Mechanisms underlying the tissue-specific and regulated activity of the Gnrhr promoter in mammals.

The GnRH receptor (GnRHR) plays a central role in the development and maintenance of reproductive function in mammals. Following stimulation by GnRH originating from the hypothalamus, GnRHR triggers multiple signaling events that ultimately stimulate the synthesis and the periodic release of the gonadotropins, luteinizing-stimulating hormone (LH) and follicle-stimulating hormones (FSH) which, in turn, regulate gonadal functions including steroidogenesis and gametogenesis. The concentration of GnRHR at the cell surface is essential for the amplitude and the specificity of gonadotrope responsiveness.

Identification and analysis of two novel sites of rat GnRH receptor gene promoter activity: the pineal gland and retina.

Background And Aims: In mammals, activation of pituitary GnRH receptor (GnRHR) by hypothalamic GnRH increases the synthesis and secretion of LH and FSH, which, in turn, regulate gonadal functions. However, GnRHR gene (Gnrhr) expression is not restricted to the pituitary.

Methods: To gain insight into the extrapituitary expression of Gnrhr, a transgenic mouse model that expresses the human placental alkaline phosphatase reporter gene driven by the rat Gnrhr promoter was created.

Reporter transgenic mouse models highlight the dual endocrine and neural facet of GnRH receptor function.

In the pituitary of mammals, the GnRH receptor (GnRHR) plays crucial roles in the neuroendocrine control of reproductive function. This receptor is specifically expressed by the gonadotrope cells scattered among the five other endocrine cell types constituting the anterior pituitary; it is also expressed in other organs, such as the gonads and brain where its function is not well defined. To gain insight into GnRHR function, distribution, and regulation, several transgenic approaches have been developed using a range of reporter genes under the control of the mouse, rat, or ovine GnRHR gene (Gnrhr) promoters.

GnRH receptor gene expression in the developing rat hippocampus: transcriptional regulation and potential roles in neuronal plasticity.

In the pituitary of mammals, the GnRH receptor (GnRHR) plays a primary role in the control of reproductive function. It is further expressed in the hippocampus, where its function, however, is not well defined. By quantitative RT-PCR analyses, we demonstrate herein that the onset of GnRHR gene (Gnrhr) expression in the rat hippocampus was unexpectedly delayed as compared to the pituitary and only occurred after birth.

The GnRH receptor and the response of gonadotrope cells to GnRH pulse frequency code. A story of an atypical adaptation of cell function relying on a lack of receptor homologous desensitization.

Brain control of the reproductive system is mediated through hypothalamic gonadotropin-releasing hormone (GnRH) which activates specific receptors (GnRHR) present at the surface of the pituitary gonadotropes to trigger secretion of the two gonadotropins LH and FSH. A unique feature of this system is the high dependence on the secretion mode of GnRH, which is basically pulsatile but undergoes considerable fluctuations in pulse frequency pattern in response to endogenous or external factors. How the physiological fluctuations of GnRH secretion that orchestrate normal reproduction are decoded by the gonadotrope cell machinery to ultimately control gonadotropin release and/or subunit gene transcription has been the subject of intensive studies during the past decades.

What is the role of PACAP in gonadotrope function?

Strong evidence in favor of a direct action of hypothalamic PACAP at the pituitary to modulate gonadotrope function has been acquired mainly by in vitro studies using cultured pituitary cells or gonadotrope cell lines. In particular, PACAP has been shown to cooperate with GnRH, the primary regulator of gonadotropes, to regulate/modulate gonadotropin subunit gene expression, gonadotropin release as well as gonadotrope responsiveness. These effects of PACAP appear to be due essentially to its high potent stimulatory action on the cAMP/protein kinase pathway.

The LIM-homeodomain proteins Isl-1 and Lhx3 act with steroidogenic factor 1 to enhance gonadotrope-specific activity of the gonadotropin-releasing hormone receptor gene promoter.

The GnRH receptor (GnRH-R) plays a central role in mammalian reproductive function throughout adulthood. It also appears as an early marker gene of the presumptive gonadotrope lineage in developing pituitary. Here, using transient transfections combined with DNA/protein interaction assays, we have delineated cis-acting elements within the rat GnRH-R gene promoter that represent targets for the LIM-homeodomain (LIM-HD) proteins, Isl-1 and Lhx3.

Gonadotropin-releasing hormone and the control of gonadotrope function.

Normal gametogenesis and steroidogenesis is highly dependent on the pulsatile release of hypothalamic GnRH that binds high-affinity receptors present at the surface of pituitary gonadotrophs thereby triggering the synthesis and release of the gonadotropins LH and FSH. The mammalian GnRH receptor displays the classical heptahelical structure of G protein-coupled receptors with, however, a unique feature, the lack of a C-terminal tail. Accordingly, it does not desensitise sensu stricto, and internalises very poorly.

[An ambiguous role of steroidogenic factor 1 in the rat GnRH receptor gene expression. Lessons from transgenic mice].

Because the GnRH receptor plays a paramount role within the reproductive axis, the understanding of the molecular apparatus that governs the tissue-specific expression and regulation of this gene must lead to a better knowledge of the physiology and the physiopathology of the gonadotrope function. To elucidate these mechanisms, we have used two complementary in vivo and in vitro approaches. Firstly, we have isolated the pituitary promoter of the rat GnRH receptor gene and investigated its activity using transient transfection into two gonadotrope-derived cell lines, the alphaT3-1 and the LbetaT2 cell lines.

The promoter of the rat gonadotropin-releasing hormone receptor gene directs the expression of the human placental alkaline phosphatase reporter gene in gonadotrope cells in the anterior pituitary gland as well as in multiple extrapituitary tissues.

Previous studies dealing with the mechanisms underlying the tissue-specific and regulated expression of the GnRH receptor (GnRH-R) gene led us to define several cis-acting regulatory sequences in the rat GnRH-R gene promoter. These include functional sites for steroidogenic factor 1, activator protein 1, and motifs related to GATA and LIM homeodomain response elements as demonstrated primarily in transient transfection assays in mouse gonadotrope-derived cell lines. To understand these mechanisms in more depth, we generated transgenic mice bearing the 3.

Cloning and modeling of CD8 beta in the amphibian ambystoma Mexicanum. Evolutionary conserved structures for interactions with major histocompatibility complex (MHC) class I molecules.

Mammalian and avian T-cells exhibit a large number of well characterized surface molecules associated with their maturation degree. Very little is known in comparison with T-cell differentiation in ectothermic vertebrates. This is mainly due to the lack of probes to identify T-cell subsets.

PACSIN2 is a regulator of the metalloprotease/disintegrin ADAM13.

ADAM13 is a cell surface metalloprotease expressed in cephalic neural crest cells during early Xenopus development. The cytoplasmic domain of ADAM13 contains three potential SH3 (Src homology type 3) binding sites, suggesting that this region may support interactions with intracellular proteins. In this report we describe the identification, by a new strategy, of three proteins that bind the ADAM13 cytoplasmic domain in vitro: X-Src1, X-An4, and X-PACSIN2.

Selective loss of mouse embryos due to the expression of transgenic major histocompatibility class I molecules early in embryogenesis.

Among the numerous hypotheses proposed to explain the absence of fetal rejection by the mother in mammals, it has been suggested that regulation of expression of the polymorphic major histocompatibility complex (MHC) at the fetal-maternal interface plays a major role. In addition to a lack of MHC gene expression in the placenta throughout gestation, the absence of polymorphic MHC molecules on the early embryo, as well as their low level of expression after midgestation, could contribute to this important biologic phenomenon. In order to test this hypothesis, we have produced transgenic mice able to express polymorphic MHC class I molecules early in embryogenesis.

A mouse placental immunoregulatory factor different from transforming growth factor beta.

Of the growth-promoting factors, transforming growth factor beta (TGF-beta) has been most clearly shown to act as a potent regulator of inflammation and immunity. It is highly suppressive for T and B lymphocyte proliferation, cytotoxic T lymphocyte generation, and lymphokine-activated killer cell development, as well as natural killer cell activity. Moreover, there is accumulating evidence that TGF-beta also may contribute to impaired immune surveillance of tumor development.

A mouse monoclonal antibody specific for the V beta 5.3 chain of the human TcR recognizes a subgroup of the mouse TcR V beta 8.2 chains.

We have analyzed the reactivity of a mouse monoclonal antibody directed against the human T cell receptor for antigen (TCR). This antibody (111-427) of immunoglobulin G1 isotype has been produced in a BALB/c mouse immunized with HPB-ALL cells and normal human peripheral blood leukocytes. It reacts specifically with the HPB-ALL lymphoma and 2 to 7% of normal human blood lymphocytes, on which it has a mitogenic effect in vitro.

Biochemical and functional characterization of an avian homolog of the integrin GPIIb-IIIa present on chicken thrombocytes.

We have analyzed the reactivity of a new mouse monoclonal antibody (mAb), 11C3, which identifies a cell marker detected on the surface of chicken thrombocytes. Tissue distribution studies have shown that only cells of the thrombocytic lineage in blood, spleen, and bone marrow are stained by 11C3. However, it does not react with other species such as quail, mouse, and man.

Functional and biochemical properties of a mouse placental immunoregulatory factor.

The authors have a long standing interest in immune regulations which control the absence of rejection of a semi-allogeneic fetus by the mother. A previous work described a soluble 40 kDa factor extracted from mouse placenta and capable of inhibiting secondary immune responses in vitro. The present paper reports the following on its mode of action in vivo: (1) it is active even in a fully allogeneic host; (2) it can be administered i.

A new marker on chicken hematopoietic cells is defined by a monoclonal antibody raised against a V beta chain of the human TCR.

In this paper, we show that a mouse monoclonal antibody, 111-427, specific for the V beta 5.3 chain of the human T-cell receptor (TCR) for antigen, also reacts with chicken hematopoietic cells. Our data indicate that the majority of 111-427 positive cells among peripheral blood leucocytes (PBL) are thrombocytes.

Comparison between autoantibodies arising during Trypanosoma cruzi infection in mice and natural autoantibodies.

The autoantibodies induced in (C57BL/6 x BALB/c)F1 mice during Trypanosoma cruzi (CL strain) infection were analyzed and compared with natural autoantibodies present in healthy mice. Mice were killed at intervals after infection and their sera were tested by enzyme immunoassay against a panel of self- and non-self-Ag: actin, myoglobin, myosin, tubulin, DNA, and TNP-OVA. The level of IgM and IgG autoantibodies against all Ag started to increase from day 15 until 6 wk after the parasite infection.

Antigen-specific modulation of graft-versus-host reactions by two distinct placental factors.

We have previously shown that two distinct mouse placental fractions (PF) are potent immunomodulators in vivo. A 40 kDa PF induces a marked decrease of plaque forming cell (PFC) responses, while a 60 kDa PF increases them. Both effects are specific for the priming antigen.

T cell tolerization in vitro: modulation of helper and suppressor cell activities.

This paper analyzes the conditions for in vitro tolerization of purified whole T cell populations and the consequences on helper and suppressor T cell functions. Highly purified splenic T cells from adult DBA/2 mice were incubated in vitro for 24 hr with high doses of trinitrophenyl coupled to human gamma-globulins (TNP-HGG). A profound inhibition of the TNP-specific helper function of these T lymphocytes was observed in a cooperative culture with normal purified splenic B cells and TNP-SRBC as antigen.

Simultaneous responses to TD, TI-1 and TI-2 antigens originate from both specific and multipotent precursors.

The classification of antigens into TD, TI-1 and TI-2 varieties raises the question of whether responses to these antigens are produced by distinct or identical subpopulations of B cells. In the present study we have examined the extent of intraclonal specificity variation in the progeny of PFC appearing after stimulation with two unrelated antigens. Mouse lymphoid cells were stimulated with pairs of TD and TI antigens, PFC were individually cultured and daughter PFC examined for their specificity.

Modulation of mouse anti-SRBC antibody responses by placental extracts. II. Antigen specificity and regulatory role of B and T cell populations affected by two distinct placental fractions.

Previous results from our group had shown that when CBA mice are primed to sheep red blood cells (SRBC) in the presence of various doses of placental extract (PE) (or liver extract [LE] as control), their spleen cells injected into normal syngeneic recipients have important immunoregulatory properties. Low doses of PE (0.25 to 4 mg per mouse) induce a marked decrease of the PFC response against SRBC in recipient animals.