Role of genetic abnormalities of PTEN and the phosphatidylinositol 3kinase pathway in breast and ovarian cancer tumorigenesis,prognosis and therapy

Breast and ovarian cancers exhibit several similar epidemiologic, genotypic and phenotypic characteristics suggesting that similar underlying genetic defects may contribute to the development of both tumor types. Phosphatidylinositol 3 kinase (PI3K) and the PTEN tumor suppressor gene product phosphorylate and dephosphorylate the same 3' site in the inositol ring of membrane phosphatidylinositols. Germline mutations in the PTEN tumor suppressor gene are causative of the Cowden's breast cancer predisposition syndrome and PTEN is frequently mutated or expressed at decreased levels in sporadic breast cancers. PTEN is also frequently mutated in gliomas, prostate cancer, endometrioid ovarian cancer and endometrial     

PTEN, a general negative regulator of cyclin D expression

The tumor-suppressor phosphatase with tensin homology （PTEN） is frequently mutated in many malignancies and is one of the most well studied tumor suppressor genes [ 1, 2]. PTEN, a lipid and protein dual phosphatase, plays a vital role in embryonic development, cell growth, apoptosis and cell migration. The well-known function of PTEN is phosphatidylinositol-3 （PI3）-phosphatase, which functions as a negative regulator of the PI3 kinase （PI3K） pathway. It is well established that PTEN regulates the G I-S transition by modulating the expression of cyclin D 1 and p27gipl.     

Calcium at the Cell Wall-Cytoplast Interface

Attention is given to the role of Ca2+ at the interface between the cell wall and the cytoplast, especially as seen in pollen tubes. While the cytoplasm directs the synthesis and deposition of the wall, it is less well appreciated that the wall exerts considerable self control and influences activities of the cytoplasm. Ca2+ participates as a crucial factor in this two way communication. In the cytoplasm, a [Ca2+] above 0.1 μM, regulates myriad processes, including secretion of cell wall components. In the ...     

A PCR-marker for the CMS(1) inducing cytoplasm in chives derived from recombination events affecting the mitochondrial gene atp9

The complete coding and 3′-flanking region of the mitochondrial gene atp9 of chives (Allium schoenoprasum L.) was determined in order to develop primers that allow the identification of atp9-related sequences in subsequent PCR-amplifications. One of these sequences is of a chimerical nature, consisting of atp9-homologous regions on its end, interrupted by an insertion that is composed of one atp6-homologous part and one part of unknown origin. This PCR-fragment is 762 bp in size and exclusively amplified in the sterility inducing cytoplasm of CMS₁. Thus it can be used as a PCR-marker in order to distinguish this cytoplasm type from the remaining cytoplasm types of chives. The chimerical marker sequence forms a putative open reading frame (orfA501), from which CMS₁ might originate. Received: 6 June 2001 / Accepted: 3 August 2001     

Structural and Expressional Variation Analyses of Mitochondrial Genomes Reveal Candidate Transcripts for the SV Cytoplasmic Male Sterility in Wheat (Triticum aestivum L.)

Common wheat (Triticum aestivum L.) is one of the most important crops,and intra-specific wheat hybrids have obvious heterosis in yield and protein quality.Therefore,utilization of hybrid wheat varieties offers an effective way to increase yield and nutrition.Cytoplasmic male sterility (CMS) systems are a useful genetic tool for hybrid crop breeding,and are ideal models for studying the genetic interaction and cooperative function of mitochondrial and nuclear genomes in plants (Schnable and Wise,1998;Hanson and Bentolila,2004).The breeding of hybrid wheat using male sterility caused by the cytoplasm of T.timopheevii has been studied since the early 1960's.But it is unsuccessful because there are some deficiencies in the practical application of this cytoplasm,including limited restoration resources,thin seeds,pre-harvest sprouting and lower germination rate (Wilson and Ross,1962).The Sv type of cytoplasmic male sterility (CMS-Sv) in wheat is general accessions for four types of CMS lines that were derived from four Aegilops species:Ae.kotschyi,Ae.variabilis,Ae.ventricosa,and Ae.bicornis.Based on the observation of alloplasmic lines produced in all possible combinations between 12 wheat nuclear genotypes and 47 cytoplasms of two related genera,Triticum (wheat) and Aegilops,Ogihara and Tsunewaki (1988) concluded that the D2-cytoplasm of Ae.crassa and its relatives,N-cytoplasm of Ae.uniaristata,and SV-cytoplasm of Ae.kotschyi and its relatives might be used as the alternative male sterile cytoplasm to replace the T.timopheevii cytoplasm for hybrid wheat breeding.Ikeguchi et al.(1999) proposed that spring-type hybrid wheat may be bred by combination of the 1BL-1RS chromosome and Ae.kotschyi cytoplasm with a new fertility-restorer gene discovered in a wheat variety Kitamiharu 48.Zhang et al.(1996) also proposed the use of CMS-Sv lines as the most effective male sterile cytoplasm.     

Calcium at the Cell Wall-Cytoplast Interface

Attention is given to the role of Ca2+ at the interface between the cell wall and the cytoplast, especially as seen in pollen tubes. While the cytoplasm directs the synthesis and deposition of the wall, it is less well appreciated that the wall exerts considerable self control and influences activities of the cytoplasm. Ca2+ participates as a crucial factor in this two way communication. In the cytoplasm, a [Ca2+] above 0.1 μM, regulates myriad processes, including secretion of cell wall components. In the cell wall Ca2+, at 10 μM to 10 mM, binds negative charges on pectins and imparts structural rigidity to the wall. The plasma membrane occupies a pivotal position between these two compartments, where selective channels regulate influx of Ca2+, and specific carriers pump the ion back into the wall. In addition we draw attention to different factors, which either respond to the wall or are present in the wall, and usually generate elevated [Ca2+] in the cytoplasm. These factors include: (i) stretch activated channels; (ii) calmodulin; (iii) annexins; (iv) wall associated kinases; (v) oligogalacturonides; and (vi) extracellular adenosine 5-triphosphate. Together they provide evidence for a rich and multifaceted system of communication between the cytoplast and cell wall, with Ca2+ as a carrier of information.     

Metabolic integration during the evolutionary origin of mitochondria

Although mitochondria provide eukaryotic cells with certain metabolic advantages, in other ways they may be disadvantageous. For example, mitochondria produce reactive oxygen species that damage both nucleocytoplasm and mitochondria, resulting in mutations, diseases, and aging. The relationship of mito-chondria to the cytoplasm is best understood in the context of evolutionary history. Although it is clearthat mitochondria evolved from symbiotic bacteria, the exact nature of the initial symbiosis is a matter of continuing debate. The exchange of nutrients between host and symbiont may have differed from that be-tween the cytoplasm and mitochondria in modern cells. Speculations about the initial relationships includethe following. (1) The pre-mitochondrion may have been an invasive, parasitic bacterium. The host did notbenefit. (2) The relationship was a nutritional syntrophy based upon transfer of organic acids from host tosymbiont. (3) The relationship was a syntrophy based upon H2 transfer from symbiont to host, where thehost was a methanogen. (4) There was a syntrophy based upon reciprocal exchange of sulfur compounds.The last conjecture receives support from our detection in eukaryotic cells of substantial H2S-oxidizing activity in mitochondria, and sulfur-reducing activity in the cytoplasm.     

Glucose regulates LXRα subcellular localization and function in rat pancreatic β-cells

Liver X receptors （LXRs） are members of the nuclear receptor superfamily, which have been implicated in lipid homeostasis and more recently in glucose metabolism. Here, we show that glucose does not change LXRα protein level, but affects its localization in pancreatic β-cells. LXRα is found in the nucleus at 8 mM glucose and in the cytoplasm at 4.2 mM. Addition of glucose translocates LXRα from the cytoplasm into the nucleus. Moreover, after the activation of LXR by its synthetic non-steroidal agonist （T0901317）, insulin secretion and glucose uptake are increased at 8 mM and decreased at 4.2 mM glucose in a dose-dependent manner. Furthermore, at low glucose condition, okadaic acid reversed LXRα effect on insulin secretion, suggesting the involvement of glucose signaling through a phosphorylation-dependent mechanism.     

Ultrastructural features of spermatocytes and spermatozoids in the fern Phyllitis scolopendrium (L.) Newm. subsp. scolopendrium

Phyllitis scolopendrium Newm. subsp. scolo-pendrium spermatozoids are cells 10 μm long in the form of spirals with about four turns. Their chromatin is partly honeycomb-shaped and partly highly condensed. The nuclear envelope over the latter has a regular, thin intermembrane space crossed by fibers that are probably involved in connecting the chromatin with elements of the microtubular ribbon. The cytoplasm is traversed by long cistern-shaped folds of the plasma membrane, believed to be involved in a late process of cell simplification through segregation and detachment of parts of the cytoplasm. The spermatozoids are embedded in 1–1.5 μm thick amorphous electron-transparent material containing cellulose fibrils. These fibrils are considered a network connected to the original spermatocyte wall and elements of elastic support for the amorphous material. The different polysaccharide composition of the inner and outer parts of the walls causes changes in the size and shape of the ring cells, so that the spermatozoids are pushed against and past the cap cell. The gametes are released through limited laceration of the cap cell. The laceration is due to the generally weak substructure of the cell wall. A light microscope sequence of spermatozoid release and scanning electron microscope features of newly released spermatozoids are shown. Received: 24 November 1999 / Revision accepted: 29 December 1999     

THE EFFECT OF CYTOPLASM ON NUCLEAR ACTIVITY AND GENETIC CHARACTERS IN ANIMAL DEVELOPMENT

The present report is a summary of our works, published or unpublished, on the nucleo-cytoplasmic inter-reaction, performed in the past several years. As is well known, there is a tremendous amount of data from both basic and applied research showing nuclear control of development and genetics. On this matter, there is no argument at all. However, it would be a mistake if we belittle the contribution of cytoplasm and insist on that only the nucleus is involved in the control of     

OsHK3 is a crucial regulator of abscisic acid signaling involved in antioxidant defense in rice

In this study, the role of the rice(Oryza sativa L.)histidine kinase Os HK3 in abscisic acid(ABA)-induced antioxidant defense was investigated. Treatments with ABA, H2O2,and polyethylene glycol(PEG) induced the expression of Os HK3 in rice leaves, and H2O2 is required for ABA-induced increase in the expression of Os HK3 under water stress. Subcellular localization analysis showed that Os HK3 is located in the cytoplasm and the plasma membrane. The transient expression analysis and the transient RNA interference test in rice protoplasts showed that Os HK3 is required for ABA-induced upregulation in the expression of antioxidant enzymes genes and the activities of antioxidant enzymes. Further analysis showed that Os HK3 functions upstream of the calcium/calmodulin-dependent protein kinase Os DMI3 and the mitogen-activated protein kinase Os MPK1 to regulate the activities of antioxidant enzymes in ABA signaling. Moreover, Os HK3was also shown to regulate the expression of nicotinamide adenine dinucleotide phosphate oxidase genes, Osrboh B and Osrboh E, and the production of H2O2 in ABA signaling. Our data indicate that Os HK3 play an important role in the regulation of ABA-induced antioxidant defense and in the feedback regulation of H2O2 production in ABA signaling.     

Subcellular Localization of the S Locus F-box Protein AhSLF-S2 in Pollen and Pollen Tubes of Self-Incompatible Antirrhinum

The distribution of the S locus F-box (SLF) protein was examined by immunocytochemistry and Western blot techniques using an antibody against the C-terminal part of AhSLF-S2 in self-incompatible Iines of Antirrhinum. Abundant gold particles were found where pollen tubes emerge in vitro. With the elongation of pollen tubes, binding sites for the antibody were found in the cytoplasm of the pollen tubes,including the peripheral part of the endoplasmic reticulum. After germination in vitro for 16 h, the product of AhSLF-S2 and possibly its allelic products could still be detectable, implying that the SLF protein has a role in the elongating process of pollen tubes. The present study provides evidence at the protein level that the SLF protein is present in pollen cytoplasm during pollen tube growth. These findings are discussed, as is their potential role in the self-incompatible response in Antirrhinum.     

Two Na^＋ and Cl^- Hyperaccumulators of the Chenopodiaceae

The authors found five sodium (Na^ ) and chloride (Cl^-) hyperaccumulating halophytes in the Temperate Desert of Xinjiang, China and studied two of them (Suaeda salsa (L.) Pall. and Kalidium folium (Pall.) Moq.). K. folium and S. salsa had a NaCl content of 32.1% and 29.8%, respectively, on a dry weight basis. X-ray microanalysis of the Na in the vacuole, apoplasts and cytoplasm of the two plants indicated a ratio of 7.3:5.6:1.0 in K. folium and 7.3:6.6:1.0 in S. salsa. These data show that K. folium and S. salsa both have a high Na and Cl^- accumulating capacity, which is related to high activity of tonoplast H^ -ATPase and H^ -PPase.     

Effects of Colchicine on Distribution of Mitochondria in 2-cell and Compacted 8-cell Mouse Embryos

The distribution of mitochondria during early development of mouse embryos was visualized bymitochondria-specific vital fluorescent dye, rhodamine 123(Rh 123). Mitochondrial clusters wasmarkedly conceotrated to perinuclear area in blastomere of normal 2-ccll embryos. In blastomere ofuncompacted 8-cell embryos, mitochondria were randomly distributed throughout the cytoplasm, butthey were reorganizcd to the cytocortices beneath the apposed surfaces of blastomere duringcompaction. As demonstrated in our study, colchicine (10 μg/ml) produced marked effect onmitochondrial distribution in blastomcre of 2-cell and compacted 8-cell embryos: mitochondriabecame scattered throughout the cytoplasm ofblastomere. It is suggested that the spatial distributionof mitochondria in early mouse embryo are maintained by microtubule.     

Structural Basis of Interaction of Bipartite Nuclear Localization Signal from Agrobacterium VirD2 with Rice Importin-o

Dear Editor, In the eukaryotic cell, the nuclear envelope separates genomic DNA from the rest of the cell, but ensures a molecu- lar communication between the nucleus and the cytoplasm through the nuclear pore complexes （NPCs）. Nuclear trans- port of macromolecules is an energy-dependent process, exemplified by the classical nuclear import pathway. In the cytoplasm, proteins containing classical nuclear localization signals （cNLSs） are recognized by a hetero-dimeric transport receptor （importin-α （Impα）：importin-β （Impl3） complex）. Impa is employed as an adaptor protein that specifically rec-ognizes the classical nuclear localization signal （cNLS） from the cargo protein （Marfori et al., 2011）. Translocation of the trimeric cargo：transport receptor import complex through the NPCs is mediated by transient interactions between Impβ and nucleoporins in the NPC. The directionality of the trans- port is imparted by the asymmetric distribution, between the cytoplasm and the nucleus, of the distinct nucleotide-bound （GTP/GDP） states of the small GTPase Ran （Tran et al., 2007）.     

Co-suppression in transgenic Petunia hybrida expressing chalcone synthase A (chsA)

Chalcone synthase A is a key enzyme in the anthocyanin biosynthesis pathway. Expression of chsA gene in transgenic Petunia hybrida resulted in flower color alterations and co-suppression of transgenes and endogenous genes. We fused the β-glucuronidase (uidA) gene to the C-terminal of chsA gene, and transferred the fusion gene into Petunia hybrida via Agrobac-terium tumefaciens. GUS histochemical staining analysis showed that co-suppression occurred specifically during the development of flowers and co-suppression required the mutual interaction of endogenous genes and transgenes. RNA in situ hybridization analysis suggested that co-suppression occurred in the entire plant, and RNA degradation occurred in the cytoplasm.     

Overexpression of PTEN induces cell growth arrest and apoptosis in human breast cancer ZR-75-1 cells

Phosphatase and tensin homolog （PTEN） is a tumor suppressor gene located at human chromosome 10q23, might play an important role in cell proliferation, cell cycle and apoptosis of cancer cells. In this study, the eukaryotic expression vectors pBP-wt-PTEN （containing a wild-type PTEN gene） and pBP-G129R-PTEN （containing a mutant PTEN gene） were used to transfect breast cancer ZR-75-1 cells. After transfection, ZR-75-1 cells expressing PTEN were obtained and tested. The blue exclusion assay showed the growth rate of the cells transfected with pBP-wt-PTEN was significantly lower than that of the control cells transfected with pBP-G129R-PTEN. Analysis of the cell cycle by flow cytometry showed that the progression from the G1 to the S phase was arrested in cells expressing wild-type PTEN. Some typical morphological changes of apoptosis were also observed in cells transfected with pBP-wt-PTEN, but not in those transfected with pBP-G 129R-PTEN. This study shows that overexpression of PTEN in ZR-75-1 cells leads to cell growth arrest and apoptosis.     

Dynamic distribution of Ser-10 phosphorylated histone H3 in cytoplasm of MCF-7 and CHO cells during mitosis

The dynamic distribution of phosphorylated Histone H3 on Serl 0 (phospho-H3) in cells was investigated to determine its function during mitosis. Human breast adenocarcinoma cells MCF-7, and Chinese hamster cells CHO were analyzed by indirect immunofluorescence staining with an antibody against phospho-H3. We found that the phosphorylation begins at early prophase, and spreads throughout the chromosomes at late prophase. At metaphase, most of the phospho-H3 aggregates at the end of the condensed entity of chromosomes at equatorial plate. During anaphase and telophase,the fluorescent signal of phospho-H3 is detached from chromosomes into cytoplasm. At early anaphase, phospho-H3 shows ladder bands between two sets of separated chromosome, and forms “sandwich-like structure” when the chromosomes condensed. With the cleavage progressing, the “ladders” of the histone contract into a bigger bright dot. Then the histone aggregates and some of compacted microtubules in the midbody region are composed into a “bar-like”complex to separate daughter cells. The daughter cells seal their plasma membrane along with the ends of the “bar”,inside which locates microtubules and modified histones, to finish the cytokinesis and keep the “bar complex” out of the cells. The specific distribution and kinetics of phospho-H3 in cytoplasm suggest that the modified histones may take part in the formation of midbody and play a crucial role in cytokinesis.