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PubMed1998

Association of the TLX-2 homeodomain and 14-3-3eta signaling proteins.

Homeodomain proteins play important roles in various developmental processes, and their functions are modulated by polypeptide cofactors. Here we report that both in vitro and in vivo, 14-3-3eta is associated with the TLX-2 homeodomain transcription factor that is required for mouse embryogenesis. Expression of 14-3-3eta shifts the predominant localization of TLX-2 in COS cells from the cytoplasm to the nucleus. Tlx-2 and 14-3-3eta are expressed in the developing peripheral nervous system with spatially and temporally overlapping patterns, and they are also coexpressed in PC12 cells. Increased expression of either gene by transfection considerably inhibited nerve growth factor-induced neurite outgrowth of PC12 cells, and cotransfection of both genes led to a synergistic effect of suppression. These findings define 14-3-3eta as a functional modulator of the TLX-2 homeodomain transcription factor and suggest that the in vivo function of TLX-2 in neural differentiation is likely regulated by signaling mediated by 14-3-3eta.

14-3-3 Proteins↗
PubMed2000

Cell-type-specific regulation of the retinoic acid receptor mediated by the orphan nuclear receptor TLX.

Malformations in the eye can be caused by either an excess or deficiency of retinoids. An early target gene of the retinoid metabolite, retinoic acid (RA), is that encoding one of its own receptors, the retinoic acid receptor beta (RARbeta). To better understand the mechanisms underlying this autologous regulation, we characterized the chick RARbeta2 promoter. The region surrounding the transcription start site of the avian RARbeta2 promoter is over 90% conserved with the corresponding region in mammals and confers strong RA-dependent transactivation in primary cultured embryonic retina cells. This response is selective for RAR but not retinoid X receptor-specific agonists, demonstrating a principal role for RAR(s) in retina cells. Retina cells exhibit a far higher sensitivity to RA than do fibroblasts or osteoblasts, a property we found likely due to expression of the orphan nuclear receptor TLX. Ectopic expression of TLX in fibroblasts resulted in increased sensitivity to RA induction, an effect that is conserved between chick and mammals. We have identified a cis element, the silencing element relieved by TLX (SET), within the RARbeta2 promoter region which confers TLX- and RA-dependent transactivation. These results indicate an important role for TLX in autologous regulation of the RARbeta gene in the eye.

Amino Acid Sequence↗
PubMed1998

The Tlx-2 homeobox gene is a downstream target of BMP signalling and is required for mouse mesoderm development.

TGFbeta-related factors are critical regulators of vertebrate mesoderm development. However, the signalling cascades required for their function during this developmental process are poorly defined. Tlx-2 is a homeobox gene expressed in the primitive streak of mouse embryos. Exogenous BMP-2 rapidly activates Tlx-2 expression in the epiblast of E6.5 embryos. A Tlx-2 promoter element responds to BMP-2 signals in P19 cells, and this response is mediated by BMP type I receptors and Smad1. These results suggest that Tlx-2 is a downstream target gene for BMP signalling in the primitive streak where BMP-4 and other TGFbeta-related factors are expressed. Furthermore, disruption of Tlx-2 function leads to early embryonic lethality. Similar to BMP4 and ALK3 mutants, the mutant embryos display severe defects in primitive streak and mesoderm formation. These experiments thus define a BMP/Tlx-2 signalling pathway that is required during early mammalian gastrulation.

Activin Receptors↗
PubMed1987

HLA and TLX antigen expression on the human oocyte, zona pellucida and granulosa cells.

The expression of human leukocyte antigen (HLA) class I and class II molecules and one trophoblast-lymphocyte crossreactive (TLX) antigen by human oocytes and granulosa cells was investigated. Well-defined monoclonal antibodies directed against HLA class I and class II molecules as well as beta 2-microglobulin and a TLX molecule were used in a standard indirect immunofluorescence test and some immunogold techniques at the electron microscopic level. Single unfertilizable or multiply fertilized oocytes and granulosa cells obtained from an in-vitro fertilization programme as well as oocytes in primary, secondary and tertiary follicles of ovaries were studied. Neither HLA class I or class II molecules, nor beta 2-microglobulin, nor a TLX molecule were detected on cultured oocytes or oocytes in human ovarian follicles or in their zona pellucida. Granulosa cells taken from a culture medium and those in follicles at various stages of development expressed class I antigens, while granulosa cells from tertiary follicles also expressed HLA-DR antigens. These results confirm that the female human gamete belongs to that very small group of cells that lack major histocompatibility complex antigens. Since spermatozoa also lack HLA antigens, human germ cells are entirely different from other nucleated human cells with regard to the antigenic structures expressed on the cell surface. This would prevent recognition of these cells by the cellular immune system. Furthermore, HLA and TLX antigens are not involved in fertilization and early differentiation.

Antibodies, Monoclonal↗
PubMed2006

Tlx acts as a proangiogenic switch by regulating extracellular assembly of fibronectin matrices in retinal astrocytes.

In response to hypoxia, hypoxia-inducible factors act as the primary proangiogenic triggers by regulating transcription levels of target genes, including VEGF. However, little is known about the specific factors that control other components of the angiogenic process, particularly formation of matrix scaffolds that promote adhesion and migration of endothelial cells. We show that in the postnatal mouse retina, the orphan nuclear receptor tailless (Tlx) is strongly expressed in the proangiogenic astrocytes, which secrete VEGF and fibronectin. Tlx expression by retinal astrocytes is controlled by oxygen concentration and rapidly downregulated upon contact with blood vessels. In mice null for Tlx, retinal astrocytes maintain VEGF expression; however, the extracellular assembly of fibronectin matrices by astrocytes is severely impaired, leading to defective scaffold formation and a complete failure of normal retinal vascular development. This work identifies Tlx as an essential component of the molecular network involved in the hypoxia-inducible proangiogenic switch in retinal astrocytes.

Animals↗
PubMed1990

The human cell-surface glycoproteins HuLy-m5, membrane co-factor protein (MCP) of the complement system, and trophoblast leucocyte-common (TLX) antigen, are CD46.

The non-lineage restricted human CD46 antigen, with two glycoproteins of 56,000 molecular weight (MW) and 66,000 MW, was defined using a panel of monoclonal antibodies (mAb) that included the E4.3 mAb to the HuLy-m5 antigen. Here the E4.3 mAb is used to show that two other human cell-surface molecules, membrane co-factor protein (MCP) of the complement system and trophoblast leucocyte-common antigen (TLX), are the same as HuLy-m5; thus, these three independently identified molecules are equivalently CD46. A mouse mAb to TLX (H316) and a specific rabbit antiserum to purified MCP (RA-MCP) blocked the binding of FITC-labelled E4.3 to the surface of human peripheral blood leucocytes (PBL). In sequential immunoprecipitation studies, E4.3 cleared all molecules detected by H316 and the RA-MCP antiserum. Immunoprecipitation from Chinese hamster ovary cells expressing transfected MCP cDNA showed that E4.3 detects both the mature 66,000 higher MW form of MCP and its 48,000 MW pro-MCP precursor, which lacks O-linked carbohydrate and bears only simple high-mannose-type N-linked carbohydrate. The IgG fraction of a polyclonal antiserum to purified MCP blocked factor I-mediated cleavage of C3b, whereas the E4.3 mAb did not. These data establish that three independently identified antigen systems are indeed the same: HuLy-m5, which shares a cross-reactive epitope with some primate retroviral gp 70 molecules and can be physically associated with class I major histocompatibility complex (MHC) chains in the cell membrane; MCP, of interest as a member of the regulators of complement activation gene family thought to protect autologous cells from complement activation; and TLX, a polymorphic molecule of interest for its potential role at the foeto-maternal tissue interface during pregnancy. Thus, the human CD46 antigen amalgamates the HuLy-m5, MCP and TLX cell-membrane glycoproteins.

Antibodies, Monoclonal↗
PubMed1998

The human homologue of the Drosophila tailless gene (TLX): characterization and mapping to a region of common deletion in human lymphoid leukemia on chromosome 6q21.

Deletion of the long arm of chromosome 6 (6q) is one of the most common chromosomal abnormalities in human hematological malignancies. Two distinct regions of minimal deletion have been identified by loss of heterozygosity studies at 6q25 to 6q27 (RMD-1) and at 6q21 to 6q23 (RMD-2), suggesting the presence of one or more tumor suppressor genes. We have cloned sequences within RMD-2 and screened for novel genes using a combination of direct sequencing, cDNA library screening, and exon trapping. Sequences generated from a cosmid fragment, mapping within RMD-2, showed homology to the Drosophila tailless gene (tll). The human homologue of the Drosophila tailless gene (human tlx; MGMW-approved symbol, TLX) was subsequently cloned from a fetal brain cDNA library. The gene is a member of the steroid nuclear receptor superfamily and is homologous to tll genes from other species that are involved in brain development. TLX is predominately expressed in the brain and maps to RMD-2 at 6q21 between DNA markers FYN and D6S447, in a YAC clone that also contains marker D6S246. The contributions of this gene to human B-cell leukemia and to brain development are unknown at present.

Amino Acid Sequence↗
PubMed1994

Relationship between Drosophila gap gene tailless and a vertebrate nuclear receptor Tlx.

We report here the identification of a unique vertebrate nuclear receptor, Tlx, which is expressed exclusively in the neuroepithelium of the embryonic brain. Sequence comparison reveals striking similarity to the product of the Drosophila terminal/gap gene tailless (tll), which is expressed in the embryonic brain and is required for brain development in flies. In vitro DNA-binding assays demonstrated that Tlx and Tll proteins share a target gene specificity that is unique among the nuclear receptor superfamily. Ectopic expression of Tlx in fly embryos caused a repression of segmentation comparable to that elicited by Tll. The similarities in structure, expression pattern, target gene specificity and phenotypes in transgenic flies suggest conservation of genetic programs upstream and downstream of this Tlx/Tll class of nuclear receptors during embryogenesis.

Amino Acid Sequence↗
PubMed2002

Proper development of relay somatic sensory neurons and D2/D4 interneurons requires homeobox genes Rnx/Tlx-3 and Tlx-1.

Trigeminal nuclei and the dorsal spinal cord are first-order relay stations for processing somatic sensory information such as touch, pain, and temperature. The origins and development of these neurons are poorly understood. Here we show that relay somatic sensory neurons and D2/D4 dorsal interneurons likely derive from Mash1-positive neural precursors, and depend on two related homeobox genes, Rnx and Tlx-1, for proper formation. Rnx and Tlx-1 maintain expression of Drg11, a homeobox gene critical for the development of pain circuitry, and are essential for the ingrowth of trkA+ nociceptive/thermoceptive sensory afferents to their central targets. We showed previously that Rnx is necessary for proper formation of the nucleus of solitary tract, the target for visceral sensory afferents. Together, our studies demonstrate a central role for Rnx and Tlx-1 in the development of two major classes of relay sensory neurons, somatic and visceral.

Animals↗
PubMed1983

Human trophoblast-lymphocyte cross-reactive (TLX) antigens define a new alloantigen system.

Antisera to human syncytiotrophoblast microvillous cell surface membranes from different placentas are cytotoxic for lymphocytes from some people but not others, demonstrating the presence of allotypic trophoblast-lymphocyte cross-reactive (TLX) antigens. Exploratory principal components factor analysis, performed on limited data consisting of 300 cytotoxic reactions produced by ten separate trophoblast antisera on a panel of lymphocytes from 30 random donors, suggested the presence of three distinct TLX antigen groupings. It is proposed that such TLX alloantigens are central in establishing maternal recognition and protection of the blastocyst, and that lack of recognition results in implantation failure and spontaneous abortion. These findings are compatible with contemporary results of immunotherapy to prevent recurrent spontaneous abortions, and their implications extend to other conditions of allogeneic coexistence, such as organ transplantation and the tumor-host relationship.

Antigens, Surface↗
PubMed1982

Allotypic trophoblast-lymphocyte cross-reactive (TLX) cell surface antigens.

Evidence id presented for the presence of trophoblast-lymphocyte cross-reaction (TLX) cell surface antigens. Complement-dependent lymphocytotoxicity studies with antitrophoblast sera (Ce) raised to ten separate placentas showed variable reaction patterns on peripheral blood leukocytes isolated from 30 random HLA-typed donors. No correlation with any known antigens of the major histocompatibility complex was evident. Absorption studies with chromatographically prepared fractions of solubilized trophoblast membranes from individual placentas and absorptions with both normal and transformed lymphoid cells removed cytotoxicity from some but not other Ce-antisera when tested on a single donor, thus providing serological evidence for allotypic variations among the TLX antigens.

Absorption↗
PubMed2005

T-box and homeobox genes from the ctenophore Pleurobrachia pileus: comparison of Brachyury, Tbx2/3 and Tlx in basal metazoans and bilaterians.

Most animals are classified as Bilateria and only four phyla are still extant as outgroups, namely Porifera, Placozoa, Cnidaria and Ctenophora. These non-bilaterians were not considered to have a mesoderm and hence mesoderm-specific genes. However, the T-box gene Brachyury could be isolated from sponges, placozoans and cnidarians. Here, we describe the first Brachyury and a Tbx2/3 homologue from a ctenophore. In addition, analysing T-box and homeobox genes under comparable conditions in all four basal phyla lead to the discovery of novel T-box genes in sponges and cnidarians and a Tlx homeobox gene in the ctenophore Pleurobrachia pileus. The conservation of the T-box and the homeobox genes suggest that distinct subfamilies with different roles in bilaterians were already split in non-bilaterians.

Amino Acid Sequence↗
PubMed1996

Association between long-term kidney graft survival and the presence of pre-transplant cytotoxic anti-HLA and/or non-MHC 'Fc gamma RII blocking' (anti-TLX) alloantibody.

One hundred kidney graft recipients were analysed retrospectively with regard to the presence of Fc gamma RII (EAI) blocking or cytotoxic HLA antibody induced by pretransplant transfusion. Previous studies suggested that transfusion induces the production of EAI blocking antibody which may have specificity to TLX/CD46/MCP alloantigens. A superior graft survival (65%/9 yr) was found in the presence of EAI alloantibody compared to graft survival in the absence of this antibody (40%/9 yr). Further analysis showed the following survival rates in relation to the combined appearance of HLA cytotoxic and EAI antibody (EAI positive, HLA negative 67%/9 yr; EAI positive, HLA positive 60%/9 yr; EAI negative, HLA positive 0%/9 yr; EAI negative, HLA negative 40%/9 yr). There was striking low graft failure in the first 6 months in patients with EAI antibody. Taking into consideration that the HLA B/DR mismatching grade in all various groups were the same and no considerable difference was found in association to graft survival, the presence or absence of alpha EAI (anti-TLX) antibody solely seems to have superior or additional effect on graft survival as compared to HLA matching.

Antibodies, Anti-Idiotypic↗