Human placental protein 14 gene: sequence and characterization of a short duplication

Higher follicular fluid glycodelin levels are negatively correlated with embryonic development in assisted reproduction

OBJECTIVE

To investigate the possible effect of follicular fluid glycodelin levels on the quality of developing oocytes and subsequent in vitro embryo development.

METHODS

Follicular fluid glycodelin levels of 145 patients undergoing assisted reproductive treatment were analyzed and the correlation between glycodelin levels and ART outcomes were evaluated.

RESULTS

We found that glycodelin levels were negatively correlated with the number of high quality embryos on day 3 (r=-0.20, p=0.05). Additionally, higher glycodelin levels were correlated with higher FSH levels (r=0.18, p=0.04). However, glycodelin levels were not predictive for implantation (p=0.67) or ongoing pregnancy rates (p=0.99).

CONCLUSION

Glycodelin in the follicular environment might be one of the factors that influence the competence of growing oocytes and affect the quality of subsequent in vitro embryo development.

The dimeric crystal structure of the human fertility lipocalin glycodelin reveals a protein scaffold for the presentation of complex glycans

Structural study of human glycodelin, which is involved in reproduction, reveals a homodimeric structure ideally suited as scaffold for the presentation of distinct glycans, whereas bioinformatic analysis indicated exclusive occurrence in suborders of primates that have a menstrual cycle.

Effect of myomectomy on endometrial glutathione peroxidase 3 (GPx3) and glycodelin mRNA expression at the time of the implantation window

BACKGROUND

In fertile women, glycodelin and glutathione peroxidase 3 (GPx3) genes expression rises during the luteal phase, with a peak occurring during the implantation window. The expression of these genes decreases in women with myomas. To determine whether myomectomy would reverse glycodelin and GPx3 expression, we evaluated the transcript levels of these genes in the endometrium of patients before and after myomectomy.

METHODS

Expression of glycodelin and GPx3 genes were examined prospectively during the midluteal phase in the endometrium obtained from infertile women with myoma (n = 12) before and three months after myomectomy. Endometrial expression of these genes was evaluated using quantitative real-time RT-PCR.

RESULTS

Endometrial glycodelin mRNA expression levels (normalized to 18S rRNA expression) were increased significantly in endometrium of patients after myomectomy (P = 0.02). GPx3 mRNA expression was increased insignificantly after myomectomy (P = 0.43).

CONCLUSION

The results showed that myomectomy increased endometrial glycodelin (significantly) and GPx3 (not significantly) gene expression after 3 months. Study at different times and detecting expression of these genes can reveal more details.

Endometrial gene expression reveals compromised progesterone signaling in women refractory to embryo implantation

BACKGROUND

Endometrial function is essential for embryo implantation. The aim of this study was to analyze gene expression profiles from individual endometrial samples obtained from women with repeated implantation failure after IVF in oocyte donation programs.

METHODS

Seventeen volunteers were recruited: women who had previously participated as recipients in oocyte donation cycles and repeatedly exhibited implantation failure (Group A, study group, n = 5) or had at least one successful cycle (Group B, control group, n = 6) and spontaneously fertile women (Group C, normal fertility group, n = 6). An endometrial cycle was induced with exogenous estradiol (E2) and progesterone (P) and an endometrial sample was collected on the seventh day of P treatment.

RESULTS

Transcriptome analysis showed 82 genes with consistent differential gene expression when comparing A vs. B and A vs. C. One hundred transcripts differentially expressed in group A vs. B have been shown to be regulated by P, suggesting compromised P signaling in the endometrium. The P receptor (PR) mutation PROGINS was not detected in women from group A. Semi-quantitation of immunoreactive PRA/B, PRB and Sp1 (a transcription factor related to P signaling) in paraffin-embedded endometrial sections, did not show statistically significant differences amongst groups. However immunostaining glycodelin was significantly decreased in endometrial samples from group A.

CONCLUSIONS

We conclude that some cases of repeated implantation failure could be associated with an aberrant gene expression profile. Compromised P signaling might be the underlying mechanism for such endometrial gene expression deregulation in women with repeated implantation failure.

The endometrial epigenome and its response to steroid hormones

The human endometrium undergoes cyclic morphological and functional changes during the menstrual cycle. These changes are driven mainly by steroid hormones and orchestrated by a myriad of genes - many of which have been identified recently as being epigenetically regulated. Epigenetic modifications, including DNA methylation and histone acetylations, are shown recently to be involved in functional changes in endometrium and endometrial diseases. Since epigenetics itself is a rapidly evolving field, this review starts with an overview of epigenetics and its intrinsic connections with endometrial response to steroid hormones, highlighting its various levels of complexities. This is followed by a review of published and unpublished work on "writers", "erasers", and other players of endometrial epigenome. In the end, areas in need for future research in this area will be exposed.

The bovine lactation genome: insights into the evolution of mammalian milk

Comparison of milk protein and mammary genes in the bovine genome with those from other mammals gives insights into the evolution of lactation.

Background

The newly assembled Bos taurus genome sequence enables the linkage of bovine milk and lactation data with other mammalian genomes.

Results

Using publicly available milk proteome data and mammary expressed sequence tags, 197 milk protein genes and over 6,000 mammary genes were identified in the bovine genome. Intersection of these genes with 238 milk production quantitative trait loci curated from the literature decreased the search space for milk trait effectors by more than an order of magnitude. Genome location analysis revealed a tendency for milk protein genes to be clustered with other mammary genes. Using the genomes of a monotreme (platypus), a marsupial (opossum), and five placental mammals (bovine, human, dog, mice, rat), gene loss and duplication, phylogeny, sequence conservation, and evolution were examined. Compared with other genes in the bovine genome, milk and mammary genes are: more likely to be present in all mammals; more likely to be duplicated in therians; more highly conserved across Mammalia; and evolving more slowly along the bovine lineage. The most divergent proteins in milk were associated with nutritional and immunological components of milk, whereas highly conserved proteins were associated with secretory processes.

Conclusions

Although both copy number and sequence variation contribute to the diversity of milk protein composition across species, our results suggest that this diversity is primarily due to other mechanisms. Our findings support the essentiality of milk to the survival of mammalian neonates and the establishment of milk secretory mechanisms more than 160 million years ago.

Peptides and proteins in the human endometrium

Human endometrium is composed of three layers: stratum compactum, stratum spongiosum and stratum basale. Stratum compactum is the superficial layer made up of openings of the uterine glands and some stromal cells. Stratum spongiosum is the middle layer containing mainly dilated glands and little stroma. Stratum basale is the deepest layer adjoining the muscularis. It consists of primordial glands and compact stroma. Stratum compactum and stratum spongiosum form stratum functionale which is subject to cyclic changes and is removed during menstruation.

Increased expression of glycodelin mRNA and protein in rat lungs during ovalbumin-induced allergic airway inflammation

Asthma is a chronic inflammatory disease accompanied by airway obstruction and hyper-responsiveness. Asthmatic inflammation is characterized by the expression of multiple genes for inflammatory mediators. Glycodelin is a glycoprotein with several functions in cell recognition and differentiation. There is substantial evidence that glycodelin may be a mediator for immunomodulatory and immunosuppressive effects on several human tissues. To determine the potential role of glycodelin in the pulmonary immune response, we examined the distribution of the glycodelin mRNA and protein in an experimental rat model of allergen-induced airway inflammation. The experimental model developed an airway response to inhaled nebulized ovalbumin in adult rats. Two groups of rats (ovalbumin and saline) were challenged for 3 weeks, lungs were fixed and embedded, and sections were studied for expression of glycodelin mRNA by in situ hybridization and protein by immunohistochemistry. Glycodelin is expressed in Clara cells of bronchial epithelium, type II pneumocytes and alveolar macrophages. Densitometric analyses show a significant increase of the glycodelin mRNA and protein expression in rat lungs after ovalbumin challenge. Induced glycodelin amounts in tissue, particularly in Clara cells and alveolar macrophages were found. The altered expression pattern of glycodelin may contribute to the pulmonary immune response in asthmatic inflammation.

Glycosylation related actions of glycodelin: gamete, cumulus cell, immune cell and clinical associations

Glycodelin is an example of a glycoprotein whose complex-type glycans mediate biological actions in human reproduction and immune reactions. Being attached to an identical protein backbone, glycodelin oligosaccharides vary significantly from one reproductive tissue to another and have an effect on its own secretion and role in cell communication. For instance, uterine glycodelin-A inhibits sperm-oocyte interaction by binding on the sperm head. This is a glycosylation-dependent phenomenon, in which fucosyltransferase-5 plays a key role. Glycodelin-S from seminal plasma binds evenly around the sperm head and maintains an uncapacitated state in the spermatozoa, until the isoform is detached during sperm passage through the cervix. Glycodelin-F from follicular fluid and Fallopian tube binds to the acrosomal region of the sperm head, thereby inhibiting both the sperm-oocyte binding and premature progesterone-induced acrosome reaction. The cumulus cells surrounding the oocyte can capture glycodelin-A and -F from the surrounding environment and convert these isoforms to a cumulus cell isoform, glycodelin-C. It differs by glycosylation from the other isoforms, and it too attaches on the sperm head, with the highest density in the equatorial region. Glycodelin-C is capable of detaching the sperm-bound inhibitory isoforms so that the sperm-oocyte binding is enhanced. Glycodelin-A also has immunosuppressive actions directed to cellular, humoral and innate immunity. Although these actions depend mainly on the protein backbone, glycosylation also plays a part. Glycosylated glycodelin may be involved in the protection of spermatozoa against maternal immune reactions, and glycodelin also has apoptogenic activity. Some glycosylation patterns of glycodelin may mask its apoptogenic domain. This review updates the recent research and clinical associations of glycodelin, highlighting the role of glycosylation.

Survivin and glycodelin transcriptional activity in node-positive early breast cancer: mRNA expression of two key regulators of cell survival

INTRODUCTION

Glycodelin and survivin are key polypeptide regulators of cellular proliferation, apoptosis and angiogenesis. In view of contradictory reports on their functional role in tumors, we studied their transcriptional levels in localized breast cancer.

PATIENTS AND METHODS

Glycodelin and survivin messenger ribonucleic acid (mRNA) was isolated and amplified by quantitative reverse-trancription PCR from paraffin-embedded breast carcinomas of 275 women. A normalized score was calculated by the use of GAPDH, RPL37A reference genes and was correlated with clinicopathologic/molecular parameters and patient outcome.

RESULTS

A total of 272 patients were eligible, most harbored stage III node-positive breast carcinomas larger than 2 cm. Glycodelin mRNA was expressed in 68 patients (25%), more frequently in premenopausal women (P = 0.01) and those with HER2 mRNA-positive tumors (P = 0.02). Survivin mRNA was present in 263 tumors (97%) and its levels correlated significantly with high nuclear grade, VEGF mRNA and p53 mRNA presence (P < 0.05). At a median follow-up of 64 months, neither glycodelin nor survivin mRNA expression demonstrated prognostic utility for overall or disease-free survival at univariate and multivariate analysis.

CONCLUSIONS

Glycodelin and survivin transcriptional activity are associated with adverse clinicopathologic and molecular characteristics of node-positive primary breast cancer but do not predict patient outcome. Further study is needed for illumination of their functional roles in tumorigenesis.

Glycodelin is present in pinopodes of receptive-phase human endometrium and is associated with down-regulation of progesterone receptor B

OBJECTIVE

To test the hypothesis that glycodelin is localized on pinopodes and correlates with temporal immunostaining of leukemia inhibitory factor (LIF), LIF receptor (LIFR), and progesterone receptor B (PRB).

DESIGN

Prospective clinical study.

SETTING

Hospital-based reproductive health unit and research laboratories.

PATIENT(S)

Twenty-five healthy fertile women with normal menstrual cycles.

INTERVENTION(S)

Endometrial biopsy specimens were obtained from healthy fertile women in the luteal phase of the menstrual cycle.

MAIN OUTCOME MEASURE(S)

Immunohistochemical staining of glycodelin, ultrastructural immunostaining of glycodelin, and double staining of glycodelin and PRB.

RESULT(S)

Glycodelin is present in the glands when pinopodes appear. Glycodelin is localized on pinopodes but is also secreted from luminal epithelial cells regardless of pinopode formation. There was a negative correlation between glycodelin secretion from the glands and PRB staining. A weak correlation between the presence of LIFR (but not LIF) and glycodelin was found.

CONCLUSION(S)

Pinopode appearance, intense staining of LIFR in pinopodes and glycodelin staining in the glands are synchronized events. Down-regulation of PRB in the endometrium is concomitant with the presence of glycodelin in the endometrium, suggesting interaction.

Roles of glycodelin in modulating sperm function

Glycodelin is a glycoprotein with three well-defined isoforms. They are named as glycodelin-S, glycodelin-A and glycodelin-F. The three isoforms have similar protein core but different carbohydrate moieties. Glycodelin-S is abundant in the human seminal plasma. It suppresses sperm capacitation and in doing so, it maintains the spermatozoa in an uncapacitated state before they enter into the uterine cavity. Glycodelin-A is abundant in the amniotic fluid. It is also secreted from endometrial glands into uterine fluid and is produced by the fallopian tube. Glycodelin-A is the first endogenous glycoprotein that was found to inhibit the binding of spermatozoa to the zona pellucida. The immunosuppressive properties of glycodelin-A suggest that the molecule may protect the spermatozoa from immune attack in the maternal reproductive tract. Glycodelin-F was first found in the follicular fluid, hence its name. It also inhibits spermatozoa-zona pellucida binding. In addition, glycodelin-F suppresses progesterone-induced acrosome reaction, and may serve to prevent premature acrosome reaction. Preliminary findings suggest possible presence of yet another glycodelin isoform in the extracellular matrix of cumulus oophorus. Unlike glycodelin-A and -F, it stimulates spermatozoa-zona pellucida binding. In summary, different isoforms of glycodelin have different biological roles on sperm function, and they act in succession to contribute to the success of fertilization.

Mitogen-activated protein kinase is involved in the progesterone-mediated induction of baboon glycodelin

In the human and non-human primate the major secretory product of the uterine glandular epithelial cells is glycodelin. The expression of glycodelin is associated with elevated progesterone levels as its production peaks during the late luteal phase of the menstrual cycle and in early pregnancy. Consistent with our previous studies, we found that the majority of the progestin responsiveness of the baboon glycodelin promoter was retained in the -20+48 region, a region devoid of progestin- and Sp1-response elements. Using serial 5' and 3' deletions of 10 basepairs of the promoter within the pGL3Basic vector, we identified the 5' and 3' limits required for progestin responsiveness as -22 and +18, respectively. When the same regions were cloned into the pGL3Promoter vector, a construct that contains the heterologous SV40 promoter, progestin did not enhance expression. Mutation of the DNA binding domain of the progesterone receptor, which disrupts its ability to activate the progesterone response element, does not obliterate its ability to induce expression via the baboon glycodelin promoter. Inhibitors of protein tyrosine kinases, genistein and AG18, blocked the progestin-mediated induction as did an inhibitor of MEK, PD98059, but not an inhibitor of p38 MAP kinase, SB202190. These findings imply that glycodelin induction in response to progestins involves a nongenomic mechanism through the ERK1/2 branch of the MAP kinase pathway. The ultimate target may be a factor involved in the initiation of glycodelin gene transcription.

Immunolocalization of glycodelin in the genital tract of rats

Glycodelin, also known as placental protein 14 has been predominantly localized to organs of the human genital tract. Unfortunately the physiological role of glycodelin is largely unknown since it depends on limited availability of tissues. Therefore, a suitable animal model to study the role of glycodelin would be desirable. Previously, it was shown that glycodelin mRNA is expressed in the genital tract of male and female rats. In the present study, we demonstrate the expression of glycodelin protein in male and female rats by immunohistochemistry and Western blot analysis. For this purpose a polyclonal antibody was generated against glycodelin peptide. In female rats, glycodelin was found in the epithelial gland cells of the uterus, epithelial cells of the fallopian tube as well as in corpora lutea, interstitial and theca cells of the ovary. Glycodelin was distributed in all epithelial cells of the epididymis and the seminal vesicle. In the seminiferous epithelium, glycodelin was seen in all developmental stages of spermatogonia and spermatocytes and in Sertoli cells. Whereas in the rat male reproductive tract glycodelin expression is slightly different from human or primate tissues, in organs of the rat female genital tract glycodelin expression is similar to humans and primates.

2,3,7,8-Tetrachlorodibenzo-p-dioxin increases glycodelin gene and protein expression in human endometrium

CONTEXT

Glycodelin (GdA) is an immunosuppressive endometrial glycoprotein critical for embryonic implantation and pregnancy establishment.

OBJECTIVE

The aim of the present study was to examine the effect of dioxin [2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)] on GdA production in human endometrial cells.

DESIGN

Controlled endometrial explant (EE) and cell cultures were used in this study.

SETTING

Work was conducted at university hospital research laboratories in Bern, Switzerland, and in San Francisco, California.

PATIENTS

Ovulatory women provided endometrial biopsies in the proliferative or secretory phase.

INTERVENTION(S)

EEs and cells were cultured without and with TCDD.

MAIN OUTCOME MEASURE(S)

GdA protein and gene expression were quantified.

RESULTS

A 2.5-fold increase in GdA production was demonstrated in EEs treated with 10 nm TCDD for 9 d. Fluorography revealed a 3- to 4-fold increase in new GdA biosynthesis and secretion in TCDD-treated endometrial epithelial cells. Because the action of dioxin is mediated by the aryl hydrocarbon receptor (AhR), we ascertained that primary epithelial and Ishikawa cells express AhR. Dose responses to TCDD and expressed AhR were established in transiently transfected Ishikawa cells using luciferase fusion vectors containing 1.0 kb of 5' flanking DNA relative to the GdA transcriptional start site but not when shorter promoter constructs were used. A dioxin response element was mapped to nucleotides -539 to -533 of the gene promoter and verified by site-directed mutagenesis.

CONCLUSIONS

We demonstrated a direct AhR-mediated effect of dioxin on GdA gene transcription and protein secretion that might influence human female fertility.

Glycodelin responses to hyperinsulinaemic clamp vary according to basal serum glycodelin concentration

OBJECTIVE

Treatment with metformin, an insulin-lowering agent, increases serum glycodelin, a progesterone-regulated lipocalin protein of the reproductive axis that may play a role in foeto-maternal defence mechanisms. This finding led to the hypothesis that insulin might decrease serum glycodelin concentration.

DESIGN, PATIENTS AND MEASUREMENTS

Euglycaemic hyperinsulinaemic clamp experiments (n = 50) were carried out on 28 women of reproductive age (range 25-47 years; mean +/- SEM 39 +/- 1.0 years), and the results were analysed with respect to their baseline serum progesterone (< 10 or > or = 10 nmol/l) and glycodelin (< 10 or > or = 10 microg/l, equivalent to < 357 or > or = 357 pmol/l) concentrations at the onset of the clamp. Ten clamp experiments were performed on five women wearing a levonorgestrel-releasing intrauterine device (IUD), and these were analysed as a separate group.

RESULTS

Contrary to the hypothesis, no acute glycodelin-lowering effect of insulin was found in any of the groups studied. All the small rises in glycodelin levels detected during acute hyperinsulinaemia occurred in the comparisons of medians and not means, and all such changes took place within the limits seen in the women with no progesterone exposure. In the group with low progesterone/low glycodelin (n = 21), glycodelin showed a small but significant increase at 30 and 90 min of the clamp (P < 0.01). In the group with elevated progesterone/low glycodelin (n = 11), there was a slight glycodelin increase at 30 min (P < 0.05), whereas no increase was found in the group with elevated glycodelin levels (n = 8). In the clamp experiments on women with levonorgestrel-releasing IUD, the basal glycodelin level was low in all cases and, as in the other women with low glycodelin levels, glycodelin was slightly increased at 30, 60 and 90 min of hyperinsulinaemia (P < 0.01).

CONCLUSIONS

The results rule out any acute glycodelin-reducing effects of insulin, although indirect long-term effects mediated by insulin on glycodelin secretion cannot be excluded.

Advances in uterine protein research: reproduction and cancer

Uterine protein research has advanced from the measurements of specific compounds to detailed analysis of the genes that regulate protein synthesis and build up the complex carbohydrate structures that play important functional roles. Some 80% of all human proteins are glycoproteins. Functional glycomics highlights the importance of glycosylation in glycoprotein function. Glycodelin is a representative example of functional glycomics because its various glycoforms have different functions. In the uterus, synthesis of glycodelin-A is temporally regulated by progesterone. During the estrogen-dominated fertile window, absence of glycodelin synthesis is significant because uterine glycodelin-A potently and dose-dependently inhibits sperm-egg binding, the initial step in fertilization. The anti-fertilization propensity of glycodelin-A during the luteal phase of the cycle is highly glycosylation-dependent, and there is an intricate functional interplay between spermatozoa, zona pellucida and the various glycodelin isoforms present in the uterine fluid, seminal plasma and follicular fluid, respectively. Endometrial glycodelin synthesis can be induced during the fertile window by administration of progestagens, such as in levonorgestrel hormone-releasing IUD and contraceptive implants. Glycodelin can be chemically modified in such a fashion that it blocks the binding site on CD4 for the HIV surface glycoprotein, synthesis of viral gp 120, and infection of peripheral blood mononuclear cells by the primary HIV isolate THA/93/051, thus potentially inhibiting HIV transmission. Now that a cell line producing the contraceptive isoform has been identified by recombinant technology, these findings may have application for locally applied antiviral contraception. Glycodelin also has immunosuppressive properties, suggesting that the recognition mechanisms in immune and reproductive systems may have converged. Given its inhibitory activity on natural killer cells, abundant at the fetomaternal interphase, the high glycodelin concentration at the same site suggests a role in fetomaternal defense mechanisms. This may be relevant in women with recurrent miscarriage, in whom both the serum and uterine fluid glycodelin concentrations are decreased. Experiments on cancer cell lines have demonstrated increased epithelial differentiation by glycodelin cDNA transfection, and also by co-culture of cancer cells with normal stromal cells in the presence of basement membrane components. Both approaches result in glycodelin expression concomitant with decreased cell proliferation and reversion of the malignant phenotype. These results suggest an active role of normal stromal cells, basement membrane components and glycodelin in epithelial differentiation and glandular morphogenesis. This disposition of glycodelin is significant in patients with certain carcinomas, in which glycodelin-expressing tumors carry better prognosis than glycodelin-negative tumors of the same clinical stage and histological grade. Research on functional glycomics continues to produce significant information on fundamental aspects of fertilization, implantation, pregnancy and cancer.

Laboratory testing for endometriosis

BACKGROUND

Typically, endometriosis is diagnosed surgically by laparoscopy. CA-125 is the principal serum marker used in the diagnosis and management of late-stage endometriosis. The search for a body fluid marker of early stage disease has included studies of serum, peritoneal fluid (PF), and/or tissue levels of secretory proteins, cell adhesion molecules, cytokines, tumor necrosis and vascular endothelial growth factors (VEGFs), chemokines, antiendometrial antibodies, autoantibodies to oxidized lipoproteins, aromatase P-450 expression, cytokeratins, and hormone receptors. We compared the diagnostic accuracy and clinical utility of these various types of substances in the non-surgical identification of patients with endometriosis.

METHOD

We reviewed the MEDLINE database for all publications on serum, peritoneal fluid and tissue markers of endometriosis.

RESULTS

Except for serum interleukin (IL)-6 and peritoneal fluid tumor necrosis factor (TNF)-alpha levels, the diagnostic accuracy of other markers of endometriosis was either similar or worse than that of CA-125 (sensitivity 24-94%; specificity 83-93%). The diagnostic accuracy of IL-6 and TNF-alpha was 90-100% (sensitivity) and 67-89% (specificity).

CONCLUSION

CA-125 has limited diagnostic accuracy in the identification of early stage endometriosis and none of the other markers we reviewed dramatically outperformed CA-125 in this regard with the possible exception of serum IL-6 and peritoneal fluid TNF-alpha levels.

Hox proteins activate the IGFBP-1 promoter and suppress the function of hPR in human endometrial cells

Previous studies have shown that progestin activates the transcription of IGFBP-1 (insulin-like growth factor binding protein-1). Four regions in the IGFBP-1 promotor have been identified to enhance the transcription. Two of the regions, located at -73 to -65 bp and -319 to -311 bp formed identical DNA-protein complexes with the nuclear extracts of endometrial stromal/decidual cells. To identify the binding protein(s) in endometrial cells that interact with these two regions, we have used the TGTCAATTA repeats (-319 to -11 bp of the IGFBP-1 promoter) to screen the human decidual cDNA library by yeast one-hybrid system. We found that Hox A10, HoxA11, HoxB2, HoxB4, and HoxD11 interacted with the TGTCAATTA repeats in yeast cells. Among these hox genes, the full-length coding region of HoxA10, HoxA11, and HoxB4 were used for functional analysis in three types of endometrial cells, undifferentiated endometrial stromal cells, decidual cells (differentiated stromal cells) and endometrial adenocarcinoma cell line (HEC1-B). All these endometrial cells produce IGFBP-1. Transient transfection assay showed that HoxA10 expression vector increased the promoter activity (the IGFBP-1 proximal promoter containing TGC/TCAATTA and two functional PRE sites) in endometrial stromal cells and in HEC-1B cells, but not in decidual cells. HoxB4 enhanced the promoter activity only in decidual cells, while HoxA11 had no apparent effect in all three types of cells. To evaluate whether Hox proteins would interact with progesterone receptor (hPR), cells were transfected with the promoter construct, Hox and hPR expression vectors. hPR alone activated the IGFBP-1 promoter activity, but expression of Hox gene suppressed the activation. Hox proteins also suppressed the hPR enhanced promoter activities of MMTV (containing consensus-PRE sites) and glycodelin (GdA, containing Sp1 site which mediates the hPR function). These data showed that Hox genes selectively activate the transcription of the IGFBP-1 and GdA genes in different types of endometrial cells. Hox genes, however, suppress the hPR enhanced activities. In addition, we found that HoxB4 expression was induced by estrogen and progestin. Other investigators have shown that HoxA10 and 11 were stimulated by progestin. These findings show that Hox proteins are molecular mediators of the steroid hormones during endometrial cell development.

Emerging role of genomics in endometriosis research

OBJECTIVE

Rapidly evolving methods in genomics and proteomics research already are changing the nature of biomedical investigation. In this report we briefly review some of the seminal technological advances that inspired the genomics revolution and describe their application in the field of endometriosis research.

DESIGN

Review of different techniques successfully applied to endometriosis research.

SETTING

Collaborative investigation in academic and pharmaceutical industry laboratories.

PATIENT(S)

Biopsies were obtained from consenting ovulatory women on no medications, with or without laparoscopically proven endometriosis.

RESULT(S)

Genomics techniques have confirmed gene products shown to be abnormally expressed in endometriotic tissues by prior studies. In addition, identification of novel transcripts not previously appreciated in this condition were discovered. Examples of dysregulated genes in endometriosis include glycodelin, complement, early growth response-1 and transducer of erbB-1.

CONCLUSION(S)

Global gene profiling studies are poised to revolutionize the diagnosis and treatment of endometriosis and other human diseases.

Glycodelin: a major lipocalin protein of the reproductive axis with diverse actions in cell recognition and differentiation

Glycodelin is a glycoprotein that belongs to the lipocalin superfamily. Depending on glycosylation, glycodelin appears in various isoforms. In the uterus, glycodelin-A is the major progesterone-regulated glycoprotein secreted into uterine luminal cavity by secretory/decidualized endometrial glands. The other tissues expressing glycodelin include fallopian tubes, ovary, breast, seminal vesicle, bone marrow, and eccrine glands. Glycodelin-A potently and dose-dependently inhibits human sperm-egg binding, whereas differently glycosylated glycodelin-S from seminal plasma has no such effect. Absence of contraceptive glycodelin-A in the uterus during periovulatory midcycle is consistent with an open "fertile window." Glycodelin induced by local or systemic administration of progestogens may potentially reduce the fertilizing capacity of sperm in any phase of the menstrual cycle. Glycodelin also has immunosuppressive activity. Its high concentration at the fetomaternal interface may contribute to protection of the embryonic semiallograft. Besides being an epithelial differentiation marker, glycodelin appears to play a role in glandular morphogenesis, as transfection of glycodelin cDNA into a glycodelin-negative breast cancer cells resulted in formation of gland-like structures, restricted proliferation, and induction of other epithelial markers. These various properties, as well as the chemistry, biology, and clinical aspects of glycodelin, continue to be areas of active investigation reviewed in this communication.

Endometrial expression of glycodelin in women with levonorgestrel-releasing subdermal implants

OBJECTIVE

To determine whether subdermal levonorgestrel implants induce endometrial expression of glycodelin.

DESIGN

Cross-sectional, blinded study.

SETTING

University clinic.

PATIENT(S)

One hundred and eight women with subdermal implants and 19 postmenopausal women.

INTERVENTION(S)

Endometrial biopsies, curettages, and hysterectomies.

MAIN OUTCOME MEASURE(S)

Endometrial glycodelin expression was examined through immunohistochemistry, in situ hybridization, and morphologic endometrial dating.

RESULT(S)

Overall, 80% of the endometrial specimens obtained from women with subdermal levonorgestrel implants stained positive for glycodelin. Endometrial morphology of these women showed proliferative (71%), inactive/weakly proliferative (19%), menstrual or regenerating (6.5%), and other patterns (2.8%). Of these, 79%, 71%, 100%, and 100% were glycodelin positive, respectively. Nineteen specimens were obtained during the midcycle when glycodelin is not normally expressed: of these, 89% stained positive for glycodelin. Implant-related amenorrhea was associated with endometrial glycodelin expression in 58% of the women, whereas the endometrium specimens obtained from women with postmenopausal hypoestrogenic amenorrhea contained no detectable glycodelin.

CONCLUSION(S)

Subdermal levonorgestrel implant use is often associated with endometrial expression of glycodelin. Because glycodelin has been shown to inhibit sperm-egg binding, the induction of glycodelin may contribute to the contraceptive activity of the implant.

Placental protein 14 induces apoptosis in T cells but not in monocytes

Substantial evidence exists in literature to suggest that placental protein 14 (PP14) (recently renamed glycodelin A), exhibits immunosuppressive properties and is an indispensable macromolecule in the maternal system for the establishment, maintenance, and progression of pregnancy. Though there are several reports substantiating the above, the mechanism of its action at the molecular level has not been elucidated as yet. In this paper we provide data that suggest that amniotic fluid PP14 and recombinant PP14 expressed in Pichia pastoris induce apoptosis in human peripheral blood lymphocytes upon activation, independent of monocytes. That PP14 has a direct apoptotic action on T cells but not on monocytes was also demonstrated by utilizing human cell lines. PP14 was shown to induce apoptosis in the human T cell lines, Jurkat and MOLT-4 cells, but not in the human monocytic cell line, U937.

Ligand activated hPR modulates the glycodelin promoter activity through the Sp1 sites in human endometrial adenocarcinoma cells

Human endometrium produces glycodelin-A (GdA). The GdA mRNA is highly expressed in progestin-sensitized human endometrial glandular epithelial cells. The mechanism of GdA gene expression, however, is not clear. To understand the cell specific GdA gene transcription, our first approach was to identify the cis-element in the GdA promoter using transfection assay in a human endometrial adenocarcinoma cell line (HEC-1B, a cell line originally derived from the glandular component of the endometrium). The GdA promoter (-1900 to +20 bp) was linked to the luciferase reporter gene to construct p1900Luc, along with two shorter promoter constructs, p1100Luc and p304Luc. Deletion analysis showed that the basal promoter activity was derived from the region between -304 to +20 bp. This region contains three putative Sp1 binding sites (Sp1-1, -243 to -238 bp; Sp1-2, -207 to -202 bp; and Sp1-3, -56 to -49 bp). Mutation analysis at the Sp1 sites showed that p304Spm2Luc and p304Spm3Luc reduced the activity by 80%, while p304Spm1-2-3Luc reduced the activity by 95%. Sp1-1 mutation, however, had no effect. These results showed that two of the three Sp1 cis-elements mediate the basal promoter activity of the GdA gene. Electrophoretic gel mobility shift showed that at least two specific binding proteins in the nuclear extracts of HEC-1B cells bound to the oligo containing Sp1-2 or Sp1-3 cis-element. Sp1 antibody reduced the specific binding complex by 70% suggesting that Sp1 transcription factor regulates GdA gene expression. In addition, over expression of Sp1 increased the promoter activity. To determine whether progestin would modulate the promoter activity, HEC-1B cells were transfected with p304Luc and with progesterone receptor (either hPR-A or hPR-B) expression vector. Medroxyprogesterone acetate increased the promoter activity (3-fold) derived from p304Luc but not from the mutant, p304Spm1-2-3Luc. In contrast, the promoter activity was slightly reduced in cells treated with estradiol and co-transfected with estrogen receptor expression vector. These data indicate that ligand-activated PR stimulates GdA gene expression mediated through the functional Sp1 sites.

Glycodelins

Glycodelin is a major glycoprotein that is synthesized in the endometrium in response to progesterone and relaxin exposure. Endometrium-derived glycodelin-A has contraceptive and immunosuppressive properties. Glycodelin is absent from the endometrium during the fertile periovulatory phase, but is synthesized in this tissue during the peri-implantation phase and is abundant during the last week of the luteal phase. Changes in local and/or circulating glycodelin concentrations have been observed in women with reproductive disorders. The chemical modification of glycodelins has resulted in compounds with antiviral activity.

Glycodelin: a reproduction-related lipocalin

Glycodelin, a human lipocalin, is a major endometrial protein with at least two differentially glycosylated isoforms. Glycodelin-A (GdA) is purified from human mid-trimester amniotic fluid, where it is secreted from the decidualized endometrium. Glycodelin-S (GdS) is synthesized in the male reproductive tract, mainly in the seminal vesicles, and secreted into seminal plasma. These two glycodelin isoforms, glycosylated in a completely different manner, serve as a good model for studying the effects of glycosylation on protein function and physicochemical properties. We have reviewed here the structure, expression and biological functions of glycodelin.

Melanocortin-4 receptor mutations are a frequent and heterogeneous cause of morbid obesity

By integrating an agonist satiety signal, provided by alpha-melanocyte-stimulating hormone (alpha-MSH), and an antagonist signal, provided by agouti-related protein (AGRP), the melanocortin-4 receptor (MC4-R) is a key element in the hypothalamic control of food intake. Inactivation of the gene encoding this G protein-coupled receptor causes obesity in mice. In humans, frameshift mutations in MC4-R cause an early-onset dominant form of obesity in two families. In this study we find a high frequency (4%) of rare heterozygous MC4-R mutations in a large population of morbidly obese patients. No such mutations were found in controls. By analyzing the phenotypes of the probands carrying these mutations, we demonstrate that these patients display a common, nonsyndromic form of obesity. Interestingly, functional analysis of the mutant receptors indicates that obesity-associated defects in MC4-R range from loss of function to constitutive activation. Transmission of these mutations in the families of the carriers indicates a variable expressivity that is not related to the functional severity of the mutations. This variable expressivity of MC4-R-associated obesity is not due to variations in genes for alpha-MSH or AGRP. Taken together, these results demonstrate that MC4-R mutations are a frequent but heterogeneous genetic cause of morbid obesity.

Effects of progestins and relaxin on glycodelin gene expression in human endometrial cells

OBJECTIVE

Glycodelin is an endometrial protein proposed to play an important role in embryonic implantation. We examined the effects of progestins and relaxin on glycodelin transcription, synthesis, and secretion.

STUDY DESIGN

Northern blotting, metabolic labeling, and fluorography were used to assess glycodelin messenger ribonucleic acid and protein synthesis in endometrial tissue and cells. Luciferase reporter constructs transfected into endometrial adenocarcinoma cells (Ishikawa cells) were used to determine whether progestins or relaxin could activate the glycodelin gene promoter.

RESULTS

Progestins but not relaxin stimulated glycodelin secretion in primary epithelial cell cultures. A 452-base pair fragment of the glycodelin gene promoter was activated 4.3 +/- 0.7 times normal by 10-nmol/L promegestone; however, addition of relaxin to the same construct repressed progestin-stimulate promoter activation by >30%.

CONCLUSION

Glycodelin transcription, synthesis, and secretion by endometrial epithelial cells were stimulated by progestins. However, relaxin failed to stimulate production of this immunomodulatory protein and, in fact, repressed progestin-stimulated activation of the glycodelin gene promoter.

The effect of hormone replacement therapy on the immunoreactive concentrations in the endometrium of oestrogen and progesterone receptor, heat shock protein 27, and human beta-lactoglobulin

We determined the expression of oestrogen receptor (ER), progesterone receptor (PR), heat shock protein 27 (HSP27) and human beta-lactoglobulin in the endometrium under hormone replacement therapy (HRT). The immunohistochemical expression during the late progestogenic phase of sequential HRT was compared semi-quantitatively and using image analysis, to the early, mid-, and late luteal phase of the physiological cycle. Under sequential HRT, smaller glands were positive for the ER but larger glands with more advanced secretory features were negative. ER expression was lower in the stroma under HRT, and the difference was statistically significant compared with the early luteal phase (P < 0.05). Expression of HSP27 under HRT was lower in the epithelium but higher in the stroma compared with the physiological luteal phase. Epithelial PR expression was lower under HRT compared with the early, but not the mid- or the late luteal phase. The number of PR-positive stromal cells under HRT was lower compared with the physiological cycle, and the difference was statistically significant in comparison with the early luteal phase (P < 0.05). The glandular area expressing human beta-lactoglobulin during the late progestogenic phase was statistically significantly higher compared with the early, but lower in comparison with the mid- or the late luteal phase (P < 0.05). The study demonstrates a sub-physiological progestogenic response superimposed on evidence of a hypo-oestrogenism, and a differential response in the epithelium and stroma.

Expression of glycodelin in human breast and breast cancer

Glycodelin is a 28 kDa glycoprotein with structural homology to beta-lactoglobulins, particularly expressed in steroid-responsive tissues of the female reproductive tract. We previously found that transfection of glycodelin cDNA into MCF-7 breast cancer cells induces differentiation into organized acinar epithelium and up-regulation of epithelial markers. In this study, we used immunohistochemistry, Northern blotting and reverse transcription-polymerase chain reaction (RT-PCR) analyses to study glycodelin expression in normal and in malignant breast tissues. The results were compared with the expression of estrogen (ER) and progesterone receptors (PR) and p53 tumor suppressor protein. Glycodelin was found in ductal and lobular epithelium of 6/6 normal breast tissues, 27/29 morphologically normal breast tissues from breast cancer patients, 6/6 benign lactating adenomas, 21/35 ductal carcinomas, 9/9 tubular carcinomas, 9/9 mucinous carcinomas, 3/3 mixed ductal/tubular carcinomas and 7/11 lobular carcinomas. In the latter, of particular interest was the presence of glycodelin in paranucleolar vacuoles of carcinoma cells. Northern blot analysis of fresh frozen tissues revealed the normal full length 0.9 kb mRNA of glycodelin in ductal breast carcinoma. Using RT-PCR analysis, glycodelin messenger ribonucleic acid was found in 13/13 ductal and in 3/3 tubular tumor tissues. We also detected a splicing variant lacking exon 4, which includes the nucleotide sequence encoding the potential N-glycosylation site at Asn-85. Our results demonstrate the synthesis of glycodelin in normal breast and breast cancer. In addition, we show that the paranuclear vacuole, characteristically present in lobular breast cancer cells, contains abundant amounts of glycodelin.

Epithelial expression of glycodelin in biphasic synovial sarcomas

Glycodelin is a 28 kDa glycoprotein of the lipocalin family that was previously considered to be specific for the reproductive tract. Glycodelin is found in the secretory glandular epithelium of endometrium and in seminal vesicles. Given the cyclic differentiation of normal endometrial epithelium, we studied by immunohistochemistry a possible expression of glycodelin in other tissues displaying stroma-to-epithelium maturation. We report here that 11/11 biphasic synovial sarcomas expressed glycodelin in the cells exhibiting epithelial or glandular differentiation while the sarcomatous spindle cells remained negative. Glycodelin was also found in secreted material in the lumina of the gland-like structures. In only 1 of the 7 monophasic synovial sarcomas studied, focal glycodelin reactivity was seen in some flattened spindle cells. The expression of glycodelin in biphasic synovial sarcoma tissue was further verified by the demonstration of glycodelin mRNA by reverse transcriptase-polymerase chain reaction. Considering the monoclonal origin of synovial sarcomas, our findings raise the intriguing possibility that activation of expression of the glycodelin gene is involved in the molecular regulation of mesenchyme-to-epithelium differentiation.

Characterization of a caprine beta-lactoglobulin pseudogene, identification and chromosomal localization by in situ hybridization in goat, sheep and cow

A beta-lactoglobulin (beta-LG) pseudogene has been isolated and sequenced (7634 bp) in goat. Its structure is remarkably similar to that of the beta-LG gene with all seven exons placed in the same relative position. The pseudogene seems to have originated by gene duplication, but a non uniform distribution of similarities along the sequence suggests that events of gene conversion have also occurred during its evolution. The comparison of the predicted ancestral protein encoded by the pseudogene shows its evolutionary relationship to the monomeric beta-LG II forms of the beta-LG reported in some non-ruminant species. Southern-blot analysis shows that similar pseudogenes are also found in the genome of sheep and cow. The pseudogene has been mapped by fluorescent in situ hybridization (FISH) to sheep chromosome 3p28 and cattle and goat chromosomes 11q28, in the same mapped position as that found for the beta-LG gene in all these species.

Habitual abortion is accompanied by low serum levels of placental protein 14 in the luteal phase of the fertile cycle

OBJECTIVE

To study serum levels of placental protein 14 (PP14) in relation to endometrial function in women with a history of habitual abortion.

DESIGN

Prospective study.

SETTING

Departments I and II of Obstetrics and Gynecology, University Central Hospital of Helsinki, Helsinki, Finland.

PATIENTS

Fifty patients (26 primary and 24 secondary habitual aborters) and 38 controls without a history of abortion studied during a regular cycle.

RESULTS

Habitual aborters as a whole or when subgrouped into those with normal cycles (n = 40) or with a luteal phase defect (LPD; n = 10) and control women demonstrated a distinct increase in PP14 levels from late follicular to late luteal phases. In the luteal phase, serum PP14 levels were lower in the patients than in the controls (27.2 +/- 3.1 versus 48.5 +/- 10.1 micrograms/L), but the differences in PP14 levels between habitual aborters with or without LPD was not significant (16.3 +/- 4.3 versus 29.9 +/- 3.7 micrograms/L).

CONCLUSIONS

Habitual aborters exhibit lower serum PP14 levels in the late luteal phase compared with normal fertile women.

Genomic structure of the human complement protein C8 gamma: homology to the lipocalin gene family

Human C8 is one of five complement components (C5b, C6, C7, C8, C9) that interact to form the cytolytic C5b-9 complex on target cells. It contains three subunits (C8 alpha, C8 beta, C8 gamma) which are encoded in separate genes. In relation to other proteins of the complement system, C8 gamma is unusual in that it is not structurally related to any other component nor does it have an obvious function. Based on weak but significant sequence similarity, it is proposed to be a member of the lipocalin family of widely distributed proteins that bind and transport small hydrophobic ligands. In this study, the human C8 gamma gene has been characterized and found to contain seven exons spanning approximately 1.8 kb. S1 nuclease and anchored PCR were used to identify the transcription initiation site. This site is preceded by putative regulatory elements that include two SP1 binding sites, several glucocorticoid response elements, and two SV40 enhancer core consensus sequences. A comparison to genes of other lipocalins reveals a remarkably close correlation in exon number, lengths, and phases. A close correspondence in exon boundaries is also observed and suggests that C8 gamma contains the same discrete structural elements that define the characteristic beta-barrel shape of the lipocalins. These results establish that C8 gamma is indeed ancestrally related to the lipocalin family and strengthens the likelihood that its role in the complement system is to bind an as yet unidentified ligand.

Structural organization of the genes for rat von Ebner's gland proteins 1 and 2 reveals their close relationship to lipocalins

The rat von Ebner's gland protein 1 (VEGP 1) is a secretory protein, which is abundantly expressed in the small acinar von Ebner's salivary glands of the tongue. Based on the primary structure of this protein we have previously suggested that it is a member of the lipocalin superfamily of lipophilic-ligand carrier proteins. Although the physiological role of VEGP 1 is not clear, it might be involved in sensory or protective functions in the taste epithelium. Here, we report the purification of VEGP 1 and of a closely related secretory polypeptide, VEGP 2, the isolation of a cDNA clone encoding VEGP 2, and the isolation and structural characterization of the genes for both proteins. Protein purification by gel-filtration and anion-exchange chromatography using Mono Q revealed the presence of two different immunoreactive VEGP species. N-terminal sequence determination of peptide fragments isolated after protease Asp-N digestion allowed the identification of a new VEGP, named VEGP 2, in addition to the previously characterized VEGP 1. The complete VEGP 2 sequence was deduced from a cDNA clone isolated from a von Ebner's gland cDNA library. The VEGP 2 cDNA encodes a protein of 177 amino acids and is 94% identical to VEGP 1. DNA sequence analysis of the rat VEGP 1 and 2 genes isolated from rat genomic libraries revealed that both span about 4.5 kb and contain seven exons. The VEGP 1 and 2 genes are non-allelic distinct genes in the rat genome and probably arose by gene duplication. The high degree of nucleotide sequence identity in introns A-C (94-100%) points to a recent gene conversion event that included the 5' part of the genes. The genomic organization of the rat VEGP genes closely resembles that found in other lipocalins such as beta-lactoglobulin, mouse urinary proteins (MUPs) and prostaglandin D synthase, and therefore provides clear evidence that VEGPs belong to this superfamily of proteins.

Structural organization of the gene encoding the human lipocalin tear prealbumin and synthesis of the recombinant protein in Escherichia coli

The genomic DNA fragment encoding the human lipocalin tear prealbumin (LCN1), a new member of the superfamily of hydrophobic molecule transporters, has been isolated and sequenced. The entire gene is approximately 6.2 kb in size and contains six protein-coding exons and a 3'-nontranslated exon. All exon/intron splice junctions exactly follow the GT/AG rule. The structure of the LCN1 gene is highly similar, in terms of numbers and sizes of exons and in intron phasing, to that of the genes encoding ovine beta-lactoglobulin, human placental protein P14, rat alpha 2-urinary globulin, rat prostaglandin D synthase and human alpha 1-microglobulin, thus supporting the close evolutionary relationship of these genes. The 5'-noncoding region of LCN1 contains, besides a TATA and CAAT box, several motifs that resemble regulatory elements of other eukaryotic genes, including potential metal-responsive elements (MRE) and a cAMP-responsive element (CRE). As a basis for further investigations concerning the structure-function relationship and to generate a source of recombinant protein for X-ray crystallography studies, LCN1 was produced in Escherichia coli as a fusion with maltose-binding protein.

Structure and function of milk protein genes

Interspecies comparisons of cDNA and mosaic milk protein genes have confirmed their high rate of evolution, but the overall gene organization has been conserved. The three Ca-sensitive casein genes, which share common motifs in the promoter region and contain similar sequences that encode signal peptide and multiple phosphorylation sites, probably derived from a common ancestor. alpha s1- and alpha s2-casein genes, divided into many small exons, undergo complex splicing, and the deleted caseins arise from exon skipping. The four bovine casein genes are clustered on 200 kb of chromosome 6. alpha-Lactalbumin and beta-lactoglobulin pseudogenes occur in ruminants. Study of the expression of native and modified milk protein genes in mammary cell lines and transgenic animals and DNA footprinting have shown the occurrence of important regulatory motifs in the proximal 5' flanking region, including one recognized by a specific mammary nuclear factor. Good stage- and tissue-specific expression has been obtained in transgenic animals with milk protein genes having less than a 3-kb 5' flanking region. Better knowledge of both the structure and function of milk protein genes, which has already allowed the use of powerful techniques for the rapid identification of alleles, offers the potential for the genetic modification of milk composition.

Structural organization of the gene for prostaglandin D synthase in the rat brain

A 3-kilobase-pair gene for rat brain prostaglandin D synthase [(5Z,13E)-(15S)-9 alpha,11 alpha-epidoxy-15-hydroxyprosta-5,13- dienoate D-isomerase, EC 5.3.99.2], which belongs to the lipocalin family, was isolated from a rat genomic DNA library by plaque hybridization with the cDNA for the enzyme. The gene contains seven exons, and all the splice donor and acceptor sites conform to the GT/AG rule. Transcription initiates at a guanine residue 39 base pairs upstream of the translation initiation codon, as determined by primer-extension analysis of rat brain mRNA. The 5'-flanking region of the gene lacks typical transcriptional regulatory sequences, such as TATA and CAAT boxes, but contains several sets of inverted repeats, direct repeats, and sequences resembling the transcriptional factor Sp1-binding site. The gene structure of prostaglandin D synthase is remarkably analogous to those of other lipocalins, such as beta-lactoglobulin, alpha 2-urinary globulin, placental protein 14, and alpha 1-microglobulin, in terms of number and sizes of exons and phase of splicing of introns. Furthermore, in a multiple alignment of the deduced amino acid sequences, positions of exon/intron junction of the prostaglandin D synthase gene are highly conserved and located around the positions of those of the genes for other lipocalins despite a weak homology.

Transformation of a novel direct-repeat repressor element into a promoter and enhancer by multimerisation

Studies on the regulation of interferon (IFN) responsive genes have mainly been centred on the highly conserved IFN stimulated responsive elements (ISREs) which can mediate type I and II IFN inducibility. To date little is known about other functional cis-acting regulatory motifs in IFN responsive genes. We report here on the identification of a repressor element in the human MxA gene defined to a 19 base pair (bp) region which houses a 9 bp direct repeat. DNA-specific protein binding on this element is not affected by IFN treatment and is distinct from ISRE binding proteins. Remarkably, contrary to expectations, when the repressor element is multimerised and spliced, in either orientation, to a reporter gene it behaves like a functional, constitutive promoter. Positioning the multimerised element in front of the SV40 enhancerless promoter also led to enhanced expression. The same protein(s) seem to bind to both the single repressor element and its multimerised form. This discovery of phenotypic reversal on a repressor element via multimerisation may have important implications in vivo.