Messenger RNA encoding an estrogen-dependent oviduct secretory protein in the sheep is localized in the apical tips and basal compartments of fimbria and ampulla epithelial cells implying translation at unique cytoplasmic foci

A Comparative View on the Oviductal Environment during the Periconception Period

The oviduct plays important roles in reproductive events: sperm reservoir formation, final gamete maturation, fertilization and early embryo development. It is well known that the oviductal environment affects gametes and embryos and, ultimately, the health of offspring, so that in vivo embryos are better in terms of morphology, cryotolerance, pregnancy rates or epigenetic profile than those obtained in vitro. The deciphering of embryo-maternal interaction in the oviduct may provide a better understanding of the embryo needs during the periconception period to improve reproductive efficiency. Here, we perform a comparative analysis among species of oviductal gene expression related to embryonic development during its journey through the oviduct, as described to date. Cross-talk communication between the oviduct environment and embryo will be studied by analyses of the secreted or exosomal proteins of the oviduct and the presence of receptors in the membrane of the embryo blastomeres. Finally, we review the data that are available to date on the expression and characterization of the most abundant protein in the oviduct, oviductin (OVGP1), highlighting its fundamental role in fertilization and embryonic development.

Cyclic regulation of apoptotic gene expression in the mouse oviduct

The oviduct is a dynamic structure whose function relies upon cyclic changes in the morphology of both ciliated and secretory luminal epithelial cells. Unfortunately, infection of these epithelial cells by sexually transmitted pathogens can lead to pelvic inflammatory disease, ectopic pregnancies and infertility. The disruption of normal, cyclic apoptosis in the oviducal epithelium appears to be a causal factor of oviducal pathology and therefore, these pathways represent a potential target for diagnosis and therapeutic intervention. The objective of this study was to determine the pattern of expression for apoptotic genes in the oviduct of the naturally cycling mouse, generating fundamental information that can be applied to the development of animal models for research and the identification of targets for disease intervention. Whole oviducts were collected from regular cycling mice killed at 1p.m. on each day of the oestrous cycle and the expression of 84 apoptotic genes determined by targeted PCR super-array. Intact and cleaved caspases were then evaluated by western blotting. The expression of mRNA for genes classified as pro-apoptotic (Bad, Bak1 and Bok) and anti-apoptotic (Bag3, Bnip2 and Xiap) was regulated by day (P < 0.05). Differences in the temporal expression of several p53-related genes (Trp53bp2, Trp53inp1 and Trp73), those specific to the TNF superfamily (Tnfrsf10 and Tnfsf10b) and one caspase (Casp14) were also observed (P < 0.05). The cleaved forms of Caspases-3, -6 and -12 were all detected throughout the oestrous cycle. These results represent the first pathway-wide analysis of apoptotic gene expression in the murine oviduct.

Identification of differentially expressed genes in the uterine endometrium on day 12 of the estrous cycle and pregnancy in pigs

Maternal recognition of pregnancy in pigs occurs approximately on Day (D) 12 of pregnancy and is critical for embryo implantation. The presence of the conceptus in the uterine lumen during this period changes uterine endometrial function to prepare for attachment of the conceptus to the endometrial epithelial cells and maintain luteal function in the ovary. Although much is known about endometrial gene expression, the genes expressed in the uterine endometria and the cellular and molecular mechanisms of those gene products during the period of implantation and maternal recognition of pregnancy in pigs are still not completely defined. To better understand the interactions between the maternal uterus and conceptus during the implantation process, we searched genes differentially expressed in the endometria on D12 of pregnancy compared to those on D12 of the estrous cycle. A new reverse transcription-polymerase chain reaction (RT-PCR)-based method that involves annealing control primers (ACPs) was employed. Using 120 ACPs, we sequenced 12 differentially expressed genes (DEGs) and identified those genes using the Basic Local Alignment Search Tool (BLAST). Northern blot hybridization analysis confirmed the differential expression of those DEGs in the uterine endometrium. In situ hybridization analysis determined the cell-type specific expression of the DEGs in the uterine endometrium. Further analysis of the DEGs found in this study will provide insights into the cellular and molecular basis of maternal and fetal interactions during the period of maternal recognition of pregnancy in the pig. Mol. Reprod. Dev. 76: 75-84, 2009. (c) 2008 Wiley-Liss, Inc.

Identification of cellular isoform of oviduct-specific glycoprotein: role in oviduct tissue remodeling?

The oviduct is known to secrete mucins (MUC1 and MUC9) under the influence of ovarian steroids. The secreted form of MUC1 binds gametes in the oviduct, whereas the cellular form seen in breast cancers has been implicated in cell adhesion and morphogenesis. The secreted MUC9 or oviduct-specific glycoprotein (OGP), in addition to being a mucin, belongs to family 18 glycosylhydrolases and is known to bind gametes and embryos in the oviduct. Studies in our laboratory have identified non-muscle myosin IIA (involved in cell shape, polarity, and morphogenesis) as the protein partner to OGP in gametes. In view of the crucial role of the cortical cytoskeleton in the selective internalization of tight junctions (TJs) /adherent junctions (AJs) or apical junctional complex (AJC) in simple epithelial cells during tissue remodeling, the present study has been undertaken to evaluate the existence of a cellular form of OGP in oviductal tissue, which itself undergoes cyclic tissue remodeling. In silico analysis of the deduced amino-acid sequence of OGP has revealed the presence of several conserved motifs; these imply that OGP is a component of multi-protein complexes such as TJs. Corroborative immunoelectron-microscopic analysis in peri-ovulatory oviduct epithelia in the bonnet monkey has revealed the presence of OGP at the TJ. Co-localization studies of OGP and cadherin demonstrate that, whereas OGP is localized at the tonofilaments of the TJs, cadherin is localized at the intercellular space of the AJ. The possible role of OGP in oviductal tissue remodeling is discussed in light of the present findings and those reported in the literature.

Organization of a gene coding for an oviduct-specific glycoprotein (oviductin) in the hamster

Hamster oviductin, a high molecular weight glycoprotein secreted by the oviducts, is believed to participate in fertilization and protection of the tubal epithelium. Expression of the oviductin gene is confined strictly to nonciliated secretory cells of the oviduct and is regulated by hormones. The objective of this study was to characterize the genomic organization and to identify potential regulatory elements implicated in the control of transcription of the oviductin gene. Polymerase chain reaction was performed on hamster genomic DNA, yielding 2.2 kb of the 5' flanking region as well as 13.6 kb of genomic sequence comprising the entire coding sequence of the oviductin gene distributed in 11 exons. Sequencing of the 5' flanking region revealed, among other elements, an almost perfect estrogen-responsive element (GGTCACTGTGACT), an atypical TATA box (TATTAA), and a perfect inverted Sp1 site located between the transcription start site and the atypical TATA box. Primer extension analyses indicated that the hamster oviductin transcript possesses an unusually short 5' untranslated region of only 14 nucleotides. The distinct organization of the hamster oviductin gene in the vicinity of the transcription start site provides an interesting ground for further functional studies.

Asymmetrical localization of mRNAs in enterocytes of human jejunum

Intracellular localization of specific mRNAs is known to be a mechanism for targeting proteins to specific sites within the cell. Previous studies from this laboratory have demonstrated co-localization of mRNAs and proteins for a number of genes in absorptive enterocytes of fetal rat intestine. The present study was undertaken to examine in human enterocytes the intracellular localization patterns of mRNAs for the microvillous membrane proteins lactase-phlorizin hydrolase (LPH), sucrase-isomaltase (SI), and intestinal alkaline phosphatase (IAP), and the cytoskeletal protein beta-actin. In sections of human jejunum, mRNAs were localized by in situ hybridization using digoxigenin-labeled anti-sense RNA probes. Both LPH and SI mRNAs were localized to the apical region of villous enterocytes, whereas IAP and beta-actin mRNAs were detected both apically and basally relative to the nucleus. Therefore, in contrast to LPH, SI, and beta-actin mRNAs, which co-localize with their encoded proteins, that of IAP is present in the basal region of the cell where IAP protein has not directly been demonstrated to be present. Absorptive enterocytes from humans possess the mechanisms for intracellular mRNA localization, but not all mRNAs co-localize with their encoded proteins.

Morphological features of epithelial cells in the sheep isthmus oviduct during early pregnancy

BACKGROUND

The objective of the present study was to define the morphological changes that occur in the epithelium of the isthmus oviduct of the sheep during the first few weeks of pregnancy.

MATERIALS

Isthmus oviducts were obtained from ovariectomized, estrous (day O) and pregnant (day 2, 3, 4, 6, and 16) ewes and analyzed using light and electron microscopy.

RESULTS

The epithelium was low cuboidal in the isthmus from ovariectomized sheep, significantly increased in height at estrus, underwent an additional increase at day 3, and was significantly reduced by day 4 of pregnancy. Ciliated and nonciliated epithelial cells were present at all reproductive stages. Ciliated cells were always the predominant cell type. The percentage of ciliated and nonciliated cells did not significantly change at any stage examined. In addition, a third cell type, located adjacent to the basement membrane, was present. These "basal" cells were rounded in appearance and more frequently observed in the epithelial lining of ovariectomized ewes and after day 3 of pregnancy. The secretory organelles of nonciliated epithelial cells obtained from ovariectomized ewes were poorly developed. In estrous ewes, the Golgi apparatus in nonciliated cells consisted of stacked cisternae that atrophied later in pregnancy. The most striking alterations in the secretory apparatus occurred in ciliated cells. Two populations of ciliated cells were observed at estrus-one with abundant, membrane bound supranuclear granules and one without granules. The granules in ciliated cells were rare after day 3 of pregnancy and no evidence of secretion was ever observed. Large lipid droplets were present in the cytoplasm of ciliated cells at estrus. Lysosomes were abundant in nonciliated cells by day 16 of pregnancy. Regularly arranged microvilli were present in nonciliated cells obtained from ovariectomized, estrous, and pregnant ewes. No appreciable change in nuclear shape or chromatin content was observed at any reproductive stage examined. The ultrastructural characteristics and relative abundance of other cytoplasmic organelles such as the RER, SER, mitochondria, and glycogen varied slightly during pregnancy in ciliated and nonciliated cells.

CONCLUSIONS

These data show that the epithelial lining of the isthmus oviduct in the sheep undergoes subtle, yet distinctive, structural changes during the first few weeks of pregnancy.