No description available.

No description available.

No description available.

No description available.

No description available.

Galectins are proteins with 15 known members found in nearly all living organisms. They share a conserved CRD that binds beta-galactoside sugars, and functions to cross-link glycoproteins as well as glycolipid receptors on the surface of cells to initiate biological responses. Functional studies on the extracellular and intracellular roles of galectins implicate them in cell adhesion, chemoattraction and migration as well as growth, differentiation and apoptosis. Therefore, studies were conducted to identify functional roles of galectin 15 (LGALS15) during the periimplantation period of pregnancy in the sheep. The first study was designed to develop and characterize primary ovine trophectoderm cell lines for the study of the biological functions of LGALS15. Once characterized, these cell lines were used to investigate the role of LGALS15 in trophectoderm gene expression, development, growth, and survival. Two primary trophectoderm cell lines (oTr1 and oTrF) were developed, and they had characteristics similar to in vivo conceptus trophectoderm relative to gene expression, morphology, and migration and proved suitable as an in vitro model to investigate functional roles of LGALS15. The second study investigated LGALS15 function in trophectoderm cell adhesion. A dose-dependent increase in oTr cell attachment to LGALS15 was found that could be inhibited by cyclic GRGDS, but not GRADS, peptides. Mutation of the LDVRGD integrin binding sequence of LGALS15 to LADRAD decreased its ability to promote oTr cell attachment, whereas mutation of the CRD had little effect. LGALS15 induced formation of robust focal adhesions in oTr cells that were abolished by mutation of the LDVRGD sequence. The third study tested the hypothesis that LGALS15 is a secreted regulator of trophectoderm development and gene expression, as well as growth, migration, and apoptosis of trophoblast. LGALS15 moderately increased cellular proliferation, partially inhibited staurosporine elicited apoptosis, stimulated migration that was dependent on Jun N-terminal kinase (JNK), and initiated differential gene expression of oTr cells. Collectively, these results support the hypothesis that LGALS15 has a biological role in the peri-implantation stage of early pregnancy in the ovine uterus and stimulates trophectoderm cell gene expression, migration and attachment via integrin binding and activation which are critical to blastocyst elongation and implantation.

Endogenous retroviruses (ERVs) account for a substantial portion of the genetic pool of every animal species (e.g. ~ 8% of the human genome). Despite their overwhelming abundance in nature, many questions on the basic biology of ERVs are unanswered. Sheep harbor approximately 20 copies of endogenous betaretroviruses (enJSRVs), which are related to an exogenous oncogenic virus, Jaagsiekte sheep retrovirus (JSRV). Therefore, they are an attractive model for investigation of the potential beneficial roles of ERVs in reproductive biology. Studies were conducted to determine: 1) expression of enJSRVs envelope (env) and HYAL2 mRNAs in the ovine uterus and conceptus (embryo/fetus and extraembryonic membranes) throughout gestation; 2) regulation of enJSRVs expression by progesterone; and 3) the role of enJSRVs in regulating peri-implantation placental growth and differentiation. Study One determined the localization of enJSRVs env and HYAL2 mRNAs throughout gestation. Results demonstrate that alterations in expression of enJSRVs and HYAL2 in the sheep uterus and placenta suggest the probability of a variety of physiological roles in implantation and placentation. Partial sequencing of the transcriptionally active enJSRVs from ovine uteroplacental tissues revealed expression of multiple enJSRV loci. Study Two assessed the influence of progesterone, interferon tau, and pregnancy stage on enJSRVs expression, as an effort to understand factors that may regulate enJSRVs. Results of this study support the hypothesis that expression of enJSRVs is modulated by progesterone, but not IFNτ in vivo. Study Three provides for enJSRVs regulating trophectoderm growth and differentiation in the peri-implantation conceptus. Blocking conceptus enJSRVs Env expression compromised pregnancy by retarding trophoblast outgrowth and differentiation. Inhibition of enJSRVs Env in vitro also reduced proliferation of mononuclear trophectoderm cells. Consequently, these results demonstrate that enJSRVs Env regulates trophectoderm growth and differentiation in the ovine conceptus, strongly supporting the biological significance of ERVs in placental evolution and animal reproduction Collectively, these studies illustrate that enJSRVs play an integral role in success of pregnancy. While the definitive roles of the enJSRVs have not yet been elucidated, it is evident that enJSRVs are an important component of the ovine genome and that they influence recognition and maintenance of pregnancy and placental formation.

Recurrent early pregnancy loss in the ovine uterine gland knockout (UGKO) ewe model manifests on Day 14 of pregnancy, indicating that endometrial secretions are critical for peri-implantation conceptus development. Therefore, the following studies were conducted with fertile ewes and infertile UGKO ewes to identify candidate endometrial factors essential for normal conceptus survival, utilizing both genomics and proteomics approaches. The first study used transcriptional profiling of endometrium from Day 14 cyclic, pregnant, and bred UGKO ewes, as well as ewes treated with interferon tau (IFN??) and progesterone, to identify genes important for conceptus development. A number of novel and previously known IFN??-stimulated genes, as well as progesterone-stimulated genes were identified that are higher in fertile ewes, such as galectin-15. Interactive effects of progesterone and IFN?? regulate endometrial gene expression in a temporal and cell-type specific manner. The second study characterized the endometrial expression and hormonal regulation of galectin-15, a member of the galectin family of secreted ??-galactoside lectins. Galectin-15 was secreted into the uterine lumen by the lumenal (LE) and superficial glandular epithelium (sGE), where it may promote adhesion during implantation, as well as was phagocytosed by the trophectoderm and formed intracellular crystals. The third study determined the endometrial expression of galectin-15 throughout gestation. Galectin-15 was secreted into the uterine lumen, where it was phagocytosed by the trophectoderm/chorion, transferred through placental vasculature to the fetus, and cleared through the fetal kidney to be stored in allantoic fluid. The fourth study utilized proteomic analysis of uterine flushes and endometrial explant cultures from Day 14 cyclic, pregnant and UGKO ewes to identify differences in uterine secretions. Analyses identified several genes that were expressed by the LE and sGE and may be involved in prostaglandin production and/or pH regulation. Collectively, results of these studies suggest that transcriptional profiling and analysis of uterine secretions are effective tools to determine genes important for early pregnancy. Further, identified genes are expected to reveal novel endometrial factors and metabolic pathways for support of conceptus survival and implantation, as well as provide improvements for embryo culture methods and diagnose endometrial dysfunctions leading to infertility.

Reproduction de : Thèse d'exercice : Médecine vétérinaire : Toulouse 3 : 2008. / Titre provenant de l'écran titre. Bibliogr. p. 58-62.

No description available.