Temporal and constitutive expression of homeobox-2 gene (Hu-2), human heat shock gene (hsp-70), and oncogenes C-sis and N-myc in early human trophoblast

Expression of HOX gene products in normal and abnormal trophoblastic tissue

OBJECTIVE

The expression pattern of three homeobox genes products, HOX A11, HOX B6, and HOX C6, was examined in normal human placental tissue and abnormal trophoblastic tissue derived from complete hydatidiform moles and choriocarcinoma tumors. We sought to determine whether expression of these gene products during different states of trophoblastic differentiation and proliferation is constant or demonstrates variation. Variation in expression of these respective homeobox genes may provide insight into predicting which molar tissues are likely to develop into choriocarcinoma tumors.

METHODS

Tissue sections from a total of 12 samples were studied. Among these, six full-term human placentas, three complete hydatidiform moles, and three choriocarcinoma tumors were examined for expression of the homeobox HOX A11, HOX B6, and HOX C6 gene products, using immunohistochemistry staining methods.

RESULTS

Expression of HOX homeobox gene products, HOX A11, HOX B6, and HOX C6, was detected in full-term human placenta and tissue from complete hydatiform moles. Abnormal trophoblasts from complete moles demonstrated an immunoreactivity expression pattern comparable to that of normal trophoblasts from term pregnancies. However, definitive expression of these respective homeobox genes was not identified in tissue obtained from choriocarcinoma tumors.

CONCLUSION

Variation in expression of HOX homeobox gene products, HOX A11, HOX B6, and HOX C6, was established in trophoblast tissue obtained from full-term human placentas, complete hydatiform moles, and choriocarcinoma tumors. This finding indicates that normal full-term trophoblasts and abnormal molar trophoblasts may share similar fundamental regulatory control mechanisms. The absence of definitive expression of these HOX gene products in trophoblastic cells derived from choriocarcinoma tumors indicates that while HOX A11, HOX B6, and HOX C6 genes may be involved in maintenance of some trophoblastic cell states, they may be either downregulated or have alterations in their expression in trophoblasts from choriocarcinoma tumors.

Expression of homeobox gene transcripts in trophoblastic cells

OBJECTIVE

This study was conducted to examine the dynamics of homeobox gene expression in the differentiation of trophoblasts as a key to the understanding of the regulatory mechanisms that are involved in placental development.

STUDY DESIGN

Expression of homeobox genes was examined in primary trophoblastic cells and in the BeWo choriocarcinoma model cell lines by molecular and immunocytochemistry techniques.

RESULTS

We demonstrated the expression of 3 homeobox genes (HOX B6, HOX C6, and HOX A11) in primary trophoblastic cells. BeWo cells showed an expression pattern similar to that of the primary cell lines. In both primary trophoblasts and BeWo cells, the HOX A11 gene, but not the HOX B6 or HOX C6 genes, were found to down-regulate with differentiation from single- to multinucleate giant cells.

CONCLUSION

This study demonstrates a novel expression pattern for HOX A11 gene in trophoblastic differentiation and suggests that the down-regulation of HOX A11 may be necessary for the differentiation of cytotrophoblasts into syncytiotrophoblasts.

Expression of CD44 and its isoforms in the fetal neuroblasts

CD44 is a polymorphic transmembrane glycoprotein that exists as multiple isoforms resulting from alternative splicing and posttranslational modifications. Enhanced expression of CD44 has been correlated to the tumorigenicity and metastatic behavior in different malignant tumors. In contrast, human neuroblastomas exhibit an inverse correlation between CD44 expression and tumor malignancy. To determine whether there is a CD44 silencing in sympatho-adrenal precursors as a possible explanation for the down-regulation of CD44 in neuroblastomas, the expression of standard CD44H and v6, v7, v7v8, or v10 isoforms was analyzed by immunohistochemistry in human adrenal glands of 14- to 20-week-old gestational age fetuses. All of the fetal neuroblasts localized in the adrenal gland parenchyma and migrating from the sympathetic nerve chain into the fetal adrenal cortex strongly expressed CD44H but none of the CD44 isoforms could be detected in these cells. In contrast, a strong expression of CD44v7 and v6 was detected in the fetal adrenal cells. These results indicate that, as for many other cell types, the CD44H expressed by fetal neuroblasts may contribute to controlling their migration into the adrenal medulla and that the down-regulation of CD44H in neuroblastoma cells should be explained by mechanisms other than the fetal suppression of CD44H expression in their normal counterparts.

Comparative analysis of HOXC-9 gene expression in murine hemochorial and caprine synepitheliochorial placentae by in situ hybridization

Mammalian placentae exhibit wide structural diversity among different species and are formed under intricate interplay between the embryonic trophoblast and the maternal endometrial cells. Increasing evidence in the literature indicates a possible role played by homeobox genes in the complex placental organogenesis. Although the expression of all HOX 9 paralogs has been demonstrated both in highly invasive murine hemochorial placentae and in non-invasive caprine synepitheliochorial placentae, no reports so far published in the literature described the patterns of gene expression of Hoxc-9 in the murine nor those of HOXC-9 in the caprine placenta at cellular levels. We carried out comparative analyses of the location and identity of the cells expressing Hoxc-9/HOXC-9 during various stages of placentation in the murine hemochorial and caprine synepitheliochorial placentae by means of in situ hybridization using murine Hoxc-9 or caprine HOXC-9 cRNA probe, respectively. The results demonstrated that Hoxc-9 mRNA was expressed at high levels in giant trophoblast cells of murine placentae on Days 12-19, but not on Day 8. Similar analysis of caprine Day 75 and Day 100 placentae revealed that the binucleate trophoblast cells that penetrate the uterine luminal epithelial cell layer, strongly expressed HOXC-9 mRNA. Although the functional significance of Hoxc-9/HOXC-9 gene expression in trophoblast cells remains to be elucidated, it was suggested that it might play a role in the regulation of invasiveness or endocrine activities in the murine giant trophoblast cells and/or the caprine binucleate trophoblast cells.

Murine T cell determination of pregnancy outcome

At the fetomaternal interface, maternal effector cells come in intimate contact with fetal trophoblast cells which express paternal antigens. Failure of fetal trophoblast cells to activate maternal Th1 immune responses has been attributed in part to the absence of classical Class I and Class II major histocompatibilty complex (MHC) antigen expression and elaboration of factors which reduce TcR expression and shift any immune responses which may occur to Th2. Classical TcR alphabeta(+) T cells have not been found to be able to respond to trophoblasts. Recently, TcR gammadelta(+) T cells have been characterized in the low-abortion-rate pregnant C57Bl/10 mouse decidua, and the Vgamma1(+) subset may be able to respond to trophoblasts in a non-MHC-dependent manner. Trophoblast-recognizing T cells with Vgamma1 receptors are also present in the decidua of CBA/J mice pregnant by DBA/2, an abortion-prone mating combination. To test the role of the Vgamma1 subset of decidual gammadelta T cells in abortion-prone pregnancies, we altered this subset by injecting monoclonal anti-Vgamma1.1 antibody on gestation day 5.5, 1 day after implantation. This reduced detectability of a Vgammadelta subset producing TNF-alpha and reduced the abortion rate. Anti-Vgamma2, which reacts with a similar proportion of decidual gammadelta T cells as anti-Vgamma1.1, failed to prevent abortions. Vdelta6.3(+) cells are prominent at the fetomaternal interface, and anti-Vdelta6 antibody injected on day 5.5 prevented abortions. TGF-beta2(+) gammadelta cells first appear on day 8.5 of pregnancy; anti-Vgamma1.1 antibody injection on day 8.5 depleted these cells and boosted abortions; anti-Vdelta6.3 given on day 8.5 boosted abortions to the same level. These results suggest that two populations of Vgamma1.1(+)delta6.3(+) T cells may arise in the decidua: an early population that is Th1, abortogenic, and present during the time of implantation, and a Th2/3 cell subset that is present in the decidua later during pregnancy and which is pregnancy-protective.

Why did your mother reject you? Immunogenetic determinants of the response to environmental selective pressure expressed at the uterine level

PROBLEM

Maternal "rejection" of the implanted conceptus is considered to account for a significant proportion of miscarriages (abortions) in both humans and animals. Our understanding of mechanisms has been limited, and hence, explanations for nonrejection have remained largely speculative. Losses, when they occur, could represent either random accidental failure of protective mechanisms or a more purposeful discrimination.

METHOD OF STUDY

An analysis of the most recent data.

RESULTS AND CONCLUSIONS

The embryo is most akin to a parasite, and pregnancy is most akin to a host-parasite interaction. If one excludes chromosome abnormalities in the embryo as a cause of death, activation of coagulation mechanisms, leading to vasculitis affecting the maternal blood supply to the implanted embryo, appears to represent a major loss-causing mechanisms--a form of ischemic autoamputation. Proinflammatory T-helper (Th) 1-type cytokines trigger this process via upregulation of a novel prothrombinase, fgl2. Th2/3 cytokines, such as interleukin (IL)-4, IL-10, and transforming growth factor (TGF)-beta 2, may antagonize the processes involved. Cytokine balance is determined by the genetics of the mother, which regulate her response to stress; endotoxin (LPS); and paternal antigens, selectively expressed on the trophoblast of the embryo, via imprinting. Based on studies in abortion-prone mice, where immunity to paternal alloantigens prevents loss, three distinct gene products in the embryo are proposed to determine the cytokine response to maternal lymphomyeloid cells in the uterus.

A distal-less class homeobox gene, DLX4, is a candidate for regulating epithelial-mesenchymal cell interactions in the human placenta

Homeobox genes of the Distal-less (Dlx) family are expressed in the vertebrate embryo in regions where epithelial cell layers contact adjacent mesenchymal cells. This study shows that the human Dlx family member, DLX4, is expressed in the placenta, primarily in regions where epithelial and mesenchymal cell layers contact. In situ hybridization studies at first trimester human placental sections revealed that DLX4 was expressed predominantly in the cytotrophoblast stem cell layer. In term placenta, DLX4 was expressed in the syncytiotrophoblast. Northern analysis revealed two DLX4 transcripts in first trimester placenta of 2.8 and 3.0 kb. Elevated levels of DLX4 mRNA were detected in a choriocarcinoma derived cell line when compared with a cytotrophoblast cell line and normal placenta. This is the first study to show that a member of the Dlx family of homeobox genes is expressed in regions of epithelial and mesenchymal cell layer contact in the human. Accumulated evidence from several studies suggest that a combinatorial code of homeobox genes is required to regulate epithelial-mesenchymal cell interactions in the vertebrate embryo. It is predicted that a similar combination of homeobox genes, that includes DLX4, is involved in regulating epithelial-mesenchymal cell interactions in extraembryonic tissues. DLX4 may also have a role in the regulation of the genes important for trophoblast invasion since the level of expression in trophoblast cell lines reflects invasive potential.

Isolation and identification of homeobox genes from the human placenta including a novel member of the Distal-less family, DLX4

We have carried out a DNA binding site screen of a 32-week human placental cDNA library using a consensus homeodomain binding site as a probe. This study represents the first library screen carried out to isolate homeobox genes from the human placenta. We have shown that three homeobox genes known to be expressed in the embryo, HB24, GAX and MSX2 are also expressed in the placenta. We have also identified a novel homeobox gene, DLX4, that shows 85% sequence identity with the homeodomain encoded by the Drosophila Distal-less (Dll) gene. DLX4 therefore represents a new member of the Distal-less family of homeobox genes. This is the first evidence that members of the Distal-less family of homeobox genes are expressed in the placenta. Using fluorescence in situ hybridisation (FISH), DLX4 has been assigned to human chromosome 17q21-q22. This places DLX4 in the same region of chromosome 17 as another member of the Distal-less family, DLX3 (Scherer et al., 1995), and the HOX-B homeobox gene cluster (Acampora et al., 1989: Boncinelli et al., 1991). Members of the Distal-less family (DLX1 and DLX2; DLX5 and DLX6) are found as closely linked pairs on human chromosomes (Simeone et al., 1994). We predict that DLX3 and DLX4 are closely linked and have arisen through gene duplication and divergence from a common ancestral precursor.

Assessment of stress gene mRNAs (HSP-27, 60 and 70) in obstructed rabbit urinary bladder using a semi-quantitative RT-PCR method

Stress proteins (HSPs) participate in the cellular response to various stresses including hyperthermia, hypoxia and injury. A previous work using northern blot analysis demonstrated increased expression of stress protein 70 (HSP-70) in rabbit bladder tissue subjected to partial outlet obstruction. In order to determine if the increased expression was specific for HSP-70 or, alternatively, indicated a generalized stress protein response, a modified quantitative RT-PCR technique was used to quantitate HSP mRNAs (HSP-27, 60, and 70) in normal and obstructed rabbit urinary bladder tissues. The results show the following: 1) The modified semi-quantitative RT-PCR is a sensitive and reproducible technique for detecting mRNA in bladder tissue. 2) Constitutive levels of HSP-27, HSP-60, and HSP-70 mRNAs were detected in control bladder tissues; the relative signal intensity was highest for HSP-70 and lowest for HSP-27. 3) A transient increase in HSP mRNAs was observed after obstruction; the mRNAs of HSP-27, 60 and 70 increased 4.3-, 5.6-, and 2.4-fold, respectively, at 24 h following obstruction, then gradually returned to control levels by the end of one week post-obstruction and remained stable up to 14 days post-obstruction. These data indicate that the modified quantitative RT-PCR is a useful technique for detecting mRNA in bladder tissue; the stress response which occurs in rabbit urinary bladder tissue following partial outlet obstruction is a general phenomenon.

Expression of constitutive heat shock protein-70 in normal (non-stressed) rabbit urinary bladder tissue

The expression of constitutive HSP-70 in the urinary bladder was determined by SDS-PAGE and western blotting using a mouse monoclonal antibody against HSP-70. The western blot analysis showed that the mouse anti-HSP-70 cross-reacted with a 70 kDa protein present in the extracts of the urinary bladder muscle and mucosa. Densitometric scanning of the western blots allowed us to specifically quantitate the relative amounts of the HSP-70. The quantitation of the HSP-70 by combining immunoblotting and densitometry using a laser scanner is reproducible and this technique requires only a small amount of tissue. The amounts of HSP-70 can be estimated from a standard curve of nanogram(ng) of HSP-70 vs absorption from the immunoblots. The amounts of HSP-70 in the muscular and mucosal layers in the body of the urinary bladder are more than those in the base of the bladder. The presence of HSP-70 in the muscle and mucosal epithelium of the bladder was demonstrated by immunohistochemical analysis of freshly removed tissue from the base and the body of bladder from normal animals.

A comparative analysis of N-myc and c-myc expression and cellular proliferation in mouse organogenesis

The distribution of c-myc and N-myc transcripts during mouse organogenesis was investigated by in situ hybridization and compared to proliferation in several tissues. Only c-myc expression was found during the formation of cartilage, brown adipose tissue, glandula submandibularis, thymus and liver. There was a temporally and spatially ordered expression of N-myc only during the organogenesis of brain, retina and eye lens. In some organs (e.g., in lung and tooth bud), c-myc and N-myc were expressed in a striking complementary pattern that reflected the ontogenic origins of different tissue components. Transcripts of both genes were found in the early gut epithelium, but as formation of villi began, the spatial expression pattern of N-myc and c-myc diverged. The results suggest a link between the proliferative state of cell types and the differential expression of N-myc vs. c-myc. Specifically, c-myc is only expressed in rapidly proliferating tissues, while N-myc expression often persists through cytodifferentiation, e.g., during development of eye lens, retina, telencephalon and gut epithelium. Thus, in spite of the structural similarities of N-myc and c-myc genes and proteins their developmental expression patterns suggest different functional roles.