Histone H3 lysine 27 crotonylation mediates gene transcriptional repression in chromatin.

Histone lysine acylation, including acetylation and crotonylation, plays a pivotal role in gene transcription in health and diseases. However, our understanding of histone lysine acylation has been limited to gene transcriptional activation. Here, we report that histone H3 lysine 27 crotonylation (H3K27cr) directs gene transcriptional repression rather than activation. Specifically, H3K27cr in chromatin is selectively recognized by the YEATS domain of GAS41 in complex with SIN3A-HDAC1 co-repressors. Proto-oncogenic transcription factor MYC recruits GAS41/SIN3A-HDAC1 complex to repress genes in chromatin, including cell-cycle inhibitor p21. GAS41 knockout or H3K27cr-binding depletion results in p21 de-repression, cell-cycle arrest, and tumor growth inhibition in mice, explaining a causal relationship between GAS41 and MYC gene amplification and p21 downregulation in colorectal cancer. Our study suggests that H3K27 crotonylation signifies a previously unrecognized, distinct chromatin state for gene transcriptional repression in contrast to H3K27 trimethylation for transcriptional silencing and H3K27 acetylation for transcriptional activation.

GAS41 promotes H2A.Z deposition through recognition of the N terminus of histone H3 by the YEATS domain.

Glioma amplified sequence 41 (GAS41), which has the Yaf9, ENL, AF9, Taf14, and Sas5 (YEATS) domain that recognizes lysine acetylation (Kac), regulates gene expression as a subunit of the SRCAP (SNF2-related CREBBP activator protein) complex that deposits histone H2A.Z at promoters in eukaryotes. The YEATS domains of the proteins AF9 and ENL recognize Kac by hydrogen bonding the aromatic cage to arginine situated just before K9ac or K27ac in the N-terminal tail of histone H3. Curiously, the YEATS domain of GAS41 binds most preferentially to the sequence that contains K14ac of H3 (H3K14ac) but lacks the corresponding arginine. Here, we biochemically and structurally elucidated the molecular mechanism by which GAS41 recognizes H3K14ac. First, stable binding of the GAS41 YEATS domain to H3K14ac required the N terminus of H3 (H3NT). Second, we revealed a pocket in the GAS41 YEATS domain responsible for the H3NT binding by crystallographic and NMR analyses. This pocket is away from the aromatic cage that recognizes Kac and is unique to GAS41 among the YEATS family. Finally, we showed that E109 of GAS41, a residue essential for the formation of the H3NT-binding pocket, was crucial for chromatin occupancy of H2A.Z and GAS41 at H2A.Z-enriched promoter regions. These data suggest that binding of GAS41 to H3NT via its YEATS domain is essential for its intracellular function.

Temperature-Sensitive Substrate and Product Binding Underlie Temperature-Compensated Phosphorylation in the Clock.

Temperature compensation is a striking feature of the circadian clock. Here we investigate biochemical mechanisms underlying temperature-compensated, CKIδ-dependent multi-site phosphorylation in mammals. We identify two mechanisms for temperature-insensitive phosphorylation at higher temperature: lower substrate affinity to CKIδ-ATP complex and higher product affinity to CKIδ-ADP complex. Inhibitor screening of ADP-dependent phosphatase activity of CKIδ identified aurintricarboxylic acid (ATA) as a temperature-sensitive kinase activator. Docking simulation of ATA and mutagenesis experiment revealed K224D/K224E mutations in CKIδ that impaired product binding and temperature-compensated primed phosphorylation. Importantly, K224D mutation shortens behavioral circadian rhythms and changes the temperature dependency of SCN's circadian period. Interestingly, temperature-compensated phosphorylation was evolutionary conserved in yeast. Molecular dynamics simulation and X-ray crystallography demonstrate that an evolutionally conserved CKI-specific domain around K224 can provide a structural basis for temperature-sensitive substrate and product binding. Surprisingly, this domain can confer temperature compensation on a temperature-sensitive TTBK1. These findings suggest the temperature-sensitive substrate- and product-binding mechanisms underlie temperature compensation.

Polycomb-mediated histone modifications and gene regulation.

Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) are transcriptional repressor complexes that play a fundamental role in epigenomic regulation and the cell-fate decision; these complexes are widely conserved in multicellular organisms. PRC1 is an E3 ubiquitin (ub) ligase that generates histone H2A ubiquitinated at lysine (K) 119 (H2AK119ub1), whereas PRC2 is a histone methyltransferase that specifically catalyzes tri-methylation of histone H3K27 (H3K27me3). Genome-wide analyses have confirmed that these two key epigenetic marks highly overlap across the genome and contribute to gene repression. We are now beginning to understand the molecular mechanisms that enable PRC1 and PRC2 to identify their target sites in the genome and communicate through feedback mechanisms to create Polycomb chromatin domains. Recently, it has become apparent that PRC1-induced H2AK119ub1 not only serves as a docking site for PRC2 but also affects the dynamics of the H3 tail, both of which enhance PRC2 activity, suggesting that trans-tail communication between H2A and H3 facilitates the formation of the Polycomb chromatin domain. In this review, we discuss the emerging principles that define how PRC1 and PRC2 establish the Polycomb chromatin domain and regulate gene expression in mammals.

Granulosa cell metabolism at ovulation correlates with oocyte competence and is disrupted by obesity and aging.

STUDY QUESTION: Is oocyte developmental competence associated with changes in granulosa cell (GC) metabolism? SUMMARY ANSWER: GC metabolism is regulated by the LH surge, altered by obesity and reproductive aging, and, in women, specific metabolic profiles are associated with failed fertilization versus increased blastocyst development. WHAT IS KNOWN ALREADY: The cellular environment in which an oocyte matures is critical to its future developmental competence. Metabolism is emerging as a potentially important factor; however, relative energy production profiles between GCs and cumulus cells and their use of differential substrates under normal in vivo ovulatory conditions are not well understood. STUDY DESIGN, SIZE, DURATION: This study identified metabolic and substrate utilization profiles within ovarian cells in response to the LH surge, using mouse models and GCs of women undergoing gonadotropin-induced oocyte aspiration followed by IVF/ICSI. PARTICIPANTS/MATERIALS, SETTING, METHODS: To comprehensively assess follicular energy metabolism, we used real-time metabolic analysis (Seahorse XFe96) to map energy metabolism dynamics (mitochondrial respiration, glycolysis, and fatty acid oxidation) in mouse GCs and cumulus-oocyte complexes (COCs) across a detailed time course in the lead up to ovulation. In parallel, the metabolic profile of GCs was measured in a cohort of 85 women undergoing IVF/ICSI (n = 21 with normal ovarian function; n = 64 with ovarian infertility) and correlated with clinical parameters and cycle outcomes. MAIN RESULTS AND THE ROLE OF CHANCE: Our study reveals dynamic changes in GC energy metabolism in response to ovulatory LH, with mitochondrial respiration and glycolysis differentially affected by obesity versus aging, in both mice and women. High respiration in GCs is associated with failed fertilization (P < 0.05) in a subset of women, while glycolytic reserve and mitochondrial ATP production are correlated with on-time development at Day 3 (P < 0.05) and blastocyst formation (P < 0.01) respectively. These data provide new insights into the cellular mechanisms of infertility, by uncovering significant associations between metabolism within the ovarian follicle and oocyte developmental competence. LIMITATIONS, REASONS FOR CAUTION: A larger prospective study is needed before the metabolic markers that were positively and negatively associated with oocyte quality can be used clinically to predict embryo outcomes. WIDER IMPLICATIONS OF THE FINDINGS: This study offers new insights into the importance of GC metabolism for subsequent embryonic development and highlights the potential for therapeutic strategies focused on optimizing mitochondrial metabolism to support embryonic development. STUDY FUNDING/COMPETING INTEREST(S): National Health and Medical Research Council (Australia). The authors have no competing interests. TRIAL REGISTRATION NUMBER: N/A.

Structure-based development of novel substrate-type G9a inhibitors as epigenetic modulators for sickle cell disease treatment.

The discovery and development of structurally distinct lysine methyltransferase G9a inhibitors have been the subject of intense research in epigenetics. Structure-based optimization was conducted, starting with the previously reported seed compound 7a and lead to the identification of a highly potent G9a inhibitor, compound 7i (IC50 = 0.024 µM). X-ray crystallography for the ligand-protein interaction and kinetics study, along with surface plasmon resonance (SPR) analysis, revealed that compound 7i interacts with G9a in a unique binding mode. In addition, compound 7i caused attenuation of cellular H3K9me2 levels and induction of γ-globin mRNA expression in HUDEP-2 cells in a dose-dependent manner.

Effect of globin peptide on female fertility in aging granulosa cell-specific Nrg1 knockout mice.

Ovarian fibrosis contributes to age-related ovarian dysfunction. In our previous study, we observed ovarian fibrosis in both obese and aging mice with intracellular lipid droplets in the fibrotic ovaries. Although the importance of mitochondria in ovarian fibrosis has been recognized in pharmacological studies, their role in lipid metabolism remains unclear. Globin peptide (GP), derived from hemoglobin, enhances lipid metabolism in obese mice. This study aimed to elucidate the importance of lipid metabolism in ovarian fibrosis by using GP. Treatment of ovarian stromal cells with GP increased mitochondrial oxygen consumption during ß-oxidation. Lipid accumulation was also observed in the ovaries of granulosa cell-specific Nrg1 knockout mice (gcNrg1KO), and the administration of GP to gcNrg1KO mice for two months reduced ovarian lipid accumulation and fibrosis in addition to restoring the estrous cycle. GP holds promise for mitigating lipid-related ovarian issues and provides a novel approach to safeguarding ovarian health by regulating fibrosis via lipid pathways.

Elucidation of binding preferences of YEATS domains to site-specific acetylated nucleosome core particles.

Acetylated lysine residues (Kac) in histones are recognized by epigenetic reader proteins, such as Yaf9, ENL, AF9, Taf14, and Sas5 (YEATS) domain-containing proteins. Human YEATS domains bind to the acetylated N-terminal tail of histone H3; however, their Kac-binding preferences at the level of the nucleosome are unknown. Through genetic code reprogramming, here, we established a nucleosome core particle (NCP) array containing histones that were acetylated at specific residues and used it to compare the Kac-binding preferences of human YEATS domains. We found that AF9-YEATS showed basal binding to the unmodified NCP and that it bound stronger to the NCP containing a single acetylation at one of K4, K9, K14, or K27 of H3, or to histone H4 multi-acetylated between K5 and K16. Crystal structures of AF9-YEATS in complex with an H4 peptide diacetylated either at K5/K8 or K8/K12 revealed that the aromatic cage of the YEATS domain recognized the acetylated K8 residue. Interestingly, E57 and D103 of AF9, both located outside of the aromatic cage, were shown to interact with acetylated K5 and K12 of H4, respectively, consistent with the increase in AF9-YEATS binding to the H4K8-acetylated NCP upon additional acetylation at K5 or K12. Finally, we show that a mutation of E57 to alanine in AF9-YEATS reduced the binding affinity for H4 multiacetylated NCPs containing H4K5ac. Our data suggest that the Kac-binding affinity of AF9-YEATS increases additively with the number of Kac in the histone tail.

Defining super-enhancers by highly ranked histone H4 multi-acetylation levels identifies transcription factors associated with glioblastoma stem-like properties.

BACKGROUND: Super-enhancers (SEs), which activate genes involved in cell-type specificity, have mainly been defined as genomic regions with top-ranked enrichment(s) of histone H3 with acetylated K27 (H3K27ac) and/or transcription coactivator(s) including a bromodomain and extra-terminal domain (BET) family protein, BRD4. However, BRD4 preferentially binds to multi-acetylated histone H4, typically with acetylated K5 and K8 (H4K5acK8ac), leading us to hypothesize that SEs should be defined by high H4K5acK8ac enrichment at least as well as by that of H3K27ac. RESULTS: Here, we conducted genome-wide profiling of H4K5acK8ac and H3K27ac, BRD4 binding, and the transcriptome by using a BET inhibitor, JQ1, in three human glial cell lines. When SEs were defined as having the top ranks for H4K5acK8ac or H3K27ac signal, 43% of H4K5acK8ac-ranked SEs were distinct from H3K27ac-ranked SEs in a glioblastoma stem-like cell (GSC) line. CRISPR-Cas9-mediated deletion of the H4K5acK8ac-preferred SEs associated with MYCN and NFIC decreased the stem-like properties in GSCs. CONCLUSIONS: Collectively, our data highlights H4K5acK8ac's utility for identifying genes regulating cell-type specificity.

Rational design and implementation of a chemically inducible heterotrimerization system.

Chemically inducible dimerization (CID) uses a small molecule to induce binding of two different proteins. CID tools such as the FK506-binding protein-FKBP-rapamycin-binding- (FKBP-FRB)-rapamycin system have been widely used to probe molecular events inside and outside cells. While various CID tools are available, chemically inducible trimerization (CIT) does not exist, due to inherent challenges in designing a chemical that simultaneously binds three proteins with high affinity and specificity. Here, we developed CIT by rationally splitting FRB and FKBP. Cellular and structural datasets showed efficient trimerization of split pairs of FRB or FKBP with full-length FKBP or FRB, respectively, by rapamycin. CIT rapidly induced tri-organellar junctions and perturbed intended membrane lipids exclusively at select membrane contact sites. By conferring one additional condition to what is achievable with CID, CIT expands the types of manipulation in single live cells to address cell biology questions otherwise intractable and engineer cell functions for future synthetic biology applications.

Treatment with cholesterol just after thawing maintains the fertility of bull sperm.

Freezing and thawing diminish sperm motility and fertility by disrupting the cholesterol balance in sperm plasma and organelle membranes. The aim of this study was to elucidate the mechanisms through which exogeneous cholesterol treatment enhances the quality of frozen-thawed bull sperm. The incorporation of cholesterol was investigated using boron-dipyrromethene (BODIPY)-cholesterol, and BODIPY signals were detected not only in the plasma membrane but also in the midpiece region immediately after thawing. The positive signal of cholesterol in the midpiece region was inhibited by a scavenger receptor class B Type I (SR-BI) inhibitor, block lipid transport 1 (BLT-1). To comprehend the role of exogenous cholesterol in the functions of the plasma membrane, propidium iodide (PI)/Annexin V and peanut agglutinin lectin (PNA) staining were performed. The results showed that treatment with exogenous cholesterol increased the number of acrosome-intact sperm and decreased the number of sperm with damage to the plasma membrane. Moreover, since BODIPY signals were also observed in the midpiece region, mitochondrial function was evaluated using a flux analyzer and a flow cytometer with 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl carbocyanine iodide (JC-1) staining, revealing an increase in the number of sperm with high-mitochondrial activity and oxygen consumption. Finally, to assess sperm fertility, computer-assisted sperm analysis (CASA) and IVF were carried out. Sperm velocities and fertilization rates in IVF were significantly enhanced by the addition of cholesterol just after thawing. Thus, the treatment with cholesterol after thawing protected the plasma membrane from the stress of thawing and maintained mitochondrial function, thereby preserving the fertilization ability of frozen-thawed bull sperm for conventional IVF and artificial insemination (AI). Therefore, the application of cholesterol just after thawing is a promising option for improving the fertility of frozen-thawed sperm.

Acetylated histone H4 tail enhances histone H3 tail acetylation by altering their mutual dynamics in the nucleosome.

The structural unit of eukaryotic chromatin is a nucleosome, comprising two histone H2A-H2B heterodimers and one histone (H3-H4)2 tetramer, wrapped around by ∼146 bp of DNA. The N-terminal flexible histone tails stick out from the histone core and have extensive posttranslational modifications, causing epigenetic changes of chromatin. Although crystal and cryogenic electron microscopy structures of nucleosomes are available, the flexible tail structures remain elusive. Using NMR, we have examined the dynamics of histone H3 tails in nucleosomes containing unmodified and tetra-acetylated H4 tails. In unmodified nucleosome, the H3 tail adopts a dynamic equilibrium structure between DNA-contact and reduced-contact states. In acetylated H4 nucleosome, however, the H3 tail equilibrium shifts to a mainly DNA-contact state with a minor reduced-contact state. The acetylated H4 tail is dynamically released from its own DNA-contact state to a reduced-contact state, while the H3 tail DNA-contact state becomes major. Notably, H3 K14 in the acetylated H4 nucleosome is much more accessible to acetyltransferase Gcn5 relative to unmodified nucleosome, possibly due to the formation of a favorable H3 tail conformation for Gcn5. In summary, each histone tail adopts a characteristic dynamic state but regulates one other, probably creating a histone tail network even on a nucleosome.

Activation of Toll-like receptor 7/8 encoded by the X chromosome alters sperm motility and provides a novel simple technology for sexing sperm.

In most mammals, the male to female sex ratio of offspring is about 50% because half of the sperm contain either the Y chromosome or X chromosome. In mice, the Y chromosome encodes fewer than 700 genes, whereas the X chromosome encodes over 3,000 genes. Although overall gene expression is lower in sperm than in somatic cells, transcription is activated selectively in round spermatids. By regulating the expression of specific genes, we hypothesized that the X chromosome might exert functional differences in sperm that are usually masked during fertilization. In this study, we found that Toll-like receptors 7/8 (TLR7/8) coding the X chromosome were expressed by approximately 50% of the round spermatids in testis and in approximately 50% of the epididymal sperm. Especially, TLR7 was localized to the tail, and TLR8 was localized to the midpiece. Ligand activation of TLR7/8 selectively suppressed the mobility of the X chromosome-bearing sperm (X-sperm) but not the Y-sperm without altering sperm viability or acrosome formation. The difference in sperm motility allowed for the separation of Y-sperm from X-sperm. Following in vitro fertilization using the ligand-selected high-mobility sperm, 90% of the embryos were XY male. Likewise, 83% of the pups obtained following embryo transfer were XY males. Conversely, the TLR7/8-activated, slow mobility sperm produced embryos and pups that were 81% XX females. Therefore, the functional differences between Y-sperm and X-sperm motility were revealed and related to different gene expression patterns, specifically TLR7/8 on X-sperm.

Crystal structure of eukaryotic translation initiation factor 2B.

Eukaryotic cells restrict protein synthesis under various stress conditions, by inhibiting the eukaryotic translation initiation factor 2B (eIF2B). eIF2B is the guanine nucleotide exchange factor for eIF2, a heterotrimeric G protein consisting of α-, ß- and γ-subunits. eIF2B exchanges GDP for GTP on the γ-subunit of eIF2 (eIF2γ), and is inhibited by stress-induced phosphorylation of eIF2α. eIF2B is a heterodecameric complex of two copies each of the α-, ß-, γ-, δ- and ε-subunits; its α-, ß- and δ-subunits constitute the regulatory subcomplex, while the γ- and ε-subunits form the catalytic subcomplex. The three-dimensional structure of the entire eIF2B complex has not been determined. Here we present the crystal structure of Schizosaccharomyces pombe eIF2B with an unprecedented subunit arrangement, in which the α2ß2δ2 hexameric regulatory subcomplex binds two γε dimeric catalytic subcomplexes on its opposite sides. A structure-based in vitro analysis by a surface-scanning site-directed photo-cross-linking method identified the eIF2α-binding and eIF2γ-binding interfaces, located far apart on the regulatory and catalytic subcomplexes, respectively. The eIF2γ-binding interface is located close to the conserved 'NF motif', which is important for nucleotide exchange. A structural model was constructed for the complex of eIF2B with phosphorylated eIF2α, which binds to eIF2B more strongly than the unphosphorylated form. These results indicate that the eIF2α phosphorylation generates the 'nonproductive' eIF2-eIF2B complex, which prevents nucleotide exchange on eIF2γ, and thus provide a structural framework for the eIF2B-mediated mechanism of stress-induced translational control.

Quantification of the effect of site-specific histone acetylation on chromatin transcription rate.

Eukaryotic transcription is epigenetically regulated by chromatin structure and post-translational modifications (PTMs). For example, lysine acetylation in histone H4 is correlated with activation of RNA polymerase I-, II- and III-driven transcription from chromatin templates, which requires prior chromatin remodeling. However, quantitative understanding of the contribution of particular PTM states to the sequential steps of eukaryotic transcription has been hampered partially because reconstitution of a chromatin template with designed PTMs is difficult. In this study, we reconstituted a di-nucleosome with site-specifically acetylated or unmodified histone H4, which contained two copies of the Xenopus somatic 5S rRNA gene with addition of a unique sequence detectable by hybridization-assisted fluorescence correlation spectroscopy. Using a Xenopus oocyte nuclear extract, we analyzed the time course of accumulation of nascent 5S rRNA-derived transcripts generated on chromatin templates in vitro. Our mathematically described kinetic model and fitting analysis revealed that tetra-acetylation of histone H4 at K5/K8/K12/K16 increases the rate of transcriptionally competent chromatin formation ∼3-fold in comparison with the absence of acetylation. We provide a kinetic model for quantitative evaluation of the contribution of epigenetic modifications to chromatin transcription.

Saturated fatty acids accelerate linear motility through mitochondrial ATP production in bull sperm.

PURPOSE: The present study was undertaken to clarify whether bovine sperm could take up fatty acids (FAs) and produce ATP to maintain linear motility. METHODS: Frozen bovine semen was thawed in media containing either lipid mixture (LM) or FAs, and sperm motility was analyzed. The kinetic changes in FA levels in sperm were detected using gas chromatography-mass spectrometry. The mitochondrial activity of sperm thawed in media containing LM or FAs was analyzed based on the fluorescence intensity of JC-1 staining and the oxygen consumption rate. FA transporters were observed using whole-mounted immunofluorescence. RESULTS: Sperm linear motility was significantly (P < .05) increased after thawing in media with LM and FA. Moreover, saturated fatty acids were predominant in sperm thawed in media with LM. Notably, our study revealed that frozen bovine sperm possessed FA transporters in the midpiece where the fluorescence signals were detected after treatment with fluorescence-tagged FA. Treatment with FA activated electron transport in mitochondria through ß-oxidation. CONCLUSIONS: Sperm linear motility is facilitated by FAs in the thawing media used for frozen bovine sperm. This might provide a new approach for upgrading the artificial insemination technique used in both livestock animals and human infertility care.

Cutting the ovarian surface improves the responsiveness to exogenous hormonal treatment in aged mice.

PURPOSE: Ovarian vascular abnormality and ovarian fibrosis are observed in the low responder patients and aging mice. Vascularization and fibrosis are regulated by injury-repair system, such as wound. Thus, in this study, the authors tried to investigate the effect of the surgical treatment to ovarian surface with cutting on the functions of ovary in aging mouse model, gcNrg1KO. METHOD: The ovarian surface of gcNrg1KO was surgically cut, and then the ovary was returned inside of bursa ovarica. To assess the effect of cutting on fertility, mating test, smear analysis, and exogenous hormonal treatment were done. Additionally, the histological analysis was used for observing the remodeling of ovarian stroma after the surgical approach. RESULT: Ovarian fibrosis disappeared at 7 days after surgery. With the abrogation of fibrosis, the blood vessels were fluently observed around the follicles, and the follicular development was re-started. The responses against exogenous hormone were recovered at 21 days after the surgery, and estrous cycle and delivery were also recovered by the surgery and the fertility was maintained for 3 months. CONCLUSION: This cutting method of ovarian surface becomes a good option against low responder patients.

Characterization of lysine acetylation of a phosphoenolpyruvate carboxylase involved in glutamate overproduction in Corynebacterium glutamicum.

Protein Nε-acylation is emerging as a ubiquitous post-translational modification. In Corynebacterium glutamicum, which is utilized for industrial production of l-glutamate, the levels of protein acetylation and succinylation change drastically under the conditions that induce glutamate overproduction. Here, the acylation of phosphoenolpyruvate carboxylase (PEPC), an anaplerotic enzyme that supplies oxaloacetate for glutamate overproduction was characterized. It was shown that acetylation of PEPC at lysine 653 decreased enzymatic activity, leading to reduced glutamate production. An acetylation-mimic (KQ) mutant of K653 showed severely reduced glutamate production, while the corresponding KR mutant showed normal production levels. Using an acetyllysine-incorporated PEPC protein, we verified that K653-acetylation negatively regulates PEPC activity. In addition, NCgl0616, a sirtuin-type deacetylase, deacetylated K653-acetylated PEPC in vitro. Interestingly, the specific activity of PEPC was increased during glutamate overproduction, which was blocked by the K653R mutation or deletion of sirtuin-type deacetylase homologues. These findings suggested that deacetylation of K653 by NCgl0616 likely plays a role in the activation of PEPC, which maintains carbon flux under glutamate-producing conditions. PEPC deletion increased protein acetylation levels in cells under glutamate-producing conditions, supporting the hypothesis that PEPC is responsible for a large carbon flux change under glutamate-producing conditions.

Creatine enhances the duration of sperm capacitation: a novel factor for improving in vitro fertilization with small numbers of sperm.

STUDY QUESTION: Why are many sperm required for successful fertilization of oocytes in vitro, even though fertilization occurs in vivo when only a few sperm reach the oocyte? SUMMARY ANSWER: Creatine produced in the ovary promotes efficient fertilization in vivo; however, in vitro, creatine is not contained in the in vitro fertilization (IVF) medium. WHAT IS KNOWN ALREADY: The IVF medium enables capacitation of sperm. However, the IVF medium does not fully mimic the in vivo environment during fertilization. Consequently, fertilization in vitro is more inefficient than in the oviduct. STUDY DESIGN, SIZE, DURATION: Follicular and oviductal fluids were collected and then analyzed for creatine and glucose levels. To determine the physiological functions of creatine, the creatine antagonist 3-guanidinopropionic acid (GPA) was injected into hormonally primed mice. Using conventional IVF protocols, sperm were pre-incubated in IVF medium with creatine and then co-cultured with 10 ovulated cumulus-oocyte complexes (1-1000 per oocyte) in 50 µl medium droplets. PARTICIPANTS/MATERIALS, SETTING, METHODS: Glucose and creatine levels were measured using commercial enzymatic assay kits. The effect of creatine in vivo was assessed by mating experiments using mice treated with or without GPA just before ovulation. To assess the functions of sperm incubated in IVF medium containing creatine, we analyzed (1) the motility of sperm using computer-assisted sperm assay, (2) the capacitation level of sperm by western blot analyses, and (3) the condition of sperm acrosomes by peanut agglutinin lectin-FITC staining. MAIN RESULTS AND THE ROLE OF CHANCE: Oviductal creatine levels were significantly increased following ovulation. Injecting mice with GPA just before ovulation significantly reduced the number of fertilized oocytes. The addition of creatine to IVF medium enhanced sperm capacitation by increasing ATP levels. Successful fertilization was achieved with as few as five sperm/oocyte in the creatine group, and the number of fertilized oocytes was significantly higher than in the control without creatine (P < 0.01). LIMITATIONS, REASONS FOR CAUTION: In the present study, a pharmacological approach, creatine antagonist (GPA) treatment, but not a knockout mouse model, was used to understand the role of creatine in vivo. The role of creatine in fertilization processes can only be shown in a mouse model. WIDER IMPLICATIONS OF THE FINDINGS: A modified IVF technique using creatine-containing medium was developed and shown to markedly improve fertilization with small numbers of sperm. This approach has the potential to be highly beneficial for human assisted reproductive technologies, especially for patients with a limited number of good quality sperm. STUDY FUNDING/COMPETING INTEREST(S): This work was supported in part by JSPS KAKENHI Grant numbers JP24688028, JP16H05017 (to M.S.), and JP15J05331 (to T.U.), the Japan Agency for Medical Research and Development (AMED) (16gk0110015h0001 to M.S.), and National Institutes of Health (NIH-HD-076980 to J.S.R). The authors have nothing to disclose.

Crystal Structure of LSD1 in Complex with 4-[5-(Piperidin-4-ylmethoxy)-2-(p-tolyl)pyridin-3-yl]benzonitrile.

Because lysine-specific demethylase 1 (LSD1) regulates the maintenance of cancer stem cell properties, small-molecule inhibitors of LSD1 are expected to be useful for the treatment of several cancers. Reversible inhibitors of LSD1 with submicromolar inhibitory potency have recently been reported, but their exact binding modes are poorly understood. In this study, we synthesized a recently reported reversible inhibitor, 4-[5-(piperidin-4-ylmethoxy)-2-(p-tolyl)pyridin-3-yl]benzonitrile, which bears a 4-piperidinylmethoxy group, a 4-methylphenyl group, and a 4-cyanophenyl group on a pyridine ring, and determined the crystal structure of LSD1 in complex with this inhibitor at 2.96 Å. We observed strong electron density for the compound, showing that its cyano group forms a hydrogen bond with Lys661, which is a critical residue in the lysine demethylation reaction located deep in the catalytic center of LSD1. The piperidine ring interacts with the side chains of Asp555 and Asn540 in two conformations, and the 4-methylphenyl group is bound in a hydrophobic pocket in the catalytic center. Our elucidation of the binding mode of this compound can be expected to facilitate the rational design of more-potent reversible LSD1 inhibitors.