An increase in the incidence of aneuploidy is well documented with increasing maternal age, in particular in human females. Remarkably, little is known regarding the underlying molecular basis for the age-associated increase in aneuploidy, which is a major source of decreased fertility in humans. Using mouse as a model system we find that eggs obtained from old mice (60-70 weeks of age) display a 6-fold increase in the incidence of hyperploidy as assessed by chromosome spreads. Expression profiling of transcripts in oocytes and eggs obtained from young and old mice reveals that approximately 5% of the transcripts are differentially expressed in oocytes obtained from old females when compared to oocytes obtained from young females (6-12 weeks of age) and that this fraction increases to approximately 33% in eggs. The latter finding indicates that the normal pattern of degradation of maternal mRNAs that occurs during oocyte maturation is dramatically altered in eggs obtained from old mice and could therefore be a contributing source to the decline in fertility. Analysis of the differentially expressed transcripts also indicated that the strength of the spindle assembly checkpoint is weakened and that higher errors of microtubule-kinetochore interactions constitute part of molecular basis for the age-associated increase in aneuploidy in females. Last, BRCA1 expression is reduced in oocytes obtained from old females and RNAi-mediated reduction of BRCA1 in oocytes obtained from young females results in perturbing spindle formation and chromosome congression following maturation.

Dramatic changes in chromatin structure and histone modification occur during oocyte growth, as well as a global cessation of transcription. The role of histone modifications in these processes is poorly understood. We report the effect of conditionally deleting Hdac1 and Hdac2 on oocyte development. Deleting either gene has little or no effect on oocyte development, whereas deleting both genes results in follicle development arrest at the secondary follicle stage. This developmental arrest is accompanied by substantial perturbation of the transcriptome and a global reduction in transcription even though histone acetylation is markedly increased. There is no apparent change in histone repressive marks, but there is a pronounced decrease in histone H3K4 methylation, an activating mark. The decrease in H3K4 methylation is likely a result of increased expression of Kdm5b because RNAi-mediated targeting of Kdm5b in double-mutant oocytes results in an increase in H3K4 methylation. An increase in TRP53 acetylation also occurs in mutant oocytes and may contribute to the observed increased incidence of apoptosis. Taken together, these results suggest seminal roles of acetylation of histone and nonhistone proteins in oocyte development.O ogenesis is a protracted process that encompasses meiosis and oocyte growth, and results in the only cell that, following fertilization, can develop into an organism (1). In mice, at approximately day 13.5 of gestation, oogonia undergo a final round of DNA replication and enter the first meiotic prophase, at which point they are called oocytes. By the time of birth, oocytes are arrested in diplotene of the first meiotic prophase, are approximately 15 to 20 μm in diameter, and reside in primordial follicles in which the oocyte is surrounded by a single layer of flattened follicle cells. Oocyte growth is coordinated with follicle cell proliferation; the diameter of full-grown oocytes is approximately 80 μm. During the growth phase, oocytes acquire the ability to resume meiosis (i.e., acquisition of meiotic competence) and support development to term (i.e., acquisition of developmental competence). In vivo, release of gonadotropins triggers resumption of meiosis of full-grown oocytes present in preovulatory follicles with oocytes maturing to and arresting at metaphase II; fertilization triggers resumption and completion of meiosis (2).Oocyte growth is accompanied by dramatic changes in gene expression, but starting at approximately midgrowth phase, transcription decreases such that full-grown oocytes are essentially transcriptionally inactive (3), and transcriptional quiescence appears critical for acquisition of developmental competence (4). Transcriptional quiescence is associated with chromatin condensation as well as changes in histone posttranslational modifications (PTMs) (5); histone PTMs such as phosphorylation, methylation, ubiquitination, and acetylation are intimately linked to transcriptional regulation and required for many biological processes (6, 7), with histone acetylation ...

Superimposed on activation of the embryonic genome in preimplantation mouse embryos is the formation of a chromatin-mediated transcriptionally repressive state that arises in the late two-cell embryo and becomes more pronounced with development. In this study, we investigated expression and function of Class I histone deacetylases (HDAC) HDAC1, HDAC2, and HDAC3 during preimplantation development. HDAC1 is likely a major deacetylase in preimplantation embryos and its expression inversely correlates with changes in the acetylation state of histone H4K5 during preimplantation development. RNAi-mediated reduction of HDAC1 leads to hyperacetylation of histone H4 and a developmental delay even though expression of HDAC2 and HDAC3 is significantly induced in Hdac1-suppressed embryos; increased expression of p21(Cip1/Waf) may contribute to the observed developmental delay. RNAi-mediated reduction of HDAC2 has no noticeable effect on preimplantation development, suggesting that individual HDACs have distinct functions during preimplantation development. Although RNAi-mediated targeting of Hdac3 mRNA was very efficient, maternal HDAC3 protein was stable during preimplantation development, thereby preventing an examination of its role. HDAC1 knockdown does not increase the rate of global transcription in late 2-cell embryos, but does result in elevated levels of expression of a subset of genes; this increased expression correlates with hyperacetylation of histone H4. Results of these experiments suggest that HDAC1 is involved in the development of a transcriptionally repressive state that initiates in 2-cell embryos.

Changes in histone acetylation occur during oocyte development and maturation, but the role of specific histone deacetylases in these processes is poorly defined. We report here that mice harboring Hdac1 −/+/Hdac2 −/− or Hdac2 −/− oocytes are infertile or sub-fertile, respectively. Depleting maternal HDAC2 results in hyperacetylation of H4K16 as determined by immunocytochemistry—normal deacetylation of other lysine residues of histone H3 or H4 is observed—and defective chromosome condensation and segregation during oocyte maturation occurs in a sub-population of oocytes. The resulting increased incidence of aneuploidy likely accounts for the observed sub-fertility of mice harboring Hdac2 −/− oocytes. The infertility of mice harboring Hdac1 −/+/Hdac2 −/−oocytes is attributed to failure of those few eggs that properly mature to metaphase II to initiate DNA replication following fertilization. The increased amount of acetylated H4K16 likely impairs kinetochore function in oocytes lacking HDAC2 because kinetochores in mutant oocytes are less able to form cold-stable microtubule attachments and less CENP-A is located at the centromere. These results implicate HDAC2 as the major HDAC that regulates global histone acetylation during oocyte development and, furthermore, suggest HDAC2 is largely responsible for the deacetylation of H4K16 during maturation. In addition, the results provide additional support that histone deacetylation that occurs during oocyte maturation is critical for proper chromosome segregation.

No abstract

Tyro 3 family receptors contain three members—Tyro 3, Axl, and Mer—that are essential regulators of mammalian spermatogenesis. However, their exact expression patterns in testis are unclear. In this study, we examined the localizations of Tyro 3, Axl, Mer, and their ligand Gas6 in postnatal mouse testes by immunohistochemistry. All three members and their ligand were continuously expressed in different testicular cells during postnatal development. Tyro 3 was expressed only in Sertoli cells with a varied distribution during testis development. At day 3 postnatal, Tyro 3 was distributed in overall cytoplasmic membrane and cytoplasm of Sertoli cells. From day 14 to day 35 postnatal, Tyro 3 appeared on Sertoli cell processes toward the adlumenal compartment of seminiferous tubules. A stage-dependent Tyro 3 immunoexpression in Sertoli cells was shown by adulthood testis at day 56 postnatal with higher expression at stages I-VII and lower level at stages IX-XII. Axl showed a similar expression pattern to Tyro 3, except for some immunopositive Leydig cells detected in mature testis. In contrast, immunostaining of Mer was detected mainly in primitive spermatogonia and Leydig cells, whereas a relative weak signal was found in Sertoli cells. Gas6 was strongly expressed in Leydig cells, and a relative weak staining signal was seen in primitive spermatogonia and Sertoli cells. These immunoexpression patterns of Tyro 3 family receptors and ligand in testis provide a basis to further study their functions and mechanisms in regulating mammalian spermatogenesis.

Oocyte and preimplantation embryo development entail dynamic changes in chromatin structure and gene expression, which are regulated by a number of maternal and zygotic epigenetic factors. Histone deacetylases (HDACs), which tighten chromatin structure, repress transcription and gene expression by removing acetyl groups from histone or non-histone proteins. HDAC1 and HDAC2 are two highly homologous Class I HDACs and display compensatory or specific roles in different cell types or in response to different stimuli and signaling pathways. We summarize here the current knowledge about the functions of HDAC1 and HDAC2 in regulating histone modifications, transcription, DNA methylation, chromosome segregation, and cell cycle during oocyte and preimplantation embryo development. What emerges from these studies is that although HDAC1 and HDAC2 are highly homologous, HDAC2 is more critical than HDAC1 for oocyte development and reciprocally, HDAC1 is more critical than HDAC2 for preimplantation development. In eukaryotes, DNA is organized into a highly ordered nucleoprotein assembly called chromatin, whose fundamental unit is the nucleosome. The nucleosome consists of 146 bp of DNA wrapped around a histone core comprised of two molecules each of histones H2A, H2B, H3 and H4. Histone H1 is bound to linker DNA between nucleosomes. 1,2 Histones are subject to multiple post-translational modifications (PTMs), including acetylation, methylation, ubiquitylation, phosphorylation, and sumoylation. These PTMs determine open and closed chromatin conformations, which, in turn, regulate the differential access and recruitment of transcription factors and other regulatory chromatin-binding proteins to DNA. 3-5 Among these histone modifications, histone acetylation is the most well-studied modification, which occurs at the ε-amino groups of evolutionarily conserved lysine residues located at the N termini. Although all core histones are acetylated in vivo, modifications of histones H3 and H4 are more extensively characterized than those of H2A and H2B. Abbreviations: HDAC, histone deacetylase; HAT, histone acetyl transferase; PTM, post-translational modification; KDAC, lysine deacetylase; TSA, trichostatin A; NAD + , nicotinamide adenine dinucleotide; HAD, HDAC association domain ; GVBD, germinal vesicle breakdown; ChIP-seq, chromatin immunoprecipitation sequencing; TFIID, transcription factor II D; YY1, yin yang 1; Pol II CTD S2, serine 2 within the RNApolymerase II C-terminal domain; H3K4, lysine 4 of histone 3; H3K9, lysine 9 of histone 3; H4K16, lysine 16 of histone 4; SIRT, NAD-dependent deacetylase sirtuin; TBP2, TATA-binding protein 2; DNMT, DNA methyltransferases; RBAP46, retinoblastoma binding protein P46; RNAi, RNA interference; aa, amino acidic; BrUTP, 5-Bromouridine 5′-triphosphate; qRT-PCR, quantitative reverse transcription polymerase chain reaction;

Long noncoding RNAs (lncRNAs) have been shown to play a critical role in cancer development and progression. LncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT-1) is a kidney cancer-associated onco-lncRNA involved in the progression of renal cell carcinoma (RCC). However, the pathological role of lncRNA MALAT-1 in RCC proliferation and metastasis remains poorly understood. This study was designed to investigate the biological role and mechanism of MALAT-1 in RCC proliferation and metastasis. The experiments were performed in human tissues, renal carcinoma cell lines, and nude mice. The expression of lncRNA MALAT-1, Livin mRNA, and the Livin protein was determined by quantitative real-time PCR (qRT-PCR) or a Western blot. The interaction between MALAT-1 and Livin was evaluated by RNA pull-down and RNA binding protein immunoprecipitation (RIP). Cell viability and apoptosis in RCC cell lines were detected using CCK-8 and TUNEL assays. LncRNA MALAT-1 and the Livin protein were highly expressed in RCC tissues, as well as in RCC 786-O and Caki-1 cell lines. MALAT-1 interference contributed to an increase in cell apoptosis and a reduction in the cell viability of 786-O and Caki-1 cells. The increase in apoptosis by si-MALAT-1 was reversed by overexpression of Livin. The RIP results showed that MALAT-1 promoted the expression of the Livin protein in 786-O and Caki-1 cells by enhancing the stability of the protein. Furthermore, the volume of si-MALAT-1-786-O cell xenograft was significantly suppressed. These data indicate that lncRNA MALAT-1-mediated promotion of RCC proliferation and metastasis may be due to the upregulation of the expression of Livin.