Glycogen synthase kinase-3 regulation of chromatin segregation and cytokinesis in mouse preimplantation embryos

The Impact of Essential Trace Elements on Ovarian Response and Reproductive Outcomes following Single Euploid Embryo Transfer

Essential trace elements are required in extremely small amounts and obtained through diet. This research focuses on detecting major trace elements in different biofluids of sixty women undergoing ICSI with PGT-A and SET/FET at IVI-RMA, New Jersey, and assessing their impact on their IVF outcomes. Urine, plasma, and follicular fluid samples were collected on the vaginal oocyte retrieval day to measure the concentrations of eight essential trace elements (copper, zinc, molybdenum, lithium, selenium, manganese, chromium, and iron) using ICP-MS. After analysis, ovarian response and preimplantation outcomes had significant positive associations with both copper alone and the copper/zinc ratio in the follicular fluid and plasma, in addition to plasma manganese. Alternatively, elevated follicular fluid lithium concentrations were significantly associated with poor preimplantation outcomes while the urinary molybdenum concentration was significantly associated with a lower probability of implantation, clinical pregnancy, and live birth. Urinary lithium and chromium concentrations were significantly associated with a lower probability of achieving a live birth. Our results suggest that the essential trace elements present in follicular fluid, plasma, and urine of women are directly associated with their reproductive outcomes, with copper and manganese exerting positive effects and lithium and molybdenum exerting negative effects.

Suppression of TGF-β and ERK Signaling Pathways as a New Strategy to Provide Rodent and Non-Rodent Pluripotent Stem Cells

Stem cells are unspecialized cells and excellent model in developmental biology and a promising approach to the treatment of disease and injury. In the last 30 years, pluripotent embryonic stem (ES) cells were established from murine and primate sources, and display indefinite replicative potential and the ability to differentiate to all three embryonic germ layers. Despite large efforts in many aspects of rodent and non-rodent pluripotent stem cell culture, a number of diverse challenges remain. Natural and synthetic small molecules (SMs) strategy has the potential to overcome these hurdles. Small molecules are typically fast and reversible that target specific signaling pathways, epigenetic processes and other cellular processes. Inhibition of the transforming growth factor-β (TGF-β/Smad) and fibroblast growth factor 4 (FGF4)/ERK signaling pathways by SB431542 and PD0325901 small molecules, respectively, known as R2i, enhances the efficiency of mouse, rat, and chicken pluripotent stem cells passaging from different genetic backgrounds. Therefore, the application of SM inhibitors of TGF-β and ERK1/2 with leukemia inhibitory factor (LIF) allows the cultivation of pluripotent stem cells in a chemically defined condition. In this review, we discuss recently emerging evidence that dual inhibition of TGF-β and FGF signaling pathways plays an important role in regulating pluripotency in both rodent and non-rodent pluripotent stem cells.

Lithium chloride inhibits StAR and progesterone production through GSK-3β and ERK1/2 signaling pathways in human granulosa-lutein cells

Lithium chloride (LiCl) is a widely-used medication to treat neurological disorders that has undesirable side effects on the female reproductive system. It has been show that LiCl can inhibit ovarian folliculogenesis, promote follicle atresia and suppress steroid hormone production in rodents. However, the effects of LiCl on human ovarian steroidogenesis remain completely unknown. In this study, both primary and immortalized human granulosa-lutein (hGL) cells were used to investigate the effects of LiCl on progesterone production and its related enzyme expression as well as the underlying mechanisms. Our results showed that LiCl significantly down-regulated the steroidogenic acute regulatory protein (StAR) expression and subsequent progesterone production in hGL cells. Additionally, LiCl induced the phosphorylation of GSK-3β and ERK1/2 but not AKT or CREB. Knockdown of endogenous GSK-3β or inhibition of ERK1/2 partially reversed LiCl-induced down-regulation of StAR. Furthermore, by using dual inhibition approaches, the results showed that both GSK-3β and ERK1/2 signaling mediated the regulatory effect of LiCl on StAR expression. Our findings deepen our understanding of the pathological effects and the underlying molecular mechanisms of how lithium might affect the female reproductive system.

A speculative outlook on embryonic aneuploidy: Can molecular pathways be involved?

The journey of embryonic development starts at oocyte fertilization, which triggers a complex cascade of events and cellular pathways that guide early embryogenesis. Recent technological advances have greatly expanded our knowledge of cleavage-stage embryo development, which is characterized by an increased rate of whole-chromosome losses and gains, mixoploidy, and atypical cleavage morphokinetics. Embryonic aneuploidy significantly contributes to implantation failure, spontaneous miscarriage, stillbirth or congenital birth defects in both natural and assisted human reproduction. Essentially, early embryo development is strongly determined by maternal factors. Owing to considerable limitations associated with human oocyte and embryo research, the use of animal models is inevitable. However, cellular and molecular mechanisms driving the error-prone early stages of development are still poorly described. In this review, we describe known events that lead to aneuploidy in mammalian oocytes and preimplantation embryos. As the processes of oocyte and embryo development are rigorously regulated by multiple signal-transduction pathways, we explore the putative role of signaling pathways in genomic integrity maintenance. Based on the existing evidence from human and animal data, we investigate whether critical early developmental pathways, like Wnt, Hippo and MAPK, together with distinct DNA damage response and DNA repair pathways can be associated with embryo genomic instability, a question that has, so far, remained largely unexplored.

An Eye Organoid Approach Identifies Six3 Suppression of R-spondin 2 as a Critical Step in Mouse Neuroretina Differentiation

Recent advances in self-organizing, 3-dimensional tissue cultures of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) provided an in vitro model that recapitulates many aspects of the in vivo developmental steps. Using Rax-GFP-expressing ESCs, newly generated Six3-/- iPSCs, and conditional null Six3delta/f;Rax-Cre ESCs, we identified Six3 repression of R-spondin 2 (Rspo2) as a required step during optic vesicle morphogenesis and neuroretina differentiation. We validated these results in vivo by showing that transient ectopic expression of Rspo2 in the anterior neural plate of transgenic mouse embryos was sufficient to inhibit neuroretina differentiation. Additionally, using a chimeric eye organoid assay, we determined that Six3 null cells exert a non-cell-autonomous repressive effect during optic vesicle formation and neuroretina differentiation. Our results further validate the organoid culture system as a reliable and fast alternative to identify and evaluate genes involved in eye morphogenesis and neuroretina differentiation in vivo.

Lithium Chloride Increases COX-2 Expression and PGE2 Production in a Human Granulosa-Lutein SVOG Cell Line Via a GSK-3β/β-Catenin Signaling Pathway

Lithium chloride (LiCl) is widely prescribed for the treatment of bipolar disorders and is associated with a higher incidence of reproductive adverse effects. Cyclooxygenase (COX)-2 and its derivative, prostaglandin E2 (PGE2), play regulatory roles in the human ovulatory process. Whether LiCl affects ovulation by regulating COX2 expression and PGE2 production in the human ovary is still largely unknown. The aim of this study was to investigate the effect of LiCl on the expression of COX-2 and production of PGE2 in human granulosa-lutein (hGL) cells, as well as the mechanisms underlying this effect. Both immortalized and primary hGL cells were used as research models. Using dual inhibition approaches, our results show that LiCl initiates the hGL cellular action by inhibiting the activity of glycogen synthase kinase-3β [GSK-3β (phosphorylation of GSK-3β)] and activation of extracellular signal-regulated kinase 1/2 (ERK1/2), but not by affecting protein kinase B or cAMP response element binding protein signaling. Additionally, the phosphorylation of GSK-3β, but not ERK1/2, resulted in the stabilization and nuclear localization of β-catenin. Furthermore, knockdown of either β-catenin or GSK-3β reversed the LiCl-induced upregulation of COX-2 expression. These results indicate that LiCl upregulates the expression of COX-2 and the subsequent production of PGE2 through the canonical GSK-3β/β-catenin signaling pathway in hGL cells.

Application Of Small Molecules Favoring Naïve Pluripotency during Human Embryonic Stem Cell Derivation

In mice, inhibition of both the fibroblast growth factor (FGF) mitogen-activated protein kinase kinase/extracellular-signal regulated kinase (MEK/Erk) and the Wnt signaling inhibitor glycogen synthase-3β (GSK3β) enables the derivation of mouse embryonic stem cells (mESCs) from nonpermissive strains in the presence of leukemia inhibitory factor (LIF). Whereas mESCs are in an uncommitted naïve state, human embryonic stem cells (hESCs) represent a more advanced state, denoted as primed pluripotency. This burdens hESCs with a series of characteristics, which, in contrast to naïve ESCs, makes them not ideal for key applications such as cell-based clinical therapies and human disease modeling. In this study, different small molecule combinations were applied during human ESC derivation. Hereby, we aimed to sustain the naïve pluripotent state, by interfering with various key signaling pathways. First, we tested several combinations on existing, 2i (PD0325901 and CHIR99021)-derived mESCs. All combinations were shown to be equally adequate to sustain the expression of naïve pluripotency markers. Second, these conditions were tested during hESC derivation. Overall, the best results were observed in the presence of medium supplemented with 2i, LIF, and the noncanonical Wnt signaling agonist Wnt5A, alone and combined with epinephrine. In these conditions, outgrowths repeatedly showed an ESC progenitor-like morphology, starting from day 3. Culturing these "progenitor cells" did not result in stable, naïve hESC lines in the current conditions. Although Wnt5A could not promote naïve hESC derivation, we found that it was sustaining the conversion of established hESCs toward a more naïve state. Future work should aim to distinct the effects of the various culture formulations, including our Wnt5A-supplemented medium, reported to promote stable naïve pluripotency in hESCs.

GSK-3β Phosphorylation of Cytoplasmic Dynein Reduces Ndel1 Binding to Intermediate Chains and Alters Dynein Motility

Glycogen synthase kinase 3 (GSK‐3) has been linked to regulation of kinesin‐dependent axonal transport in squid and flies, and to indirect regulation of cytoplasmic dynein. We have now found evidence for direct regulation of dynein by mammalian GSK‐3β in both neurons and non‐neuronal cells. GSK‐3β coprecipitates with and phosphorylates mammalian dynein. Phosphorylation of dynein intermediate chain (IC) reduces its interaction with Ndel1, a protein that contributes to dynein force generation. Two conserved residues, S87/T88 in IC‐1B and S88/T89 in IC‐2C, have been identified as GSK‐3 targets by both mass spectrometry and site‐directed mutagenesis. These sites are within an Ndel1‐binding domain, and mutation of both sites alters the interaction of IC's with Ndel1. Dynein motility is stimulated by (i) pharmacological and genetic inhibition of GSK‐3β, (ii) an insulin‐sensitizing agent (rosiglitazone) and (iii) manipulating an insulin response pathway that leads to GSK‐3β inactivation. Thus, our study connects a well‐characterized insulin‐signaling pathway directly to dynein stimulation via GSK‐3 inhibition.

Loss of glycogen synthase kinase 3 isoforms during murine oocyte growth induces offspring cardiac dysfunction

Glycogen synthase kinase-3 (GSK3) is a constitutively active serine threonine kinase with 1) two isoforms (GSK3A and GSK3B) that have unique and overlapping functions, 2) multiple molecular intracellular mechanisms that involve phosphorylation of diverse substrates, and 3) implications in pathogenesis of many diseases. Insulin causes phosphorylation and inactivation of GSK3 and mammalian oocytes have a functional insulin-signaling pathway whereby prolonged elevated insulin during follicle/oocyte development causes GSK3 hyperphosphorylation, reduced GSK3 activity, and altered oocyte chromatin remodeling. Periconceptional diabetes and chronic hyperinsulinemia are associated with congenital malformations and onset of adult diseases of cardiovascular origin. Objectives were to produce transgenic mice with individual or concomitant loss of GSK3A and/or GSK3B and investigate the in vivo role of oocyte GSK3 on fertility, fetal development, and offspring health. Wild-type males bred to females with individual or concomitant loss of oocyte GSK3 isoforms did not have reduced fertility. However, concomitant loss of GSK3A and GSK3B in the oocyte significantly increased neonatal death rate due to congestive heart failure secondary to ventricular hyperplasia. Individual loss of oocyte GSK3A or GSK3B did not induce this lethal phenotype. In conclusion, absence of oocyte GSK3 in the periconceptional period does not alter fertility yet causes offspring cardiac hyperplasia, cardiovascular defects, and significant neonatal death. These results support a developmental mechanism by which periconceptional hyperinsulinemia associated with maternal metabolic syndrome, obesity, and/or diabetes can act on the oocyte and affect offspring cardiovascular development, function, and congenital heart malformation.

MiRNA-320 in the human follicular fluid is associated with embryo quality in vivo and affects mouse embryonic development in vitro

Previous work from our laboratory demonstrated the existence of miRNAs in human follicular fluid. In the current study, we have sought to identify miRNAs that might affect oocyte/embryo quality in patients undergoing intracytoplasmic sperm injection and to investigate their roles in in vitro fertilization outcomes in mouse oocytes. 53 samples were classified as Group 1 (high quality) if the day-3 embryos had seven and more cells or as Group 2 (low quality) if the embryos had six and fewer cells. TaqMan Human microRNAs cards and qRT-PCR were performed to verify differently expressed miRNAs. The function of the corresponding miRNA was investigated in mouse oocytes by injecting them with miRNA-inhibitor oligonucleotides. We found that hsa-miR-320a and hsa-miR-197 had significantly higher expression levels in the Group 1 follicular fluids than in Group 2 (p = 0.0073 and p = 0.008, respectively). Knockdown of mmu-miR-320 in mouse oocytes strongly decreased the proportions of MII oocytes that developed into two-cell and blastocyst stage embryos (p = 0.0048 and p = 0.0069, respectively). Wnt signaling pathway components had abnormal expression level in miR-320 inhibitor-injected oocytes. This study provides the first evidence that miRNAs in human follicular fluid are indicative of and can influence embryo quality.

Metabolic control of oocyte development: linking maternal nutrition and reproductive outcomes

Obesity, diabetes, and related metabolic disorders are major health issues worldwide. As the epidemic of metabolic disorders continues, the associated medical co-morbidities, including the detrimental impact on reproduction, increase as well. Emerging evidence suggests that the effects of maternal nutrition on reproductive outcomes are likely to be mediated, at least in part, by oocyte metabolism. Well-balanced and timed energy metabolism is critical for optimal development of oocytes. To date, much of our understanding of oocyte metabolism comes from the effects of extrinsic nutrients on oocyte maturation. In contrast, intrinsic regulation of oocyte development by metabolic enzymes, intracellular mediators, and transport systems is less characterized. Specifically, decreased acid transport proteins levels, increased glucose/lipid content and elevated reactive oxygen species in oocytes have been implicated in meiotic defects, organelle dysfunction and epigenetic alteration. Therefore, metabolic disturbances in oocytes may contribute to the diminished reproductive potential experienced by women with metabolic disorders. In-depth research is needed to further explore the underlying mechanisms. This review also discusses several approaches for metabolic analysis. Metabolomic profiling of oocytes, the surrounding granulosa cells, and follicular fluid will uncover the metabolic networks regulating oocyte development, potentially leading to the identification of oocyte quality markers and prevention of reproductive disease and poor outcomes in offspring.

Tuning of β-catenin activity is required to stabilize self-renewal of rat embryonic stem cells

Stabilization of β-catenin, through inhibition of glycogen synthase kinase 3 (GSK3) activity, in conjunction with inhibition of mitogen-activated protein kinase kinase 1/2 (MEK) promotes self-renewal of naïve-type mouse embryonic stem cells (ESC). In developmentally more advanced, primed-type, epiblast stem cells, however, β-catenin activity induces differentiation. We investigated the response of rat ESCs to β-catenin signaling and found that when maintained on feeder-support cells in the presence of a MEK inhibitor alone (1i culture), the derivation efficiency, growth, karyotypic stability, transcriptional profile, and differentiation potential of rat ESC cultures was similar to that of cell lines established using both MEK and GSK3 inhibitors (2i culture). Equivalent mouse ESCs, by comparison, differentiated in identical 1i conditions, consistent with insufficient β-catenin activity. This interspecies difference in reliance on GSK3 inhibition corresponded with higher overall levels of β-catenin activity in rat ESCs. Indeed, rat ESCs displayed widespread expression of the mesendoderm-associated β-catenin targets, Brachyury and Cdx2 in 2i medium, and overt differentiation upon further increases in β-catenin activity. In contrast, mouse ESCs were resistant to differentiation at similarly elevated doses of GSK3 inhibitor. Interestingly, without feeder support, moderate levels of GSK3 inhibition were necessary to support effective growth of rat ESC, confirming the conserved role for β-catenin in ESC self-renewal. This work identifies β-catenin signaling as a molecular rheostat in rat ESC, regulating self-renewal in a dose-dependent manner, and highlights the potential importance of controlling flux in this signaling pathway to achieve effective stabilization of naïve pluripotency.

A new chemical approach to the efficient generation of mouse embryonic stem cells

Here, we present a highly efficient and reproducible method for the establishment of mouse embryonic stem cells (mESCs) from embryonic day 3.5 (E3.5) whole blastocysts. This protocol involves the use of small molecules SB431542 and PD0325901, which inhibit transforming growth factor-β (TGF-β) and extracellular signal-regulated kinases (ERK1/2), respectively. This protocol is universal in the derivation of mESC lines from NMRI, C57BL/6, BALB/c, DBA/2, and FVB/N strains, which have previously been considered refractory or non-permissive for ESC establishment. The efficiency of mESC lines generation is 100%, regardless of genetic background.

Differential glycolytic and glycogenogenic transduction pathways in male and female bovine embryos produced in vitro

Previous studies have shown that developmental kinetic rates following IVF are lower in female than in male blastocysts and that this may be related to differences in glucose metabolism. In addition, an inhibition of phosphatidylinositol 3-kinase (PI3-K) inhibits glucose uptake in murine blastocysts. Therefore, the aim of this study was to identify and compare the expression of proteins involved in glucose metabolism (hexokinase-I, HK-I; phosphofructokinase-1, PFK-1; pyruvate kinase 1/2, PK1/2; glyceraldehyde-3-phosphate dehydrogenase, GAPDH; glucose transporter-1, GLUT-1; and glycogen synthase kinase-3, GSK-3) in male and female bovine blastocysts to determine whether PI3-K has a role in the regulation of the expression of these proteins. Hexokinase-I, PFK-1, PK1/2, GAPDH and GLUT-1 were present in bovine embryos. Protein expression of these proteins and GSK-3 was significantly higher in male compared with female blastocysts. Inhibition of PI3-K with LY294002 significantly decreased the expression of HK-I, PFK-1, GAPDH, GSK-3A/B and GLUT-1. Results showed that the expression of glycolytic proteins HK-I, PFK-1, GAPDH and PK1/2, and the transporters GLUT-1 and GSK-3 is regulated by PI3-K in bovine blastocysts. Moreover, the differential protein expression observed between male and female blastocysts might explain the faster developmental kinetics seen in males, as the expression of main proteins involved in glycolysis and glycogenogenesis was significantly higher in male than female bovine embryos and also could explain the sensitivity of male embryos to a high concentration of glucose, as a positive correlation between GLUT-1 expression and glucose uptake in embryos has been demonstrated.

Insulin increases epiblast cell number of in vitro cultured mouse embryos via the PI3K/GSK3/p53 pathway

High-quality embryos give rise to embryonic stem cells (ESCs) at greater efficiencies than poor-quality embryos. However, most embryos available for human ESC derivation are of a reduced quality as a result of culture in relatively simple media up to 10 years earlier, before cryopreservation, or before compaction. In the present study, we used a mouse model to determine whether a culture with insulin from the 8-cell stage could increase the number of ESC progenitor epiblast cells in blastocysts, as well as endeavor to determine the molecular mechanism of the insulin's effect. Culture in media containing 1.7 ρM insulin increased epiblast cell number (determined by Oct4 and Nanog co-expression), and proportion in day 6 blastocysts. The inhibition of phosphoinositide 3 kinase (PI3K) (via LY294002), an early second messenger of the insulin receptor, blocked this effect. The inhibition of glycogen synthase kinase 3 (GSK3) or p53, 2 s messengers inactivated by insulin signaling (via CT99021 or pifithrin-α, respectively), increased epiblast cell numbers. When active, GSK3 and p53 block the transcription of Nanog, which is important for maintaining pluripotency. A simultaneous inhibition of GSK3 and p53 had no synergistic effects on epiblast cell number. The induced activation of GSK3 and p53, via the inhibition of proteins responsible for their inactivation (PKA via H-89 and SIRT-1 via nicotinamide, respectively), blocked the insulin's effect on the epiblast.From our findings, we conclude that insulin increases epiblast cell number via the activation of PI3K, which ultimately inactivates GSK3 and p53. Furthermore, we suggest that the inclusion of insulin in culture media could be used as a strategy for increasing the efficiency with which the ESC lines can be derived from cultured embryos.

Embryonic stem cells require Wnt proteins to prevent differentiation to epiblast stem cells

Pluripotent stem cells exist in naive and primed states, epitomized by mouse embryonic stem cells (ESCs) and the developmentally more advanced epiblast stem cells (EpiSCs; ref. 1). In the naive state of ESCs, the genome has an unusual open conformation and possesses a minimum of repressive epigenetic marks. In contrast, EpiSCs have activated the epigenetic machinery that supports differentiation towards the embryonic cell types. The transition from naive to primed pluripotency therefore represents a pivotal event in cellular differentiation. But the signals that control this fundamental differentiation step remain unclear. We show here that paracrine and autocrine Wnt signals are essential self-renewal factors for ESCs, and are required to inhibit their differentiation into EpiSCs. Moreover, we find that Wnt proteins in combination with the cytokine LIF are sufficient to support ESC self-renewal in the absence of any undefined factors, and support the derivation of new ESC lines, including ones from non-permissive mouse strains. Our results not only demonstrate that Wnt signals regulate the naive-to-primed pluripotency transition, but also identify Wnt as an essential and limiting ESC self-renewal factor.

Effect of GSK-3 activity, enzymatic inhibition and gene silencing by RNAi on tick oviposition and egg hatching

Glycogen synthase kinase-3 (GSK-3) is classically described as a key enzyme involved in glycogen metabolism in mammals. It has been shown to be highly conserved among several organisms, mainly in the catalytic domain region. This enzyme has already been described in Rhipicephalus (Boophilus) microplus and the ovaries of females appeared to be the major site of GSK-3 transcription. The treatment with GSK-3 specific inhibitor (alsterpaullone, bromo-indirubin-oxime 6 and indirubin-3-oxime) caused a reduction in oviposition and egg hatching in completely engorged female ticks. The effect was more pronounced in partially engorged females when alsterpaullone was administrated by artificial capillary feeding. Moreover, GSK-3 gene silencing by RNAi in partially engorged females reduced significantly both oviposition and hatching. The study of tick embryogenesis and proteins that participate in this process has been suggested as an important means for the development of novel strategies for parasite control. GSK-3 is an essential protein involved in embryonic processes and for this reason it has already been suggested as a possible antigen candidate for tick control.

Glycogen synthase kinase 3B in bovine oocytes and granulosa cells: possible involvement in meiosis during in vitro maturation

Glycogen synthase kinase 3 (GSK3) regulates cellular metabolism and cell cycle via different signalling pathways. In response to insulin and growth factors GSK3 is serine-phosphorylated and inactivated. We analysed GSK3B expression and activation in bovine cumulus cells (CC) and oocytes at different meiotic stagesin vitroin parallel with MAP kinases ERK (MAPK3/MAPK1) and p38 (MAPK14). GSK3B localised to cytoplasm in granulosa cells and in oocytes throughout folliculogenesis. In mature metaphase-II (MII) oocytes, GSK3B was concentrated to the region of midzone between the oocyte and the first polar body, as well as active phospho-Thr Aurora A kinase (AURKA). Duringin vitromaturation (IVM), in oocytes, phospho-Ser9-GSK3B level increased as well as phospho-MAPK3/MAPK1, while phospho-MAPK14 decreased. In CC, phospho-MAPK14 increased upon germinal vesicle breakdown (GVBD)/metaphase-I (MI) and then decreased during transition to MII. Administration of inhibitors of GSK3 activity (lithium chloride or 2′Z,3′E -6-bromoindirubin-3′-oxime) rapidly increased phospho-Ser9-GSK3B, and led to transient decrease of phospho-MAPK3/MAPK1 and to durable enhancing of phospho-MAPK14 in granulosa primary cell culture. GSK3 inhibitors during IVM diminished cumulus expansion and delayed meiotic progression. In cumulus, phospho-MAPK14 level was significantly higher in the presence of inhibitors, comparing with control, through the time of MI/MII transition. In oocytes, phospho-GSK3B was increased and phospho-MAPK3/MAPK1 was decreased before GVBD and oocytes were mainly arrested at MI. Therefore, GSK3B might regulate oocyte meiosis, notably MI/MII transition being the part of MAPK3/1 and MAPK14 pathways in oocytes and CC. GSK3B might be also involved in the local activation of AURKA that controls this transition.

Identification of a kinase profile that predicts chromosome damage induced by small molecule kinase inhibitors

Kinases are heavily pursued pharmaceutical targets because of their mechanistic role in many diseases. Small molecule kinase inhibitors (SMKIs) are a compound class that includes marketed drugs and compounds in various stages of drug development. While effective, many SMKIs have been associated with toxicity including chromosomal damage. Screening for kinase-mediated toxicity as early as possible is crucial, as is a better understanding of how off-target kinase inhibition may give rise to chromosomal damage. To that end, we employed a competitive binding assay and an analytical method to predict the toxicity of SMKIs. Specifically, we developed a model based on the binding affinity of SMKIs to a panel of kinases to predict whether a compound tests positive for chromosome damage. As training data, we used the binding affinity of 113 SMKIs against a representative subset of all kinases (290 kinases), yielding a 113x290 data matrix. Additionally, these 113 SMKIs were tested for genotoxicity in an in vitro micronucleus test (MNT). Among a variety of models from our analytical toolbox, we selected using cross-validation a combination of feature selection and pattern recognition techniques: Kolmogorov-Smirnov/T-test hybrid as a univariate filter, followed by Random Forests for feature selection and Support Vector Machines (SVM) for pattern recognition. Feature selection identified 21 kinases predictive of MNT. Using the corresponding binding affinities, the SVM could accurately predict MNT results with 85% accuracy (68% sensitivity, 91% specificity). This indicates that kinase inhibition profiles are predictive of SMKI genotoxicity. While in vitro testing is required for regulatory review, our analysis identified a fast and cost-efficient method for screening out compounds earlier in drug development. Equally important, by identifying a panel of kinases predictive of genotoxicity, we provide medicinal chemists a set of kinases to avoid when designing compounds, thereby providing a basis for rational drug design away from genotoxicity.

Review of lithium effects on brain and blood

Clinicians have long used lithium to treat manic depression. They have also observed that lithium causes granulocytosis and lymphopenia while it enhances immunological activities of monocytes and lymphocytes. In fact, clinicians have long used lithium to treat granulocytopenia resulting from radiation and chemotherapy, to boost immunoglobulins after vaccination, and to enhance natural killer activity. Recent studies revealed a mechanism that ties together these disparate effects of lithium. Lithium acts through multiple pathways to inhibit glycogen synthetase kinase-3beta (GSK3 beta). This enzyme phosphorylates and inhibits nuclear factors that turn on cell growth and protection programs, including the nuclear factor of activated T cells (NFAT) and WNT/beta-catenin. In animals, lithium upregulates neurotrophins, including brain-derived neurotrophic factor (BDNF), nerve growth factor, neurotrophin-3 (NT3), as well as receptors to these growth factors in brain. Lithium also stimulates proliferation of stem cells, including bone marrow and neural stem cells in the subventricular zone, striatum, and forebrain. The stimulation of endogenous neural stem cells may explain why lithium increases brain cell density and volume in patients with bipolar disorders. Lithium also increases brain concentrations of the neuronal markers n-acetyl-aspartate and myoinositol. Lithium also remarkably protects neurons against glutamate, seizures, and apoptosis due to a wide variety of neurotoxins. The effective dose range for lithium is 0.6-1.0 mM in serum and >1.5 mM may be toxic. Serum lithium levels of 1.5-2.0 mM may have mild and reversible toxic effects on kidney, liver, heart, and glands. Serum levels of >2 mM may be associated with neurological symptoms, including cerebellar dysfunction. Prolonged lithium intoxication >2 mM can cause permanent brain damage. Lithium has low mutagenic and carcinogenic risk. Lithium is still the most effective therapy for depression. It "cures" a third of the patients with manic depression, improves the lives of about a third, and is ineffective in about a third. Recent studies suggest that some anticonvulsants (i.e., valproate, carbamapazine, and lamotrigene) may be useful in patients that do not respond to lithium. Lithium has been reported to be beneficial in animal models of brain injury, stroke, Alzheimer's, Huntington's, and Parkinson's diseases, amyotrophic lateral sclerosis (ALS), spinal cord injury, and other conditions. Clinical trials assessing the effects of lithium are under way. A recent clinical trial suggests that lithium stops the progression of ALS.

Proper Chromatin Condensation and Maintenance of Histone H3 Phosphorylation During Mouse Oocyte Meiosis Requires Protein Phosphatase Activity1

We have shown okadaic acid (OA) and calyculin-A (CLA) inhibition of mouse oocyte phosphoprotein phosphatase 1 (PPP1C) and/or phosphoprotein phosphatase 2A (PPP2CA) results in aberrant chromatin condensation, as evidenced by the inability to resolve bivalents. Phosphorylation of histone H3 at specific residues is thought to regulate chromatin condensation. Therefore, we examined changes in histone H3 phosphorylation during oocyte meiosis and the potential regulation by protein PPPs. Western blot and immunocytochemical analysis revealed histone H3 phosphorylation changed during mouse oocyte meiosis, with changes in chromatin condensation. Germinal vesicle-intact (GV-intact; 0 h) oocytes had no phospho-Ser10 but did have phospho-Ser28 histone H3. Oocytes that had undergone germinal vesicle breakdown (GVBD; 2 h) and progressed to metaphase I (MI; 7 h) and MII (16 h) had phosphorylated Ser10 and Ser28 histone H3 associated with condensed chromatin. To determine whether OA-induced aberrations in chromatin condensation were due to alterations in levels of histone H3 phosphorylation, we assessed phosphorylation of Ser10 and Ser28 residues following PPP inhibition. Oocytes treated with OA (1 microM) displayed increased phosphorylation of histone H3 at both Ser10 and Ser28 compared with controls. To begin to elucidate which OA-sensitive PPP is responsible for regulating chromatin condensation and histone H3 phosphorylation, we examined spatial and temporal localization of OA-sensitive PPPs, PPP1C, and PPP2CA. PPPC2A did not localize to condensed chromatin, whereas PPP1beta (PPP1CB) associated with condensing chromatin in GVBD, MI, and MII oocytes. Additionally, Western blot and immunocytochemistry confirmed presence of the PPP1C regulatory inhibitor subunit 2 (PPP1R2) in oocytes at condensed chromatin during meiosis and indicated a change in PPP1R2 phosphorylation. Inhibition of oocyte glycogen synthase kinase 3 (GSK3) appeared to regulate phosphorylation of PPP1R2. Furthermore, inhibition of GSK3 resulted in aberrant oocyte bivalent formation similar to that observed following PPP inhibition. These data suggest that PPP1CB is the OA/CLA-sensitive PPP that regulates oocyte chromatin condensation through regulation of histone H3 phosphorylation. Furthermore, GSK3 inhibition results in aberrant chromatin condensation and appears to regulate phosphorylation of PPP1R2.

Mitotic phosphorylation of tankyrase, a PARP that promotes spindle assembly, by GSK3

The assembly and function of mitotic spindles require poly(ADP-ribosyl)ation of spindle components by tankyrase, a poly(ADP-ribose) polymerase that aggregates to spindle poles during mitosis. Tankyrase itself is phosphorylated during mitosis, but the kinases involved remain undefined. Herein we report that mitotic phosphorylation of tankyrase is abrogated in cells treated with the GSK3 inhibitors LiCl and indirubin. Moreover, the electrophoretic mobility-shift of tankyrase arising from mitotic phosphorylation can be reproduced in vitro by GSK3-mediated phosphorylation. Lastly, mutagenesis study suggested that GSK3 in vitro phosphorylates tankyrase on S978, T982, S987, and S991, residues that comprise two adjacent copies of the canonical GSK3 phospho-acceptor motif [S/T]-X-X-X-[S/T]. Collectively, our data suggest that GSK3 contributes to mitotic tankyrase phosphorylation, raising the possibility that this phosphorylation might mediate some of the established roles of GSK3 in spindle assembly and mitotic progression.