[show abstract][hide abstract] ABSTRACT: While common in viral infections and neoplasia, spontaneous cell-cell fusion, or syncytialization, is quite restricted in healthy tissues. Such fusion is essential to human placental development, where interactions between trophoblast-specific human endogenous retroviral (HERV) envelope proteins, called syncytins, and their widely-distributed cell surface receptors are centrally involved. We have identified the first host cell-encoded protein that inhibits cell fusion in mammals. Like the syncytins, this protein, called suppressyn, is HERV-derived, placenta-specific and well-conserved over simian evolution. In vitro, suppressyn binds to the syn1 receptor and inhibits syn1-, but not syn2-mediated trophoblast syncytialization. Suppressyn knock-down promotes cell-cell fusion in trophoblast cells and cell-associated and secreted suppressyn binds to the syn1 receptor, ASCT2. Identification of the first host cell-encoded inhibitor of mammalian cell fusion may encourage improved understanding of cell fusion mechanisms, of placental morphogenesis and of diseases resulting from abnormal cell fusion.
[show abstract][hide abstract] ABSTRACT: Among the now pandemic sexually transmitted infections (STIs), Chlamydia trachomatis (C. trachomatis) is the predominant bacterial pathogen and human immunodeficiency virus type 1 (HIV-1) is the most lethal of the viral pathogens. The female genital tract is the primary site for heterosexual transmission of both C. trachomatis and HIV-1. Infection with C. trachomatis, and with a variety of other STIs, increases the risk for transmission of HIV-1, although the mechanisms for this finding remain unclear. We have used in vitro modeling to assess the mechanisms by which infection with genital C. trachomatis serovars might increase the transmission of HIV-1 across the female genital tract. C. trachomatis infection of an immortalized endocervical epithelial cell line (A2EN) increases the cell surface expression of the HIV-1 alternative primary receptor, galactosyl ceramide (GalCer), and of the HIV-1 co-receptors, CXCR4 and CCR5. C. trachomatis infection also increases the binding of HIV-1 to A2EN cells, and, subsequently, increases levels of virus in co-cultures of HIV-exposed A2EN and susceptible MT4-R5 T cells. Finally, in vivo endocervical cell sampling reveals a dramatic increase in the number of CD4+, CXCR4 and/or CCR5 positive T cell targets in the endocervix of C. trachomatis positive women when compared to those who are C. trachomatis negative. This combination of in vitro and in vivo results suggests several mechanisms for increased transmission of HIV-1 across the endocervices of C. trachomatis-infected women.
Current HIV research 02/2012; 10(3):218-27. · 1.98 Impact Factor
[show abstract][hide abstract] ABSTRACT: Genital C. trachomatis infections typically last for many months in women. This has been attributed to several strategies by which C. trachomatis evades immune detection, including well-described methods by which C. trachomatis decreases the cell surface expression of the antigen presenting molecules major histocompatibility complex (MHC) class I, MHC class II, and CD1d in infected genital epithelial cells. We have harnessed new methods that allow for separate evaluation of infected and uninfected cells within a mixed population of chlamydia-infected endocervical epithelial cells to demonstrate that MHC class I downregulation in the presence of C. trachomatis is mediated by direct and indirect (soluble) factors. Such indirect mechanisms may aid in priming surrounding cells for more rapid immune evasion upon pathogen entry and help promote unfettered spread of C. trachomatis genital infections.
Infectious Diseases in Obstetrics and Gynecology 01/2011; 2011:420905.
[show abstract][hide abstract] ABSTRACT: Although previous reports suggest an antigen-presenting function for decidual stromal cells (DSCs), the relevance of cell-to-cell communication between DSCs and T cells at the human feto-maternal interface has not been fully elucidated. Therefore, we investigated the presence and function of human DSC-expressed B7-H1 and B7-DC co-stimulatory ligands. B7-H1 and B7-DC on peripheral antigen-presenting cells (APC) typically inhibit T cell activation after binding to their corresponding receptor, programmed death-1 (PD-1).
DSCs were isolated from human term decidua. The expression of B7-H1/B7-DC and HLA-DR and their alteration following IFN-gamma and/or TNF-alpha stimulation were assessed. DSCs with or without IFN-gamma pretreatment were co-cultured with allogenic CD4(+) T cells. The effect of PD-1:B7-H1/B7-DC and T cell receptor (TCR):HLA-DR interactions on T cell cytokine production was evaluated by adding blocking antibodies.
DSCs constitutively expressed B7-H1 and B7-DC, as well as small amounts of HLA-DR. Exogenous IFN-gamma and TNF-alpha up-regulated the B7-H1/-DC expression on DSCs, whereas HLA-DR expression was increased only by IFN-gamma. IFN-gamma pretreatment of DSCs stimulated T cell cytokine production through HLA-DR up-regulation. B7-H1 blockade on DSCs strongly enhanced T cell cytokine production (IFN-gamma, TNF-alpha and IL-2), whereas B7-DC blockade had similar but more modest effects. Blockade of both B7-H1 and B7-DC resulted in additive effects.
Our findings support the categorization of human DSCs as non-professional APCs and suggest that PD-1 ligands on DSCs, together with major histocompatibility complex class II, may play a crucial role in the regulation of decidual CD4(+) T cell cytokine production. This helps to maintain a balanced cytokine milieu at the feto-maternal interface.
Human Reproduction 10/2009; 24(12):3160-71. · 4.67 Impact Factor
[show abstract][hide abstract] ABSTRACT: Up to 8% of the human genome is of retroviral origin. These stably integrated retroviral sequences that characterize the human endogenous retrovirus (HERV) arose from retroviral infections that occurred more than 25 million years ago. The host and the retrovirus have subsequently coevolved as retrovirally derived genetic material is propagated in a Mendelian fashion. Although most HERV sequences are silenced, several have been described that are functional. The effects of some HERV-derived products are linked to human disease; others appear essential to human organ function. The human placenta, unique in its active expression of retroviral sequences that are not expressed in other tissues, may hold the key to an improved understanding of the functional significance of HERVs. In this review, we discuss the contribution of retroelements, particularly HERVs, to placental function and dysfunction. We describe fusogenic and immunosuppressive HERV activities and emphasize epigenetic regulation of retroelement expression.
[show abstract][hide abstract] ABSTRACT: Genetic and epigenetic factors can potentially alter susceptibility to psychiatric disorders such as schizophrenia. In order to explore the effect of epigenetics on the pathogenesis of schizophrenia, we examined the global methylation level of leukocyte DNA from 210 patients with schizophrenia (124 males and 86 females) and 237 healthy subjects (108 males and 129 females). Methylated deoxycytidine (mC) content in peripheral leukocyte DNA was measured by high performance liquid chromatography (HPLC). We confirmed in the healthy subjects our previous finding that there are sex-dependent differences in mC content (males>females; beta=0.319, p<0.001), in addition to the effect of age (beta=-0.141, p=0.022). We therefore used multiple regression to analyze the data from all subjects by sex, with age as a co-variant. In males, a tendency was observed toward lower mC content in patients than in controls (beta=-0.115, p=0.075), with a significant effect of age (beta=-0.212, p<0.001). This difference was more prominent in younger individuals. In females, no effect of age or disease status on mC content was observed. These results established that there is significant sex-dependent difference in the mC content of human peripheral leukocyte DNA, and raise the possibility that alterations in DNA methylation state are present in patients with schizophrenia.
Journal of Psychiatric Research 01/2008; 41(12):1042-6. · 4.07 Impact Factor
[show abstract][hide abstract] ABSTRACT: The purpose of the present study was to understand the tissue specificity of DNA methylation and the relationship between methylation and expression of genes with essential roles in neurodevelopment and brain function. We chose dopamine receptor genes (DRD1 and DRD2), NCAM, and COMT as examples of genes with CpG islands around the promoter region, and serotonin receptor genes (HTR2A and HTR3A), HCRT, and DRD3 as genes without CpG islands. Methylation states were investigated in fetal brain, fetal liver, placenta, and in adult peripheral leukocytes from three individuals by Southern blot and bisulfite-modified DNA sequencing. A repetitive sequence, human endogenous retrovirus (HERV)-K was also examined. All genes examined were almost completely unmethylated in brains. The genes with CpG islands were unmethylated regardless of their expression state. In contrast, genes without CpG islands showed various methylation patterns, which did not necessarily reflect the transcriptional activity of the genes. Most HERV-K loci were methylated, but some loci showed relatively low methylation in the placenta and liver. Interestingly, we found inter-individual differences in methylation levels in HTR2A and HCRT in the placenta and in some loci of HERV-K in the placenta and liver. The sample with the lowest methylation levels in the two unique genes showed higher methylation of HERV-K loci than the other samples. These results provide detailed information about the methylation states of the genes analyzed and evidence for inter-individual variations in methylation in both unique and repetitive sequences.
Journal of Human Genetics 02/2006; 51(5):440-50. · 2.37 Impact Factor
[show abstract][hide abstract] ABSTRACT: The evolutional and biological roles of human endogenous retroviruses (HERVs) are less recognized compared to those of L1. In the present study, we focused on the transcriptional activity of HERVs in normal human tissues and found five HERV loci that are actively expressed in normal tissues. All but one showed tissue specificity of expression: one was expressed in stomach and small intestine and three were in placenta. We subsequently examined by TaqMan-based RT-PCR assays the temporal expression profiles of the three placenta-specific HERVs along with syncytin and syncytin 2 and observed three patterns. Syncytin and HERV-Fb showed almost constant expression through gestations. Syncytin 2 gradually decreased as pregnancy proceeded. In contrast, expression from the HERV-H/F and HERV-K(HML-6) loci increased remarkably in term placentas. Term placentas in general showed larger interindividual differences in HERV expression levels. Our results suggest that HERVs might have more diverse effects than currently thought.
[show abstract][hide abstract] ABSTRACT: The goal of the present study was to investigate inter-individual and age-dependent variation of global DNA methylation in human tissues. In this work, we examined 5-methyldeoxycytidine ((met)C) content by HPLC in human peripheral blood leukocytes obtained from 76 healthy individuals of ages varying from 4 to 94 years (yr), and 39 human placentas from various gestational stages. The HPLC analysis revealed a significant variation of (met)C across individuals and is consistent with the previous findings of age-dependent decrease of global methylation levels in human tissues. The age-dependent decrease of (met)C was relatively small, but statistically highly significant (p= 0.0002) in the aged group (65.9 +/- 8.9 [mean age +/- SD] yr; n = 22) in comparison to the young adult group (19.3 +/- 1.4 yr; n = 21). Males showed a subtle but statistically significant higher mean (met)C content than females. In contrast to the peripheral blood samples, DNA extracted from placentas exhibited gestational stage-dependent increase of methylation levels that appeared to inversely correlate with the expression levels of human endogenous retroviruses. These data may be helpful in further studies of DNA methylation, such as inheritance of epigenetic patterns, environment-induced changes, and involvement of epigenetic changes in disease.
Annals of Human Genetics 06/2004; 68(Pt 3):196-204. · 2.22 Impact Factor
[show abstract][hide abstract] ABSTRACT: Genetic studies of neuropsychiatric disorders have often produced conflicting results, which might partly result from the involvement of epigenetic modifications. We intended to explore the possible implication of DNA methylation and human endogenous retroviruses (HERVs) in neuropsychiatric disorders. In the present study, we identified two HERV loci that are expected to retain the transcriptional activity in the brain. One was located on chromosome 1q21-q22 and the other on 22q12. Interestingly, these regions were overlapped with or included in those of schizophrenia-susceptible loci, SCZD9 and SCZD4, respectively. Particularly, the HERV on 22q12 was located in the opposite direction 4 kb downstream of the Synapsin III gene. These HERV loci could afford clear targets for methylation and expression analyses in postmortem brains of patients with psychiatric disorders such as schizophrenia. In addition, we confirmed our previous finding that only a few of particular HERV-K loci were activated among a number of highly homologous loci in teratocarcinoma cell lines. These activated loci included ones common to all teratocarcinoma cell lines analyzed and depending on their male or female origin.
Journal of Human Genetics 02/2003; 48(11):575-81. · 2.37 Impact Factor
[show abstract][hide abstract] ABSTRACT: Preceding the isolation of transcriptionally active HERV-K genes, expression status was examined by RT-PCR and sequence analysis of mRNA from various tissues. In addition to the detection of IDDMK(1,2)22/HERV-K18 expression in peripheral leukocytes, three novel members of the family, which are expressed in multiple tissues, were identified. The novel HERV-K genes (HGMW-approved symbols ERVK4 and ERVK5) were isolated from a BAC library using oligonucleotide probes and assigned by RH mapping to chromosomal regions 3q21-q25.2, 3cen-q13, and 1q21-q23. Although their expression could not be confirmed in any normal tissues by Northern blot analysis, substantial promoter activity of their 5' LTRs was demonstrated in luciferase assays using teratocarcinoma cell lines. Thus, they seem to have the potential to be actively transcribed. The results, combined with those of the expression analysis by RT-PCR and subsequent sequencing of cloned products, also suggest that LTR sequences with subtle base changes might play a role in gene regulation, such as tissue specificity of HERV-K expression.
[show abstract][hide abstract] ABSTRACT: To investigate the possible involvement of IDDMK1,2 22/HERV-K18 in childhood type I diabetes mellitus, we identified two nonsynonymous A/G polymorphisms in the superantigen-coding region of IDDMK1,2 22 at the 290- and 461-nucleotide (nt) positions from the initial methionine codon and compared their frequencies in 74 Japanese patients with type 1 diabetes and in 54 nondiabetic controls. Although the G substitution was observed more frequently at either site in the patients than it was in the controls (7% vs. 4% at 290 nt, and 29% vs. 20% at 461 nt), the differences were not statistically significant. A weak significance of difference in the frequency of 461G was obtained only in an early-onset group of patients manifesting the disease at 5 years of age or less (n = 24) when compared with controls (38% vs. 20%; P = 0.03). However, in addition to the common absence of a particular allele among the expected four alleles, remarkable differences in allele frequencies were present between Japanese and European populations. This first trial investigating the association of IDDMK1,12 22 with type 1 diabetes presents intriguing suggestions for the role of this region in the etiology of autoimmune and infectious diseases.
Journal of Human Genetics 02/2001; 46(12):712-6. · 2.37 Impact Factor
[show abstract][hide abstract] ABSTRACT: To elucidate possible physiological functions of human endogenous retroviruses (HERVs) and their role in the pathogenesis of human diseases, we have developed a strategy to identify transcriptionally active HERV genes. By this approach, we have identified and isolated an active HERV-E gene that was mapped to 17q11. Although the gene was predicted to produce no intact viral particles due to the presence of stop codons, long open reading frames were retained in each gag and pol region. Northern blot analyses revealed in the pancreas (and thyroid) two major transcripts, 3.3 and 4.1 kb in size, associated with 500- to 600-nucleotide-longer minor bands. Preferential expression in pancreas and thyroid gland tissues may suggest a role for this gene in physiological functions common to these tissues.
Journal of Human Genetics 02/2001; 46(11):619-25. · 2.37 Impact Factor