oocyte nuclear and cytoplasmic quality. In this study, we generated a type 1 diabetes (T1D) mouse model by STZ injection to study the effects of T1D on zona pellucida and genomic DNA methylation of oocytes and granulosa cells. T1D mice showed fewer ovulated oocytes, reduced ovarian reserve, disrupted estrus cycle, and significantly ruptured zona pellucida in 2-cell in vivo embryos compared to controls. Notably, diabetic oocytes displayed thinner zona pellucida and treatment of oocytes with high concentration glucose reduced the zona pellucida thickness. Differential methylation genes in oocytes and granulosa cells were analyzed by methylation sequencing. These genes were significantly enriched in GO terms by GO analysis, and these GO terms were involved in multiple aspects of growth and development. Most notably, the abnormal methylation genes in oocytes may be related to oocyte zona pellucida changes in diabetic mice. These findings provide novel basic data for further understanding and elucidating dysgenesis and epigenetic changes in type 1 diabetes mellitus.

Resveratrol delays postovulatory aging of mouse oocytes through activating mitophagy

Resveratrol (3,5,4'-trihydroxystilbene, RSV) is a natural potential anti-aging polyphenolic compound frequently used as a nutritional supplement against several diseases. However, the underlying mechanisms by which resveratrol regulates postovulatory aging of oocytes are still insufficiently known. In this study, we found that resveratrol could delay postovulatory aging and improve developmental competence of oocytes through activating selective mitophagy in the mouse. Resveratrol could maintain spindle morphology but it disturbed cortical granule (CG) distribution during oocyte aging. This might be due to upregulated mitophagy, since blocking mitophagy by cyclosporin A (CsA) treatment affected oocyte quality by damaging mitochondrial function and it decreased embryonic development. In addition, we also observed an involvement of FoxO3a in regulating mitophagy in aging oocytes following resveratrol treatment. Taken together, our results provide evidence that mitophagy induced by resveratrol is a potential mechanism to protect against postovulatory oocyte aging.

Protein phosphatase 6 is a key factor regulating spermatogenesis

Protein phosphatase 6 (PP6) is a member of the PP2A-like subfamily, which plays a critical role in many fundamental cellular processes. We recently reported that PP6 is essential for female fertility. Here, we report that PP6 is involved in meiotic recombination and that germ cell-specific deletion of PP6 by Stra8-Cre causes defective spermatogenesis. The PP6-deficient spermatocytes were arrested at the pachytene stage and defects in DSB repair and crossover formation were observed, indicating that PP6 facilitated meiotic double-stranded breaks (DSB) repair. Further investigations revealed that depletion of PP6 in the germ cells affected chromatin relaxation, which was dependent on MAPK pathway activity, consequently preventing programmed DSB repair factors from being recruited to proper positions on the chromatin. Taken together, our results demonstrate that PP6 has an important role in meiotic recombination and male fertility.

Deletion of Ck2β gene causes germ cell development arrest and azoospermia in male mice

Objectives

In humans, non‐obstructive azoospermia (NOA) is a major cause of male infertility. However, the aetiology of NOA is largely unknown. Previous studies reported that protein CK2β was abundantly and broadly expressed in spermatogenic cells. Here, we investigate whether protein CK2β participates in spermatogenesis.

Materials and Methods

In this study, we separated spermatogenic cells using STA‐PUT velocity sedimentation, analysed the expression pattern of protein CK2β by immunoblotting, specifically deleted Ck2β gene in early‐stage spermatogenic cells by crossing Ck2β^fl mice with Stra8‐Cre⁺ mice and validated the knockout efficiency by quantitative RT‐PCR and immunoblotting. The phenotypes of Ck2β^fl/Δ;SCre⁺ mice were studied by immunohistochemistry and immunofluorescence. The molecular mechanisms of male germ cell development arrest were elucidated by immunoblotting and TUNEL assay.

Results

Ablation of Ck2β gene triggered excessive germ cell apoptosis, germ cell development arrest, azoospermia and male infertility. Inactivation of Ck2β gene caused distinctly reduced expression of Ck2α′ gene and CK2α′ protein.

Conclusions

Ck2β is a vital gene for germ cell survival and male fertility in mice.

Resveratrol increases resistance of mouse oocytes to postovulatory aging in vivo

After ovulation, metaphase II oocytes undergo a time-dependent deterioration in vivo or in vitro, which is referred to as postovulatory oocyte aging, a process during which a series of deleterious molecular and cellular changes occur. In this study, we found that short-term injection of resveratrol (3,5,4'-trihydroxystilbene) effectively ameliorated oxidative stress-induced damage in postovulatory oocyte aging of middle-aged mice in vivo. Resveratrol induced changes that delayed the aging-induced oocyte deterioration including the elevated expression of the anti-aging molecule Sirtuin 1 (SIRT1); it reduced intracellular reactive oxygen species (ROS) level, and improved mitochondria function. In addition, these beneficial changes may also help to prevent apoptosis. Taken together, our data suggest that resveratrol can effectively protect against postovulatory oocyte aging in vivo primarily by preventing ROS production.

Immunodiagnostics and Immunotherapy Possibilities for Prostate Cancer

Despite significant progress in early detection and improved treatment modalities prostate cancer remains the second leading cause of cancer death in American men which results in about 30,000 deaths per year in the USA. An aggressive phenotype leading to 2.58% risk of dying from prostate cancer still exists and immunotherapy has offered new possibilities to treat metastatic prostate cancer that cannot be treated by other modalities. Cancer immunotherapy is a rapidly growing field of research aimed at identifying biomarkers in immunodiagnosis and to develop new therapies by enabling the immune system to detect and destroy cancer cells. Immunotherapy falls into three different broad categories which are checkpoint inhibitors, cytokines, and vaccine immunotherapy. While immunotherapy to treat prostate cancer is still limited progress has been made; for treatment of advanced prostate cancer sipuleucel-T has been administered to patients in personalized doses to destroy prostate cancer cells which is promising and invites further research to determine immunotherapies for advanced prostate cancer. Antibody-based targeted immunotherapy and dendritic-cell-based vaccination are among the therapies that are currently being evaluated as promising approaches to treat prostate cancer. Combination immunotherapies include prostate cancer vaccines and radiotherapy for castration resistant prostate cancer. Microbial vectors for prostate cancer immunotherapy have been developed and bacterial strains have been engineered to express cancer-specific antigens, cytokines, and prodrug-converting cytokines. These approaches are addressed in the present review.

Glucocorticoid exposure affects female fertility by exerting its effect on the uterus but not on the oocyte: lessons from a hypercortisolism mouse model

STUDY QUESTION

What is the impact of glucocorticoid (GC) on female reproduction?

SUMMARY ANSWER

Corticosterone (CORT) exposure causes little damage to oocyte quality or developmental competence but has an adverse effect on the uterus, which causes decreased implantation, embryo death and subsequent infertility.

WHAT IS KNOWN ALREADY

Chronic treatment with high GC doses is effective in controlling most allergic diseases but may lead to metabolic disorders such as obesity that are closely related with reproductive function.

STUDY DESIGN, SIZE, DURATION

Hypercortisolism was induced in a female mouse model by supplementing the drinking water with 100 μg/ml of CORT. Controls received vehicle (1% v/v ethanol) only. After 4 weeks treatment mice were either mated or killed in estrus for hormone and organ measurements. In the first experiment, treatment with CORT or control continued during pregnancy but in the second CORT treatment was stopped after mating. To identify the effects of GC exposure on the uterus, blastocysts were generated by IVF of oocytes from CORT and control mice and replaced into recipients receiving the opposite treatment.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The effects of hypercortisolism on female mice were first characterized by living body fat content, body weight, food intake, hormone and biochemical measurements, a glucose tolerance test and an insulin resistance test. Fertility was determined with or without CORT-treatment during pregnancy. Oocyte quality was assessed by oocyte maturation, mitochondrial distribution, reactive oxygen species production, mitochondrial DNA mutations and morphology of blastocysts produced in vivo or in vitro. Blastocyst cross-transfer was done to evaluate the causes of embryonic development failure. Fetus development and uterus morphology evaluation as well as culture of oocytes in vitro with gradient concentrations of CORT were also carried out.

MAIN RESULTS AND THE ROLE OF CHANCE

In the hypercortisolism female mouse model, body weight and food intake were much higher than in the control, and corticosterone, estradiol, cholesterol (CHO) and triglycerides (TG) in the plasma of CORT-treated mice was significantly increased. The hypercortisolism female mice were infertile when CORT-treatment was sustained during pregnancy but fertile if CORT-treatment was stopped after mating. The rate of successful implantation in hypercortisolism mice with sustained CORT-treatment during pregnancy was significantly lower than in the control, and the implanted embryos could not develop beyond 13.5 dpc. Blastocyst cross-transfer showed that blastocysts from CORT-treated mice could develop to term in the uterus of control mice, but blastocysts from control mice failed to develop to term when they were transferred into CORT-treated mice, providing evidence that the infertility was mainly caused by an altered uterine environment. CORT administration did not affect oocyte maturation, mitochondrial distribution, ROS production and blastocyst morphology, but increased mitochondrial DNA mutations. Culture of oocytes in vitro with gradient concentrations of CORT showed that only very high concentrations of CORT caused damage to oocyte developmental competence.

LARGE SCALE DATA

NA.

LIMITATIONS, REASONS FOR CAUTION

The mouse model has the advantages of a consistent genetic and physiological background and openness to experimental manipulation over clinical studies but may not represent the human situation.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings show that special care should be taken when administering CORT during pregnancy, and provide important information concerning female reproduction when treating patients by subjecting them to chronic GC exposure.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Key R&D Program of China (Nos. 2016YFA0100400 and 2017YFC1000600) and the National Natural Science Foundation of China (31472055). The authors have no conflicts of interest.

Absence of mitochondrial DNA methylation in mouse oocyte maturation, aging and early embryo development

Mitochondrial DNA (mtDNA) is important for oxidative phosphorylation; dysfunctions can play a role in many mitochondrial diseases and can also affect the aging of cells and individuals. DNA methylation is an important epigenetic modification that plays a critical role in regulating gene expression. While recent studies have revealed the existence of mtDNA methylation there are still controversies about mtDNA methylation due to the special structure of mtDNA. Mitochondria and DNA methylation are both essential for regulating oocyte maturation and early embryo development, but whether mtDNA methylation changes during this process is unknown. By employing bisulfite sequencing, we found that in the process of mouse oocyte maturation, postovulatory oocyte aging, and early embryo development, all analyzed mitochondrial genes, including 16S-CpGI, DCR, ND6, 12S, and ATP8, lacked 5'mC. Thus, mtDNA methylation does not occur in the oocyte and early embryo.

PKCβ1 regulates meiotic cell cycle in mouse oocyte

PKCβI, a member of the classical protein kinase C family, plays key roles in regulating cell cycle transition. Here, we report the expression, localization and functions of PKCβI in mouse oocyte meiotic maturation. PKCβI and p-PKCβI (phosphor-PKCβI) were expressed from germinal vesicle (GV) stage to metaphase II (MII) stage. Confocal microscopy revealed that PKCβI was localized in the GV and evenly distributed in the cytoplasm after GV breakdown (GVBD), and it was concentrated at the midbody at telophase in meiotic oocytes. While, p-PKCβI was concentrated at the spindle poles at the metaphase stages and associated with midbody at telophase. Depletion of PKCβI by specific siRNA injection resulted in defective spindles, accompanied with spindle assembly checkpoint activation, metaphase I arrest and failure of first polar body (PB1) extrusion. Live cell imaging analysis also revealed that knockdown of PKCβI resulted in abnormal spindles, misaligned chromosomes, and meiotic arrest of oocytes arrest at the Pro-MI/MI stage. PKCβI depletion did not affect the G2/M transition, but its overexpression delayed the G2/M transition through regulating Cyclin B1 level and Cdc2 activity. Our findings reveal that PKCβI is a critical regulator of meiotic cell cycle progression in oocytes. Abbreviations: PKC, protein kinase C; COC, cumulus-oocyte complexes; GV, germinal vesicle; GVBD, germinal vesicle breakdown; Pro-MI, first pro-metaphase; MI, first metaphase; Tel I, telophase I; MII, second metaphase; PB1, first polar body; SAC, spindle assembly checkpoint.

Type 2 diabetes increases oocyte mtDNA mutations which are eliminated in the offspring by bottleneck effect

BACKGROUND

Diabetes induces many complications including reduced fertility and low oocyte quality, but whether it causes increased mtDNA mutations is unknown.

METHODS

We generated a T2D mouse model by using high-fat-diet (HFD) and Streptozotocin (STZ) injection. We examined mtDNA mutations in oocytes of diabetic mice by high-throughput sequencing techniques.

RESULTS

T2D mice showed glucose intolerance, insulin resistance, low fecundity compared to the control group. T2D oocytes showed increased mtDNA mutation sites and mutation numbers compared to the control counterparts. mtDNA mutation examination in F1 mice showed that the mitochondrial bottleneck could eliminate mtDNA mutations.

CONCLUSIONS

T2D mice have increased mtDNA mutation sites and mtDNA mutation numbers in oocytes compared to the counterparts, while these adverse effects can be eliminated by the bottleneck effect in their offspring. This is the first study using a small number of oocytes to examine mtDNA mutations in diabetic mothers and offspring.

Mettl14 is required for mouse postimplantation development by facilitating epiblast maturation

N6-methyladenosine (m⁶A) is the most prevalent and reversible internal modification of mammalian messenger and noncoding RNAs mediated by specific m⁶A writer, reader, and eraser proteins. As an m⁶A writer, the methyltransferase-like 3-methyltransferase-like 14 (METTL14)-Wilms tumor 1-associated protein complex dynamically regulates m⁶A modification and plays important roles in diverse biologic processes. However, our knowledge about the complete functions of this RNA methyltransferase complex, the contributions of each component to the methylation, and their effects on different biologic pathways are still limited. By using both in vivo and in vitro models, we here report that METTL14 is indispensable for postimplantation embryonic development by facilitating the conversion from naive to primed state of the epiblast. Depletion of Mettl14 leads to conspicuous embryonic growth retardation from embryonic d 6.5, mainly as a result of resistance to differentiation, which further leads to embryonic lethality early in gestation. Our data highlight the critical function of METTL14 as an m⁶A modification regulator in orchestrating early mouse embryogenesis.-Meng, T.-G., Lu, X., Guo, L., Hou, G.-M., Ma, X.-S., Li, Q.-N., Huang, L., Fan, L.-H., Zhao, Z.-H., Ou, X.-H., OuYang, Y.-C., Schatten, H., Li, L., Wang, Z.-B., Sun, Q.-Y. Mettl14 is required for mouse postimplantation development by facilitating epiblast maturation.

Mitochondrial regulation of [Ca2+]i oscillations during cell cycle resumption of the second meiosis of oocyte

Oocyte is arrested at metaphase of the second meiosis until fertilization switching on [Ca²⁺]i oscillations. Oocyte activation inefficiency is the most challenging problem for failed fertilization and embryonic development. Mitochondrial function and intracellular [Ca²⁺]i oscillations are two critical factors for the oocyte's developmental potential. We aimed to understand the possible correlation between mitochondrial function and [Ca²⁺]i oscillations in oocytes. To this end, mitochondrial uncoupler CCCP which damages mitochondrial function and two small molecule mitochondrial agonists, L-carnitine (LC) and BGP-15, were used to examine the regulation of [Ca²⁺]i by mitochondrial functions. With increasing CCCP concentrations, [Ca²⁺]i oscillations were gradually diminished and high concentrations of CCCP led to oocyte death. LC enhanced mitochondrial membrane potential and [Ca²⁺]i oscillations and even improved the damage induced by CCCP, however, BGP-15 had no beneficial effect on oocyte activation. We have found that mitochondrial function plays a vital role in the generation of [Ca²⁺]i oscillations in oocytes, and thus mitochondria may interact with the ER to generate [Ca²⁺]i oscillations during oocyte activation. Improvement of mitochondrial functions with small molecules can be expected to improve oocyte activation and embryonic development in infertile patients without invasive micromanipulation.

Ablation of beta subunit of protein kinase CK2 in mouse oocytes causes follicle atresia and premature ovarian failure

Premature ovarian failure (POF), a major cause of female infertility, is a complex disorder, but the molecular mechanisms underlying the disorder are only poorly understood. Here we report that protein kinase CK2 contributes to maintaining follicular survival through PI3K/AKT pathway and DNA damage response pathway. Targeted deletion of CK2β in mouse oocytes from the primordial follicle stage resulted in female infertility, which was attributed to POF incurring by massive follicle atresia. Downregulated PI3K/AKT signaling was found after CK2β deletion, indicated by reduced level of phosphorylated AKT (S473, T308, and S129) and altered AKT targets related to cell survival. Further studies discovered that CK2β-deficient oocytes showed enhanced γH2AX signals, indicative of accumulative unrepaired DSBs, which activated CHK2-dependant p53 and p63 signaling. The suppressed PI3K/AKT signaling and failed DNA damage response signaling probably contribute to large-scale oocyte loss and eventually POF. Our findings provide important new clues for elucidating the mechanisms underlying follicle atresia and POF.

Brief Overview of Prostate Cancer Statistics, Grading, Diagnosis and Treatment Strategies

This chapter provides a brief overview of prostate cancer statistics, grading, diagnosis and treatment strategies that are discussed in more detail in the subsequent chapters of this book and the companion book titled "Clinical Molecular and Diagnostic Imaging of Prostate Cancer and Treatment Strategies". It also points to websites that provide additional useful information for patients affected by prostate cancer and for students and teachers to obtain practical and updated information on research, new diagnostic modalities and new therapies including new updated clinical trials. Three sections are focused on overview of prostate cancer statistics; overview of detection, diagnosis, stages and grading of prostate cancer; and treatment possibilities and options.

Geminin deletion in pre-meiotic DNA replication stage causes spermatogenesis defect and infertility

Geminin plays a critical role in cell cycle regulation by regulating DNA replication and serves as a transcriptional molecular switch that directs cell fate decisions. Spermatogonia lacking Geminin disappear during the initial wave of mitotic proliferation, while geminin is not required for meiotic progression of spermatocytes. It is unclear whether geminin plays a role in pre-meiotic DNA replication in later-stage spermatogonia and their subsequent differentiation. Here, we selectively disrupted Geminin in the male germline using the Stra8-Cre/loxP conditional knockout system. Geminin-deficient mice showed atrophic testes and infertility, concomitant with impaired spermatogenesis and reduced sperm motility. The number of undifferentiated spermatogonia and spermatocytes was significantly reduced; the pachytene stage was impaired most severely. Expression of cell proliferation-associated genes was reduced in Gmnn^fl/Δ; Stra8-Cre testes compared to in controls. Increased DNA damage, decreased Cdt1, and increased phosphorylation of Chk1/Chk2 were observed in Geminin-deficient germ cells. These results suggest that geminin plays important roles in pre-meiotic DNA replication and subsequent spermatogenesis.

Oocyte-specific deletion of furin leads to female infertility by causing early secondary follicle arrest in mice

The process of follicular development involves communications between oocyte and surrounding granulosa cells. FURIN is a member of the family of proprotein convertases that is involved in the activation of a large number of zymogens and proproteins by cleavage at its recognition motif. To investigate the functions of FURIN in female fertility, furin^flox/flox (fur^fl/fl) mice were crossed with Zp3-Cre mice and Gdf9-Cre, respectively, to achieve oocyte-specific disruption of FURIN. Here we report for the first time that FURIN is dispensable for primordial follicle maintenance and activation but important for early secondary follicular development, as ablation of FURIN in oocytes caused failure of follicle development beyond the type 4 and/or 5a follicles in mutant mice, resulting in increased number of early secondary follicles and the severely decreased number of mature follicles, thus anovulation and infertility. We also found that the developmental arrest of early secondary follicles might be rooted in the loss of the mature form of ADAMTS1 (85-kDa prodomain truncated) and compromised proliferation of granulosa cells in mutant mice. Taken together, our data highlight the importance of FURIN in follicle development beyond the early secondary follicle stage and indicate that compromised FURIN function leads to follicular dysplasia and female infertility in mice.

RNA-associated protein LSM family member 14 controls oocyte meiotic maturation through regulating mRNA pools

LSM family member 14 (LSM14) belongs to the RNA-associated protein (RAP) family that is widely expressed in different species, and whose functions include associating and storing mRNAs. In the present study, we found that LSM14b was essential for oocyte meiotic maturation. Lack of LSM14b caused oocyte meiotic arrest at metaphase, and misalignment of chromosomes, as well as abnormal spindle assembly checkpoint (SAC) and maturation promoting factor (MPF) activation. Cyclin B1 and Cdc20 mRNAs, whose contents changed with LSM14b expression, were likely direct targets of LSM14b. We conclude that LSM14b, by functioning as a container of mRNAs, controls protein expression, and thus regulates the oocyte meiotic maturation process.

Centrosome and microtubule functions and dysfunctions in meiosis: implications for age-related infertility and developmental disorders

The effects of oocyte aging on meiotic spindle dynamics have been well recognised, but the mechanisms underlying the effects are not well understood. In this paper we review the role of centrosomes and the microtubule cytoskeleton in meiotic spindle formation and maintenance, and the impact of oocyte aging on spindle integrity resulting in centrosome and microtubule dysfunctions that are associated with aneuploidy. Loss of spindle integrity includes dispersion of proteins from the centrosome core structure and loss of attachment of microtubules to centrosomes and kinetochores, which will result in abnormal chromosome separation. The inability of centrosomal proteins to accurately associate with the centrosome structure may be the result of destabilisation of the core structure itself or of microtubule destabilisation at the centrosome-facing microtubule areas that are acetylated in fresh oocytes but may not be acetylated in aging oocytes. Microtubule destabilisation prevents accurate motor-driven transport of centrosomal proteins along microtubules to form and maintain a functional centrosome. Other factors to form and maintain the MII spindle include signal transductions that affect microtubule dynamics and stability. Understanding the mechanisms underlying centrosome and microtubule dysfunctions during oocyte aging will allow diagnosis and analysis of oocyte quality and abnormalities as important aspects for targeted treatment of aging oocytes to extend or restore viability and developmental capacity. New therapeutic approaches will allow improvements in reproductive success rates in IVF clinics, as well as improvements in reproductive success rates in farm animals. This review is focused on: (1) centrosome and microtubule dynamics in fresh and aging oocytes; (2) regulation of centrosome and/or microtubule dynamics and function; and (3) possible treatments to extend the oocyte's reproductive capacity and viability span.

CenpH regulates meiotic G2/M transition by modulating the APC/CCdh1-cyclin B1 pathway in oocytes

Meiotic resumption (G2/M transition) and progression through meiosis I (MI) are two key stages for producing fertilization-competent eggs. Here, we report that CenpH, a component of the kinetochore inner plate, is responsible for G2/M transition in meiotic mouse oocytes. Depletion of CenpH by morpholino injection decreased cyclin B1 levels, resulting in attenuation of maturation-promoting factor (MPF) activation, and severely compromised meiotic resumption. CenpH protects cyclin B1 from destruction by competing with the action of APC/C^Cdh1. Impaired G2/M transition after CenpH depletion could be rescued by expression of exogenous cyclin B1. Unexpectedly, blocking CenpH did not affect spindle organization and meiotic cell cycle progression after germinal vesicle breakdown. Our findings reveal a novel role of CenpH in regulating meiotic G2/M transition by acting via the APC/C^Cdh1-cyclin B1 pathway.

Summary: CenpH, a component of the kinetochore inner plate protein, is necessary for cyclin B1 stabilization and is responsible for the G2/M transition in meiotic mouse oocytes.

LKB1 acts as a critical gatekeeper of ovarian primordial follicle pool

Liver Kinase b1 (LKB1/STK11)is a tumor suppressor responsible for the Peutz-Jeghers syndrome, an autosomal-dominant, cancer-prone disorder in which patients develop neoplasms in several organs, including the oviduct, ovary, and cervix. Besides, the C allele of a SNP in the Lkb1 gene impedes the likelihood of ovulation in polycystic ovary syndrome (PCOS) in women treated with metformin, a known LKB1-AMPK activator. It is very likely that LKB1 plays roles in female fertility. To identify the physiological functions of LKB1 in the mouse ovary, we selectively disrupted LKB1 in oocytes by the Cre-LoxP conditional knockout system and found that Lkb1^fl/fl; Gdf9-Cre mice were severely subfertile with significantly enlarged ovaries compared to Lkb1^fl/fl mice. Interestingly, without Lkb1 expression in oocytes from the primordial follicle stage, the entire primordial follicle pool was activated but failed to mature and ovulate, subsequently causing premature ovarian failure (POF). Further investigation demonstrated that elevated mTOR signaling regulated by an AKT-independent LKB1-AMPK pathway was responsible for the excessive follicle activation and growth. Our findings reveal the role of LKB1 as an indispensable gatekeeper for the primordial follicle pool, offer new functional understanding for the tumor suppressor genes in reproductive organs, and might also provide valuable information for understanding POF and infertility.

Protein Phosphatase 6 Protects Prophase I-Arrested Oocytes by Safeguarding Genomic Integrity

Mammalian oocytes are arrested at prophase of the first meiotic division in the primordial follicle pool for months, even years, after birth depending on species, and only a limited number of oocytes resume meiosis, complete maturation, and ovulate with each reproductive cycle. We recently reported that protein phosphatase 6 (PP6), a member of the PP2A-like subfamily, which accounts for cellular serine/threonine phosphatase activity, functions in completing the second meiosis. Here, we generated mutant mice with a specific deletion of Ppp6c in oocytes from the primordial follicle stage by crossing Ppp6c^F/F mice with Gdf9-Cre mice and found that Ppp6c^F/F; GCre+ mice are infertile. Depletion of PP6c caused folliculogenesis defects and germ cell loss independent of the traditional AKT/mTOR pathway, but due to persistent phosphorylation of H2AX (a marker of double strand breaks), increased susceptibility to DNA damage and defective DNA repair, which led to massive oocyte elimination and eventually premature ovarian failure (POF). Our findings uncover an important role for PP6 as an indispensable guardian of genomic integrity of the lengthy prophase I oocyte arrest, maintenance of primordial follicle pool, and thus female fertility.

Formation of haploid gametes from diploid germ cells requires a specialized reductive cell division known as meiosis. In contrast to male meiosis that takes place continuously, a unique feature of female meiosis in mammals is the long arrest in meiosis I, which lasts up to 50 years in humans. Because the size of the germ cell pool determines the reproductive lifespan of females, it is important to discover mechanisms preserving the germ cell pool during the lengthy meiotic arrest. In this study, we examined the physiological role of a member of the PP2A-like serine/threonine phosphatase subfamily, protein phosphatase 6, in mouse oocytes during ovarian follicular development. This is the first study linking PP6 to the maintenance of the female germ cell pool and fertility. We find PP6 is an indispensable protector of arrested oocytes by safeguarding genomic integrity during their dormancy in the mouse ovary.

Salmonella Bacterial Monotherapy Reduces Autochthonous Prostate Tumor Burden in the TRAMP Mouse Model

Attenuated Salmonella typhimurium injected in the circulatory system of mammals selectively targets tumors. Using weekly intraperitoneal injections of attenuated Salmonella strain CRC2631, we tested for regression and/or inhibition of tumor development in the TRAMP prostate tumor mouse model, which utilizes SV40 early region expression for autochthonous formation of prostate tumors that progress into metastatic, poorly differentiated prostatic carcinomas in an immunocompetent murine model. Thirteen weekly intraperitoneal administrations of 10⁵–10⁷ CFU CRC2631 into 10 week old mice were well tolerated by the TRAMP model. Sacrifice and histological analysis of TRAMP prostates at 22 weeks indicated that Salmonella monotherapy at administrated levels decrease visible tumor size (>29%) but did not significantly inhibit previously described SV40 expression-driven TRAMP tumor progression to undifferentiated carcinomas when histologically examined. In conclusion, this work demonstrates baseline results for CRC2631 Salmonella monotherapy using the immunocompetent TRAMP prostate tumor model in preparation for study of combination therapies that resolve autochthonously generated TRAMP prostate tumors, further reduce tumor size, or inhibit prostate tumor progression.

Oocyte-specific deletion of N-WASP does not affect oocyte polarity, but causes failure of meiosis II completion

STUDY QUESTION

There is an unexplored physiological role of N-WASP (neural Wiskott-Aldrich syndrome protein) in oocyte maturation that prevents completion of second meiosis.

SUMMARY ANSWER

In mice, N-WASP deletion did not affect oocyte polarity and asymmetric meiotic division in first meiosis, but did impair midbody formation and second meiosis completion.

WHAT IS KNOWN ALREADY

N-WASP regulates actin dynamics and participates in various cell activities through the RHO-GTPase-Arp2/3 (actin-related protein 2/3 complex) pathway, and specifically the Cdc42 (cell division cycle 42)-N-WASP-Arp2/3 pathway. Differences in the functions of Cdc42 have been obtained from in vitro compared to in vivo studies.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

By conditional knockout of N-WASP in mouse oocytes, we analyzed its in vivo functions by employing a variety of different methods including oocyte culture, immunofluorescent staining and live oocyte imaging. Each experiment was repeated at least three times, and data were analyzed by paired-samples t-test.

MAIN RESULTS AND THE ROLE OF CHANCE

Oocyte-specific deletion of N-WASP did not affect the process of oocyte maturation including spindle formation, spindle migration, polarity establishment and maintenance, and homologous chromosome or sister chromatid segregation, but caused failure of cytokinesis completion during second meiosis (P < 0.001 compared to control). Further analysis showed that a defective midbody may be responsible for the failure of cytokinesis completion.

LIMITATIONS, REASONS FOR CAUTION

The present study did not include a detailed analysis of the mechanisms underlying the results, which will require more extensive further investigations.

WIDER IMPLICATIONS OF THE FINDINGS

N-WASP may play an important role in mediating and co-ordinating the activity of the spindle (midbody) and actin (contractile ring constriction) when cell division occurs. The findings are important for understanding the regulation of oocyte meiosis completion and failures in this process that affect oocyte quality.

LARGE SCALE DATA

None.

STUDY FUNDING AND COMPETING INTERESTS

This work was supported by the National Basic Research Program of China (No. 2012CB944404) and the National Natural Science Foundation of China (Nos 30930065, 31371451, 31272260 and 31530049). There are no potential conflicts of interests.

SIRT1, 2, 3 protect mouse oocytes from postovulatory aging

The quality of metaphase II oocytes will undergo a time-dependent deterioration following ovulation as the result of the oocyte aging process. In this study, we determined that the expression of sirtuin family members (SIRT1, 2, 3) was dramatically reduced in mouse oocytes aged in vivo or in vitro. Increased intracellular ROS was observed when SIRT1, 2, 3 activity was inhibited. Increased frequency of spindle defects and disturbed distribution of mitochondria were also observed in MII oocytes aged in vitro after treatment with Nicotinamide (NAM), indicating that inhibition of SIRT1, 2, 3 may accelerate postovulatory oocyte aging. Interestingly, when MII oocytes were exposed to caffeine, the decline of SIRT1, 2, 3 mRNA levels was delayed and the aging-associated defective phenotypes could be improved. The results suggest that the SIRT1, 2, 3 pathway may play a potential protective role against postovulatory oocyte aging by controlling ROS generation.

Rab3A, Rab27A, and Rab35 regulate different events during mouse oocyte meiotic maturation and activation

Rab family members play important roles in membrane trafficking, cell growth, and differentiation. Almost all components of the cell endomembrane system, the nucleus, and the plasma membrane are closely related to RAB proteins. In this study, we investigated the distribution and functions of three members of the Rab family, Rab3A, Rab27A, and Rab35, in mouse oocyte meiotic maturation and activation. The three Rab family members showed different localization patterns in oocytes. Microinjection of siRNA, antibody injection, or inhibitor treatment showed that (1) Rab3A regulates peripheral spindle and cortical granule (CG) migration, polarity establishment, and asymmetric division; (2) Rab27A regulates CG exocytosis following MII-stage oocyte activation; and (3) Rab35 plays an important role in spindle organization and morphology maintenance, and thus meiotic nuclear maturation. These results show that Rab proteins play important roles in mouse oocyte meiotic maturation and activation and that different members exert different distinct functions.

Geminin deletion in mouse oocytes results in impaired embryo development and reduced fertility

Geminin is an important regulator of DNA replication and cell differentiation, but its role in female reproduction remains uncertain. Maternal geminin does not regulate oocyte meiotic maturation but does control accurate DNA replication. Geminin deletion in oocytes results in impaired embryo development and reduced fertility.

Geminin controls proper centrosome duplication, cell division, and differentiation. We investigated the function of geminin in oogenesis, fertilization, and early embryo development by deleting the geminin gene in oocytes from the primordial follicle stage. Oocyte-specific disruption of geminin results in low fertility in mice. Even though there was no evident anomaly of oogenesis, oocyte meiotic maturation, natural ovulation, or fertilization, early embryo development and implantation were impaired. The fertilized eggs derived from mutant mice showed developmental delay, and many were blocked at the late zygote stage. Cdt1 protein was decreased, whereas Chk1 and H2AX phosphorylation was increased, in fertilized eggs after geminin depletion. Our results suggest that disruption of maternal geminin may decrease Cdt1 expression and cause DNA rereplication, which then activates the cell cycle checkpoint and DNA damage repair and thus impairs early embryo development.

The Dynamics and Regulatory Mechanism of Pronuclear H3k9me2 Asymmetry in Mouse Zygotes

H3K9 methylation is an important histone modification that is correlated with gene transcription repression. The asymmetric H3K9 dimethylation (H3K9me2) pattern between paternal and maternal genomes is generated soon after fertilization. In the present study, we carefully determined the dynamics of H3K9me2 changes in mouse zygotes, and investigated the regulatory mechanisms. The results indicated that histone methyltransferase G9a, but not GLP, was involved in the regulation of asymmetric H3K9me2, and G9a was the methyltransferase that induced the appearance of H3K9me2 in the male pronucleus of the zygote treated with cycloheximide. We found that there were two distinct mechanisms that regulate H3K9me2 in the male pronucleus. Before 8 h of in vitro fertilization (IVF), a mechanism exists that inhibits the association of G9a with the H3K9 sites. After 10 h of IVF the inhibition of G9a activity depends on yet unknown novel protein(s) synthesis. The two mechanisms of transfer take place between 8-10 h of IVF, and the novel protein failed to inhibit G9a activity in time, resulting in the appearance of a low level de novo H3K9me2 in the male pronucleus.

Cep55 regulates spindle organization and cell cycle progression in meiotic oocyte

Cep55 is a relatively novel member of the centrosomal protein family. Here, we show that Cep55 is expressed in mouse oocytes from the germinal vesicle (GV) to metaphase II (MII) stages. Immuostaining and confocal microscopy as well as time lapse live imaging after injection of mRNA encoding fusion protein of Cep55 and GFP identified that Cep55 was localized to the meiotic spindle, especially to the spindle poles at metaphase, while it was concentrated at the midbody in telophase in meiotic oocytes. Knockdown of Cep55 by specific siRNA injection caused the dissociation of γ-tubulin from the spindle poles, resulting in severely defective spindles and misaligned chromosomes, leading to metaphase I arrest and failure of first polar body (PB1) extrusion. Correspondingly, cyclin B accumulation and spindle assembly checkpoint (SAC) activation were observed in Cep55 knockdown oocytes. Our results suggest that Cep55 may act as an MTOC-associated protein regulating spindle organization, and thus cell cycle progression during mouse oocyte meiotic maturation.

Loss of protein phosphatase 6 in oocytes causes failure of meiosis II exit and impaired female fertility

Dynamic protein phosphorylation and dephosphorylation, mediated by a conserved cohort of protein kinases and phosphatases, regulate cell cycle progression. Among the well-known PP2A-like protein phosphatases, protein phosphatase 6 (PP6) has been analyzed in mammalian mitosis, and Aurora A has recently been identified as its key substrate. However, the functions of PP6 in meiosis are still entirely unknown. To identify the physiological role of PP6 in female gametogenesis, Ppp6c(F/F) mice were first generated and crossed with Zp3-Cre mice to selectively disrupt Ppp6c expression in oocytes. Here, we report for the first time that PP6c is dispensable for oocyte meiotic maturation but essential for exit from meiosis II (MII) after fertilization. Depletion of PP6c caused an abnormal MII spindle and disrupted MII cytokinesis, resulting in zygotes with high risk of aneuploidy and defective early embryonic development, and thus severe subfertility. We also reveal that PP6 inactivation interferes with MII spindle formation and MII exit owing to increased Aurora A activity, and that Aurora A inhibition with MLN8237 can rescue the PP6c depletion phenotype. In conclusion, our findings uncover a hitherto unknown role for PP6 as an indispensable regulator of oocyte meiosis and female fertility.

Different fates of oocytes with DNA double-strand breaks in vitro and in vivo

In female mice, despite the presence of slight DNA double-strand breaks (DSBs), fully grown oocytes are able to undergo meiosis resumption as indicated by germinal vesicle breakdown (GVBD); however, severe DNA DSBs do reduce and delay entry into M phase through activation of the DNA damage checkpoint. But little is known about the effect of severe DNA DSBs on the spindle assembly checkpoint (SAC) during oocyte maturation. We showed that nearly no first polar body (PB1) was extruded at 12 h of in vitro maturation (IVM) in severe DNA DSBs oocytes, and the limited number of oocytes with PB1 were actually at telophase. However, about 60% of the severe DNA DSBs oocytes which underwent GVBD at 2 h of IVM released a PB1 at 18 h of IVM and these oocytes did reach the second metaphase (MII) stage. Chromosome spread at MI and MII stages showed that chromosomes fragmented after GVBD in severe DNA DSBs oocytes. The delayed PB1 extrusion was due to the disrupted attachment of microtubules to kinetochores and activation of the SAC. At the same time, misaligned chromosome fragments became obvious at the first metaphase (MI) in severe DNA DSBs oocytes. These data implied that the inactivation of SAC during the metaphase-anaphase transition of first meiosis was independent of chromosome integrity. Next, we induced DNA DSBs in vivo, and found that the number of superovulated oocytes per mouse was significantly reduced; moreover, this treatment increased the percentage of apoptotic oocytes. These results suggest that DNA DSBs oocytes undergo apoptosis in vivo.

Cyclin B3 controls anaphase onset independent of spindle assembly checkpoint in meiotic oocytes

Cyclin B3 is a relatively new member of the cyclin family whose functions are little known. We found that depletion of cyclin B3 inhibited metaphase-anaphase transition as indicated by a well-sustained MI spindle and cyclin B1 expression in meiotic oocytes after extended culture. This effect was independent of spindle assembly checkpoint activity, since both Bub3 and BubR1 signals were not observed at kinetochores in MI-arrested cells. The metaphase I arrest was not rescued by either Mad2 knockdown or cdc20 overexpression, but it was rescued by securin RNAi. We conclude that cyclin B3 controls the metaphase-anaphase transition by activating APC/C(cdc20) in meiotic oocytes, a process that does not rely on SAC activity.

Enriched environment-induced maternal weight loss reprograms metabolic gene expression in mouse offspring

The global prevalence of weight loss is increasing, especially in young women. However, the extent and mechanisms by which maternal weight loss affects the offspring is still poorly understood. Here, using an enriched environment (EE)-induced weight loss model, we show that maternal weight loss improves general health and reprograms metabolic gene expression in mouse offspring, and the epigenetic alterations can be inherited for at least two generations. EE in mothers induced weight loss and its associated physiological and metabolic changes such as decreased adiposity and improved glucose tolerance and insulin sensitivity. Relative to controls, their offspring exhibited improved general health such as reduced fat accumulation, decreased plasma and hepatic lipid levels, and improved glucose tolerance and insulin sensitivity. Maternal weight loss altered gene expression patterns in the liver of offspring with coherent down-regulation of genes involved in lipid and cholesterol biosynthesis. Epigenomic profiling of offspring livers revealed numerous changes in cytosine methylation depending on maternal weight loss, including reproducible changes in promoter methylation over several key lipid biosynthesis genes, correlated with their expression patterns. Embryo transfer studies indicated that oocyte alteration in response to maternal metabolic conditions is a strong factor in determining metabolic and epigenetic changes in offspring. Several important lipid metabolism-related genes have been identified to partially inherit methylated alleles from oocytes. Our study reveals a molecular and mechanistic basis of how maternal lifestyle modification affects metabolic changes in the offspring.

Quantitative proteomic identification of host factors involved in the Salmonella typhimurium infection cycle

Quantitative proteomics, based on stable isotope labeling by amino acids in cell culture (SILAC), can be used to identify host proteins involved in the intracellular interplay with pathogens. This method allows identification of proteins subject to degradation or upregulation in response to intracellular infection. It can also be used to study intracellular dynamics (trafficking) of proteins in response to the infection. Here, we describe the analysis of changes in protein profiles determined in Golgi-enriched fractions isolated from cells that were either mock-infected or infected with Salmonella typhimurium. Using the SILAC approach we were able to identify 105 proteins in Golgi-enriched fractions that were significantly changed in their abundance as a result of Salmonella infection.

Nuf2 is required for chromosome segregation during mouse oocyte meiotic maturation

Nuf2 plays an important role in kinetochore-microtubule attachment and thus is involved in regulation of the spindle assembly checkpoint in mitosis. In this study, we examined the localization and function of Nuf2 during mouse oocyte meiotic maturation. Myc6-Nuf2 mRNA injection and immunofluorescent staining showed that Nuf2 localized to kinetochores from germinal vesicle breakdown to metaphase I stages, while it disappeared from the kinetochores at the anaphase I stage, but relocated to kinetochores at the MII stage. Overexpression of Nuf2 caused defective spindles, misaligned chromosomes, and activated spindle assembly checkpoint, and thus inhibited chromosome segregation and metaphase-anaphase transition in oocyte meiosis. Conversely, precocious polar body extrusion was observed in the presence of misaligned chromosomes and abnormal spindle formation in Nuf2 knock-down oocytes, causing aneuploidy. Our data suggest that Nuf2 is a critical regulator of meiotic cell cycle progression in mammalian oocytes.

Polar bodies in assisted reproductive technology: current progress and future perspectives

During meiotic cell-cycle progression, unequal divisions take place, resulting in a large oocyte and two diminutive polar bodies. The first polar body contains a subset of bivalent chromosomes, whereas the second polar body contains a haploid set of chromatids. One unique feature of the female gamete is that the polar bodies can provide beneficial information about the genetic background of the oocyte without potentially destroying it. Therefore, polar body biopsies have been applied in preimplantation genetic diagnosis to detect chromosomal or genetic abnormalities that might be inherited by the offspring. Besides the traditional use in preimplantation diagnosis, recent findings suggest additional important roles for polar bodies in assisted reproductive technology. In this paper, we review the new roles of polar bodies in assisted reproductive technology, mainly focusing on single-cell sequencing of the polar body genome to deduce the genomic information of its sibling oocyte and on polar body transfer to prevent the transmission of mtDNA-associated diseases. We also discuss additional potential roles for polar bodies and related key questions in human reproductive health. We believe that further exploration of new roles for polar bodies will contribute to a better understanding of reproductive health and that polar body manipulation and diagnosis will allow production of a greater number of healthy babies.

The impact of mitochondrial function/dysfunction on IVF and new treatment possibilities for infertility

Mitochondria play vital roles in oocyte functions and they are critical indicators of oocyte quality which is important for fertilization and development into viable offspring. Quality-compromised oocytes are correlated with infertility, developmental disorders, reduced blastocyst cell number and embryo loss in which mitochondrial dysfunctions play a significant role. Increasingly, women affected by metabolic disorders such as diabetes or obesity and oocyte aging are seeking treatment in IVF clinics to overcome the effects of adverse metabolic conditions on mitochondrial functions and new treatments have become available to restore oocyte quality. The past decade has seen enormous advances in potential therapies to restore oocyte quality and includes dietary components and transfer of mitochondria from cells with mitochondrial integrity into mitochondria-impaired oocytes. New technologies have opened up new possibilities for therapeutic advances which will increase the success rates for IVF of oocytes from women with compromised oocyte quality.

Environmental epigenetic inheritance through gametes and implications for human reproduction

BACKGROUND

Traditional studies focused on DNA as the heritable information carrier that passes the phenotype from parents to offspring. However, increasing evidence suggests that information, that is independent of the DNA sequence, termed epigenetic information, can be inherited between generations. Recently, in our lab, we found that prediabetes in fathers increases the susceptibility to diabetes in offspring through gametic cytosine methylation changes. Paternal prediabetes changed overall methylation patterns in sperm, and a large portion of differentially methylated loci can be transmitted to pancreatic islets of offspring up to the second generation. In this review, we survey the extensive examples of environmentally induced epigenetic inheritance in various species, ranging from Caenorhabditis elegans to humans. We focus mainly on elucidating the molecular basis of environmental epigenetic inheritance through gametes, which is an emerging theme and has important implications for explaining the prevalence of obesity, type 2 diabetes and other chronic non-genetic diseases, which is also important for understanding the influence of environmental exposures on reproductive and overall health in offspring.

METHODS

For this review, we included relevant data and information obtained through a PubMed database search for all English language articles published up to August 2014 which included the term 'environmental epigenetic inheritance' and 'transgenerational epigenetic inheritance'. We focused on research papers using animal models including Drosophila, C. elegans, mouse and rat. Human data were also included.

RESULTS

Evidence from animal models suggests that environmental epigenetic inheritance through gametes exists in various species. Extensive molecular evidence suggests that epigenetic information carriers including DNA methylation, non-coding RNAs and chromatin proteins in gametes play important roles in the transmission of phenotypes from parents to offspring.

CONCLUSIONS

Given the large number of experimental evidence from various organisms, it is clear that parental environmental alterations can affect the phenotypes of offspring through gametic epigenetic alterations. This more recent thinking based on new data may have implications in explaining the prevalence of obesity, type 2 diabetes and other chronic non-genetic diseases. This also implies that, in the near future, epigenetic factors which are heritable should be regarded important in determining the risk of certain diseases. Moreover, identification of epigenetic markers in gametes (polar body or sperm) may hold great promise for predicting susceptibility to and preventing certain non-genetic diseases in offspring, as well as providing indications on parental environmental exposures.

Oocyte ageing and epigenetics

It has become a current social trend for women to delay childbearing. However, the quality of oocytes from older females is compromised and the pregnancy rate of older women is lower. With the increased rate of delayed childbearing, it is becoming more and more crucial to understand the mechanisms underlying the compromised quality of oocytes from older women, including mitochondrial dysfunctions, aneuploidy and epigenetic changes. Establishing proper epigenetic modifications during oogenesis and early embryo development is an important aspect in reproduction. The reprogramming process may be influenced by external and internal factors that result in improper epigenetic changes in germ cells. Furthermore, germ cell epigenetic changes might be inherited by the next generations. In this review, we briefly summarise the effects of ageing on oocyte quality. We focus on discussing the relationship between ageing and epigenetic modifications, highlighting the epigenetic changes in oocytes from advanced-age females and in post-ovulatory aged oocytes as well as the possible underlying mechanisms.

Molecules and mechanisms controlling the active DNA demethylation of the mammalian zygotic genome

The active DNA demethylation in early embryos is essential for subsequent development. Although the zygotic genome is globally demethylated, the DNA methylation of imprinted regions, part of repeat sequences and some gamete-specific regions are maintained. Recent evidence has shown that multiple proteins and biological pathways participate in the regulation of active DNA demethylation, such as TET proteins, DNA repair pathways and DNA methyltransferases. Here we review the recent understanding regarding proteins associated with active DNA demethylation and the regulatory networks controlling the active DNA demethylation in early embryos.

Scaffold subunit Aalpha of PP2A is essential for female meiosis and fertility in mice

Ppp2r1a encodes the scaffold subunit Aalpha of protein phosphatase 2A (PP2A), which is an important and ubiquitously expressed serine threonine phosphatase family and plays a critical role in many fundamental cellular processes. To identify the physiological role of PP2A in female germ cell meiosis, we selectively disrupted Ppp2r1a expression in oocytes by using the Cre-Loxp conditional knockout system. Here we report for the first time that oocyte-specific deletion of Ppp2r1a led to severe female subfertility without affecting follicle survival, growth, and ovulation. PP2A-Aalpha was essential for regulating oocyte meiotic maturation because depletion of PP2A-Aalpha facilitated germinal vesicle breakdown, causing elongation of the MII spindle and precocious separation of sister chromatids. The resulting eggs had high risk of aneuploidy, though they could be fertilized, leading to defective embryonic development and thus subfertility. Our findings provide strong evidence that PP2A-Aalpha within the oocyte plays an indispensable role in oocyte meiotic maturation, though it is dispensable for folliculogenesis in the mouse ovary.