Talk:Trophoblast - Protein Expression

2014

Professor Guy Whitley Position: Professor of cell biology St George's, University of London, Cranmer Terrace, London SW17

trophoblast cell line contacted March 2014
extravillous-like trophoblast cell line, SGHPL-4

Mst1 and mst2 are essential regulators of trophoblast differentiation and placenta morphogenesis

PLoS One. 2014 Mar 4;9(3):e90701. doi: 10.1371/journal.pone.0090701. eCollection 2014.

Du X1, Dong Y1, Shi H1, Li J1, Kong S1, Shi D1, Sun LV1, Xu T2, Deng K1, Tao W1. Author information

Abstract

The placenta is essential for survival and growth of the fetus because it promotes the delivery of nutrients and oxygen from the maternal circulation as well as fetal waste disposal. Mst1 and Mst2 (Mst1/2), key components of the mammalian hpo/Mst signaling pathway, encode two highly conserved Ser/Thr kinases and play important roles in the prevention of tumorigenesis and autoimmunity, control of T cell development and trafficking, and embryonic development. However, their functions in placental development are not fully understood, and the underlying cellular and molecular mechanisms remain elusive. Here, we investigated the functions of Mst1/2 in mouse placental development using both conventional and conditional (endothelial) Mst1/2 double knockout mice. We found that the number of trophoblast giant cells dramatically increased while spongiotrophoblast cells almost completely disappeared in Mst1/2 deficient placentas. We showed that Mst1/2 deficiency down regulated the expression of Mash2, which is required for suppressing the differentiation of trophoblast giant cells. Furthermore, we demonstrated that endothelial-specific deletion of Mst1/2 led to impaired placental labyrinthine vasculature and embryonic lethality at E11.5, but neither affected vasculature in yolk sac and embryo proper nor endocardium development. Collectively, our findings suggest that Mst1/2 regulate placental development by control of trophoblast cell differentiation and labyrinthine vasculature at midgestation and Mst1/2 control labyrinth morphogenesis in trophoblast- and fetal endothelial-dependent manners. Thus, our studies have defined novel roles of Mst1/2 in mouse placental development.

PMID 24595170

2013

Molecular pathways: human leukocyte antigen G (HLA-G)

Clin Cancer Res. 2013 Oct 15;19(20):5564-71. doi: 10.1158/1078-0432.CCR-12-3697. Epub 2013 Jul 29.

Curigliano G1, Criscitiello C, Gelao L, Goldhirsch A. Author information

Abstract Human leukocyte antigen G (HLA-G) is a nonclassical MHC class I molecule that exerts important tolerogenic functions. Its main physiologic expression occurs in the placenta, where it participates in the maternal tolerance toward the fetus. HLA-G expression was found in embryonic tissues, in adult immune privileged organs, and in cells of the hematopoietic lineage. It is expressed in various types of primary solid (melanoma, head and neck, lung, urogenital, gastrointestinal, and breast cancers) and hematologic malignancies (acute leukemia, lymphomas) and metastases. HLA-G ectopic expression is observed in cancer, suggesting that its expression is one strategy used by tumor cells to escape immune surveillance. In this review, we will focus on HLA-G expression in cancers and its association with the prognosis. We will highlight the underlying molecular mechanisms of impaired HLA-G expression, the immune tolerant function of HLA-G in tumors, and the potential diagnostic use of membrane-bound and soluble HLA-G as a biomarker to identify tumors and to monitor disease stage. As HLA-G is a potent immunoinhibitory molecule, its blockade remains an attractive therapeutic strategy against cancer. Elimination of HLA-G-expressing cancer cells would be important in the efficacy of anticancer therapies. ©2013 AACR.

PMID 23897901

2012

MiRNA-mediated control of HLA-G expression and function

PLoS One. 2012;7(3):e33395. doi: 10.1371/journal.pone.0033395. Epub 2012 Mar 16.

Manaster I1, Goldman-Wohl D, Greenfield C, Nachmani D, Tsukerman P, Hamani Y, Yagel S, Mandelboim O. Author information

Abstract

HLA-G is a non-classical HLA class-Ib molecule expressed mainly by the extravillous cytotrophoblasts (EVT) of the placenta. The expression of HLA-G on these fetal cells protects the EVT cells from immune rejection and is therefore important for a healthy pregnancy. The mechanisms controlling HLA-G expression are largely unknown. Here we demonstrate that miR-148a and miR-152 down-regulate HLA-G expression by binding its 3'UTR and that this down-regulation of HLA-G affects LILRB1 recognition and consequently, abolishes the LILRB1-mediated inhibition of NK cell killing. We further demonstrate that the C/G polymorphism at position +3142 of HLA-G 3'UTR has no effect on the miRNA targeting of HLA-G. We show that in the placenta both miR-148a and miR-152 miRNAs are expressed at relatively low levels, compared to other healthy tissues, and that the mRNA levels of HLA-G are particularly high and we therefore suggest that this might enable the tissue specific expression of HLA-G.

PMID 22438923

HLA-G 2012 conference: the 15-year milestone update

Tissue Antigens. 2013 Mar;81(3):127-36. doi: 10.1111/tan.12053. Epub 2013 Jan 24.

Loustau M1, Wiendl H, Ferrone S, Carosella ED. Author information

Abstract The non-classical human leukocyte antigen (HLA) Class I molecule HLA-G is best known for its tolerogenic function at the maternal-fetal interface, where it protects the fetus from destruction by the immune system of its mother. Yet, HLA-G has been the topic of intense investigations and its functions reach much further than originally believed. International conferences on HLA-G have taken place every 3 years since 1998, and the Sixth International Conference on HLA-G, that took place in Paris in July 2012. It counted 180 attendees from 28 countries, 35 speakers in plenary sessions, and 63 presentations of research in symposia and poster sessions, bringing new insight in HLA-G research. Here we summarize the major advances on the function and nature of HLA-G molecule that were reported, with particular interest on the findings in new mechanisms of action through regulatory cells, its relevance in cancer as well as in the molecular structure and functions of HLA-G, which are key for its clinical application. © 2013 John Wiley & Sons A/S.

PMID 23347068

Multimeric structures of HLA-G isoforms function through differential binding to LILRB receptors

Cell Mol Life Sci. 2012 Jul 17. [Epub ahead of print]

Howangyin KY1, Loustau M, Wu J, Alegre E, Daouya M, Caumartin J, Sousa S, Horuzsko A, Carosella ED, Lemaoult J. Author information

Abstract The non-classical Human leukocyte antigen G (HLA-G) differs from classical HLA class I molecules by its low genetic diversity, a tissue-restricted expression, the existence of seven isoforms, and immuno-inhibitory functions. Most of the known functions of HLA-G concern the membrane-bound HLA-G1 and soluble HLA-G5 isoforms, which present the typical structure of classical HLA class I molecule: a heavy chain of three globular domains α(1)-α(2)-α(3) non-covalently bound to β-2-microglobulin (B2M) and a peptide. Very little is known of the structural features and functions of other HLA-G isoforms or structural conformations other than B2M-associated HLA-G1 and HLA-G5. In the present work, we studied the capability of all isoforms to form homomultimers, and investigated whether they could bind to, and function through, the known HLA-G receptors LILRB1 and LILRB2. We report that all HLA-G isoforms may form homodimers, demonstrating for the first time the existence of HLA-G4 dimers. We also report that the HLA-G α(1)-α(3) structure, which constitutes the extracellular part of HLA-G2 and HLA-G6, binds the LILRB2 receptor but not LILRB1. This is the first report of a receptor for a truncated HLA-G isoform. Following up on this finding, we show that the α(1)-α(3)-Fc structure coated on agarose beads is tolerogenic and capable of prolonging the survival of skin allografts in B6-mice and in a LILRB2-transgenic mouse model. This study is the first proof of concept that truncated HLA-G isoforms could be used as therapeutic agents.

PMID 22802125

Figure 1 HLA-G isoforms - Alternative splicing of HLA-G primary transcript yields 7 isoforms. Excision of one or two exons encoding globular domain generates truncated isoforms, and translation of intron 4 or intron 2 yield secreted isoforms that lack the transmembrane domain.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3884069/figure/F1

"Taken together, these data clearly show that HLA-G isoforms present important structural variations which may correspond to different biological functions. As mentioned before, HLA-G1 and HLA-G5 (α1–α2–α3 associated to B2M) are the most extensively studied isoforms, probably because of their alleged higher abundance, their availability for in vitro experiments, and the existence of specific antibodies directed against them. Thus, these isoforms are believed to be the main isoforms responsible immune regulation in vivo. However, we do not know to which extent this is true. Isoforms and B2M-free HLA-G structures may also play a specific role. Not knowing the precise structure of HLA-G truncated isoforms implies that we do not know which receptors they bind to, either. For instance, in this work, we studied the HLA-G2 or -G6 interaction with LILRB2 because this isoform contains the α3 domain and could potentially bind to LILRB2. However, we do not know what the HLA-G3 receptor could be, or that of HLA-G4, despite our data indicating that this isoform may bind LILRB2. A recent work [47] describes binding of B2M-associated and B2M-free forms of MHC to members of the LILR family, and demonstrates that in addition to LILRB2, B2M-free forms are recognized by several members of the LILR family. In fact, “activating” members of the LILR family show a preference for these forms. It is therefore possible that it is also the case for HLA-G. This would support the notion that HLA-G structural variations may be relevant in biological function modulations. It is also intriguing to consider that, similarly to classical HLA Class I molecules, HLAG has activating receptors. Indeed, it is possible that other HLA-G receptors exist, isoform-specific or not, and studying HLA-G structures other than that of B2M-associated HLA-G1 and -G5 might allow us to identify them. Finally, our data highlight the fact that even though we do know the physiological importance of HLA-G, we do not know which of its structures are relevant in vivo."

2006

HLA-G in human reproduction: aspects of genetics, function and pregnancy complications

Hum Reprod Update. 2006 May-Jun;12(3):209-32. Epub 2005 Nov 9.

Hviid TV. Author information

Abstract

The non-classical human leukocyte antigen (HLA) class Ib genes, HLA-E, -G and -F, are located on chromosome 6 in the human major histocompatibility complex (MHC). HLA class Ib antigens resemble the HLA class Ia antigens in many ways, but several major differences have been described. This review will, in particular, discuss HLA-G and its role in human reproduction and in the human MHC. HLA-G seems to be important in the modulation of the maternal immune system during pregnancy and thereby the maternal acceptance of the semiallogenic fetus. Recent findings regarding aspects of HLA-G polymorphism, the possible significance of this polymorphism in respect to HLA-G function and certain complications of pregnancy (such as pre-eclampsia and recurrent spontaneous abortions (RSA)) are discussed together with possible importance to IVF. Finally, aspects of a possible role of HLA-G in organ transplantation and in inflammatory or autoimmune disease, and of HLA-G in an evolutionary context, are also briefly examined.

PMID 16280356

The non-classical Human Leukocyte Antigen G (HLA-G) differs from classical HLA class I molecules by its low genetic diversity, a tissue-restricted expression, the existence of seven isoforms, and immuno-inhibitory functions.

trophoblast cells, which originate from the fetus, do not express classical HLA class Ia and II antigens, except for a possible weak expression of HLA-C

Major histocompatibility complex (MHC)

short arm of chromosome 6, ∼4 Mb and encodes at least ∼130 functional genes.
classical HLA class Ia and II genes (HLA-A, -B, -C, -DR, -DQ and -DP)
non-classical HLA class Ib genes
HLA class Ib antigens, HLA-E, -F and -G

fetus inherits one HLA haplotype from the mother and one from the father and is thereby semiallogenic for the mother.

HLA-G

gene is located on chromosome 6 close to HLA-A
inhibit cytotoxic T-lymphocyte (CTL) response
inhibit natural killer (NK) functions
in both cases by direct interaction with the receptors ILT2 and ILT4 and with the killer Ig-like receptor 2 DL4 (KIR2DL4 receptor)

short cytoplasmic tail important for reduced spontaneous endocytosis of HLA-G
seven HLA-G mRNA and protein isoforms are generated by alternative splicing of mRNA.
- four membrane-bound isoforms (HLA-G1 to -G4)
- three soluble isoforms (HLA-G5, -G6, -G7)
HLA-G mRNA has been detected in many different tissues, HLA-G protein expression has been described repeatedly only on and by the trophoblast cells in placenta on and by certain immune cells (in most cases monocytes) and in the thymus

Figure 2. human leukocyte antigen-G (HLA-G) gene and expression. http://humupd.oxfordjournals.org/content/12/3/209/F2.large.jpg

Figure 4. Expression of human leukocyte antigen (HLA) molecules during pregnancy http://humupd.oxfordjournals.org/content/12/3/209/F4.large.jpg

Crystal structure of HLA-G: a nonclassical MHC class I molecule expressed at the feral-maternal interface

Proc Natl Acad Sci U S A. 2005 Mar 1;102(9):3360-5. Epub 2005 Feb 17.

Clements CS1, Kjer-Nielsen L, Kostenko L, Hoare HL, Dunstone MA, Moses E, Freed K, Brooks AG, Rossjohn J, McCluskey J. Author information

Abstract HLA-G is a nonclassical major histocompatibility complex class I (MHC-I) molecule that is primarily expressed at the fetal-maternal interface, where it is thought to play a role in protecting the fetus from the maternal immune response. HLA-G binds a limited repertoire of peptides and interacts with the inhibitory leukocyte Ig-like receptors LIR-1 and LIR-2 and possibly with certain natural killer cell receptors. To gain further insights into HLA-G function, we determined the 1.9-A structure of a monomeric HLA-G complexed to a natural endogenous peptide ligand from histone H2A (RIIPRHLQL). An extensive network of contacts between the peptide and the antigen-binding cleft reveal a constrained mode of binding reminiscent of the nonclassical HLA-E molecule, thereby providing a structural basis for the limited peptide repertoire of HLA-G. The alpha3 domain of HLA-G, a candidate binding site for the LIR-1 and -2 inhibitory receptors, is structurally distinct from the alpha3 domains of classical MHC-I molecules, providing a rationale for the observed affinity differences for these ligands. The structural data suggest a head-to-tail mode of dimerization, mediated by an intermolecular disulfide bond, that is consistent with the observation of HLA-G dimers on the cell surface.

PMID 15718280

http://www.pnas.org/content/102/9/3360.long

2003

CXCL12 expression by invasive trophoblasts induces the specific migration of CD16- human natural killer cells

Blood. 2003 Sep 1;102(5):1569-77. Epub 2003 May 1.

Hanna J1, Wald O, Goldman-Wohl D, Prus D, Markel G, Gazit R, Katz G, Haimov-Kochman R, Fujii N, Yagel S, Peled A, Mandelboim O. Author information

Abstract

In the maternal decidua, natural killer (NK) cells, characterized by lack of CD16, are found in direct contact with the fetal extravillous trophoblasts (EVTs). It is yet unknown which factors contribute to the specific homing of this unique NK subset to the decidua. In this study we analyze the chemokine receptor repertoire on various NK populations derived from the peripheral blood and decidua. We show that CXCR4 and CXCR3 receptors are preferentially expressed on CD16- NK subsets derived either from the peripheral blood or the decidua and that these receptors are involved in migration of all NK subsets to their ligands. We further demonstrate in vivo that invading EVTs that eventually perform endovascular invasion express CXCL12, the ligand for CXCR4, but not ligands for CXCR3. Indeed, specific accumulation of the CD16- NK cells at the expense of CD16+ cells was observed only when in vitro migration was performed with ligands for CXCR4. Finally, incubation of the peripheral blood CD16- NK cells with cytokines present in the decidua, especially interleukin 15 (IL-15), resulted in the expression of chemokine receptor repertoire similar to that observed on decidual NK cells, suggesting an additional important regulatory effect of local decidual cytokines.

PMID 12730110