The lack of Tex44 causes severe subfertility with flagellar abnormalities in male mice

By analyzing a mouse Interspecific Recombinant Congenic Strain (IRCS), we previously identified a quantitative trait locus (QTL), called Mafq1 on mouse chromosome 1, that is associated with male hypofertility and ultrastructural sperm abnormalities. Within this locus, we identified a new candidate gene that could be implicated in a reproductive phenotype: Tex44 (Testis-expressed protein 44). We thus performed a CRISPR/Cas9-mediated complete deletion of this gene in mice in order to study its function. Tex44-KO males were severely hypofertile in vivo and in vitro due to a drastic reduction of sperm motility which itself resulted from important morphological sperm abnormalities. Namely, Tex44-KO sperm showed a disorganized junction between the midpiece and the principal piece of the flagellum, leading to a 180° flagellar bending in this region. In addition, the loss of some axonemal microtubule doublets and outer dense fibers in the flagellum's principal piece has been observed. Our results suggest that, in mice, TEX44 is implicated in the correct set-up of the sperm flagellum during spermiogenesis and its absence leads to flagellar abnormalities and consequently to severe male hypofertility.

Oocyte ERM and EWI Proteins Are Involved in Mouse Fertilization

In mammalian fertilization, the link between the oocyte plasma membrane and underneath cytoskeleton has often been associated to key elements of successful gamete fusion, like microvilli shaping or CD9 function, but its effective role has poorly been studied. EWI-2 and EWI-F as cis partners of CD9, and ERM proteins (Ezrin, Radixin and Moesin) that both attach to the actin cytoskeleton and to the EWI are part of the molecules that make the link between the oocyte membrane and its cytoskeleton. This study aims to assay through siRNA inhibition, the involvement of these ERM and EWI molecules in mouse fertilization, their role in the microvilli morphology of the egg but also their possible contribution to the cortical tension, a parameter that reflects the mechanical behavior of the oocyte cortex. Whereas inhibiting separately the expression of each protein had no effect on fertilization, the combined inhibition of either EWI-2/EWI-F or the three ERM triggered a significant decrease of the fertilization index. This inhibition seems to correlate with an increase in the radius of curvature of the oocyte microvilli. It also causes a decrease of the oocyte cortical tension. These results show the importance of EWI-2 and EWI–F and ERM proteins in the smooth running of a fertilization event and support their involvement in the microvilli architecture of the oocyte and in its mechanical properties.

Identification of a New QTL Region on Mouse Chromosome 1 Responsible for Male Hypofertility: Phenotype Characterization and Candidate Genes

Male fertility disorders often have their origin in disturbed spermatogenesis, which can be induced by genetic factors. In this study, we used interspecific recombinant congenic mouse strains (IRCS) to identify genes responsible for male infertility. Using ultrasonography, in vivo and in vitro fertilization (IVF) and electron microscopy, the phenotyping of several IRCS carrying mouse chromosome 1 segments of Mus spretus origin revealed a decrease in the ability of sperm to fertilize. This teratozoospermia included the abnormal anchoring of the acrosome to the nucleus and a persistence of residual bodies at the level of epididymal sperm midpiece. We identified a quantitative trait locus (QTL) responsible for these phenotypes and we have proposed a short list of candidate genes specifically expressed in spermatids. The future functional validation of candidate genes should allow the identification of new genes and mechanisms involved in male infertility.

Partial Sperm beta1 Integrin Subunit Deletion Proves its Involvement in Mouse Gamete Adhesion/Fusion

We have previously shown, using antibodies, that the sperm alpha6beta1 integrin is involved in mouse gamete fusion in vitro. Here we report the conditional knockdown of the sperm Itgb1 gene. It induced a drastic failure of sperm fusogenic ability with sperm accumulation in the perivitelline space of in vitro inseminated oocytes deleted or not for the Itgb1 gene. These data demonstrate that sperm, but not oocyte, beta1 integrin subunit is involved in gamete adhesion/fusion. Curiously, knockdown males were fertile in vivo probably because of the incomplete Cre-mediated deletion of the sperm Itgb1 floxed gene. Indeed, this was shown by Western blot analysis and confirmed by both the viability and litter size of pups obtained by mating partially sperm Itgb1 deleted males with females producing completely deleted Itgb1 oocytes. Because of the total peri-implantation lethality of Itgb1 deletion in mice, we assume that sperm that escaped the Itgb1 excision seemed to be preferentially used to fertilize in vivo. Here, we showed for the first time that the deletion, even partial, of the sperm Itgb1 gene makes the sperm unable to normally fertilize oocytes. However, to elucidate the question of the essentiality of its role during fertilization, further investigations using a mouse expressing a recombinase more effective in male germ cells are necessary.

FOXD1 mutations are related to repeated implantation failure, intra-uterine growth restriction and preeclampsia

Background

Human reproductive disorders consist of frequently occurring dysfunctions including a broad range of phenotypes affecting fertility and women’s health during pregnancy. Several female-related diseases have been associated with hypofertility/infertility phenotypes, such as recurrent pregnancy loss (RPL). Other occurring diseases may be life-threatening for the mother and foetus, such as preeclampsia (PE) and intra-uterine growth restriction (IUGR). FOXD1 was defined as a major molecule involved in embryo implantation in mice and humans by regulating endometrial/placental genes. FOXD1 mutations in human species have been functionally linked to RPL’s origin.

Methods

FOXD1 gene mutation screening, in 158 patients affected by PE, IUGR, RPL and repeated implantation failure (RIF), by direct sequencing and bioinformatics analysis. Plasmid constructs including FOXD1 mutations were used to perform in vitro gene reporter assays.

Results

Nine non-synonymous sequence variants were identified. Functional experiments revealed that p.His267Tyr and p.Arg57del led to disturbances of promoter transcriptional activity (C3 and PlGF genes). The FOXD1 p.Ala356Gly and p.Ile364Met deleterious mutations (previously found in RPL patients) have been identified in the present work in women suffering PE and IUGR.

Conclusions

Our results argue in favour of FOXD1 mutations’ central role in RPL, RIF, IUGR and PE pathogenesis via C3 and PlGF regulation and they describe, for the first time, a functional link between FOXD1 and implantation/placental diseases. FOXD1 could therefore be used in clinical environments as a molecular biomarker for these diseases in the near future.

Keywords

Recurrent pregnancy loss, Preeclampsia, Intra-uterine growth restriction, FOXD1

Electronic supplementary material

The online version of this article (10.1186/s10020-019-0104-3) contains supplementary material, which is available to authorized users.

IFPA meeting 2014 workshop report: Animal models to study pregnancy pathologies; new approaches to study human placental exposure to xenobiotics; biomarkers of pregnancy pathologies; placental genetics and epigenetics; the placenta and stillbirth and fetal growth restriction

Workshops are an important part of the IFPA annual meeting as they allow for discussion of specialized topics. At IFPA meeting 2014 there were six themed workshops, five of which are summarized in this report. These workshops related to various aspects of placental biology but collectively covered areas of animal models, xenobiotics, pathological biomarkers, genetics and epigenetics, and stillbirth and fetal growth restriction.

Nitroso-redox balance and mitochondrial homeostasis are regulated by STOX1, a pre-eclampsia-associated gene

AIMS

Storkhead box 1 (STOX1) is a winged-helix transcription factor that is implicated in the genetic forms of a high-prevalence human gestational disease, pre-eclampsia. STOX1 overexpression confers pre-eclampsia-like transcriptomic features to trophoblastic cell lines and pre-eclampsia symptoms to pregnant mice. The aim of this work was to evaluate the impact of STOX1 on free radical equilibrium and mitochondrial function, both in vitro and in vivo.

RESULTS

Transcriptome analysis of STOX1-transgenic versus nontransgenic placentas at 16.5 days of gestation revealed alterations of mitochondria-related pathways. Placentas overexpressing STOX1 displayed altered mitochondrial mass and were severely biased toward protein nitration, indicating nitroso-redox imbalance in vivo. Trophoblast cells overexpressing STOX1 displayed an increased mitochondrial activity at 20% O2 and in hypoxia, despite reduction of the mitochondrial mass in the former. STOX1 overexpression is, therefore, associated with hyperactive mitochondria, resulting in increased free radical production. Moreover, nitric oxide (NO) production pathways were activated, resulting in peroxynitrite formation. At low oxygen pressure, STOX1 overexpression switched the free radical balance from reactive oxygen species (ROS) to reactive nitrogen species (RNS) in the placenta as well as in a trophoblast cell line.

INNOVATION

In pre-eclamptic placentas, NO interacts with ROS and generates peroxynitrite and nitrated proteins as end products. This process will deprive the maternal organism of NO, a crucial vasodilator molecule.

CONCLUSION

Our data posit STOX1 as a genetic switch in the ROS/RNS balance and suggest an explanation for elevated blood pressure in pre-eclampsia.

The Gpr1/Zdbf2 locus provides new paradigms for transient and dynamic genomic imprinting in mammals

Many loci maintain parent-of-origin DNA methylation only briefly after fertilization during mammalian development. Whether this form of transient genomic imprinting could functionally impact mammalian genome regulation is unknown. Here, Duffié et al. describe a mechanism by which a transient maternal imprint at the mouse Gpr1/Zdbf2 locus regulates the paternal-specific expression of long isoforms of Zdbf2 (Liz) in the early embryo. This study demonstrates the potential for short-term and long-term effects of genomic imprinting on mammalian genome regulation.

Many loci maintain parent-of-origin DNA methylation only briefly after fertilization during mammalian development: Whether this form of transient genomic imprinting can impact the early embryonic transcriptome or even have life-long consequences on genome regulation and possibly phenotypes is currently unknown. Here, we report a maternal germline differentially methylated region (DMR) at the mouse Gpr1/Zdbf2 (DBF-type zinc finger-containing protein 2) locus, which controls the paternal-specific expression of long isoforms of Zdbf2 (Liz) in the early embryo. This DMR loses parental specificity by gain of DNA methylation at implantation in the embryo but is maintained in extraembryonic tissues. As a consequence of this transient, tissue-specific maternal imprinting, Liz expression is restricted to the pluripotent embryo, extraembryonic tissues, and pluripotent male germ cells. We found that Liz potentially functions as both Zdbf2-coding RNA and cis-regulatory RNA. Importantly, Liz-mediated events allow a switch from maternal to paternal imprinted DNA methylation and from Liz to canonical Zdbf2 promoter use during embryonic differentiation, which are stably maintained through somatic life and conserved in humans. The Gpr1/Zdbf2 locus lacks classical imprinting histone modifications, but analysis of mutant embryonic stem cells reveals fine-tuned regulation of Zdbf2 dosage through DNA and H3K27 methylation interplay. Together, our work underlines the developmental and evolutionary need to ensure proper Liz/Zdbf2 dosage as a driving force for dynamic genomic imprinting at the Gpr1/Zdbf2 locus.

Trophoblasts, invasion, and microRNA

MicroRNAs (miRNAs) have recently become essential actors in various fields of physiology and medicine, especially as easily accessible circulating biomarkers, or as modulators of cell differentiation. To this respect, terminal differentiation of trophoblasts (the characteristic cells of the placenta in Therian mammals) into syncytiotrophoblast, villous trophoblast, or extravillous trophoblast constitutes a good example of such a choice, where miRNAs have recently been shown to play an important role. The aim of this review is to provide a snapshot of what is known today in placentation mechanisms that are mediated by miRNA, under the angles of materno–fetal immune dialog regulation, trophoblast differentiation, and angiogenesis at the materno–fetal interface. Also, two aspects of regulation of these issues will be highlighted: the part played by oxygen concentration and the specific function of imprinted genes in the developing placenta.

miR-34a expression, epigenetic regulation, and function in human placental diseases

Preeclampsia (PE) is the major pregnancy-induced hypertensive disorder responsible for maternal and fetal morbidity and mortality that can be associated with intrauterine growth restriction (IUGR). PE and IUGR are thought to be due to a placental defect, occurring early during pregnancy. Several placental microRNAs (miRNAs) have been shown to be deregulated in the context of placental diseases and could thus play a role in the pathophysiology of PE. Here, we show that pri-miR-34a is overexpressed in preeclamptic placentas and that its placental expression is much higher during the first trimester of pregnancy than at term, suggesting a possible developmental role. We explored pri-miR-34a regulation and showed that P53, a known activator of miR-34a, is reduced in all pathological placentas and that hypoxia can induce pri-miR-34a expression in JEG-3 cells. We also studied the methylation status of the miR-34a promoter and revealed hypomethylation in all preeclamptic placentas (associated or not with IUGR), whereas hypoxia induced a hypermethylation in JEG-3 cells at 72 h. Despite the overexpression of pri-miR-34a in preeclampsia, there was a striking decrease of the mature miR-34a in this condition, suggesting preeclampsia-driven alteration of pri-miR-34a maturation. SERPINA3, a protease inhibitor involved in placental diseases, is elevated in IUGR and PE. We show here that miR-34a overexpression in JEG-3 downregulates SERPINA3. The low level of mature miR-34a could thus be an important mechanism contributing to SERPINA3 upregulation in placental diseases. Overall, our results support a role for miR-34a in the pathophysiology of preeclampsia, through deregulation of the pri-miRNA expression and its altered maturation.

Preeclampsia-like symptoms induced in mice by fetoplacental expression of STOX1 are reversed by aspirin treatment

Preeclampsia (PE) is a common human-specific pregnancy disorder defined by hypertension and proteinuria during gestation and responsible for maternal and fetal morbimortality. STOX1, encoding a transcription factor, was the first gene associated with PE as identified by positional cloning approaches. Its overexpression in choriocarcinoma cells mimics the transcriptional consequences of PE in the human placenta. Here, we created transgenic mouse strains overexpressing human STOX1. Wild-type female mice crossed with transgenic male mice reproduce accurately the symptoms of severe PE: gestational hypertension, proteinuria, and elevated plasma levels of soluble fms-like tyrosine kinase 1 and soluble endoglin. Placental and kidney histology were altered. Symptoms were prevented or alleviated by aspirin treatment. STOX1-overexpressing mice constitute a unique model for studying PE, allow testing therapeutic approaches, and assessing the long-term effects of the preeclamptic syndrome.

EG-VEGF controls placental growth and survival in normal and pathological pregnancies: case of fetal growth restriction (FGR)

Identifiable causes of fetal growth restriction (FGR) account for 30 % of cases, but the remainders are idiopathic and are frequently associated with placental dysfunction. We have shown that the angiogenic factor endocrine gland-derived VEGF (EG-VEGF) and its receptors, prokineticin receptor 1 (PROKR1) and 2, (1) are abundantly expressed in human placenta, (2) are up-regulated by hypoxia, (3) control trophoblast invasion, and that EG-VEGF circulating levels are the highest during the first trimester of pregnancy, the period of important placental growth. These findings suggest that EG-VEGF/PROKR1 and 2 might be involved in normal and FGR placental development. To test this hypothesis, we used placental explants, primary trophoblast cultures, and placental and serum samples collected from FGR and age-matched control women. Our results show that (1) EG-VEGF increases trophoblast proliferation ([(3)H]-thymidine incorporation and Ki67-staining) via the homeobox-gene, HLX (2) the proliferative effect involves PROKR1 but not PROKR2, (3) EG-VEGF does not affect syncytium formation (measurement of syncytin 1 and 2 and β hCG production) (4) EG-VEGF increases the vascularization of the placental villi and insures their survival, (5) EG-VEGF, PROKR1, and PROKR2 mRNA and protein levels are significantly elevated in FGR placentas, and (6) EG-VEGF circulating levels are significantly higher in FGR patients. Altogether, our results identify EG-VEGF as a new placental growth factor acting during the first trimester of pregnancy, established its mechanism of action, and provide evidence for its deregulation in FGR. We propose that EG-VEGF/PROKR1 and 2 increases occur in FGR as a compensatory mechanism to insure proper pregnancy progress.

A genome-wide approach reveals novel imprinted genes expressed in the human placenta

Genomic imprinting characterizes genes with a monoallelic expression, which is dependent on the parental origin of each allele. Approximately 150 imprinted genes are known to date, in humans and mice but, though computational searches have tried to extract intrinsic characteristics of these genes to identify new ones, the existing list is probably far from being comprehensive. We used a high-throughput strategy by diverting the classical use of genotyping microarrays to compare the genotypes of mRNA/cDNA vs. genomic DNA to identify new genes presenting monoallelic expression, starting from human placental material. After filtering of data, we obtained a list of 1,082 putative candidate monoallelic SNPs located in more than one hundred candidate genes. Among these, we found known imprinted genes, such as IPW, GRB10, INPP5F and ZNF597, which contribute to validate the approach. We also explored some likely candidates of our list and identified seven new imprinted genes, including ZFAT, ZFAT-AS1, GLIS3, NTM, MAGI2, ZC3H12Cand LIN28B, four of which encode zinc finger transcription factors. They are, however, not imprinted in the mouse placenta, except for Magi2. We analyzed in more details the ZFAT gene, which is paternally expressed in the placenta (as ZFAT-AS1, a non-coding antisense RNA) but biallelic in other tissues. The ZFAT protein is expressed in endothelial cells, as well as in syncytiotrophoblasts. The expression of this gene is, moreover, downregulated in placentas from complicated pregnancies. With this work we increase by about 10% the number of known imprinted genes in humans.

Genetic and epigenetic mechanisms collaborate to control SERPINA3 expression and its association with placental diseases

SERPINA3 (Serpin peptidase inhibitor clade A member 3), also known as a1-antichymotrypsin, is a serine protease inhibitor involved in a wide range of biological processes. Recently, it has been shown to be up-regulated in human placental diseases in association with a hypomethylation of the 5' region of the gene. In the present study, we show that the promoter of SERPINA3 is transcriptionally activated by three transcription factors (TFs) (SP1, MZF1 and ZBTB7B), the level of induction being dependent on the rs1884082 single nucleotide polymorphism (SNP) located inside the promoter, the T allele being consistently induced to a higher level than the G, with or without added TFs. When the promoter was methylated, the response to ZBTB7B was allele specific (the G allele was strongly induced, while the T allele was strongly down-regulated). We propose an adaptive model to explain the interest of such a regulation for placental function and homeostasis. Overexpression of SERPINA3 in JEG-3 cells, a trophoblast cell model, decreased cell adhesion to the extracellular matrix and to neighboring cells, but protects them from apoptosis, suggesting a way by which this factor could be deleterious at high doses. In addition, we show in different human populations that the T allele appears to predispose to Intra Uterine Growth Restriction (IUGR), while a G allele at a second SNP located in the second exon (rs4634) increases the risk of preeclampsia. Our results provide mechanistic views inside the involvement of SERPINA3 in placental diseases, through its regulation by a combination of epigenetic, genetic and TF-mediated regulations.

The intensity of IUGR-induced transcriptome deregulations is inversely correlated with the onset of organ function in a rat model

A low-protein diet applied during pregnancy in the rat results in intrauterine growth restricted (IUGR) fetuses. In humans, IUGR is associated with increased perinatal morbidity, higher incidence of neuro-developmental defects and increased risk of adult metabolic anomalies, such as diabetes and cardiovascular disease. Development and function of many organs are affected by environmental conditions such as those inducing fetal and early postnatal growth restriction. This phenomenon, termed "fetal programming" has been studied unconnectedly in some organs, but very few studies (if any) have investigated at the same time several organs, on a more comparative basis. However, it is quite probable that IUGR affects differentially most organ systems, with possible persistent changes in gene expression. In this study we address transcriptional alterations induced by IUGR in a multi-organ perspective, by systematic analysis of 20-days rat fetuses. We show that (1) expressional alterations are apparently stronger in organs functioning late in foetal or postnatal life than in organs that are functioning early (2) hierarchical classification of the deregulations put together kidney and placenta in one cluster, liver, lungs and heart in another; (3) the epigenetic machinery is set up especially in the placenta, while its alterations are rather mild in other organs; (4) the genes appear deregulated in chromosome clusters; (5) the altered expression cascades varies from organ to organ, with noticeably a very significant modification of the complement and coagulation cascades in the kidney; (6) we found a significant increase in TF binding site for HNF4 proteins specifically for liver genes that are down-regulated in IUGR, suggesting that this decrease is achieved through the action of HNF transcription factors, that are themselves transcriptionnally induced in the liver by IUGR (x 1.84 fold). Altogether, our study suggests that a combination of tissue-specific mechanisms contributes to bring about tissue-driven modifications of gene cascades. The question of these cascades being activated to adapt the organ to harsh environmental condition, or as an endpoint consequence is still raised.

Combination of promoter hypomethylation and PDX1 overexpression leads to TBX15 decrease in vascular IUGR placentas

Preeclampsia (PE) and vascular intra-uterine growth restriction (vIUGR) are two pathological obstetrical conditions originating from placental dysfunction. Recently, methylation changes at the placental level have been shown to be indicative of these diseases. The alteration of such epigenetic marks is therefore a novel pathway that might be critical for these pathologies. Here, we identified a region located in the distal promoter of the T-box-containing transcription factor TBX15 that is differentially methylated in pathological placentas. The level of methylation correlated significantly with the weight and stature of the newborn. The promoter was found to be hypomethylated in vIUGR coinciding with the down-regulation of its expression. PDX1, a transcription factor important for the regulation of insulin metabolism regulation was able to repress the TBX15 promoter in a methylation-dependent manner, which might, at least partially, explain the specific mRNA decrease of TBX15 observed in vIUGR placentas. Overall, the data presented herein suggest that TBX15 might be involved in the pathophysiology of placental diseases.

Research resource: genome-wide profiling of methylated promoters in endometriosis reveals a subtelomeric location of hypermethylation

Several lines of evidence indicate that endometriosis could be partially due to selective epigenetic deregulations. Promoter hypermethylation of some key genes, such as progesterone receptor and aromatase, has been associated with the silencing of these genes and might contribute to the disease. However, it is unknown whether global alterations in DNA methylation patterns occur in endometriosis and to what extent they are involved in its pathogenesis. We conducted a whole-genome scanning of methylation status in more than 25,000 promoters, using methylated DNA immunoprecipitation with hybridization to promoter microarrays. We detailed the methylation profiles for each subtype of the disease (superficial endometriosis, endometriomas, and deep infiltrating endometriosis) and compared them with the profile obtained for the eutopic endometrium. In line with the current theory of the endometrial origin of endometriosis, the overall methylation profile was highly similar between the endometrium and the lesions. It showed promoter regions consistently hypomethylated or hypermethylated (more than 1.5-times, as compared with endometrium) and others specific to one given subtype. Albeit there was no systematic correlation between promoter methylation and expression of nearby genes, 35 genes had both methylation and expressional alterations in the lesions. These genes, reported here for the first time, might be of interest in the development of endometriosis. In addition, hypermethylated regions were located at the ends of the chromosomes, whereas hypomethylated regions were randomly distributed all along the chromosomes. We postulated that this original observation might participate to the chromosomal stability and protect the endometriotic lesion against malignancy.

In vitro fertilization and embryo culture strongly impact the placental transcriptome in the mouse model

Background

Assisted Reproductive Technologies (ART) are increasingly used in humans; however, their impact is now questioned. At blastocyst stage, the trophectoderm is directly in contact with an artificial medium environment, which can impact placental development. This study was designed to carry out an in-depth analysis of the placental transcriptome after ART in mice.

Methodology/Principal Findings

Blastocysts were transferred either (1) after in vivo fertilization and development (control group) or (2) after in vitro fertilization and embryo culture. Placentas were then analyzed at E10.5. Six percent of transcripts were altered at the two-fold threshold in placentas of manipulated embryos, 2/3 of transcripts being down-regulated. Strikingly, the X-chromosome harbors 11% of altered genes, 2/3 being induced. Imprinted genes were modified similarly to the X. Promoter composition analysis indicates that FOXA transcription factors may be involved in the transcriptional deregulations.

Conclusions

For the first time, our study shows that in vitro fertilization associated with embryo culture strongly modify the placental expression profile, long after embryo manipulations, meaning that the stress of artificial environment is memorized after implantation. Expression of X and imprinted genes is also greatly modulated probably to adapt to adverse conditions. Our results highlight the importance of studying human placentas from ART.

STOX1 overexpression in choriocarcinoma cells mimics transcriptional alterations observed in preeclamptic placentas

BACKGROUND

Mutations in STOX1 were proposed to be causal for predisposing to preeclampsia, a hypertensive disorder originating from placental defects, affecting up to 10% of human pregnancies. However, after the first study published in 2005 three other groups have dismissed the polymorphism described in the first paper as a causal mutation.

METHODOLOGY AND PRINCIPAL FINDINGS

In the present study, we have produced a choriocarcinoma cell line overexpressing STOX1. This overexpression results in transcriptional modification of 12.5% of the genes, some of them being direct targets as shown by chromatin immunoprecipitation. STOX1 overexpression correlates strongly and specifically with transcriptomic alterations in preeclamptic placentas (r = 0.30, p = 9.10(-7)). Numerous known key modulators of preeclampsia (such as Endoglin, Syncytin, human chorionic gonadotrophin -hCG-, and Glial Cell Missing Homolog -GCM1-) were modified in these transformed choriocarcinoma cells.

CONCLUSIONS

Our results contribute to reconcile contradictory data concerning the involvement of STOX1 in preeclampsia. In addition, they strongly suggest that anomalies in STOX1 expression are associated with the onset of preeclampsia, thus indicating that this gene should be the target of future studies. Our cellular model could constitute an invaluable resource for studying specific aspects of this human disease.

Polymorphisms in 33 inflammatory genes and risk of myocardial infarction--a system genetics approach

The hypothesis of a causal link between inflammation and atherosclerosis would be strengthened if variants of inflammatory genes were associated with disease. Polymorphisms of 33 genes encoding inflammatory molecules were tested for association with myocardial infarction (MI). Patients with MI and a parental history of MI (n = 312) and controls from the UK (n = 317) were genotyped for 162 polymorphisms. Thirteen polymorphisms were associated with MI (P values ranging from 0.003 to 0.041). For three genes, ITGB1, SELP, and TNFRSF1B haplotype frequencies differed between patients and controls (P values < 0.01). We further assessed the simultaneous contribution of all polymorphisms and relevant covariates to MI using a two-step strategy of data mining relying on Random Forest and DICE algorithms. In a replication study involving two independent samples from the UK (n = 649) and France (n = 706), one interaction between the ITGA4/R898Q polymorphism and current smoking status was replicated. This study illustrates a strategy for assessing the joint effect of a large number of polymorphisms on a phenotype that may provide information that single locus or single gene analysis may fail to uncover. Overall, there was weak evidence for an implication of inflammatory polymorphisms on susceptibility to MI.

Differential haplotypic expression of the interleukin-18 gene

Interleukin 18 (IL-18) is suspected to play an important role in atherosclerosis and plaque vulnerability. We had previously shown that haplotypes combining two IL18 gene polymorphisms in complete linkage disequilibrium, C-105T (rs360717) in 5'-untranslated region (UTR) and A+183G (rs5744292) in 3'-UTR, were related to IL-18 circulating levels and cardiovascular outcome, the C(-105) G(+183) haplotype being associated with lower IL-18 levels and lower cardiovascular risk. This study was aimed at investigating the functional role of the two polymorphisms and their haplotypes on IL18 expression levels. Allelic imbalance experiments conducted in 24 and 20 subjects heterozygous for the C-105T and the A+183G polymorphisms did not detect any difference when subjects were considered as a whole (-0.009+/-0.044, P=0.85 and +0.114+/-0.082, P=0.18, respectively). However, when splitting individuals according to their haplo-genotype, the haplotype C(-105) G(+183) was associated with a lower expression level than C(-105) A(+183) (-0.287+/-0.076, P=0.005), but did not differ from T(-105) A(+183) (-0.138+/-0.083, P=0.13). The lower expression associated with C(-105) G(+183) was confirmed by real-time reverse transcription-PCR. Transfection of different haplotypic versions of the 3'-UTR did not show any difference in the expression of an upstream reporter gene. A 10-h study of the mRNA degradation kinetics by allelic imbalance with the A+183G polymorphism did not show any differential allelic degradation. In conclusion, the haplotype associated with lower IL-18 circulating concentrations and a lower cardiovascular risk was consistently associated with decreased IL18 expression levels, although the exact functional mechanisms remain to be elucidated.

Haplotypes of the Caspase-1 Gene, Plasma Caspase-1 Levels, and Cardiovascular Risk

Caspase-1 processes the interleukin (IL)-1beta and IL-18 inactive precursors to the biologically active cytokines that are known to have proatherogenic effects. The present study investigated the genetic variability of the CASP1 gene and plasma levels of caspase-1 in relation to cardiovascular risk. In Europeans, 3 tag SNPs captured 4 common haplotypes of the CASP1 gene. Among these, the A(in6) allele of the G+7/in6A polymorphism was less frequent in 246 cases with myocardial infarction and a parental history of disease than in 253 controls free of familial history of disease (0.13+/-0.02 versus 0.20+/-0.02; P=0.005). However, in a larger case/control study (n=1774), these effects are borderline restricted to the UK population. In a prospective cohort of 1168 patients with coronary artery disease followed up during a median period of 6.0 years, the A(in6) allele exhibited a borderline association with future cardiovascular death (hazard ratio [HR]: 0.64, 0.41 to 1.01; P=0.053) and was associated with lower serum IL-18 levels (P=0.014). Baseline caspase-1 levels in the top quartile of the distribution were predictive of cardiovascular deaths (HR=3.62, 1.81 to 7.27; P=0.0003 compared with the bottom quartile). Finally, in vitro assays of allelic imbalance showed that the CASP1 haplotype carrying the A(in6) allele was associated with a lower mRNA expression. These results indicate that caspase-1 levels are predictive of future cardiovascular death in patients with coronary artery disease. The role of CASP1 genetic variations in the susceptibility to myocardial infarction requires further investigation.

Genetic analysis of the interleukin-18 system highlights the role of the interleukin-18 gene in cardiovascular disease

BACKGROUND

Interleukin (IL)-18 plays a key role in atherosclerosis and its complications. The present study investigated the genetic variability of 4 genes of the IL-18 system-IL18, IL18R1, IL18RAP, and IL18BP-in relation to circulating IL-18 levels and cardiovascular mortality.

METHODS AND RESULTS

Twenty-two polymorphisms were genotyped in 1288 patients with coronary artery disease prospectively followed up during a median period of 5.9 years. The end point was death from cardiovascular causes (n=142). Baseline IL-18 levels were predictive of cardiovascular deaths occurring during < or =4 years of follow-up (HR=2.96, 95% CI 1.54 to 5.70, P=0.001 for the top compared with the bottom quartile) but not of later deaths. Haplotypes of the IL18 gene were associated with IL-18 levels (P=0.002) and cardiovascular mortality (P=0.006) after adjustment for cardiovascular risk factors. The same haplotype was associated with both a 9% lowering effect on IL-18 levels and a protective effect on risk (HR=0.57, 95% CI 0.36 to 0.92). IL18 haplotypes explained only 2% of IL-18 variability. Adjustment for baseline IL-18 levels abolished the association of haplotypes with cardiovascular risk. The haplotype associated with phenotypes was the only one carrying the minor allele of the IL18/A+183G polymorphism located in the 3'untranslated region and potentially affecting mRNA stability. The other genes of the system were not related to IL-18 levels or cardiovascular outcome.

CONCLUSIONS

Variations of the IL18 gene consistently influence circulating levels of IL-18 and clinical outcome in patients with coronary artery disease, which supports the hypothesis of a causal role of IL-18 in atherosclerosis and its complications.

The human T locus and spina bifida risk

The transcription factor T is essential for mesoderm formation and axial development during embryogenesis. Embryonic genotype for a single-nucleotide polymorphism in intron 7 of T ( TIVS7 T/C) has been associated with the risk of spina bifida in some but not all studies. We developed a novel genotyping assay for the TIVS7 polymorphism using heteroduplex generator methodology. This assay was used to genotype spina bifida case-parent trios and the resulting data were analyzed using the transmission disequilibrium test and log-linear analyses. Analyses of these data demonstrated that heterozygous parents transmit the TIVS7-C allele to their offspring with spina bifida significantly more frequently than expected under the assumption of Mendelian inheritance (63 vs 50%, P=0.02). Moreover, these analyses suggest that the TIVS7-C allele acts in a dominant fashion, such that individuals carrying one or more copies of this allele have a 1.6-fold increased risk of spina bifida compared with individuals with zero copies. In silico analysis of the sequence surrounding this polymorphism revealed a potential target site for olfactory neuron-specific factor-1, a transcription factor expressed in the neural tube during development, spanning the polymorphic site. Several other putative, developmentally important and/or environmentally responsive transcription factor-binding sites were also identified close to the TIVS7 polymorphism. The TIVS7 polymorphism or a variant that is in linkage disequilibrium with the TIVS7 polymorphism may, therefore, play a role in T gene expression and influence the risk of spina bifida.

SELPLG gene polymorphisms in relation to plasma SELPLG levels and coronary artery disease

P-selectin and P-selectin glycoprotein ligand (SELPLG, selectin P ligand) constitute a receptor/ligand complex that is likely to be involved in the development of atherosclerosis and its complications. While the genetic variability of P-selectin has already been investigated in depth, that of the SELPLG gene has not yet been extensively explored. The coding and regulatory sequences of the SELPLG were screened and nine polymorphisms were identified. The identified polymorphisms were genotyped in the AtheroGene study, a case-control study of coronary artery disease (CAD). Haplotype analysis revealed that two polymorphisms of SELPLG, the M62I and the VNTR, independently influenced plasma SELPLG levels. Conversely, haplotypes of SELPLG were not associated with CAD risk.

Adhesion molecules and atherosclerosis

One early phase of atherosclerosis involves the recruitment of inflammatory cells from the circulation and their transendothelial migration. This process is predominantly mediated by cellular adhesion molecules, which are expressed on the vascular endothelium and on circulating leukocytes in response to several inflammatory stimuli. Selectins (P, E and L) and their ligands (mainly P-selectin ligand) are involved in the rolling and tethering of leukocytes on the vascular wall. Intercellular adhesion molecules (ICAMs) and vascular cell adhesion molecules (VCAM-1), as well as some of the integrins, induce firm adhesion of inflammatory cells at the vascular surface, whereas platelet endothelial cellular adhesion molecules (PECAM-1) are involved in extravasation of cells from the blood compartment into the vessel and underlying tissue. For most of the cellular adhesion molecules, except integrins, soluble forms have been identified in the circulation although their origins are not fully understood. Several lines of evidence support a crucial role of adhesion molecules in the development of atherosclerosis and plaque instability. Expression of VCAM-1, ICAM-1 and L-selectin has been consistently observed in atherosclerotic plaques. There is accumulating evidence from prospective studies for a predictive role of elevated circulating levels of sICAM-1 in initially healthy people, and of sVCAM-1 in patients at high risk or with overt CAD. A large number of common polymorphisms has been identified in the genes encoding the different adhesion molecules, but studies investigating their relationship either with soluble forms or with CAD are still sparse and often based on small samples. Further research is needed to firmly establish the potential clinical and therapeutic utilities of (soluble) adhesion molecules, but results in both fields hold the promise that in future, adhesion molecules might add information for clinical risk prediction and serve as therapeutic targets.

Maternal genetic effects, exerted by genes involved in homocysteine remethylation, influence the risk of spina bifida

There is currently considerable interest in the relationship between variation in genes that are involved in the folate-homocysteine metabolic axis and the risk of spina bifida. The evaluation of this relationship is, however, complicated by the potential involvement of both the maternal and the embryonic genotype in determination of disease risk. The present study was designed to address questions regarding both maternal and embryonic genetic risk factors for spina bifida by use of the two-step transmission/disequilibrium test. Analysis of data on variants of two genes involved in homocysteine remethylation/methionine biosynthesis--methionine synthase (MTR) A2756G and methionine synthase reductase (MTRR) A66G--provided evidence that both variants influence the risk of spina bifida via the maternal rather than the embryonic genotype. For both variants, the risk of having a child with spina bifida appears to increase with the number of high-risk alleles in the maternal genotype: MTR (R1=2.16, 95% CI 0.92-5.06; R2=6.58, 95% CI 0.87-49.67) and MTRR (R1=2.05, 95% CI 1.05-3.99; R2=3.15, 95% CI 0.92-10.85). These findings highlight the importance of considering both the maternal and embryonic genotype when evaluating putative spina bifida susceptibility loci.

Specific haplotypes of the P-selectin gene are associated with myocardial infarction

P-selectin is a cellular adhesion molecule that may be involved in the development of atherosclerosis and its complications. We have previously identified thirteen polymorphisms of the P-selectin gene among which five were located in the coding region of the gene (S290N, N562D, V599L, T715P, T741T (A/G)). These polymorphisms were tested individually for association with myocardial infarction (MI) and only the T715P polymorphism was shown to be associated with MI. We here extend this work by performing a haplotype analysis which enables us to assess the consequences on the phenotype of the co-presence of several variants on the same chromosome. For this purpose, a new maximum likelihood method was developed for estimating simultaneously haplotype frequencies and haplotype-phenotype effects. While haplotypes defined by the polymorphisms located in the promoter region of the gene were unrelated to MI, those defined by the polymorphisms in the coding region were globally associated with MI in a sample of 582 cases and 630 controls from the Etude Cas-Témoin sur l'Infarctus du Myocarde. Detailed haplotype analysis confirmed the protective effect of the P715 allele but additionally revealed that the presence of two asparagine codons at sites S290N and N562D was associated with a higher risk of MI, consistenly in France and Northern Ireland, but only when they were carried by the same haplotype. This finding illustrates the complexity of the relationship between gene variability and disease and the necessity to explore in detail the polymorphisms of candidate genes.

Heterogeneity of linkage disequilibrium in human genes has implications for association studies of common diseases

Linkage disequilibrium (LD) is the central concept of genetic association studies. Although LD has been shown not to be uniformly distributed across the genome, limited information is available about the characteristics of LD within candidate genes at large. We screened coding and regulatory regions of 50 candidate genes for cardiovascular diseases and identified 228 polymorphisms. The overall sequence diversity was 3.81 +/- 0.31 x 10(-4). Intragenic LD was generally very strong, with 40% of the 464 pairs of polymorphisms exhibiting a complete LD. However, if we consider /D'/ = 0.7 as an arbitrary limit for useful LD in association studies, 26% of the pairs fell below this threshold, half of which being in negative LD, a situation where LD is even more difficult to detect. Non-synonymous coding polymorphisms, which are more likely to have a functional role, were more represented among low-frequency alleles and were more often in complete negative LD with other polymorphisms. This implies that in many situations the power to detect the effect of a non-synonymous polymorphism by measuring a nearby marker might be low. Although intragenic LD was partly a function of physical distance, gene-specific patterns of LD were observed, making it difficult to provide general guidelines for selecting the most useful polymorphisms in association studies. For all these reasons, association studies should concentrate on the overall sequence variation of functionally important regions of candidate genes and not only on a few polymorphisms. The variability of important intergenic regions identified by different approaches including comparative genomics will also have to be assessed.

The methionine synthase reductase (MTRR) A66G polymorphism is a novel genetic determinant of plasma homocysteine concentrations

Epidemiological evidence has revealed that an elevated plasma homocysteine level (hyperhomocysteinemia) confers an increased risk of cardiovascular disease and neural tube defects. Hyperhomocysteinemia is caused by both nutritional (e.g. folate, vitamins B(6) and B(12)) and genetic factors, including functional polymorphisms of key enzymes involved in homocysteine metabolism. One such enzyme, methionine synthase reductase (MTRR), maintains adequate levels of methylcob(III)alamin, the activated cofactor for methionine synthase, which catalyzes the remethylation of homocysteine to methionine. A common MTRR polymorphism, i.e. a 66 A-->G substitution specifying an isoleucine to methionine substitution (I22M), was recently identified. To assess the influence of this polymorphism on total plasma homocysteine (tHcy), we undertook a genotype/phenotype analysis in a study population of 601 Northern-Irish men, aged 30--49, for which biochemical and genetic data relevant to folate/homocysteine metabolism had already been acquired. The 66AA genotype has a frequency of 29% in this population. We established that there was a significant influence of MTRR genotype on tHcy ranking (P=0.004) and that the 66AA genotype contributes to a moderate increase in tHcy levels across the distribution [OR 1.59 (95% CI: 1.10--2.25) for the 66AA genotype to be in the upper half of the tHcy distribution, P=0.03]. The homocysteine-elevating effect of the 66AA genotype is independent of serum folate, vitamin B(12) and vitamin B(6) levels. Based on published estimates of the enhanced cardiovascular disease risk conferred by defined increments of plasma tHcy, we estimate that 66AA homozygotes have, on average, an approximately 4% increase in cardiovascular disease risk compared to 66GG homozygotes. This study provides the first evidence that the MTRR A66G polymorphism significantly influences the circulating tHcy concentration.

Use of degenerate oligonucleotide primed PCR (DOP-PCR) for the genotyping of low-concentration DNA samples

Degenerate oligonucleotide primed amplification (DOP-PCR) is an efficient method for performing whole genome amplification. We analysed the yield of DNA using this technique starting with various quantities of material. We used DOP-PCR products to genotype single nucleotide polymorphisms and insertion/deletion polymorphisms. DOP-PCR also proved usable for SSCP analysis.

Sex chromosome mosaicism in males carrying Y chromosome long arm deletions

Microdeletions of the long arm of the Y chromosome (Yq) are a common cause of male infertility. Since large structural rearrangements of the Y chromosome are commonly associated with a 45,XO/46,XY chromosomal mosaicism, we studied whether submicroscopic Yq deletions could also be associated with the development of 45,XO cell lines. We studied blood samples from 14 infertile men carrying a Yq microdeletion as revealed by polymerase chain reaction (PCR). Patients were divided into two groups: group 1 (n = 6), in which karyotype analysis demonstrated a 45,X/46,XY mosaicism, and group 2 (n = 8) with apparently a normal 46,XY karyotype. 45,XO cells were identified by fluorescence in-situ hybridization (FISH) using X and Y centromeric probes. Lymphocytes from 11 fertile men were studied as controls. In addition, sperm cells were studied in three oligozoospermic patients in group 2. Our results showed that large and submicroscopic Yq deletions were associated with significantly increased percentages of 45,XO cells in lymphocytes and of sperm cells nullisomic for gonosomes, especially for the Y chromosome. Moreover, two isodicentric Y chromosomes, classified as normal by cytogenetic methods, were detected. Therefore, Yq microdeletions may be associated with Y chromosomal instability leading to the formation of 45,XO cell lines.

The human and mouse methylenetetrahydrofolate reductase (MTHFR) genes: genomic organization, mRNA structure and linkage to the CLCN6 gene

Methylenetetrahydrofolate reductase (MTHFR), a pivotal enzyme in folate metabolism, regulates the proportional distribution of one-carbon moieties between cellular methylation reactions and nucleic acid synthesis. The organization of the MTHFR gene and the structure of its mRNA were characterized in human and mouse. There are three mRNA transcripts of 2.8, 7.2 and 9.8 kb in human and two of 3.2 and 7.5 kb in mouse. Northern blot analysis revealed that human MTHFR MRNA is only present at low abundance in most tissues tested. Five kilobases of sequence flanking the 3' end of the human gene were isolated, and polyadenylation sites were defined by 3' RACE. The shorter 2.8 kb transcript and the two larger 7.2 and 9.8 kb transcripts utilize different polyadenylation signal sequences, 629 and 4937 bp downstream of the stop codon, respectively. The two mRNA species in mouse also result from differential polyadenylation. Approximately 7 and 3.5 kb upstream of the human and mouse genes, respectively, were isolated and sequenced. Transcription start sites in human MTHFR were mapped using 5' RACE. The 2.8 and 7.2 kb mRNAs originate from one of two transcription start sites that are 206 and 243 bp upstream of the ATG initiation codon, whereas transcription of the 9.8 kb mRNA is initiated at a start site located 2.8 kb upstream of the translation start codon. The putative MTHFR promoter does not have a TATA box but contains CpG islands and multiple potential Sp1 binding sites. The MTHFR gene was finely mapped to interval 16 of chromosome 1p36.3, a region deleted in many tumors, by establishing a close linkage to CLCN6, a putative chloride channel gene. A novel CA-repeat polymorphism identified within intron 2 of the CLCN6 gene may be useful in assessing loss of heterozygosity in such tumors. The multiple MTHFR mRNA species identified in this report may reflect an underlying complex set of gene regulatory mechanisms acting through an alternative transcription start site and/or polyadenylation signal sequence utilization.

Accurate and rapid "multiplex heteroduplexing" method for genotyping key enzymes involved in folate/homocysteine metabolism

BACKGROUND

Hyperhomocysteinemia, which is often associated with low folate status, is an independent risk factor for cardiovascular diseases and several other pathologies. The four most common functional polymorphisms in genes involved in folate/homocysteine metabolism are methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, methionine synthase (MS) A2756G, and cystathionine beta-synthase (CBS) 844ins68. The pathogenic impact of these variants is under active investigation in many laboratories. However, conventional genotyping methods, mostly using PCR followed by restriction enzyme digestion, often are compromised by partial fragment digestion. There is, therefore, a need to develop more reliable approaches to genotyping the above polymorphisms that may be applied in large-scale studies.

METHODS

Sequence-specific heteroduplex generators for each of the MTHFR and MS single nucleotide polymorphisms were generated by site-directed mutagenesis. These were subcloned into a single construct, pHcyHG-1, which could be multiplexed with a simple PCR amplification across the CBS 844ins68 polymorphic site to generate composite genotype-specific banding patterns from individual genomic DNA samples that could be electrophoretically resolved.

RESULTS

The "multiplex heteroduplexing" method yielded unambiguous MTHFR, MS, and CBS genotypes in a single-tube reaction that could be analyzed in a single gel run.

CONCLUSIONS

This method permits unambiguous genotyping of the four most common functional variants of enzymes involved in folate/homocysteine metabolism. It is rapid, reproducible, and inexpensive, and requires no special preparative or analytic facilities; consequently, it will facilitate large-scale studies of the genetic basis of hyperhomocysteinemia and the many pathologies that have been associated with this phenotype.

Accurate and Rapid “Multiplex Heteroduplexing” Method for Genotyping Key Enzymes Involved in Folate/Homocysteine Metabolism

Background: Hyperhomocysteinemia, which is often associated with low folate status, is an independent risk factor for cardiovascular diseases and several other pathologies. The four most common functional polymorphisms in genes involved in folate/homocysteine metabolism are methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C, methionine synthase (MS) A2756G, and cystathionine β-synthase (CBS) 844ins68. The pathogenic impact of these variants is under active investigation in many laboratories. However, conventional genotyping methods, mostly using PCR followed by restriction enzyme digestion, often are compromised by partial fragment digestion. There is, therefore, a need to develop more reliable approaches to genotyping the above polymorphisms that may be applied in large-scale studies.

Methods: Sequence-specific heteroduplex generators for each of the MTHFR and MS single nucleotide polymorphisms were generated by site-directed mutagenesis. These were subcloned into a single construct, pHcyHG-1, which could be multiplexed with a simple PCR amplification across the CBS 844ins68 polymorphic site to generate composite genotype-specific banding patterns from individual genomic DNA samples that could be electrophoretically resolved.

Results: The “multiplex heteroduplexing” method yielded unambiguous MTHFR, MS, and CBS genotypes in a single-tube reaction that could be analyzed in a single gel run.

Conclusions: This method permits unambiguous genotyping of the four most common functional variants of enzymes involved in folate/homocysteine metabolism. It is rapid, reproducible, and inexpensive, and requires no special preparative or analytic facilities; consequently, it will facilitate large-scale studies of the genetic basis of hyperhomocysteinemia and the many pathologies that have been associated with this phenotype.

Polymorphisms of genes controlling homocysteine/folate metabolism and cognitive function

Elevated concentrations of the amino acid homocysteine and/or folate deficiency have been reported to affect neural development/function in both human patients and animal models. We have investigated the distribution of functional polymorphisms in genes involved in homocysteine/folate metabolism in children with high IQ and in children with average IQ. No differences in the frequencies of genetic variants in the methionine synthase or methylenetetrahydrofolate reductase genes were found. However, the cystathionine beta-synthase (CBS) 844ins68 allele was significantly underrepresented in children with high IQ. The mechanism by which a functional genetic variant in the CBS gene may influence cognitive function remains to be determined.

Ullrich-Turner syndrome: relevance of searching for Y chromosome fragments

Forty consecutive patients with Ullrich-Turner syndrome (UTS) were followed-up and investigated for the presence of Y chromosome fragments in their genomes. We used the polymerase chain reaction (PCR) to detect SRY (sex-determining region on the Y chromosome) and the sequence-tagged sites (STS) sY57, sY59, sY85, sY94, sY124 and sY157--which correspond to regions 3C (sY57 and 59), 5C, 5G, 5P, and 6F, respectively, of the Y chromosome--searching for Y fragments that could bear the putative locus (loci) for gonadoblastoma (GBY). It has been shown that the presence of GBY greatly increases the risk of dysgenic gonads to undergo malignant transformation. Among our 40 patients, we found Y-derived sequences--including SRY and the region spanning from sY57 to sY94--in two. These two patients had a marker chromosome detected by conventional cytogenetic analysis (45,X/46,X + mar). Their gonads were excised and found to be streaks. In one of the patients, we found foci of primitive sex cords (amidst the gonadal stroma), oviducts and Wolffian remnants. Fluorescence in situ hybridization (FISH) did not show Y chromosome material in her gonad-derived fibroblasts. The other girl had hyperplastic Leydig cells in the gonadal stroma, oviducts and Wolffian remnants, with signs of epididymal differentiation. PCR assays performed on DNA extracted from paraffin-embedded gonadal tissue were negative for SRY sequences in both patients. These findings show that all UTS patients should be examined for Y chromosome material, and that positive cases should have their dysgenic gonads excised due to the high risk of malignancy.

A high frequency of Y chromosome deletions in males with nonidiopathic infertility

Microdeletions of the long arm of the human Y chromosome are associated with spermatogenic failure and have been used to define three regions of Yq (AZFa, AZFb, and AZFc) that are recurrently deleted in infertile males. In a blind study we screened 131 infertile males (46 idiopathic and 85 nonidiopathic) for Y chromosome microdeletions. Nineteen percent of idiopathic males, with an apparently normal 46,XY chromosome complement had microdeletions of either the AZFa, AZFb, or AZFc region. There was no strict correlation between the extent or location of the deletion and the phenotype. The AZFb deletions did not include the active RBM gene. Significantly, a high frequency of microdeletions (7%) was found in patients with known causes of infertility and a 46,XY chromosome complement. These included deletions of the AZFb and AZFc regions, with no significant difference in the location or extent of the deletion compared with the former group. It is recommended that all males with reduced or absence sperm counts seeking assisted reproductive technologies be screened for deletions of the Y chromosome.

The human SRY protein is present in fetal and adult Sertoli cells and germ cells

Sex determination in mammals is controlled by the Y chromosome located SRY gene. Despite recent advances towards understanding the mechanisms that regulate sex determination in mammals, the expression profile of the SRY protein in human tissues is unknown. To localize the SRY protein and determine its cellular distribution, we prepared monoclonal antibodies (mAb) against the recombinant SRY protein. One antibody, LSRY1.1, recognizes a SRY-specific epitope and was used to localize the protein in different cells and tissues. The mAb recognizes a protein of 27 kDa in total lysates of HeLa SRYB3 cells. Immunocytochemical staining showed a nuclear localization of the protein. Immunohistochemical studies performed on gonadal tissue of a fetus, a one month-old boy and an adult man, demonstrated the presence of SRY protein in the nucleus of Sertoli and germ cells. In addition two 46,XX SRY(+) males had the SRY protein in their gonadal tissues. All other samples were negative, including all female tissue studied and the testis of a 46,XX SRY(-) male. The presence of SRY protein in fetal and adult gonadal tissues including germ cells suggests that SRY may have other male-specific functions in addition to sex determinism.

High frequency of well-defined Y-chromosome deletions in idiopathic Sertoli cell-only syndrome

Idiopathic Sertoli cell-only syndrome (SCOS) is characterized by azoospermia, small testes, absence of germ cells in the testes, elevated follicle stimulating hormone and normal testosterone concentrations. The Y-chromosome is involved in the regulation of spermatogenesis and in the pathogenesis of a fraction of idiopathic male infertility. An azoospermia factor (AZF) is present on the Y-chromosome long arm euchromatic region (Yq11) and two gene families (DAZ and RBM) have been identified within this region. The aim of this study was to investigate whether a specific pattern of Yq11 microdeletions may be associated with idiopathic SCOS. Eighteen idiopathic subjects showing a testicular cytological picture of bilateral SCOS were selected and tested by polymerase chain reaction for a set of 29 Y-specific sequence-tagged sites (STS). We found Yq microdeletions in 10 out of 18 patients (55.5%) while the fathers or brothers of six out of 10 patients deleted for Yq were shown to carry an intact Y-chromosome. These deletions may therefore be considered as de-novo deletions and the cause of SCOS. The analysis of the microdeletions allowed us to identify two homogeneous regions that have a high incidence of deletion. The smallest deletion, common to all patients, is located in Yq interval 5. We therefore speculate that there is a relationship between specific, well-characterized Yq11 microdeletions and a testicular picture of SCOS, identifying an Y-related region frequently deleted in this syndrome. In conclusion, the findings of this study demonstrate that a large percentage of idiopathic SCOS may be genetically determined and identify an Y-related region that seems to possess one or more still unknown genes essential for spermatogenesis.