Genome-wide single nucleotide polymorphism array analysis unveils the origin of heterozygous androgenetic complete moles

Genetics and Genomics of Gestational Trophoblastic Disease

This article focuses on hydatidiform mole (HM), which is the most common form of gestational trophoblastic disease and the most studied at the genomic and genetic levels. We summarize current laboratory methods to diagnose HM, discuss their limitations and advantages, and share the lessons we have learned. We also provide an overview of the history of recurrent HM, their known genetic etiologies, and the mechanisms of their formation.

Aneuploidy is frequent in heterozygous diploid and triploid hydatidiform moles

Hydatidiform moles are abnormal conceptuses. Many hydatidiform moles are diploid androgenetic, and of these, most are homozygous in all loci. Additionally, most hydatidiform moles are euploid. Using Single Nucleotide Polymorphism (SNP) array analysis, in two studies a higher frequency of aneuploidy was observed in diploid androgenetic heterozygous conceptuses, than in their homozygous counterparts. In the Danish Mole Project, we analyze conceptuses suspected to be hydatidiform moles due to the clinical presentation, using karyotyping and Short Tandem Repeat (STR) analysis. Among 278 diploid androgenetic conceptuses, 226 were homozygous in all loci and 52 (18.7%) were heterozygous in several loci. Among 142 triploid diandric conceptuses, 141 were heterozygous for paternally inherited alleles in several loci. Here we show that the frequencies of aneuploidy in diploid androgenetic heterozygous and triploid diandric heterozygous conceptuses were significantly higher than the frequency of aneuploidy in diploid androgenetic homozygous conceptuses. In diploid androgenetic and triploid diandric conceptuses that are heterozygous for paternally inherited alleles, the two paternally inherited sets of genomes originate in two spermatozoa. Each spermatozoon provides one pair of centrioles to the zygote. The presence of two pairs of centrioles may cause an increased risk of aneuploidy.

Single-nucleotide polymorphism array and fluorescence in situ hybridization analysis to decode the cytogenetic profile of atypical partial hydatidiform moles diagnosed by short tandem repeat polymorphism analysis

Accurate diagnosis of partial hydatidiform moles (PHMs) is crucial for improving outcomes of gestational trophoblastic neoplasia. The use of short tandem repeat (STR) polymorphism analysis to distinguish between PHM and hydropic abortuses is instrumental; however, its diagnostic power has not been comprehensively assessed. Herein, we evaluated the diagnostic efficacy of STR in differentiating between PHM and hydropic abortus, thus providing an opportunity for early measurement of human chorionic gonadotropin for PHMs. We reviewed charts of STR polymorphism analysis performed on fresh villous specimens and patient blood samples using a commercial kit for 16 loci. The genetic classification of 79 PHMs was confirmed. STR was reliable in differentiating PHMs when at least 15 loci were available. Typically, PHMs are characterized by their triploidy, including two paternal and one maternal haploid contribution. In our sample, seven PHMs lacked the three-allelic loci, requiring fluorescence in situ hybridization (FISH) analysis to investigate imbalanced biparental conceptus and single-nucleotide polymorphism array analysis to reveal cytogenetic details. Of these PHMs, two, three, and one were identified as androgenetic/biparental mosaics (diploids), monospermic diandric monogynic triploids, and a typical dispermic diandric monogynic triploid, respectively. The remaining case was monospermic origin, but its ploidy details could not be available. Therefore, STR differentiated PHM from a biparental diploid abortus in most cases. However, PHM diagnosis may be compromised when STR is used as the sole method for cases displaying distinct cytogenetic patterns lacking the three-allelic loci, including androgenetic/biparental mosaicism. Therefore, FISH should be considered to confirm the diagnosis.

Auxiliary and experimental diagnostic techniques for hydatidiform moles

Hydatidiform moles are classified into complete hydatidiform moles (CHMs), which are androgenetic and diploid, and partial hydatidiform moles (PHM), which are triploid with two paternal chromosomes and one maternal chromosome. The incidence of gestational trophoblastic neoplasia differs substantially between CHM and PHM. However, they are occasionally difficult to diagnose. In this review, auxiliary and experimental methods based on cytogenetic features and advanced molecular detection techniques applied to the diagnosis and analysis of hydatidiform moles are summarized, including basic principles, characteristics, and clinical implications. Short tandem repeat polymorphism analysis is considered the gold standard for the genetic diagnosis of hydatidiform moles. In clinical settings, immunohistochemical analyses of p57^KIP2 , an imprinted gene product, are widely used to differentiate CHMs from other conceptuses, including PHMs. Recently, new molecular genetic techniques, such as single nucleotide polymorphism arrays, have been applied to research on hydatidiform moles. In addition to insights from classical methods, such as chromosome analysis, recently developed approaches have yielded novel findings related to the mechanism underlying the development of androgenetic CHMs.

Recurrent Androgenetic Complete Hydatidiform Moles with p57KIP2-Positive in a Chinese Family

Androgenetic complete hydatidiform moles (CHMs) are associated with an increased risk of gestational trophoblastic neoplasia. P57^KIP2 expression in hydatidiform moles is thought to be a powerful marker for differentiating CHMs from partial hydatidiform moles (PHMs). However, since there are so few such families clinically, very few studies have addressed the importance of p57^KIP2-positive in the diagnosis and prognosis of CHM. This study aimed to emphasize the significance of the accurate diagnosis of rare CHM and careful follow-up. The classification of the hydatidiform mole was based on morphologic examination and p57^KIP2 expression was determined by p57^KIP2 immunohistochemical staining. Copy number variation sequencing was used to determine the genetic make-up of the mole tissues. In addition, the short tandem repeat polymorphism analysis was used to establish the parental origin of the moles. Finally, whole-exome sequencing was performed to identify the causal genetic variants associated with this case. In one Chinese family, the proband had numerous miscarriages throughout her two marriages. Morphologic evaluation and molecular genotyping accurately sub-classified two molar specimens as uniparental disomy CHM of androgenetic origin. Furthermore, p57^KIP2 expression was found in cytotrophoblasts and villous stromal cells. In the tissue, there were hyperplasia trophoblastic cells and heteromorphic nuclei. In this family, no deleterious variant genes associated with recurrent CHM were detected. It is important to evaluate the prognostic value of p57^KIP2 expression in androgenetic recurrent CHM. This knowledge may help to minimize erroneous diagnosis of CHMs as PHMs, as well as making us aware of the need to manage potential gestational trophoblastic neoplasia.

Parentage analysis using genome-wide high-density SNP microarray

OBJECTIVE

Parentage analysis is a technology that uses genetic methods to verify or exclude relationships between individuals. STR technology is often used in parentage analysis. We received three sets of samples from three families. Each set of samples consisted of a male individual and a female individual. Their test requirements were meant to determine whether they were a paternity relationship, a sibling relationship, or grandparent-grandchild relationship. However, only one STR locus mismatch was detected in each group. Other family members to assist in testing could not be identified; therefore, other methods were needed to assist in judgment. Using high-density SNP microarrays, we analyzed the feasibility of its application in paternity analysis.

RESULTS

A total of 180 samples were tested, including 100 unrelated samples, and 74 samples from 30 families, and six samples from three families. The data were analyzed, grouped according to the chromosome of SNP, and the mismatching rate was counted. The total mismatching rate of SNP in unrelated individuals was 8-10 times higher than that of parent-child individuals. Individuals with a total mismatch rate of more than 5.3% were defined as individuals with no kinship, and the individuals with a total mismatch rate of less than 0.6% were defined as the individuals with a parent-child relationship.

CONCLUSIONS

Through the use of high-density gene chips for analysis, we also completed an auxiliary analysis of the kinship of the three families. The gene chip is a better method for auxiliary analysis of the kinship between individuals.

Spermatogonium-Derived Complete Hydatidiform Mole

A complete hydatidiform mole (CHM) is a conceptus with only sperm-derived chromosomes. Here, we report on a CHM with genomic DNA identical to that of the paternal somatic cells. The CHM developed in a woman who had undergone intrauterine implantation of a blastocyst obtained through in vitro injection of a presumed round spermatid into one of her oocytes. The CHM was genetically identical to peripheral white cells of her husband and contained no maternally derived nuclear DNA. We hypothesize that a spermatogonium, rather than a round spermatid, was inadvertently selected for the procedure. The CHM developed into a gestational trophoblastic neoplasia, which resolved after chemotherapy. (Funded by the Japan Society for the Promotion of Science.).

Androgenetic Complete Hydatidiform Moles With p57KIP2-Positive Immunostaining

OBJECTIVES

Complete hydatidiform moles (CHMs) are androgenetic and have a high rate of progression to gestational trophoblastic neoplasia (GTN). CHMs are negative when immunostained for p57KIP2 protein, the product of the maternally expressed gene on chromosome 11p15.5, whereas biparental partial hydatidiform moles and hydropic abortion are positive for p57KIP2. This study presents two cases of p57KIP2-positive androgenetic CHMs and explores the cause of this inconsistency.

METHODS

Androgenetic CHMs were diagnosed using multiplex short tandem repeat polymorphism analysis. Single-nucleotide polymorphism arrays were performed for molecular karyotyping.

RESULTS

Among the consecutive 188 androgenetic CHMs, two cases were positive for p57KIP2. The first case remitted spontaneously, whereas the second case developed into low-risk GTN. The first case was positive for p57KIP2 in all villi. The karyotype was 48,XX,+7,+11, with the additional chromosome 11 confirmed to be of maternal origin. The second case presented a mosaic of both positively and negatively stained villi. The karyotype was 46,XX.

CONCLUSIONS

The cause of one of the CHMs was trisomy with an additional maternal chromosome 11. Although rare, the confirmation of p57KIP2-positive androgenetic CHM status is necessary to manage GTN risk.

Invasive mole with lung metastasis after an abdominal complete hydatidiform mole treatment

A 27-year-old woman, gravida 1, para 0, was transferred to our hospital with acute abdominal pain. Her serum human chorionic gonadotropin level was 60 231 mIU/mL. Transabdominal ultrasound revealed an echo-free space, and emergency laparoscopy-assisted surgery was performed with a preoperative diagnosis of ruptured ectopic pregnancy. The pelvic cavity was filled with clots, and the peritoneal surface of the uterine fundus was swollen and showed continuous bleeding. The lesion was located on peritoneum and not connected with the uterine cavity. Histological examination of the conceptus showed features of a complete hydatidiform mole. After a mild decrease, hCG levels adversely increased 3 weeks later with multiple lung nodules. With a diagnosis of invasive moles, the patient was administered chemotherapy. This case demonstrates that it is important to recognize the potential of ectopic hydatidiform moles through abdominal pregnancy. This is the first report of an invasive abdominal hydatidiform mole, and hCG monitoring seemed to be essential for gestational trophoblastic neoplasia detection.

Parental contribution to trisomy in heterozygous androgenetic complete moles

Complete hydatidiform moles (CHMs) comprise a proliferative trophoblastic disorder and are known to be androgenetic and diploid. Androgenetic CHMs are classified as having monospermic and dispermic origins. Rarely, some CHMs have other genetic constitutions, such as biparental diploid or tetraploid. Previous studies have shown the possibility that androgenetic heterozygous CHMs have an additional chromosome with high frequency. This study aimed to comprehensively analyse the molecular karyotyping of androgenetic dispermic CHMs and the parental contribution of their additional chromosomes. Single-nucleotide polymorphism arrays were performed with the genomic DNA of CHMs and patients. The B allele frequency and selected B allele frequency plotting of CHM were visualised. Among the 31 dispermic CHMs, eight showed trisomy and one showed double trisomy; of the 10 additional chromosomes, seven were of maternal original and three were of paternal origin. In addition, three disomic chromosomes comprised one maternal and one paternal chromosome, although these should theoretically have had two paternal chromosomes in the case of androgenetic CHMs. The subclassification of heterozygous CHMs, with or without maternal contribution, is a new approach and could be a candidate indicator of gestational trophoblastic neoplasia risk.