SRSF2 is required for mRNA splicing during spermatogenesis

BACKGROUND

RNA splicing plays significant roles in fundamental biological activities. However, our knowledge about the roles of alternative splicing and underlying mechanisms during spermatogenesis is limited.

RESULTS

Here, we report that Serine/arginine-rich splicing factor 2 (SRSF2), also known as SC35, plays critical roles in alternative splicing and male reproduction. Male germ cell-specific deletion of Srsf2 by Stra8-Cre caused complete infertility and defective spermatogenesis. Further analyses revealed that deletion of Srsf2 disrupted differentiation and meiosis initiation of spermatogonia. Mechanistically, by combining RNA-seq data with LACE-seq data, we showed that SRSF2 regulatory networks play critical roles in several major events including reproductive development, spermatogenesis, meiotic cell cycle, synapse organization, DNA recombination, chromosome segregation, and male sex differentiation. Furthermore, SRSF2 affected expression and alternative splicing of Stra8, Stag3 and Atr encoding critical factors for spermatogenesis in a direct manner.

CONCLUSIONS

Taken together, our results demonstrate that SRSF2 has important functions in spermatogenesis and male fertility by regulating alternative splicing.

SRSF1-mediated alternative splicing is required for spermatogenesis

Alternative splicing (AS) plays significant roles in a multitude of fundamental biological activities. AS is prevalent in the testis, but the regulations of AS in spermatogenesis is only little explored. Here, we report that Serine/arginine-rich splicing factor 1 (SRSF1) plays critical roles in alternative splicing and male reproduction. Male germ cell-specific deletion of Srsf1 led to complete infertility by affecting spermatogenesis. Mechanistically, by combining RNA-seq data with LACE-seq data, we showed that SRSF1 affected the AS of Stra8 in a direct manner and Dazl, Dmc1, Mre11a, Syce2 and Rif1 in an indirect manner. Our findings demonstrate that SRSF1 has crucial functions in spermatogenesis and male fertility by regulating alternative splicing.

Effectiveness of non-invasive chromosomal screening for normal karyotype and chromosomal rearrangements

Purpose: To study the accuracy of non-invasive chromosomal screening (NICS) results, in normal chromosomes and chromosomal rearrangement groups and to investigate whether using trophoblast cell biopsy along with NICS, to choose embryos for transfer can improve the clinical outcomes of assisted pregnancy.

Methods: We retrospectively analyzed 101 couples who underwent preimplantation genetic testing at our center from January 2019 to June 2021 and collected 492 blastocysts for trophocyte (TE) biopsy. D3-5 blastocyst culture fluid and blastocyst cavity fluid were collected for the NICS. Amongst them, 278 blastocysts (58 couples) and 214 blastocysts (43 couples) were included in the normal chromosomes and chromosomal rearrangement groups, respectively. Couples undergoing embryo transfer were divided into group A, in which both the NICS and TE biopsy results were euploid (52 embryos), and group B, in which the TE biopsy results were euploid and the NICS results were aneuploid (33 embryos).

Results: In the normal karyotype group, concordance for embryo ploidy was 78.1%, sensitivity was 94.9%, specificity was 51.4%, the positive predictive value (PPV) was 75.7%, and the negative predictive value (NPV) was 86.4%. In the chromosomal rearrangement group, concordance for embryo ploidy was 73.1%, sensitivity was 93.3%, specificity was 53.3%, the PPV was 66.3%, and the NPV was 89%. In euploid TE/euploid NICS group, 52 embryos were transferred; the clinical pregnancy rate was 71.2%, miscarriage rate was 5.4%, and ongoing pregnancy rate was 67.3%. In euploid TE/aneuploid NICS group, 33 embryos were transferred; the clinic pregnancy rate was 54.5%, miscarriage rate was 5.6%, and ongoingpregnancy rate was 51.5%. The clinical pregnancy and ongoing pregnancy rates were higher in the TE and NICS euploid group.

Conclusion: NICS was similarly effective in assessing both normal and abnormal populations. Identification of euploidy and aneuploidy alone may lead to the wastage of embryos due to high false positives. More suitable reporting methods for NICS and countermeasures for a high number of false positives in NICS are needed. In summary, our results suggest that combining biopsy and NICS results could improve the outcomes of assisted pregnancy.

Transient inhibition of CDK2 activity prevents oocyte meiosis I completion and egg activation in mouse

Mammalian oocytes are arrested at the diplotene stage of prophase I during fetal or postnatal development. It was reported that cyclin-dependent kinases (CDK1) was the sole CDK to drive the resumption of meiosis and CDK2 was dispensable for meiosis progression in mouse oocytes according to the conditional knockout studies. However, a recent study showed that CDK2 activity is essential for meiotic division and gametogenesis by means of gene-directed mutagenesis, which avoids the compensatory activation of other CDKs. Taken the compensatory effect between CDKs after gene knockout, the physiological function of CDK2 activity in oocyte maturation remains unclear. To address this issue, we applied a specific small-molecule inhibitor to restrain CDK2 activity transiently during oocyte meiotic maturation. Surprisingly, transient inhibition of CDK2 activity severely prevented the meiosis I completion although the meiotic resumption was not affected. Then we found that CDK2 activity was required for establishment of normal spindle and chromosome dynamics. Notably, CDK2 inhibition interrupted the anaphase-promoting complex/cyclosome (APC/C)-dependent degradation pathway by maintaining the activation of spindle assembly checkpoint (SAC). Interestingly, CDK2 inhibition prevented the egg activation as well. Overall, our data demonstrate that CDK2 kinase activity is required for proper dynamics of spindle and chromosomes, whose disturbance induces the continuous SAC activation and subsequent inactivation of APC/C activity in oocyte meiosis.

Measurement of Bone Metastatic Tumor Growth by a Tibial Tumorigenesis Assay

Bone metastasis is a frequent and lethal complication of many cancer types (i.e., prostate cancer, breast cancer, and multiple myeloma), and a cure for bone metastasis remains elusive. To recapitulate the process of bone metastasis and understand how cancer cells metastasize to bone, intracardiac injection and intracaudal arterial animal models were developed. The intratibial injection animal model was established to investigate the communication between cancer cells and the bone microenvironment and to mimic the setting of prostate cancer patients with bone metastasis. Given that detailed protocols of intratibial injection and its quantitative analysis are still insufficient, in this protocol, we provide hands-on procedures for how to prepare cells, perform the tibial injection, monitor tibial tumor growth, and quantitatively evaluate the tibial tumors in pathological samples. This manuscript provides a ready-to-use experimental protocol for investigating cancer cell behaviors in bone and developing novel therapeutic strategies for bone metastatic cancer patients.

Toxic effects of patulin on mouse oocytes and its possible mechanisms

Patulin is a secondary metabolite mainly secreted by fungi and is the most common mycotoxin found in apples and apple-based products. For the past few years, numerous studies suggested the wide distribution and toxicity of patulin. In this study, we investigated the toxic effect of patulin on mouse oocytes and its possible mechanisms. The results showed that patulin treatment did not affect meiotic resumption, but inhibited oocyte maturation as indicated by failure of first polar body extrusion. Further mechanistic study showed that patulin treatment disturbed normal spindle assembly, chromosome alignment and morphology. We also found increased oxidative stress by testing the level of ROS and decreased mitochondrial membrane potential, indicating mitochondria dysfunction. In summary, our results suggest that patulin treatment causes oocyte meiotic arrest by disturbing normal spindle assembly and chromosome alignment, which may be caused by dysfunctions of mitochondria.

Specific deletion of protein phosphatase 6 catalytic subunit in Sertoli cells leads to disruption of spermatogenesis

Protein phosphatase 6 (PP6) is a member of the PP2A-like subfamily, which plays significant roles in numerous fundamental biological activities. We found that PPP6C plays important roles in male germ cells recently. Spermatogenesis is supported by the Sertoli cells in the seminiferous epithelium. In this study, we crossed Ppp6cF/F mice with AMH-Cre mice to gain mutant mice with specific depletion of the Ppp6c gene in the Sertoli cells. We discovered that the PPP6C cKO male mice were absolutely infertile and germ cells were largely lost during spermatogenesis. By combing phosphoproteome with bioinformatics analysis, we showed that the phosphorylation status of β-catenin at S552 (a marker of adherens junctions) was significantly upregulated in mutant mice. Abnormal β-catenin accumulation resulted in impaired testicular junction integrity, thus led to abnormal structure and functions of BTB. Taken together, our study reveals a novel function for PPP6C in male germ cell survival and differentiation by regulating the cell-cell communication through dephosphorylating β-catenin at S552.

Cell Division Cycle 5-Like Regulates Metaphase-to-Anaphase Transition in Meiotic Oocyte

The quality of oocytes is a vital factor for embryo development. Meiotic progression through metaphase I usually takes a relatively long time to ensure correct chromosome separation, a process that is critical for determining oocyte quality. Here, we report that cell division cycle 5-like (Cdc5L) plays a critical role in regulating metaphase-to-anaphase I transition during mouse oocyte meiotic maturation. Knockdown of Cdc5L by small interfering RNA injection did not affect spindle assembly but caused metaphase I arrest and subsequent reduced first polar body extrusion due to insufficient anaphase-promoting complex/cyclosome activity. We further showed that Cdc5L could also directly interact with securin, and Cdc5L knockdown led to a continuous high expression level of securin, causing severely compromised meiotic progression. The metaphase-to-anaphase I arrest caused by Cdc5L knockdown could be rescued by knockdown of endogenous securin. In summary, we reveal a novel role for Cdc5L in regulating mouse oocyte meiotic progression by interacting with securin.

Evaluation of the Genetic Variation Spectrum Related to Corneal Dystrophy in a Large Cohort

Aims

To characterize the genetic landscape and mutation spectrum of patients with corneal dystrophies (CDs) in a large Han ethnic Chinese Cohort with inherited eye diseases (IEDs).

Methods

Retrospective study. A large IED cohort was recruited in this study, including 69 clinically diagnosed CD patients, as well as other types of eye diseases patients and healthy family members as controls. The 792 genes on the Target_Eye_792_V2 chip were used to screen all common IEDs in our studies, including 22 CD-related genes.

Results

We identified 2334 distinct high-quality variants on 22 CD-related genes in a large IEDs cohort. A total of 21 distinct pathogenic or likely pathogenic mutations were identified, and the remaining 2313 variants in our IED cohort had no evidence of CD-related pathogenicity. Overall, 81.16% (n = 56/69) of CD patients received definite molecular diagnoses, and transforming growth factor-beta-induced protein (TGFBI), CHTS6, and SLC4A11 genes covered 91.07, 7.14, and 1.79% of the diagnosed cases, respectively. Twelve distinct disease-associated mutations in the TGFBI gene were identified, 11 of which were previously reported and one is novel. Four of these TGFBI mutations (p.D123H, p.M502V, p.P501T, and p.P501A) were redefined as likely benign in our Han ethnic Chinese IED cohort after performing clinical variant interpretation. These four TGFBI mutations were detected in asymptomatic individuals but not in CD patients, especially the previously reported disease-causing mutation p.P501T. Among 56 CD patients with positive detected mutations, the recurrent TGFBI mutations were p.R124H, p.R555W, p.R124C, p.R555Q, and p.R124L, and the proportions were 32.14, 19.64, 14.29, 10.71, and 3.57%, respectively. Twelve distinct pathogenic or likely pathogenic mutations of CHTS6 were detected in 28 individuals. The recurrent mutations were p.Y358H, p.R140X, and p.R205W, and the proportions were 25.00, 21.43, and 14.29%, respectively. All individuals associated with TGFBI were missense mutations; 74.19% associated with CHTS6 mutations were missense mutations, and 25.81% were non-sense mutations. Hot regions were located in exons 4 and 12 of TGFBI individuals and located in exon 3 of CHTS6 individuals. No de novo mutations were identified.

Conclusion

For the first time, our large cohort study systematically described the variation spectrum of 22 CD-related genes and evaluated the frequency and pathogenicity of all 2334 distinct high-quality variants in our IED cohort. Our research will provide East Asia and other populations with baseline data from a Han ethnic population-specific level.

The Cyclin B2/CDK1 Complex Conservatively Inhibits Separase Activity in Oocyte Meiosis II

Recently, we have reported that the cyclin B2/CDK1 complex regulates homologous chromosome segregation through inhibiting separase activity in oocyte meiosis I, which further elucidates the compensation of cyclin B2 on cyclin B1’s function in meiosis I. However, whether cyclin B2/CDK1 complex also negatively regulates separase activity during oocyte meiosis II remains unknown. In the present study, we investigated the function of cyclin B2 in meiosis II of oocyte. We found that stable cyclin B2 expression impeded segregation of sister chromatids after oocyte parthenogenetic activation. Consistently, stable cyclin B2 inhibited separase activation, while introduction of non-phosphorylatable separase mutant rescued chromatid separation in the stable cyclin B2-expressed oocytes. Therefore, the cyclin B2/CDK1 complex conservatively regulates separase activity via inhibitory phosphorylation of separase in both meiosis I and meiosis II of mouse oocyte.

Critical Functions of PP2A-Like Protein Phosphotases in Regulating Meiotic Progression

Meiosis is essential to the continuity of life in sexually-reproducing organisms through the formation of haploid gametes. Unlike somatic cells, the germ cells undergo two successive rounds of meiotic divisions after a single cycle of DNA replication, resulting in the decrease in ploidy. In humans, errors in meiotic progression can cause infertility and birth defects. Post-translational modifications, such as phosphorylation, ubiquitylation and sumoylation have emerged as important regulatory events in meiosis. There are dynamic equilibrium of protein phosphorylation and protein dephosphorylation in meiotic cell cycle process, regulated by a conservative series of protein kinases and protein phosphatases. Among these protein phosphatases, PP2A, PP4, and PP6 constitute the PP2A-like subfamily within the serine/threonine protein phosphatase family. Herein, we review recent discoveries and explore the role of PP2A-like protein phosphatases during meiotic progression.

Cyclins regulating oocyte meiotic cell cycle progression†

Oocyte meiotic maturation is a vital and final process in oogenesis. Unlike somatic cells， the oocyte needs to undergo two continuous meiotic divisions (meiosis I and meiosis II) to become a haploid gamete. Notably, oocyte meiotic progression includes two rounds of unique meiotic arrest and resumption. The first arrest occurs at the G2 (germinal vesicle) stage and meiosis resumption is stimulated by a gonadotropin surge; the second arrest takes place at the metaphase II stage, the stage from which it is released when fertilization takes place. The maturation-promoting factor, which consists of cyclin B1 (CCNB1) and cyclin-dependent kinase 1 (CDK1), is responsible for regulating meiotic resumption and progression, while CDK1 is the unique CDK that acts as the catalytic subunit of maturation-promoting factor. Recent studies showed that except for cyclin B1, multiple cyclins interact with CDK1 to form complexes, which are involved in the regulation of meiotic progression at different stages. Here, we review and discuss the control of oocyte meiotic progression by cyclins A1, A2, B1, B2, B3, and O.

Efficacy of intrauterine perfusion of peripheral blood mononuclear cells (PBMC) for infertile women before embryo transfer: meta-analysis

This meta-analysis was intended to evaluate the effects of intrauterine perfusion of peripheral blood mononuclear cells (PBMC) on the pregnancy outcomes including clinical pregnancy rates, embryo implantation rates, live birth rates and miscarriage rates of infertile women who were undergoing in vitro fertilisation (IVF) treatment. By searching Pubmed, Embase database, five articles meeting the inclusion criteria were included, and 1173 women were enrolled (intrauterine PBMC group: n = 514; NO-PBMC group: n = 659). For the entire IVF/ICSI population and one or two embryo transfer failure patients, there was no significant difference in endometrial thickness, embryo implantation rates, live birth rates, and miscarriage rates between the PBMC group and NO-PBMC group. Although the clinical pregnancy rates of the PBMC group were higher than that of the NO-PBMC group, the confidence interval was close to the line of unity. As for the patients with three or more implantation failures, the clinical pregnancy rates, embryo implantation rates and live birth rates were much higher in the PBMC group than that of the NO-PBMC group. In summary, current evidence suggests that intrauterine perfusion of PBMC can significantly improve pregnancy outcomes in patients who have three or more implantation failures.Impact statementWhat is already known on this subject? An increasing number of studies have shown that immune cells play an important role in embryo transfer. There is no reliable evidence to confirm the clinical efficacy of intrauterine perfusion of PBMC.What do the results of this study add? The current evidence suggests that intrauterine perfusion of PBMC can significantly improve pregnancy outcomes in patients who have three or more implantation failures.What are the implications of these findings for clinical practice and/or further research? To the best of our knowledge, this meta-analysis is the first to evaluate the effect of intrauterine perfusion of PBMC on pregnancy outcomes before embryo transfer. Our study indicated that intrauterine perfusion of PBMC significantly increased clinical pregnancy rates, embryo implantation rates, and live birth rates in patients who failed more than three implants.

Treatment of Infertile Women with Unilateral Tubal Occlusion Diagnosed by Hysterosalpingography: The Role of Intrauterine Insemination

The optimal assisted reproductive treatment strategy for infertile women with unilateral tubal obstruction remains uncertain. To investigate the role of intrauterine insemination (IUI) in the treatment of infertile women with unilateral tubal occlusion, the data of 148 couples were retrospectively collected and analyzed. Seventy-eight infertile women with unilateral occlusion diagnosed by hysterosalpingography (HSG) were categorized as the study group and 70 others with unexplained infertility as the control group. The study group was divided into a proximal occlusion subgroup and a mid-distal occlusion subgroup for further analysis. The main outcomes, namely the clinical pregnancy rate (CPR), ongoing pregnancy rate (OPR), and live birth rate (LBR) per cycle, were analyzed. Our results showed a tendency of lower CPR, OPR, and LBR in the study group than in the control group, without statistical significance. Further investigations revealed that the unilateral proximal occlusion subgroup had similar CPR, OPR, and LBR as the control group, while the unilateral mid-distal occlusion subgroup had significantly lower CPR (5.1% vs. 20.0%, P=0.035), OPR (5.1% vs. 20.0%, P=0.035), and LBR (5.1% vs. 20.0%, P=0.035) than the control group. In conclusion, the clinical outcomes of IUI were worse in patients with unilateral tubal occlusion than in those with unexplained infertility. This might be primarily caused by the worse outcome of patients with unilateral mid-distal tubal occlusion instead of proximal occlusion.

Overexpression of cyclin A1 promotes meiotic resumption but induces premature chromosome separation in mouse oocyte

Mammalian cyclin A1 is prominently expressed in testis and essential for meiosis in the male mouse, however, it shows weak expression in ovary, especially during oocyte maturation. To understand why cyclin A1 behaves in this way in the oocyte, we investigated the effect of cyclin A1 overexpression on mouse oocyte meiotic maturation. Our results revealed that cyclin A1 overexpression triggered meiotic resumption even in the presence of germinal vesicle breakdown inhibitor, milrinone. Nevertheless, the cyclin A1-overexpressed oocytes failed to extrude the first polar body but were completely arrested at metaphase I. Consequently, cyclin A1 overexpression destroyed the spindle morphology and chromosome alignment by inducing premature separation of chromosomes and sister chromatids. Therefore, cyclin A1 overexpression will prevent oocyte maturation although it can promote meiotic resumption. All these results show that decreased expression of cyclin A1 in oocytes may have an evolutional significance to keep long-lasting prophase arrest and orderly chromosome separation during oocyte meiotic maturation.

CDC6 regulates both G2/M transition and metaphase-to-anaphase transition during the first meiosis of mouse oocytes

Cell division cycle protein, CDC6, is essential for the initiation of DNA replication. CDC6 was recently shown to inhibit the microtubule-organizing activity of the centrosome. Here, we show that CDC6 is localized to the spindle from pro-metaphase I (MI) to MII stages of oocytes, and it plays important roles at two critical steps of oocyte meiotic maturation. CDC6 depletion facilitated the G2/M transition (germinal vesicle breakdown [GVBD]) through regulation of Cdh1 and cyclin B1 expression and CDK1 (CDC2) phosphorylation in a GVBD-inhibiting culture system containing milrinone. Furthermore, GVBD was significantly decreased after knockdown of cyclin B1 in CDC6-depleted oocytes, indicating that the effect of CDC6 loss on GVBD stimulation was mediated, at least in part, by raising cyclin B1. Knockdown of CDC6 also caused abnormal localization of γ-tubulin, resulting in defective spindles, misaligned chromosomes, cyclin B1 accumulation, and spindle assembly checkpoint (SAC) activation, leading to significant pro-MI/MI arrest and PB1 extrusion failure. These phenotypes were also confirmed by time-lapse live cell imaging analysis. The results indicate that CDC6 is indispensable for maintaining G2 arrest of meiosis and functions in G2/M checkpoint regulation in mouse oocytes. Moreover, CDC6 is also a key player regulating meiotic spindle assembly and metaphase-to-anaphase transition in meiotic oocytes.

The cyclin B2/CDK1 complex inhibits separase activity in mouse oocyte meiosis I

Chromosome segregation is driven by separase, activity of which is inhibited by binding to securin and cyclin B1/CDK1. In meiosis, premature separase activity will induce aneuploidy or abolish chromosome segregation owing to the untimely destruction of cohesin. Recently, we have proved that cyclin B2 can compensate for cyclin B1 in CDK1 activation for the oocyte meiosis G2/M transition. In the present study, we identify an interaction between cyclin B2/CDK1 and separase in mouse oocytes. We find that cyclin B2 degradation is required for separase activation during the metaphase I-anaphase I transition because the presence of stable cyclin B2 leads to failure of homologous chromosome separation and to metaphase I arrest, especially in the simultaneous absence of securin and cyclin B1. Moreover, non-phosphorylatable separase rescues the separation of homologous chromosomes in stable cyclin B2-arrested cyclin B1-null oocytes. Our results indicate that cyclin B2/CDK1 is also responsible for separase inhibition via inhibitory phosphorylation to regulate chromosome separation in oocyte meiosis, which may not occur in other cell types.

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.

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.

Cyclin B2 can compensate for Cyclin B1 in oocyte meiosis I

Cyclin B1 and its interaction with CDK1 are thought to be critical for meiosis I progression in oocytes. However, using oocyte-specific conditional knockouts, Li et al. show that Cyclin B2 activity can compensate for Cyclin B1 to trigger meiosis resumption.

Mammalian oocytes are arrested at the prophase of the first meiotic division for months and even years, depending on species. Meiotic resumption of fully grown oocytes requires activation of M-phase–promoting factor (MPF), which is composed of Cyclin B1 and cyclin-dependent kinase 1 (CDK1). It has long been believed that Cyclin B1 synthesis/accumulation and its interaction with CDK1 is a prerequisite for MPF activation in oocytes. In this study, we revealed that oocyte meiotic resumption occurred in the absence of Cyclin B1. Ccnb1-null oocytes resumed meiosis and extruded the first polar body. Without Cyclin B1, CDK1 could be activated by up-regulated Cyclin B2. Ccnb1 and Ccnb2 double knockout permanently arrested the oocytes at the prophase of the first meiotic division. Oocyte-specific Ccnb1-null female mice were infertile due to failed MPF activity elevation and thus premature interphase-like stage entry in the second meiotic division. These results have revealed a hidden compensatory mechanism between Cyclin B1 and Cyclin B2 in regulating MPF and oocyte meiotic resumption.

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.

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.

Age-associated changes in gene expression of goat oocytes

Oocyte aging severely decreases the quality of oocytes, which hampers fertilization and subsequent embryo development. In the present study, age-dependent molecular changes in goat oocytes were investigated. First, the quality of goat oocytes with various in vitro culture times (24, 30, 36, 48, and 60 hours) was evaluated on the basis of developmental rates of parthenogenetically activated embryos and apoptosis of cumulus cells (CCs). Second, relative gene expression of six genes (mitochondrial genes: PGC-1α and NRF-1; epigenetic modification genes: SNRPN and HAT1; mitotic spindle checkpoint protein: SMAD2; and hyaluronan synthase gene: HAS3) were analyzed during oocyte aging. Third, we further studied the changes of seven genes (PGC-1α and NRF-1; apoptotic-related genes: BAX and BCL2; hyaluronan synthase gene: HAS2; metabolism-related gene: STAR; and superoxide dismutase gene: SOD1) in CCs during oocyte aging. In these studies, the blastocyst rate gradually decreased and the number of apoptotic cells significantly increased as the culture time increased (P < 0.05). Moreover, relative gene expressions of PGC-1α, NRF-1 and SMAD2 significantly decreased from 24 to 36 hours (P < 0.05), whereas the levels of HAT1 and HAS3 slowly increased as culture was prolonged. Furthermore, the levels of PGC-1α, BCL2, HAS2 and SOD1 quickly reduced, and BAX significantly increased from 24 to 36 hours in aged CCs (P < 0.05). In conclusion, goat oocytes started to age at 30 hours in vitro culture, and gene expression patterns of oocytes and CCs significantly changed as the oocytes aged. Gene expression pattern changes in CCs may provide a convenient and effective way to detect oocyte aging without compromising oocyte integrity.

Maternal diabetes causes abnormal dynamic changes of endoplasmic reticulum during mouse oocyte maturation and early embryo development

BACKGROUND

The adverse effects of maternal diabetes on oocyte maturation and embryo development have been reported.

METHODS

In this study, we used time-lapse live cell imaging confocal microscopy to investigate the dynamic changes of ER and the effects of diabetes on the ER's structural dynamics during oocyte maturation, fertilization and early embryo development.

RESULTS

We report that the ER first became remodeled into a dense ring around the developing MI spindle, and then surrounded the spindle during migration to the cortex. ER reorganization during mouse early embryo development was characterized by striking localization around the pronuclei in the equatorial section, in addition to larger areas of fluorescence deeper within the cytoplasm. In contrast, in diabetic mice, the ER displayed a significantly higher percentage of homogeneous distribution patterns throughout the entire ooplasm during oocyte maturation and early embryo development. In addition, a higher frequency of large ER aggregations was detected in GV oocytes and two cell embryos from diabetic mice.

CONCLUSIONS

These results suggest that the diabetic condition adversely affects the ER distribution pattern during mouse oocyte maturation and early embryo development.

B cells and T cells are critical for the preservation of bone homeostasis and attainment of peak bone mass in vivo

Bone homeostasis is regulated by a delicate balance between osteoblastic bone formation and osteoclastic bone resorption. Osteoclastogenesis is controlled by the ratio of receptor activator of NF-kappaB ligand (RANKL) relative to its decoy receptor, osteoprotegerin (OPG). The source of OPG has historically been attributed to osteoblasts (OBs). While activated lymphocytes play established roles in pathological bone destruction, no role for lymphocytes in basal bone homeostasis in vivo has been described. Using immunomagnetic isolation of bone marrow (BM) B cells and B-cell precursor populations and quantitation of their OPG production by enzyme-linked immunosorbent assay (ELISA) and real-time reverse transcriptase-polymerase chain reaction (RT-PCR), cells of the B lineage were found to be responsible for 64% of total BM OPG production, with 45% derived from mature B cells. Consistently B-cell knockout (KO) mice were found to be osteoporotic and deficient in BM OPG, phenomena rescued by B-cell reconstitution. Furthermore, T cells, through CD40 ligand (CD40L) to CD40 costimulation, promote OPG production by B cells in vivo. Consequently, T-cell-deficient nude mice, CD40 KO mice, and CD40L KO mice display osteoporosis and diminished BM OPG production. Our data suggest that lymphocytes are essential stabilizers of basal bone turnover and critical regulators of peak bone mass in vivo.

[Minute chromosome rearrangement detected by human telomeric band painting probes]

In order to assess the value of applying human chromosomal telomeric band painting probes (TBPs) in genetic diagnosis, we used three human telomeric band painting probes in fluorescence in situ hybridization (FISH) to analyze two cases who had a history of habitual abortion and were suspected to carrying a minute translocation. The probes were prepared by microdissection, and the covered regions were 11q23.3-->qter12q24.1-->qter and 22q13.1-->qter, respectively. According to the FISH results, both the cases were cryptic minute translocation carriers. The involved chromosomes were chromosome 11 and 12 in case 1, and chromosome 11 and 22 in case 2. Combined with chromosome G banding, their breakpoints were 11q23.3, 12q24.1, and 22q13.1, respectively. The results showed that the telomeric band painting probes can be used as a tool to determine minute chromosomal abnormality and the precise breakpoints.

An IL-7-dependent rebound in thymic T cell output contributes to the bone loss induced by estrogen deficiency

The bone wasting induced by estrogen deficiency is, in part, a consequence of increased T cell production of the osteoclastogenic cytokine TNF-alpha. This phenomenon is due to an expansion of T cells, but the responsible mechanism is unknown. We now show that ovariectomy (ovx) disregulates T lymphopoiesis and induces bone loss by stimulating, through a rise in IL-7 levels, both thymic-dependent differentiation of bone marrow-derived progenitors and thymic-independent, peripheral expansion of mature T cells. Attesting to the relevance of the thymic effects, thymectomy decreases by approximately 50% the bone loss and the stimulation of T lymphopoiesis induced by ovx. In contrast, in vivo attenuation of the elevated IL-7 completely prevents the stimulation of T lymphopoiesis and the bone loss that follow ovx. Thus, the disruption of both T cell and bone homeostasis induced by ovx is mediated by IL-7 and due to both the thymic and extrathymic mechanisms. We conclude that IL-7 is a pivotal upstream target through which estrogen regulates hematopoietic and immune functions that are critical for bone homeostasis.

Rapid quantification of semen hepatitis B virus DNA by real-time polymerase chain reaction

AIM: To examine the sensitivity and accuracy of real-time polymerase chain reaction (PCR) for the quantification of hepatitis B virus (HBV) DNA in semen.

METHODS: Hepatitis B viral DNA was isolated from HBV carriers’ semen and sera using phenol extraction method and QIAamp DNA blood mini kit (Qiagen, Germany). HBV DNA was detected by conventional PCR and quantified by TaqMan technology-based real-time PCR (quantitative polymerase chain reaction (qPCR)). The detection threshold was 200 copies of HBV DNA for conventional PCR and 10 copies of HBV DNA for real time PCR per reaction.

RESULTS: Both methods of phenol extraction and QIAamp DNA blood mini kit were suitable for isolating HBV DNA from semen. The value of the detection thresholds was 500 copies of HBV DNA per mL in the semen. The viral loads were 7.5 × 10⁷ and 1.67 × 10⁷ copies of HBV DNA per mL in two HBV infected patients’ sera, while 2.14 × 10⁵ and 3.02 × 10⁵ copies of HBV DNA per mL in the semen.

CONCLUSION: Real-time PCR is a more sensitive and accurate method to detect and quantify HBV DNA in the semen.

[Cytogenetic study of 1780 cases of spontaneous abortion]

OBJECTIVE

To explore the relationship between chromosome anomaly and spontaneous abortion, and to provide useful information for genetic counseling and prenatal diagnosis in reproductive clinic.

METHODS

A total of 1 780 patients who had a history of spontaneous abortion before 24 weeks of gestation were enrolled. The lymphocyte culture and harvest were performed according to standard methods. Karyotypes were analyzed by G-banding in all cases and C- banding in some cases in addition.

RESULTS

Altogether 57 abnormal karyotypes were found and the overall incidence of chromosomal abnormalities was 3.20% (women 3.32%; men 2.12%). Among them 23 cases were the balanced translocation; 14 cases were the Robertsonian translocation, 3 cases were the complex chromosomal rearrangement, and the other 17 cases were the other abnormalities. In women with 1, 2, 3 or more spontaneous abortion, the incidence of chromosomal abnormalities was 1.7%, 2.3%, and 5.8%, respectively.

CONCLUSION

Translocations are the major abnormal karyotpes associated with spontaneous abortions. The chance of finding chromosomal aberration increases with the number of abortions. Chromosomal abnormalities are more common in women with 3 or more spontaneous abortions.

Estrogen prevents bone loss through transforming growth factor beta signaling in T cells

Estrogen (E) deficiency leads to an expansion of the pool of tumor necrosis factor (TNF)-producing T cells through an IFN-gamma-dependent pathway that results in increased levels of the osteoclastogenic cytokine TNF in the bone marrow. Disregulated IFN-gamma production is instrumental for the bone loss induced by ovariectomy (ovx), but the responsible mechanism is unknown. We now show that mice with T cell-specific blockade of type beta transforming growth factor (TGFbeta) signaling are completely insensitive to the bone-sparing effect of E. This phenotype results from a failure of E to repress IFN-gamma production, which, in turn, leads to increased T cell activation and T cell TNF production. Furthermore, ovx blunts TGFbeta levels in the bone marrow, and overexpression of TGFbeta in vivo prevents ovx-induced bone loss. These findings demonstrate that E prevents bone loss through a TGFbeta-dependent mechanism, and that TGFbeta signaling in T cells preserves bone homeostasis by blunting T cell activation. Thus, stimulation of TGFbeta production in the bone marrow is a critical "upstream" mechanism by which E prevents bone loss, and enhancement of TGFbeta levels in vivo may constitute a previously undescribed therapeutic approach for preventing bone loss.

An effective method for quantitative evaluation of proteins adsorbed on biomaterial surfaces

An effective method for the quantitative evaluation of proteins adsorbed on biomaterial surfaces has been developed. First, the kinetic behavior of a range of human fibrinogen (Fib) adsorbed onto polystyrene (PS) films was investigated by using a reflectometry interference spectroscopy setup. The specific molecular number of adsorbed proteins, N(p,) was then defined. According to the definition, the numbers of Fib molecules adsorbed on PS films were calculated. An atomic force microscope (AFM) was used to scan the lateral distribution of the Fib molecules adsorbed on the PS films. From the AFM images, the practical specific molecular numbers were obtained by direct counting of the molecules. In order that the adsorbed number of Fib molecules on a unit area of the PS films could be counted easily, the solution concentration of proteins was reduced to 5 ag/mL (10(-18)g/mL). There was good consistency between the numbers calculated with the formula defined by us and the numbers counted from AFM images. Therefore, the results of the present study prove the validity of our definition of the specific molecular number of adsorbed proteins and the effectiveness of the reflectometry interference spectroscopy-based method for quantitative evaluation of adsorptive proteins.

IL-7 induces bone loss in vivo by induction of receptor activator of nuclear factor kappa B ligand and tumor necrosis factor alpha from T cells

IL-7, a powerful lymphopoietic cytokine, is elevated in rheumatoid arthritis (RA) and known to induce bone loss when administered in vivo. IL-7 has been suggested to induce bone loss, in part, by stimulating the proliferation of B220(+) cells, a population capable of acting as early osteoclast (OC) precursors. However, the mechanism by which IL-7 leads to differentiation of precursors into mature OCs remains unknown. We previously reported that, in vitro, IL-7 up-regulated T cell cytokines including receptor activator of nuclear factor kappaB ligand (RANKL). To demonstrate the importance of T cells to the bone-wasting effect of IL-7 in vivo, we have now examined IL-7-induced bone loss in T cell-deficient nude mice. We show that T cell-replete mice undergo significant osteoclastic bone loss after IL-7 administration, concurrent with induction of RANKL and tumor necrosis factor alpha (TNF-alpha) secretion by splenic T cells. In contrast, nude mice were resistant to IL-7-induced bone loss and showed no detectable increase in either RANKL or TNF-alpha, despite an up-regulation of B220(+) cells. Importantly, T cell adoptive transfer into nude mice restored IL-7-induced bone loss, and RANKL and TNF-alpha secretion, demonstrating that T cells are essential mediators of IL-7-induced bone loss in vivo.