Genomic imprinting in gestational trophoblastic disease--a review

Detection of Parental Contribution to Molar Genome Leads to Diagnosis of Recurrent Hydatidiform Mole in a Family with NLRP7 Variants

Introduction: Genetically, complete hydatidiform mole (CHM) is androgenetic diploid, containing two sets of paternal chromosomes. In most cases, recurrent HM (RHM) is CHM but has diploid biparental chromosome constitution. Case report: We report a mother with RHM, both with biparental diploidy. The mother was compound heterozygous for two variants, c.1720dup, p.(C574Lfs*4) and c.2165A > G, p.(D722G) of the NLRP7 gene, as was a brother who fathered 2 normal pregnancies. Conclusion: The genotype study should be obtained for patients of CHM, even in their first pregnancy, followed by genetic screening for maternal-effect variants in those with biparental moles. This strategy will identify patients in their first pregnancy with HM that have a decreased chance for a normal pregnancy, to allow genetic counseling, perhaps utilizing a donor egg.

Loss of X Chromosome Inactivation in Androgenetic Complete Hydatidiform Moles With 46, XX Karyotype

Most complete hydatidiform moles (CHMs) showcase an androgenetic nature of the nuclear genome. In the normal female embryo, one of the 2 X chromosomes is inactive. However, the status of X chromosome inactivation (XCI) in androgenetic CHMs remains unknown. Seventy-one androgenetic CHM tissues with the 46, XX karyotype were collected. Seventy-four normal female villi and 74 normal male villi were collected as controls. The expression of XCI markers (XIST, TSIX, and XACT) and an X-linked gene (CDX4) was detected by real-time polymerase chain reaction. Other XCI-associated genes were also examined, including the methylation status of the human androgen receptor gene (HUMARA) by methylation-specific polymerase chain reaction), and the expression of H3K27me3, USP21, and Nanog by Western blot and immunofluorescence, respectively. In addition, 126 CHMs and 63 normal female villous samples were collected for CDX4 immunohistochemical staining. The expression of XIST RNA was significantly lower, and TSIX RNA expression was significantly higher in androgenetic CHMs than that in normal female villi (both P<0.01). The expression of CDX4 mRNA in androgenetic CHMs was elevated compared with that in normal male and normal female villous samples (both P<0.01), and CDX4 protein expression was also higher than that in normal female villous samples (P<0.01). The expression of H3K27me3 was lower in androgenetic CHMs compared with that in normal female villi(P<0.01). The methylation pattern of HUMARA was found lacking in androgenetic CHMs. The expression of Nanog and UPS21 protein in androgenetic CHMs was higher than that in normal villi (both P<0.01). Both X chromosomes are active in androgenetic CHMs with the 46, XX karyotype, and the USP21-Nanog pathway may be involved in the disruption of XCI during this process.

Relationship of Histopathological Representation of Excessive Proliferation of Trophoblast Cells with the Possibility of Malignant Events After Complete Hydatidiform Mole

INTRODUCTION

Fifteen to twenty percent of the patients with complete hydatidiform mole transform malignancy into gestational trophoblastic tumors. The marked proliferation of trophoblastic cells is one of the characteristics that determines high risk for the occurrence of post-hydatidiform mole malignancy. The objective of the study was to analyze the histopathologic feature of the marked proliferation of trophoblastic cells as a role in post-hydatidiform mole malignancy that can be used as a determinant of the risk of malignancy post-hydatidiform mole.

METHODS

The method of the study was analytical observational with a case-control study design. The data were taken retrospectively from medical records of patients with a post-complete hydatidiform mole malignancy and patients who do not develop post-complete hydatidiform mole malignancy (n = 34). The study took place in the Department of Anatomical Pathology Laboratorium at Dr. Hasan Sadikin Hospital, Bandung, Indonesia.

RESULTS

The results showed a highly significant difference with the histopathologic characteristics of marked trophoblastic cell proliferation in post-complete hydatidiform mole malignancy, reaching up to 73.5%. In contrast, the difference between those who do not develop malignancy was 11.8%. The odds ratio (OR) was 20.83, with an interpretation that patients with a complete hydatidiform mole with the histopathological feature of marked trophoblastic cell proliferation had a risk of developing into malignancy 20.83 times higher compared to cases without marked trophoblastic cell proliferation.

CONCLUSION

The conclusion of the study was there is a significant correlation between marked trophoblastic cell proliferation with the incidence of post-complete hydatidiform mole malignancy.

Parental bias in expression and interaction of genes in the equine placenta

Most autosomal genes in the placenta show a biallelic expression pattern. However, some genes exhibit allele-specific transcription depending on the parental origin of the chromosomes on which the copy of the gene resides. Parentally expressed genes are involved in the reciprocal interaction between maternal and paternal genes, coordinating the allocation of resources between fetus and mother. One of the main challenges of studying parental-specific allelic expression (allele-specific expression [ASE]) in the placenta is the maternal cellular remnant at the fetomaternal interface. Horses (Equus caballus) have an epitheliochorial placenta in which both the endometrial epithelium and the epithelium of the chorionic villi are juxtaposed with minimal extension into the uterine mucosa, yet there is no information available on the allelic gene expression of equine chorioallantois (CA). In the current study, we present a dataset of 1,336 genes showing ASE in the equine CA (https://pouya-dini.github.io/equine-gene-db/) along with a workflow for analyzing ASE genes. We further identified 254 potentially imprinted genes among the parentally expressed genes in the equine CA and evaluated the expression pattern of these genes throughout gestation. Our gene ontology analysis implies that maternally expressed genes tend to decrease the length of gestation, while paternally expressed genes extend the length of gestation. This study provides fundamental information regarding parental gene expression during equine pregnancy, a species with a negligible amount of maternal cellular remnant in its placenta. This information will provide the basis for a better understanding of the role of parental gene expression in the placenta during gestation.

Distinct microRNA profiles for complete hydatidiform moles at risk of malignant progression

BACKGROUND

MicroRNAs are small noncoding RNAs with important regulatory functions. Although well-studied in cancer, little is known about the role of microRNAs in premalignant disease. Complete hydatidiform moles are benign forms of gestational trophoblastic disease that progress to gestational trophoblastic neoplasia in up to 20% of cases; however, there is no well-established biomarker that can predict the development of gestational trophoblastic neoplasia.

OBJECTIVE

This study aimed to investigate possible differences in microRNA expression between complete moles progressing to gestational trophoblastic neoplasia and those regressing after surgical evacuation.

STUDY DESIGN

Total RNA was extracted from fresh frozen tissues from 39 complete moles collected at the time of uterine evacuation in Brazil. In the study, 39 cases achieved human chorionic gonadotropin normalization without further therapy, and 9 cases developed gestational trophoblastic neoplasia requiring chemotherapy. Total RNA was also extracted from 2 choriocarcinoma cell lines, JEG-3 and JAR, and an immortalized normal placenta cell line, 3A-subE. MicroRNA expression in all samples was quantified using microRNA sequencing. Hits from the sequencing data were validated using a quantitative probe-based assay. Significantly altered microRNAs were then subjected to target prediction and gene ontology analyses to search for alterations in key signaling pathways. Expression of potential microRNA targets was assessed by quantitative real-time polymerase chain reaction and western blot. Finally, potential prognostic protein biomarkers were validated in an independent set of formalin-fixed paraffin-embedded patient samples from the United States (15 complete moles progressing to gestational trophoblastic neoplasia and 12 that spontaneously regressed) using quantitative immunohistochemistry.

RESULTS

In total, 462 microRNAs were identified in all samples at a threshold of <1 tag per million. MicroRNA sequencing revealed a distinct set of microRNAs associated with gestational trophoblastic neoplasia. Gene ontology analysis of the most altered transcripts showed that the leading pathway was related to response to ischemia (P<.001). Here, 2 of the top 3 most significantly altered microRNAs were mir-181b-5p (1.65-fold; adjusted P=.014) and mir-181d-5p (1.85-fold; adjusted P=.014), both of which have been shown to regulate expression of BCL2. By quantitative real-time polymerase chain reaction, BCL2 messenger RNA expression was significantly lower in the complete moles progressing to gestational trophoblastic neoplasia than the regressing complete moles (-4.69-fold; P=.018). Reduced expression of BCL2 was confirmed in tissue samples by western blot. Immunohistochemistry in the independent patient samples revealed significantly lower cytoplasmic expression of BCL2 in the villous trophoblasts from cases destined for progression to gestational trophoblastic neoplasia compared with those that regressed, both with respect to staining intensity (optic density 0.110±0.102 vs 0.212±0.036; P<.001) and to the percentage of positive cells (16%±28% vs 49.4%±28.05%; P=.003).

CONCLUSION

Complete moles progressing to gestational trophoblastic neoplasia are associated with a distinct microRNA profile. miR-181 family members and BCL2 may be prognostic biomarkers for predicting gestational trophoblastic neoplasia risk.

A Novel Mutation in NLRP7 Related to Recurrent Hydatidiform Mole and Reproductive Failure

Background

Hydatidiform mole (HM) is an abnormal human pregnancy with excessive trophoblastic proliferation and abnormal embryonic development, dividing into two complete HM (CHM) and partial HM (PHM) groups. One subcategory of the CHMs is recurrent and familial, which is known as biparental HM (BiHMs) or recurrent HM (RHM). NLRP7, KHDC3L and PADI6 are maternal-effect genes involved in RHMs. NLRP7 is a major gene responsible for RHMs. This study was performed on patients with molar pregnancies and miscarriage. The aim of this study was to genetic screen for mutations in NLRP7 and KHDC3L genes in an affected woman with previous history of 5RHM and the sibling with history of miscarriage.

Materials and Methods

In this experimental study, DNA was extracted from blood samples. KHDC3L and NLRP7 were polymerase chain reaction (PCR) amplified. The PCR products were purified and Sanger sequenced.

Results

In this study, there is no mutation in KHDC3L gene but a novel mutation was identified in the NACHT domain of NLRP7 gene. Patient with five recurrent moles had this mutation in the homozygous state while her sister with one miscarriage and one normal child showed this mutation in the heterozygous state.

Conclusion

In this study, we identified a new mutation in NLRP7 gene of a patient with recurrent HM. Following egg donation, this patient has a normal boy. The sister of this patient with heterozygous mutation has a spontaneous abortion and one normal child that confirm the impact of a defective allele of NLRP7 on reproductive wastage in a recent finding.

Imaging in Gestational Trophoblastic Disease

Gestational trophoblastic disease (GTD) is a spectrum of disorders characterized by abnormal trophoblastic proliferation. GTD includes benign conditions such as hydatidiform moles and malignant diseases that are referred as gestational trophoblastic neoplasia (GTN). Ultrasound plays a central role in the diagnosis of patients with hydatidiform mole. Other imaging modalities are useful in molar pregnancy, mainly for evaluating pulmonary complications and atypical presentation of hydatidiform mole. GTN typically arises after 20% of molar pregnancies but can uncommonly occur after nonmolar gestations. After uterine evacuation, serial human chorionic gonadotropin levels are evaluated in patients for early detection of GTN. Once GTN is suspected, Doppler ultrasound is the primary tool to confirm the diagnosis; however, magnetic resonance imaging can also help in selected cases. Metastatic disease workup can involve various modalities, including ultrasound, X-ray, computed tomography, magnetic resonance imaging and positron emission tomography/computed tomography. In this article, we review the main imaging modalities used to evaluate patients with GTD.

Differential expression of leukemia inhibitory factor and insulin like growth factor-1 between normal pregnancies, partial hydatidiform moles and complete hydatidiform moles

INTRODUCTION

Leukemia inhibitory factor (LIF) and insulin like growth factor-1 (IGF-1) are two of the most important growth factors mediating trophoblast actions. We hypothesized that the localization and expression patterns of LIF and IGF-1 in partial and complete hydatidiform moles (HM) compared with normal first trimester placentas may provide an understanding of the proliferative processes in HMs.

METHODS

The study population included curettage material of women diagnosed as complete or partial HM as a result of histopathological and immunohistochemical examination (complete HM group, n = 8; partial HM group, n = 8) and women undergoing dilatation&curettage for unwanted pregnancies (control group, n = 8). Expression of LIF and IGF-1 among placental cell groups was evaluated immunohistochemically and given a score depending on immunostaining intensity.

RESULTS

In normal chorionic villi strong expression of LIF and IGF-1 was present. Both LIF and IGF-1 expressions were weaker in the chorionic villi of complete HMs. In complete mole decidua there was a significant decrease in glandular and endothelial IGF-1 expression along with a decrease in decidual cell LIF expression compared to normal first trimester decidua. LIF expression in extravillous trophoblasts was stronger in complete molar placentas compared to normal placentas.

DISCUSSION

LIF and IGF-1 are important regulators of trophoblast proliferation and invasion. Differential expression of LIF and IGF-1 in molar trophoblasts and chorionic villi might have a role in regulation of trophoblasts in complete moles. Decreased expression of glandular IGF-1 and decidual LIF might be related to the decidual changes during trophoblastic proliferation and invasion of decidua in complete HMs.

Allele-Specific Methylome and Transcriptome Analysis Reveals Widespread Imprinting in the Human Placenta

DNA methylation is globally reprogrammed after fertilization, and as a result, the parental genomes have similar DNA-methylation profiles after implantation except at the germline differentially methylated regions (gDMRs). We and others have previously shown that human blastocysts might contain thousands of transient maternally methylated gDMRs (transient mDMRs), whose maternal methylation is lost in embryonic tissues after implantation. In this study, we performed genome-wide allelic DNA methylation analyses of purified trophoblast cells from human placentas and, surprisingly, found that more than one-quarter of the transient-in-embryo mDMRs maintained their maternally biased DNA methylation. RNA-sequencing-based allelic expression analyses revealed that some of the placenta-specific mDMRs were associated with expression of imprinted genes (e.g., TIGAR, SLC4A7, PROSER2-AS1, and KLHDC10), and three imprinted gene clusters were identified. This approach also identified some X-linked gDMRs. Comparisons of the data with those from other mammals revealed that genomic imprinting in the placenta is highly variable. These findings highlight the incomplete erasure of germline DNA methylation in the human placenta; understanding this erasure is important for understanding normal placental development and the pathogenesis of developmental disorders with imprinting effects.

LINE-1 Methylation Patterns as a Predictor of Postmolar Gestational Trophoblastic Neoplasia

Objective. To study the potential of long interspersed element-1 (LINE-1) methylation change in the prediction of postmolar gestational trophoblastic neoplasia (GTN). Methods. The LINE-1 methylation pattern from first trimester placenta, hydatidiform mole, and malignant trophoblast specimens were compared. Then, hydatidiform mole patients from 11999 to 2010 were classified into the following 2 groups: a remission group and a group that developed postmolar GTN. Specimens were prepared for a methylation study. The methylation levels and percentages of LINE-1 loci were evaluated for their sensitivity, specificity, and accuracy for the prediction of postmolar GTN. Results. First, 12 placentas, 38 moles, and 19 malignant trophoblast specimens were compared. The hydatidiform mole group had the highest LINE-1 methylation level (p = 0.003) and the ^uC^uC of LINE-1 increased in the malignant trophoblast group (p ≤ 0.001). One hundred forty-five hydatidiform mole patients were classified as 103 remission and 42 postmolar GTN patients. The %^mC^uC and %^uC^mC of LINE-1 showed the lowest p value for distinguishing between the two groups (p < 0.001). The combination of the pretreatment β-hCG level (≥100,000 mIU/mL) with the %^mC^uC and %^uC^mC, sensitivity, specificity, PPV, NPV, and accuracy modified the levels to 60.0%, 92.2%, 77.4%, 83.8%, and 82.3%, respectively. Conclusions. A reduction in the partial methylation of LINE-1 occurs early before the clinical appearance of malignant transformation. The %^mC^uC and %^uC^mC of LINE-1s may be promising markers for monitoring hydatidiform moles before progression to GTN.

Establishment of a new diagnostic method for hydropic villi by using TSSC3 antibody

A total of 297 samples of hydropic villi were classified according to DNA polymorphisms as androgenetic moles, dispermic triploids, or biparental diploids. A subset of 267 appropriate samples was included in the study. Most of the macroscopically diagnosed complete mole cases were genetically androgenetic in origin. The partial mole cases consisted of 30 androgenetic moles and 12 dispermic triploids. For the 59 cases macroscopically categorized as hydropic abortion, the genetic analysis revealed 38 androgenetic moles, seven dispermic triploids and 14 biparental diploids. These results showed that a new diagnostic method was required for the management of patients with hydropic villi. We identified the TSSC imprint gene of which expression was shown in normal and partial mole villi but was silenced in complete mole villi. Immunohistochemistry using the TSSC3 antibody demonstrated its efficacy as the differential diagnostic method. TSSC3 play an important role in the differentiation from trophoblast stem cells to progenitors and/or labyrinth trophoblast through the TSSC3/PI3K/Akt/Mash2 signaling pathway.

Placental Mesenchymal Dysplasia

Placental mesenchymal dysplasia is a rare, incompletely understood placental stromal lesion, characterized by placentomegaly and striking ectasia and tortuosity of chorionic plate and stem villous vessels. Its prenatal ultrasonographic and gross pathologic features resemble those of a partial mole, but the fetus is typically normal and the placenta has a diploid, chromosomal complement. We discuss the pathologic features and current understanding of the etiopathogenesis of this condition, the supportive immunohistochemical and confirmatory molecular genetic studies important in its diagnosis, and its implications for pregnancy and infant outcomes.

Diagnostic utility of microsatellite genotyping for molar pregnancy testing

CONTEXT

Molecular genotyping by analysis of DNA microsatellites, also known as short tandem repeats (STRs), is an established method for diagnosing and classifying hydatidiform mole. Distinction of both complete hydatidiform mole and partial hydatidiform mole from nonmolar specimens is relevant for clinical management owing to differences in risk for persistent gestational trophoblastic disease.

OBJECTIVE

To determine the technical performance of microsatellite genotyping by using a commercially available multiplex assay, and to describe the application of additional methods to confirm other genetic abnormalities detected by the genotyping assay.

DESIGN

Microsatellite genotyping data on 102 cases referred for molar pregnancy testing are presented. A separate panel of mini STR markers, flow cytometry, fluorescence in situ hybridization, and p57 immunohistochemistry were used to characterize cases with other incidental genetic abnormalities.

RESULTS

Forty-eight cases were classified as hydatidiform mole (31, complete hydatidiform mole; 17, partial hydatidiform mole). Genotyping also revealed 11 cases of suspected trisomy and 1 case of androgenetic/biparental mosaicism. Trisomy for selected chromosomes (13, 16, 18, and 21) was confirmed in all cases by using a panel of mini STR markers.

CONCLUSIONS

This series illustrates the utility of microsatellite genotyping as a stand-alone method for accurate classification of hydatidiform mole. Other genetic abnormalities may be detected by genotyping; confirmation of the suspected abnormality requires additional testing.

Mutations in NLRP7 and KHDC3L confer a complete hydatidiform mole phenotype on digynic triploid conceptions

Digynic triploidy is classically associated with a severely growth restricted fetus and a small nonmolar placenta. However, in genotyping hydatidiform moles as part of clinical practice, we identified two digynic triploid conceptions presenting with histopathological features of classical complete hydatidiform mole (CHM). Both cases occurred in women with a history of previous molar pregnancies and no normal pregnancies. Pathological review and genotyping of other molar pregnancies in these cases showed them to be typical CHM with negative p57(KIP2) immunostaining of the cytotrophoblast cells and villous stroma and to be diploid but biparental, confirming a diagnosis of familial recurrent hydatidiform mole (FRHM). Mutation screening of NLRP7 had identified a homozygous duplication, leading to a truncated protein, in case 1 whereas mutation screening of KHDC3L (C6orf221) in case 2 showed both the proband and her sister to be compound heterozygotes for mutations in KHDC3L. The observation of a single digynic, triploid conception presenting as a CHM in women with FRHM, where other pregnancies are diploid and biparental, supports the hypothesis that the role of both NLRP7 and KHDC3L in pregnancy is in setting and/or maintaining the maternal imprint. Clinically, a diagnosis of FRHM should be considered in women with genetically unusual conceptions that are phenotypically CHM.

In vivo and in vitro differentiation of uniparental embryonic stem cells into hematopoietic and neural cell types

The biological role of genomic imprinting in adult tissue is central to the consideration of transplanting uniparental embryonic stem (ES) cell-derived tissues. We have recently shown that both maternal (parthenogenetic/gynogenetic) and paternal (androgenetic) uniparental ES cells can differentiate, both in vivo in chimeras and in vitro, into adult-repopulating hematopoietic stem and progenitor cells. This suggests that, at least in some tissues, the presence of two maternal or two paternal genomes does not interfere with stem cell function and tissue homeostasis in the adult. Here, we consider implications of the contribution of uniparental cells to hematopoiesis and to development of other organ systems, notably neural tissue for which consequences of genomic imprinting are associated with a known bias in development and behavioral disorders. Our findings so far indicate that there is little or no limit to the differentiation potential of uniparental ES cells outside the normal developmental paradigm. As a potentially donor MHC-matching source of tissue, uniparental transplants may provide not only a clinical resource but also a unique tool to investigate aspects of genomic imprinting in adults.

The spectrum of NLRP7 mutations in French patients with recurrent hydatidiform mole

OBJECTIVES

The NLRP7 gene (19q13.42) is associated with recurrent and/or familial hydatidiform moles. Several mutations, histopathological types and reproductive outcomes have been described. We studied our recurrent hydatidiform mole cases recorded since 1999 in order to identify links between clinic, histology and genetics.

STUDY

We present here the gestational history and the spectrum of NLRP7 mutations in our French series.

DESIGN

We performed a retrospective study from clinical forms received for genetic diagnosis. Cases declaration was based on a voluntary initiative coming from French practitioners, subjected to patients' agreement.

RESULTS

Among 12 recurrent hydatidiform moles investigated, we identified 3 cases of confirmed homozygous NLRP7 mutation and 3 cases of heterozygous NLRP7 mutation. One patient bore a novel mutation p.Leu880Ser in a homozygous state.

CONCLUSIONS

We here identified a new homozygous NLRP7 mutation. Unfortunately, no modern therapeutic option has proven effective to obtain evolutive pregnancies. Then, fundamental and clinical researches seem to be necessary. Moreover, collecting RHM cases is essential.

Detection of global DNA methylation and paternally imprinted H19 gene methylation in preeclamptic placentas

Preeclampsia (PE) is a severe hypertensive disorder associated with pregnancy; despite substantial research effort in the past several years, the etiology of PE is still unclear. The role of epigenetic factors in the etiology of PE, including DNA methylation, has been poorly characterized. In the present study, we investigated global DNA methylation as well as DNA methylation of the paternally imprinted H19 gene in preeclamptic placentas. Using 5-methylcytosine immunohistochemistry and Alu and LINE-1 repeat pyrosequencing, we found that the global DNA methylation level and the DNA (cytosine-5) methyltransferase 1 mRNA level were significantly higher in the early-onset preeclamptic placentas when compared with the normal controls. Data from methylation-sensitive high resolution melting demonstrated hypermethylation of the promoter region of the H19 gene, and results of real-time PCR showed decreased mRNA expression of H19 gene in the early-onset preeclamptic placentas as compared with the normal controls. Our results suggest that abnormal DNA methylation during placentation might be involved in the pathophysiology of PE, especially early-onset preeclampsia.

[Review: Repetitive hydatidiform moles]

Repetitive moles are rare. They are either sporadic or familial, with or without consanguinity. Some of them can be explained by a NLRP7 mutation, which causes genomic parental imprinting alteration, with a preferential paternal phenotypic expression. Currently, no effective therapeutic solution has been developed. Among the 1687 patients declared to the French Trophoblastic Disease Reference Center, 13 presented at least two hydatidiform moles, thus less than 1% of the patients. A mutation of the NLRP7 gene was shown in six of 12 tested patients (50%) among whom three presented a homozygous mutation and three a heterozygous mutation. For an affected patient, type of mole can indifferently be a complete hydatidiform mole or a partial hydatidiform mole. We describe these cases and compare them to those already published.

Incidence of postmolar gestational trophoblastic disease in androgenetic moles and the morphological features associated with low risk postmolar gestational trophoblastic disease

In the present study, we evaluated the incidence of postmolar gestational trophoblastic disease (GTD) in molar pregnancy. We also validated the macroscopic diagnosis based on the Japan Society of Obstetrics and Gynecology (JSOG) classification. A total of 297 samples of hydropic villi were classified according to DNA polymorphisms as androgenetic moles, dispermic triploids, or biparental diploids (hydropic abortion), clinically corresponding to complete hydatidiform mole (CHM), partial hydatidiform mole (PHM), and hydropic abortion, respectively. These samples were also classified morphologically based on the JSOG classification. A follow-up study was performed to investigate the incidence of postmolar GTD. A subset of 267 samples eligible for testing were analyzed and diagnosed as androgenetic moles (232 cases), dispermic triploids (20 cases), and biparental diploids (15 cases). Most of the macroscopically diagnosed CHM cases were genetically androgenetic in origin. The PHM cases consisted of 30 androgenetic moles and 12 dispermic triploids. We reviewed the outcomes of 200 patients (178 cases of androgenetic mole, 13 cases of dispermic triploids, and nine cases of biparental diploids). Twenty-eight cases (16%) of androgenetic moles developed postmolar GTD. None of the patients with dispermic triploids developed postmolar GTD. Among the 28 patients who developed postmolar GTD, the shortest diameter of the largest hydropic villi was significantly longer than that of patients not developing postmolar GTD. None of the patients with androgenetic moles who had hydropic villi <2 mm in their shortest diameter developed postmolar GTD. For the patients with dispermic triploids, the risk of postmolar GTD is extremely low. The risk of postmolar GTD is also low in patients with androgenetic moles with small hydropic villi. The JSOG classification based on the morphology of hydropic villi is reliable for the diagnosis of CHM, but inaccurate for the diagnosis of PHM or "microscopic" moles.

Pathogenesis of choriocarcinoma: clinical, genetic and stem cell perspectives

Choriocarcinoma is a unique malignant neoplasm composed of mononuclear cytotrophoblasts and multinucleated syncytiotrophoblasts that produce human chorionic gonadotrophin. Choriocarcinoma can occur after a pregnancy, as a component of germ cell tumors, or in association with a poorly differentiated somatic carcinoma, each with distinct clinical features. Cytogenetic and molecular studies, predominantly on gestational choriocarcinoma, revealed the impact of oncogenes, tumor suppressor genes and imprinting genes on its pathogenesis. The role of stem cells in various types of choriocarcinoma has been studied recently. This review will discuss how such knowledge can enhance our understanding of the pathogenesis of choriocarcinoma, enable exploration of novel anti-choriocarcinoma targeted therapy and possibly improve our insight on embryological and placental development.

Patterns of hybrid loss of imprinting reveal tissue- and cluster-specific regulation

BACKGROUND

Crosses between natural populations of two species of deer mice, Peromyscus maniculatus (BW), and P. polionotus (PO), produce parent-of-origin effects on growth and development. BW females mated to PO males (bwxpo) produce growth-retarded but otherwise healthy offspring. In contrast, PO females mated to BW males (POxBW) produce overgrown and severely defective offspring. The hybrid phenotypes are pronounced in the placenta and include POxBW conceptuses which lack embryonic structures. Evidence to date links variation in control of genomic imprinting with the hybrid defects, particularly in the POxBW offspring. Establishment of genomic imprinting is typically mediated by gametic DNA methylation at sites known as gDMRs. However, imprinted gene clusters vary in their regulation by gDMR sequences.

METHODOLOGY/PRINCIPAL FINDINGS

Here we further assess imprinted gene expression and DNA methylation at different cluster types in order to discern patterns. These data reveal POxBW misexpression at the Kcnq1ot1 and Peg3 clusters, both of which lose ICR methylation in placental tissues. In contrast, some embryonic transcripts (Peg10, Kcnq1ot1) reactivated the silenced allele with little or no loss of DNA methylation. Hybrid brains also display different patterns of imprinting perturbations. Several cluster pairs thought to use analogous regulatory mechanisms are differentially affected in the hybrids.

CONCLUSIONS/SIGNIFICANCE

These data reinforce the hypothesis that placental and somatic gene regulation differs significantly, as does that between imprinted gene clusters and between species. That such epigenetic regulatory variation exists in recently diverged species suggests a role in reproductive isolation, and that this variation is likely to be adaptive.

Placental mesenchymal dysplasia associated with fetal overgrowth and mosaic deletion of the maternal copy of 11p15.5

Placentae with mesenchymal dysplasia (PMD) are typically larger than average and show cystic areas on ultrasonography. Fetal outcomes are variable and are often associated with growth restriction. However, enigmatically, some associated fetuses show signs of Beckwith-Wiedemann syndrome (BWS). PMD has recently been shown to result from androgenetic (complete paternal uniparental disomy) chimerism in the placenta in pregnancies that were associated with some fetal growth restriction. Cases of PMD associated with overgrowth have not previously been investigated molecularly. We present a case of focal PMD associated with a male fetus showing overgrowth with an enlarged heart, marked fetal ascites and intrauterine fetal death at 34 weeks, but no other BWS manifestations. Mosaicism for an unbalanced translocation leading to deletion of the maternal copy of the BWS region on 11p15.5 and partial duplication of 17q was observed in placenta, but not fetal samples. While the placental findings of PMD can be caused by an unbalanced dosage of genes in 11p15.5 alone, fetal growth parameters appear to depend on the underlying mechanism and likely also the level and distribution of abnormal cells.

Mapping and identification of candidate loci responsible for Peromyscus hybrid overgrowth

Crosses between two recently diverged rodent species of the genus Peromyscus result in dramatic parent-of-origin effects on growth and development. P. maniculatus females crossed with P. polionotus males yield growth-retarded conceptuses, whereas the reciprocal cross results in overgrowth and lethality. These hybrid effects are particularly pronounced in the placenta. We previously detected linkage to two regions of the genome involved in the overgrowth effects. One locus, termed Peal, is a paternally expressed autosomal locus mapping to a domain whose house mouse equivalent contains several clusters of imprinted genes. The other locus, termed Mexl, maps to a gene-poor region of the X chromosome. Here we use an advanced intercross line to verify and narrow the regions of linkage and identify candidate genes for Mexl and Peal. While we have previously shown that Mexl affects both pre-and postnatal growth, we show here that Peal affects only prenatal growth. Utilizing criteria such as mutant phenotypes and allelic expression, we identify the loci encoding the homeobox protein Esx1 and the zinc-finger protein Pw1/Peg3 as candidates. Both loci exhibit expression changes in the hybrids.

Origin and outcome of pregnancies affected by androgenetic/biparental chimerism

BACKGROUND

Androgenetic diploid cells confined to the placenta have recently been reported in several cases of normally developed fetuses in association with placental mesenchymal dysplasia (PMD).

METHODS AND RESULTS

We investigated two singleton, mildly growth-restricted, female pregnancies ascertained on the basis of PMD. One case had liver hemangiomas and both infants had multiple skin hemangiomas. Post-natal development was normal. Molecular marker analysis confirmed the diagnosis of androgenetic and normal mixed cell populations in the placenta. Both cases derived from a single maternal genome (M1) and two distinct paternal genomes (P1 and P2). In one case, the androgenetic cell population contained both paternal genomes (P1P2), with one shared in common with the biparental (M1P1) population. In the second case, the androgenetic lineage showed complete homozygosity (P2P2) for a paternal genome not common to the biparental cell population.

CONCLUSION

These new PMD cases help to define the range of possible clinical presentations of androgenetic/biparental mosaicism or chimerism. Placentas with androgenetic/biparental chimeric cell populations may derive from a single tri-pronuclear (3PN) zygote in which one or more parental genomes are not equally apportioned to the daughter cells in the first cell division.

Intracytoplasmic sperm injection--an assisted reproduction technique that should make us cautious about imprinting deregulation

OBJECTIVE

Due to the extensive use of intracytoplasmic sperm injection (ICSI) in assisted reproduction, not only among couples with severe male factor infertility problems, but to a broader scale, a lot of concern has been raised regarding the safety of the method and its implications in epigenetic control and imprinting dysregulation. This review means to provide a comprehensive report of the published scientific data, outline putative associations between ICSI and epigenetic control, and suggest measures to improve the current state of affairs and reach more scientifically consolidated results.

METHODS

This review was conducted by studying a broad spectrum of articles dealing with the subject of epigenetic control and its relation with ICSI. We tried to view the two subjects as parallel procedures that occur in the organism and by delineating the molecular and biochemical steps that comprise them make suggestions about putative associations between ICSI and epigenetic control.

CONCLUSIONS

No hard evidence presented at the moment can prove or disapprove ICSI's implications in epigenetic control. Nevertheless, we take the view that more comprehensive, long-term, and properly designed studies are imperative to be applied on a large-scale basis. We urge cautiousness, since the welfare of our progeny is what is at stake.

Genetic evidence for a maternal effect locus controlling genomic imprinting and growth

Crosses between two species of deer mouse (Peromyscus) yield dramatic parent-of-origin effects. Female P. maniculatus (BW) crossed with male P. polionotus (PO) produce animals smaller than either parent. PO females crossed with BW males yield lethal overgrowth that has been associated with loss-of-imprinting (LOI). Previously, we mapped two loci influencing fetal growth. These two loci, however, do not account for the LOI, nor for the dysmorphic phenotypes. Here we report that maternal genetic background strongly influences the LOI. Analyses of crosses wherein maternal genetic background is varied suggest that this effect is likely due to the action of a small number of loci. We have termed these putative loci Meil. Estimation of Meil loci number was confounded by skewed allelic ratios in the intercross line employed. We show that the Meil loci are not identical to any of the DNA methyltransferases shown to be involved in regulation of genomic imprinting.

Stochastic imprinting in the progeny of Dnmt3L−/− females

The cis-acting regulatory sequences of imprinted genes are subject to germline-specific epigenetic modifications, the imprints, so that this class of genes is exclusively expressed from either the paternal or maternal allele in offspring. How genes are differentially marked in the germlines remains largely to be elucidated. Although the exact nature of the mark is not fully known, DNA methylation [at differentially methylated regions (DMRs)] appears to be a major, functional component. Recent data in mice indicate that Dnmt3a, an enzyme with de novo DNA methyltransferase activity, and the related protein Dnmt3L are required for methylation of imprinted loci in germ cells. Maternal methylation imprints, in particular, are strictly dependent on the presence of Dnmt3L. Here, we show that, unexpectedly, methylation imprints can be present in some progeny of Dnmt3L(-/-) females. This incomplete penetrance of the effect of Dnmt3L deficiency in oocytes is neither embryo nor locus specific, but stochastic. We establish that, when it occurs, methylation is present in both embryo and extra-embryonic tissues and results in a functional imprint. This suggests that this maternal methylation is inherited, directly or indirectly, from the gamete. Our results indicate that in the absence of Dnmt3L, factors such as Dnmt3a and possibly others can act alone to mark individual DMRs. However, establishment of appropriate maternal imprints at all loci does require a combination of all factors. This observation can provide a basis to understand mechanisms involved in some sporadic cases of imprinting-related diseases and polymorphic imprinting in human.

Analysis of the chromosomal region 19q13.4 in two Chinese families with recurrent hydatidiform mole

BACKGROUND

Familial recurrent hydatidiform mole is an extremely rare autosomal recessive condition in which affected individuals have a predisposition to molar pregnancies that are diploid but biparental, rather than androgenetic, in origin. A gene for this condition has been previously mapped to a 1.1 Mb region of chromosome 19q13.4. However, investigation of further families is needed to refine the location of the specific gene(s) involved.

METHODS

We have recently identified two novel Chinese families in which four affected women had recurrent pregnancy loss including 14 complete hydatidiform moles (CHM). Fluorescent microsatellite genotyping was used to determine the origin of CHM in both families. Using a panel of polymorphic microsatellite markers, genotyping and haplotype analysis of the 19q13.4 chromosomal region was performed in both families.

RESULTS

Genotyping of CHM from affected individuals confirmed their biparental origin and diagnosis of familial recurrent hydatidiform mole in both families. However, no significant homozygosity for the 19q13.4 candidate region was found in affected members of either family.

CONCLUSION

Genotyping and haplotype analysis has shown that a mutation in 19q13.4 is unlikely to be responsible for recurrent CHM in the two Chinese families investigated and provides further evidence to support the hypothesis that, although extremely rare, this condition shows genetic heterogeneity.

Epigenetic deregulation of genomic imprinting in human disorders and following assisted reproduction

Imprinted genes play important roles in the regulation of growth and development, and several have been shown to influence behavior. Their allele-specific expression depends on inheritance from either the mother or the father, and is regulated by "imprinting control regions" (ICRs). ICRs are controlled by DNA methylation, which is present on one of the two parental alleles only. These allelic methylation marks are established in either the female or the male germline, following the erasure of preexisting DNA methylation in the primordial germ cells. After fertilization, the allelic DNA methylation at ICRs is maintained in all somatic cells of the developing embryo. This epigenetic "life cycle" of imprinting (germline erasure, germline establishment, and somatic maintenance) can be disrupted in several human diseases, including Beckwith-Wiedemann syndrome (BWS), Prader-Willi syndrome (PWS), Angelman syndrome and Hydatidiform mole. In the neurodevelopmental Rett syndrome, the way the ICR mediates imprinted expression is perturbed. Recent studies indicate that assisted reproduction technologies (ART) can sometimes affect the epigenetic cycle of imprinting as well, and that this gives rise to imprinting disease syndromes. This finding warrants careful monitoring of the epigenetic effects, and absolute risks, of currently used and novel reproduction technologies.

Differential Diagnosis Between Complete and Partial Mole by TSSC3 Antibody Completely Correlates to DNA Diagnosis

Complete hydatidiform moles (CHMs) are a type of androgenetic fertilization without an ovum. Cases of CHM exhibit a generalized swelling of the villi and are known to be highly associated with persistent disease or carcinoma. In contrast, partial hydatidiform moles (PHMs) also show characteristic hydropic changes among the villi, but the incidence of secondary disease is relatively low. Because PHMs are fertilized by one ovum and two sperm and CHMs are fertilized by one or two sperm alone, we considered whether or not maternally imprinted genes might be useful for achieving a differential diagnosis. The validity of the imprinted genes in CHMs was assessed by implementation of a microarray technique. Among the genes examined, TSSC3, SLC22A1L, KCNQ1, and Decorin were shown to be down-regulated, and TSSC3 was the most markedly suppressed of these genes. In this study, 20 cases of CHM, the diagnosis of which was confirmed by DNA polymorphism, were investigated. In all of these cases, the expression of TSSC3 was completely absent, as determined by Western blot analysis. Conversely, 12 cases of PHM, also diagnosed by DNA polymorphism, were examined here; in all of these 12 cases, TSSC3 was found to be expressed normally. Immunohistochemical (IHC) analysis also produced the same results. The complete silencing of TSSC3 in cases of CHM will provide a novel, convenient strategy for the diagnosis of molar lesions in the placenta.

Androgenetic/biparental mosaicism causes placental mesenchymal dysplasia

BACKGROUND

Placental mesenchymal dysplasia (PMD) is a distinct syndrome of unknown aetiology that is associated with significant fetal morbidity and mortality. Intrauterine growth restriction is common, yet, paradoxically, many of the associated fetuses/newborns have been diagnosed with Beckwith-Wiedemann syndrome (BWS).

METHODS

We report two cases of PMD with high levels of androgenetic (complete paternal uniparental isodisomy) cells in the placenta and document, in one case, a likely androgenetic contribution to the fetus as well.

RESULTS

The same haploid paternal complement found in the androgenetic cells was present in coexisting biparental cells, suggesting origin from a single fertilisation event.

CONCLUSIONS

Preferential allocation of the normal cells into the trophoblast explains the absence of trophoblast overgrowth, a key feature of this syndrome. Interestingly, the distribution of androgenetic cells appears to differ from that reported for artificially created androgenetic mouse chimeras. Androgenetic mosaicism for the first time provides an aetiology for PMD, and may be a novel mechanism for BWS and unexplained intrauterine growth restriction.

Gestational trophoblastic diseases: recent advances in histopathologic diagnosis and related genetic aspects

Gestational trophoblastic disease refers to a spectrum of proliferative disorders of the placental trophoblast, with a wide range of histologic appearances and clinical behaviors. This review discusses the more recent developments in the diagnosis of these entities. Changes in criteria for the histologic diagnosis of these lesions due to earlier clinical diagnosis are reviewed, and the ability to make more accurate diagnoses due to the introduction of newer antibodies such as p57 is highlighted. A discussion of epithelioid trophoblastic tumor, a newly introduced tumor subtype, with its differential diagnosis from placental-site trophoblastic tumor and squamous cell carcinoma is also presented. Last, a brief discussion on the role of genetic studies and the future direction of research in elucidating the nature of this intriguing group of lesions is presented.

Differential expression of insulin-like growth factor binding protein 1 and ferritin light polypeptide in gestational trophoblastic neoplasia

BACKGROUND

Hydatidiform mole (HM), the most common type of gestational trophoblastic diseases, can be considered as placenta with abnormal chromosome composition with potential of malignant transformation. Few biologic markers can predict subsequent development of persistent gestational trophoblastic neoplasia (GTN) requiring chemotherapy.

METHODS

Suppression subtractive hybridization (SSH) combined with cDNA microarray was used to compare the differential expression pattern of HM that spontaneously regressed and that subsequently developed metastatic GTN. Tissue-specific chips were constructed from the subtracted cDNA libraries, followed by cDNA microarray analysis. Verification by quantitative RNA analysis by real-time polymerase chain reaction (PCR) and immunohistochemical analysis was performed in 23 genotyped complete HM.

RESULTS

Sixteen differentially expressed transcripts were identified. Quantitative RNA analysis confirmed down-regulation of ferritin light polypeptide (FTL) (P = 0.037) and insulin-like growth factor binding protein 1 (IGFBP1) (P = 0.037) in HM that subsequently developed GTN when compared with those HM that regressed. Immunohistochemical analysis further confirmed reduced IGFBP1 protein (P = 0.03) expression in HM that developed GTN.

CONCLUSIONS

Findings showed that reduced expression of genes related to cell invasion and immunosuppression, especially FTL and IGFBP1, were associated with development of GTN, and this finding may provide a better understanding of the pathogenesis of GTN. The potential application of FTL and IGFBP1 in management of patients with HM should be explored.

Diagnosis and outcome of complete hydatidiform mole coexisting with a live twin fetus

OBJECTIVE

The aim of this study was to highlight the outcome of complete hydatidiform mole (CHM) coexisting with a live co-twin.

METHODS

We investigated four cases of such pregnancy by ultrasound, pathological, cytogenetic, and molecular techniques. Information on clinical follow-up and outcome was also available.

RESULTS

All four pregnancies were spontaneous: two ended with the delivery of a live-born baby, while the other two were terminated because of signs of serious maternal pathology or intrauterine fetal death. The criteria for carrying on with the pregnancy are reviewed. The immediate outcome depends on the maternal criteria of serious pathology and on the likelihood of intrauterine fetal death. The risk of persistent trophoblastic disease (PTD) is the same as in the case of a singleton complete mole and also seems to be correlated with the zygosity mechanism identified by molecular analysis.

CONCLUSION

Hydatiform mole with a live co-twin fetus is a rare obstetric occurrence. In the case of a normal fetal karyotype, it is justifiable to await developments in the absence of maternal complications. However, treatment criteria still need improvement and diligent maternal follow-up is always warranted in the postpartum period.

The changes of gene expression profiles in hydatidiform mole and choriocarcinoma with hyperplasia of trophoblasts

The purpose of this study is to investigate changes of gene expression profiles in hydatidiform moles (HM) and choriocarcinoma and to explore causes of trophoblastic hyperplasia. Using cDNA microarray, 4,096 genes were analyzed in two pairs of the tissues of HM versus normal villi and in two pairs of normal primary culture trophoblasts versus JAR cell line of choriocarcinoma. The expressions of two genes in normal villi and HM, as well as in JAR and JEG-3, were examined with the help of immunohistochemistry, immunoblot, and reverse transcriptase-polymerase chain reaction in order to confirm the findings of cDNA microarray. Twenty-four genes were upregulated and 65 genes were downregulated in all HM. Four hundred thirty-three genes were upregulated and 380 genes were downregulated in JAR. Forty-six genes were upregulated in both HM and choriocarcinoma, whereas 13 genes were downregulated. Genes associated with the inhibition of cell proliferation were significantly downregulated, whereas genes associated with cell proliferation, malignant transformation, metastasis, and drug resistance were upregulated. Thymidine kinase-1 (TK-1) and small subunit ribonucleotide reductase (RRM-2) were overexpressed in HM, JAR, and JEG-3. The expressions of TK-1 and RRM-2 in moles were positively correlated with proliferative index of trophoblasts. Our results suggest that altered expression of genes exist in HM and choriocarcinoma. Trophoblastic hyperplasia may be involved in the overexpression of DNA synthetic enzymes.