Alternative splicing of the telomerase catalytic subunit in human oocytes and embryos.

The human telomerase catalytic subunit (hTCS) is a ribonucleoprotein which synthesizes telomere repeats on the ends of chromosomes. Telomerase activity is thought to be essential in maintaining normal telomere length in immortal (cancer) and germ cells. The objective of this study was to determine the gene expression of telomerase mRNA in human oocytes at different meiotic stages and in embryos. Normal and abnormal human oocytes, preimplantation embryos, and blastocysts were analysed for the presence and expression of the hTCS transcripts. Multiple telomerase mRNA products were identified by reverse transcription-polymerase chain reaction (RT-PCR) using primers within the reverse transcriptase domain. DNA sequencing of these amplicons suggest that there are alternative splicing variants which align to other telomerase reverse transcriptase (RT) consensus domains. Surprisingly, in unfertilized and immature gametes, as well as preimplantation embryos, hTCS expression revealed three different PCR product sizes, 457, 421 and 275 bp. The frequency of the 275 bp DNA product was 6.6% in oocytes (two out of 30) compared with 56.6% (17 out of 30) in poorly developing human preimplantation embryos (P < 0.005). The presence of alternately spliced mRNA variants in human preimplantation embryos may suggest a lack of telomerase activity and thus chromosomes associated with shortened telomeres.

Matrix metalloproteinase expression during mouse peri-implantation development.

PROBLEM: The purpose of this study was to define the temporal expression and to quantitate the mRNA levels of collagenase, 72 kDa, 92 kDa, and membrane-type matrix metalloproteinase during the peri-implantation period of pregnancy in the mouse uterus. Embryonic expression of 72 kDa and 92 kDa matrix metalloproteinases, as well as interleukin 1 alpha, was also investigated. METHODS: Uterine matrix metalloproteinases were detected using gelatin substrate gel electrophoresis (zymography) and reverse-transcription polymerase chain reaction methodology was used to detect and quantitate different mRNA species in the mouse uterus and blastocyst. RESULTS: Collagenase, 72 kDa, and 92 kDa matrix metalloproteinases are developmentally regulated during the peri-implantation period of pregnancy, but membrane-type matrix metalloproteinase appears to be expressed constitutively. Matrix metalloproteinase mRNA levels have been quantitated and confirm the observed developmental expression patterns. Prominent expression of bot 92 kDa matrix metalloproteinase and interleukin 1 alpha was observed in blastocysts during outgrowth while weak expression of the 72 kDa matrix metalloproteinase was detected. CONCLUSIONS: The date provide evidence of matrix metalloproteinase expression in vivo and substantiate their potential role in tissue remodeling prior to and during blastocyst implantation. Expression of interleukin 1 alpha, 92 kDa, and 72 kDa matrix metalloproteinases suggests that these proteins are important for trophoblast invasion associated with implantation of the early embryo.

Monoclonal antiphosphatidylserine antibody inhibits intercellular fusion of the choriocarcinoma line, JAR.

Naturally occurring antiphospholipid antibodies are strongly associated with placental dysfunction and severe obstetrical complications. We have produced three monoclonal antiphospholipid antibodies that differentiate between phosphatidylserine (PS)- and cardiolipin (CL)-dependent antigens, 3SB9b (CL-/PS+), BA3B5C4 (CL+/PS+), and D11A4 (CL+/PS-). We tested these monoclonal antiphospholipid antibodies in an assay for intertrophoblastic fusion. A JAR choriocarcinoma cell line was induced to undergo intercellular fusion by forskolin in the presence or absence of monoclonal antiphospholipid antibodies. The amount of syncytium formation was quantified by using fluorescein isothiocyanate (FITC)-conjugated anti-desmosome antibody to visualize intercellular membranes and propidium iodide to stain nuclei and by counting those cells with multiple nuclei. Without the presence of antiphospholipid antibodies, and in cultures containing BA3B5C4 (CL+/PS+) or D11A4 (CL+/PS-), approximately 70% of JAR formed syncytial cells after 24 h of forskolin treatment. Less than 13% of the cells formed synctia in 2-day cultures that were not exposed to forskolin or that contained forskolin in the presence of 3SB9b (CL-/PS+). These data suggest that phosphatidylserine is externalized during intertrophoblastic fusion and that antiphospholipid antibody with reactivity against PS, but not CL, can affect placental development by interfering with the normal formation of syncytiotrophoblast.

Hemobartonella-like parasites in cynomolgus monkeys (Macaca fascicularis).

Red blood cell parasites were identified electron microscopically in five anemic adult female cynomolgus monkeys (Macaca fascicularis), two of which died during anemic episodes. Organisms typically were 0.3-0.5-micron round, oval, or reniform bodies on the surface or within vacuoles of erythrocytes. Based on their size, location in the erythrocyte, and internal ultrastructural features, organisms were classified as Hemobartonella-like. The relationship between the organisms and the anemias in these monkeys was unclear. This report adds rickettsial erythrocyte infections to the list of latent infections that can complicate research studies with cynomolgus monkeys.

Expression and function of matrix metalloproteinases in development.

Extracellular matrix (ECM) remodeling accompanies cell migration, cell-cell interactions, embryo expansion, uterine implantation and tissue invasion during mammalian embryogenesis. We have found that mouse embryos express mRNA transcripts for collagenase, stromelysin and the tissue inhibitor of metalloproteinases (TIMP) and secrete functional ECM-degrading metalloproteinases, including collagenase and stromelysin. These metalloproteinases are inhibitable by TIMP and are regulated during peri-implantation development and endoderm differentiation. The involvement of a controlled proteolytic reaction, dependent on metalloproteinases, during the implantation of mouse embryos is suggested by the secretion of proteinases by trophoblast during its invasive phase and by the reciprocal expression of TIMP in the maternal deciduum. Exogenous TIMP affects the migration of parietal endoderm cells during blastocyst outgrowth in vitro. Taken together, these data suggest that metalloproteinases function in cell-ECM interactions during mammalian development.

Expression of extracellular matrix-degrading metalloproteinases and metalloproteinase inhibitors is developmentally regulated during endoderm differentiation of embryonal carcinoma cells.

The differentiation of F9 and PSA-1 embryonal carcinoma cells to embryoid bodies composed of a mixture of parietal and visceral endoderm was accompanied by changes in their secretion of metalloproteinases. Differentiation was induced by retinoic acid and dibutyryl cyclic AMP (for F9 cells) or by removing cells from a substrate of feeder cells to alter cell-cell interaction and adhesion (for PSA-1 cells). The embryoid bodies attached to gelatin-coated dishes, and the parietal endoderm cells spread out over the matrix. The differentiated cells secreted specific gelatin- and casein-degrading proteinases, including enzymes that comigrated with proenzyme forms of collagenase and stromelysin. Total proteinase activity as well as specific collagenase activity increased with the time of differentiation. All of the gelatin- and casein-degrading proteinases detectable by substrate gel zymography were inhibited by inhibitors of metalloproteinases but not by inhibitors of serine or cysteine proteinases, indicating that they were metalloproteinases. Both cell lines showed increased collagenolytic activity, which was activated by treatment with plasmin. In addition, both cell lines showed increased secretion of specific metalloproteinase inhibitors, including tissue inhibitor of metalloproteinases, with differentiation. Analysis of mRNA from undifferentiated and differentiated F9 cells by RNA blot analysis or reverse transcription coupled with the polymerase chain reaction showed that increased expression of genes for collagenase, stromelysin and tissue inhibitor of metalloproteinases is associated with differentiation of these cells. These results suggest that the expression of extracellular matrix-degrading metalloproteinases and their inhibitors is developmentally regulated during the differentiation and spreading of the parietal endoderm.

Induction of murine 8-cell blastomere polarity by F9 embryonal carcinoma cells.

The individual blastomeres of the preimplantation mouse embryo become polarized during the 8-cell stage of development. This polarity forms as a result of a specific cell-cell interaction that has been termed induction. The ability of embryonal carcinoma (EC) cells to induce 8-cell blastomere polarization has been investigated by aggregating nonpolar 8-cell blastomeres with various types of EC cells. F9, a nullipotent stem cell, induced polarization of a nonpolar 8-cell companion in 80% of the aggregates. Stimulation of differentiation of F9 cells with retinoic acid (RA), with or without dibutyryl cAMP, caused a reduction in the polarity-inducing ability of these cells. Other EC cells, PSA-1, NULLI-SCC1, 3TDM, C3HNE, and P10, all displayed less polarity-inducing activity than F9. In addition, it was observed that when any of these cell types assumed a more differentiated phenotype, either spontaneously or in response to specific stimuli, they displayed a decrease in their ability to induce 8-cell polarization. As a control, the inducing ability of cells from normal mouse tissues was examined. It was found that neither STO mouse fibroblasts nor primary cultures of mouse lymphocytes were able to induce significant polarization of 8-cell stage blastomeres. These data support the hypothesis that while undifferentiated stem cell populations retain the ability to induce 8-cell blastomere polarization, it is apparently lost upon cellular differentiation.

Genes for extracellular-matrix-degrading metalloproteinases and their inhibitor, TIMP, are expressed during early mammalian development.

Extracellular matrix (ECM) remodeling accompanies cell migration, cell-cell interactions, embryo expansion, uterine implantation, and tissue invasion during mammalian embryogenesis. We have found that mouse embryos secrete functional ECM-degrading metalloproteinases, including collagenase and stromelysin, that are inhibitable by the tissue inhibitor of metalloproteinases (TIMP) and that are regulated during peri-implantation development and endoderm differentiation. mRNA transcripts for collagenase, stromelysin, and TIMP were detected as maternal transcripts in the unfertilized egg, were present at the zygote and cleavage stages, and increased at the blastocyst stage and with endoderm differentiation. These data suggest that metalloproteinases function in cell-ECM interactions during growth, development, and implantation of mammalian embryos.

Cell specific loss of polarity-inducing ability by later stage mouse preimplantation embryos.

The individual blastomeres of the preimplantation mouse embryo become polarized during the 8-cell stage. Microvilli become restricted to the free surface of the embryo and this region of the membrane shows increased labeling with FITC-Con A and trinitrobenzenesulfonate (TNBS). Previous studies have shown that this polarity develops in response to asymmetric cell-cell contact with stage specific induction competent blastomeres. In the present study, the ability of later stage embryos to induce 8-cell polarization has been investigated. Newly-formed, nonpolar 8-cell stage blastomeres (1/8 cells) were isolated, then aggregated with morulae, inner cell clusters (from morulae), blastocysts, or inner cell masses (ICM) and cultured for 8 hr. Aggregates were then assayed for polarity. The results show a hierarchy of inducing ability, with the ICM and IC cluster possessing greater activity than the morula and polar trophectoderm of the early blastocyst, while the mural trophectoderm shows very little inducing activity. Furthermore, the inducing ability of the polar trophectoderm decreases with complete expansion and hatching of the blastocyst. These results indicate that the ability to induce 8-cell blastomere polarization is retained by the embryo beyond the 8-cell stage and that this ability is lost with further differentiation.