Biallelic NLRP7 variants in patients with recurrent hydatidiform mole: A review and expert consensus

HLA-C expression in extravillous trophoblasts is determined by an ELF3-NLRP2/NLRP7 regulatory axis

The distinct human leukocyte antigen (HLA) class I expression pattern of human extravillous trophoblasts (EVT) endows them with unique tolerogenic properties that enable successful pregnancy. Nevertheless, how this process is elaborately regulated remains elusive. Previously, E74 like ETS transcription factor 3 (ELF3) was identified to govern high-level HLA-C expression in EVT. In the present study, ELF3 is found to bind to the enhancer region of two adjacent NOD-like receptor (NLR) genes, NLR family pyrin domain-containing 2 and 7 (NLRP2, NLRP7). Notably, our analysis of ELF3-deficient JEG-3 cells, a human choriocarcinoma cell line widely used to study EVT biology, suggests that ELF3 transactivates NLRP7 while suppressing the expression of NLRP2. Moreover, we find that NLRP2 and NLRP7 have opposing effects on HLA-C expression, thus implicating them in immune evasion at the maternal-fetal interface. We confirmed that NLRP2 suppresses HLA-C levels and described a unique role for NLRP7 in promoting HLA-C expression in JEG-3. These results suggest that these two NLR genes, which arose via gene duplication in primates, are fine-tuned by ELF3 yet have acquired divergent functions to enable proper expression levels of HLA-C in EVT, presumably through modulating the degradation kinetics of IkBα. Targeting the ELF3-NLRP2/NLRP7-HLA-C axis may hold therapeutic potential for managing pregnancy-related disorders, such as recurrent hydatidiform moles and fetal growth restriction, and thus improve placental development and pregnancy outcomes.

New insights into oocyte cytoplasmic lattice-associated proteins

Oocyte maturation and preimplantation embryo development are critical to successful pregnancy outcomes and the correct establishment and maintenance of genomic imprinting. Thanks to novel technologies and omics studies in human patients and mouse models, the importance of the proteins associated with the cytoplasmic lattices (CPLs), highly abundant structures found in the cytoplasm of mammalian oocytes and preimplantation embryos, in the maternal to zygotic transition is becoming increasingly evident. This review highlights the recent discoveries on the role of these proteins in protein storage and other oocyte cytoplasmic processes, epigenetic reprogramming, and zygotic genome activation (ZGA). A better comprehension of these events may significantly improve clinical diagnosis and pave the way for targeted interventions aiming to correct or mitigate female fertility issues and genomic imprinting disorders.

Hematoxylin and Eosin Staining Helps Reduce Maternal Contamination in Short Tandem Repeat Genotyping for Hydatidiform Mole Diagnosis

Short tandem repeat (STR) genotyping provides parental origin information about aneuploidy pregnancy loss and has become the current gold standard for hydatidiform mole diagnosis. STR genotyping diagnostic support most commonly relies on formalin-fixed paraffin-embedded samples, but maternal contamination is one of the most common issues based on traditional unstained sections. To evaluate the influence of hematoxylin and eosin (H&E) staining on DNA quality and STR genotyping, DNA was isolated from unstained, deparaffinized hydrated, and H&E-stained tissue sections (i.e. 3 groups) from each of 6 formalin-fixed paraffin-embedded placentas. The macrodissected view field, DNA quality, and polymerase chain reaction amplification efficiency were compared among groups. STR genotyping analysis was performed in both the test cohort (n = 6) and the validation cohort (n = 149). H&E staining not only did not interfere with molecular DNA testing of formalin-fixed paraffin-embedded tissue but also had a clearer macrodissected field of vision. In the test cohort, H&E-stained sections were the only group that did not exhibit maternal miscellaneous peaks in STR genotyping results. In the validation cohort, 138 (92.62%) cases yielded satisfactory amplification results without maternal contamination. Thus, H&E staining helped to reduce maternal contamination in STR genotyping for hydatidiform mole diagnosis, suggesting that H&E-stained sections can be incorporated into the hydatidiform mole molecular diagnostic workflow.

Hydatidiform Mole-Between Chromosomal Abnormality, Uniparental Disomy and Monogenic Variants: A Narrative Review

A hydatidiform mole (HM) or molar pregnancy is the most common benign form of gestational trophoblastic disease characterized by a proliferation of the trophoblastic epithelium and villous edema. Hydatidiform moles are classified into two forms: complete and partial hydatidiform moles. These two types of HM present morphologic, histopathologic and cytogenetic differences. Usually, hydatidiform moles are a unique event, but some women present a recurrent form of complete hydatidiform moles that can be sporadic or familial. The appearance of hydatidiform moles is correlated with some genetic events (like uniparental disomy, triploidy or diandry) specific to meiosis and is the first step of embryo development. The familial forms are determined by variants in some genes, with NLRP7 and KHDC3L being the most important ones. The identification of different types of hydatidiform moles and their subsequent mechanisms is important to calculate the recurrence risk and estimate the method of progression to a malign form. This review synthesizes the heterogeneous mechanisms and their implications in genetic counseling.

When to Consult a Geneticist Specialising in Gestational Trophoblastic Disease

BACKGROUND

Gestational trophoblastic disease comprises hydatidiform moles and a rare group of malignancies that derive from trophoblasts. Although there are typical morphological features that may distinguish hydatidiform moles from non-molar products of conception, such features are not always present, especially at early stages of pregnancy. Furthermore, mosaic/chimeric pregnancies and twin pregnancies make pathological diagnosis challenging while trophoblastic tumours can also pose diagnostic problems in terms of their gestational or non-gestational origin.

OBJECTIVES

The aim of this study was to show that ancillary genetic testing can be used to aid diagnosis and clinical management of GTD.

METHODS

Each author identified cases where genetic testing, including short tandem repeat (STR) genotyping, ploidy analysis, next-generation sequencing, and immunostaining for p57, the product of the imprinted gene CDKN1C, facilitated accurate diagnosis and improved patient management. Representative cases were chosen to illustrate the value of ancillary genetic testing in different scenarios.

OUTCOME

Genetic analysis of placental tissue can aid in determining the risk of developing gestational trophoblastic neoplasia, facilitating discrimination between low risk triploid (partial) and high risk androgenetic (complete) moles, discriminating between a hydatidiform mole twinned with a normal conceptus and a triploid conception and identification of androgenetic/biparental diploid mosaicism/chimerism. STR genotyping of placental tissue and targeted gene sequencing of patients can identify women with an inherited predisposition to recurrent molar pregnancies. Genotyping can distinguish gestational from non-gestational trophoblastic tumours using tissue or circulating tumour DNA and can also identify the causative pregnancy which is the key prognostic factor for placental site and epithelioid trophoblastic tumours.

CONCLUSIONS AND OUTLOOK

STR genotyping and p57 immunostaining have been invaluable to the management of gestational trophoblastic disease in many situations. The use of next-generation sequencing and of liquid biopsies is opening up new pathways for GTD diagnostics. Development of these techniques has the potential to identify novel biomarkers of GTD and further refine diagnosis.

NLRP7 participates in the human subcortical maternal complex and its variants cause female infertility characterized by early embryo arrest

Successful human reproduction requires normal oocyte maturation, fertilization, and early embryo development. Early embryo arrest is a common phenomenon leading to female infertility, but the genetic basis is largely unknown. NLR family pyrin domain-containing 7 (NLRP7) is a member of the NLRP subfamily. Previous studies have shown that variants of NLRP7 are one of the crucial causes of female recurrent hydatidiform mole, but whether NLRP7 variants can directly affect early embryo development is unclear. We performed whole-exome sequencing in patients who experienced early embryo arrest, and five heterozygous variants (c.251G > A, c.1258G > A, c.1441G > A, c. 2227G > A, c.2323C > T) of NLRP7 were identified in affected individuals. Plasmids of NLRP7 and subcortical maternal complex components were overexpressed in 293 T cells, and Co-IP experiments showed that NLRP7 interacted with NLRP5, TLE6, PADI6, NLRP2, KHDC3L, OOEP, and ZBED3. Injecting complementary RNAs in mouse oocytes and early embryos showed that NLRP7 variants influenced the oocyte quality and some of the variants significantly affected early embryo development. These findings contribute to our understanding of the role of NLRP7 in human early embryo development and provide a new genetic marker for clinical early embryo arrest patients. KEY MESSAGES: Five heterozygous variants of NLRP7 (c.1441G > A; 2227G > A; c.251G > A; c.1258G > A; c.2323C > T) were identified in five infertile patients who experienced early embryo arrest. NLRP7 is a component of human subcortical maternal complex. NLRP7 variants lead to poor quality of oocytes and early embryo development arrest. This study provides a new genetic marker for clinical early embryo arrest patients.

High Risk of Gestational Trophoblastic Neoplasia Development in Recurrent Hydatidiform Moles with NLRP7 Pathogenic Variations

Objective

Pathogenic variations of the NLRP7 and KHDC3L genes are responsible for familial recurrent hydatidiform moles, a rare autosomal recessive phenomenon that can lead to severe comorbidities. Little is known about the diversity of genetic defects or the natural course of disease progression among recurrent hydatidiform mole cases from distinct ethnicities. In this study, we aimed to investigate the mutation profile and pregnancy outcomes in patients with multiple molar pregnancies.

Material and Methods

Three unrelated cases with recurrent molar pregnancies are included in this study. None of the patients had a known family history of molar pregnancy. Clinical findings and follow-up results are documented. Sanger sequencing is used to reveal genetic defects in exons and exon-intron boundaries of NLRP7 and KHDC3L genes.

Results

NLRP7 pathogenic variants were found in all three cases. In two cases, homozygous, c.2471+1G>A canonical splice cite variant was identified and in one case a homozygous, c.2571dupC (p.Ile858HisfsTer11) frameshift variant was identified. No variant in the KHDC3L gene was found in any case. In all cases, the development of gestational trophoblastic neoplasia complicated the clinical course and the treatment plans.

Conclusions

We found that defects of the NLRP7 gene are principally responsible for etiology in our region, and the mutation profile suggests a founder effect in the Turkish population. We suggest early genetic diagnosis and counseling in molar pregnancies and recommend close follow-up in terms of conversion to gestational trophoblastic neoplasia.