The genomic architecture of NLRP7 is Alu rich and predisposes to disease-associated large deletions

Recurrent Hydatidiform Moles: A Clinical Challenge-A Case Report and an Update on Management and Therapeutical Strategies

Hydatidiform mole, complete or partial (CHM/PHM), is the most common type of gestational trophoblastic disease (GTD), which is characterized by excessive trophoblastic proliferation and abnormal embryonic development. Some patients present with sporadic or familiar recurrent hydatidiform moles (RHMs), which are characterized by two or more episodes of the disease. A healthy 36-year-old woman was admitted to the Obstetrics and Gynecology Unit of Santa Maria Goretti Hospital, Latina, because of RHMs at 6 weeks of amenorrhea, with an obstetrical anamnesis of RHMs. We performed uterine dilatation and curettage with suction evacuation. The histological examination confirmed the diagnosis of PHM. The clinical follow-up was conducted according to recent guidelines on the diagnosis and management of GTD. After the return to the baseline values of the beta-human chorionic gonadotropin hormone, a combined oral contraceptive therapy was proposed, and the patient was invited to undergo in vitro fertilization (IVF) techniques, specifically oocyte donation, to reduce the possibility of similar future cases of RHMs. Although some etiopathogenetic mechanisms involved in RHMs are still unknown, all patients of childbearing age who are affected by this syndrome should be properly treated and directed towards a correct clinical path as IVF, to have a successful and safe pregnancy.

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.

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

Hydatidiform mole (HM) is an abnormal human pregnancy characterized by excessive growth of placental trophoblasts and abnormal early embryonic development. Following a first such abnormal pregnancy, the risk for women of successive molar pregnancies significantly increases. To date variants in seven maternal-effect genes have been shown to cause recurrent HMs (RHM). NLRP7 is the major causative gene for RHM and codes for NOD-like receptor (NLR) family pyrin domain containing 7, which belongs to a family of proteins involved in inflammatory disorders. Since its identification, all NLRP7 variants have been recorded in Infevers, an online registry dedicated to autoinflammatory diseases (https://infevers.umai-montpellier.fr/web/). Here, we reviewed published and unpublished recessive NLRP7 variants associated with RHM, scored their pathogenicity according to the American College of Medical Genetics classification, and recapitulated all functional studies at the level of both the patients and the conceptions. We also provided data on further variant analyses of 32 patients and genotypes of 36 additional molar pregnancies. This comprehensive review integrates published and unpublished data on NLRP7 and aims at guiding geneticists and clinicians in variant interpretation, genetic counseling, and management of patients with this rare condition.

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.

The L1-dependant and Pol III transcribed Alu retrotransposon, from its discovery to innate immunity

The 300 bp dimeric repeats digestible by AluI were discovered in 1979. Since then, Alu were involved in the most fundamental epigenetic mechanisms, namely reprogramming, pluripotency, imprinting and mosaicism. These Alu encode a family of retrotransposons transcribed by the RNA Pol III machinery, notably when the cytosines that constitute their sequences are de-methylated. Then, Alu hijack the functions of ORF2 encoded by another transposons named L1 during reverse transcription and integration into new sites. That mechanism functions as a complex genetic parasite able to copy-paste Alu sequences. Doing that, Alu have modified even the size of the human genome, as well as of other primate genomes, during 65 million years of co-evolution. Actually, one germline retro-transposition still occurs each 20 births. Thus, Alu continue to modify our human genome nowadays and were implicated in de novo mutation causing diseases including deletions, duplications and rearrangements. Most recently, retrotransposons were found to trigger neuronal diversity by inducing mosaicism in the brain. Finally, boosted during viral infections, Alu clearly interact with the innate immune system. The purpose of that review is to give a condensed overview of all these major findings that concern the fascinating physiology of Alu from their discovery up to the current knowledge.

The pivotal roles of the NOD-like receptors with a PYD domain, NLRPs, in oocytes and early embryo development†

Nucleotide-binding oligomerization domain (NOD)-like receptors with a pyrin domain (PYD), NLRPs, are pattern recognition receptors, well recognized for their important roles in innate immunity and apoptosis. However, several NLRPs have received attention for their new, specialized roles as maternally contributed genes important in reproduction and embryo development. Several NLRPs have been shown to be specifically expressed in oocytes and preimplantation embryos. Interestingly, and in line with divergent functions, NLRP genes reveal a complex evolutionary divergence. The most pronounced difference is the human-specific NLRP7 gene, not identified in rodents. However, mouse models have been extensively used to study maternally contributed NLRPs. The NLRP2 and NLRP5 proteins are components of the subcortical maternal complex (SCMC), which was recently identified as essential for mouse preimplantation development. The SCMC integrates multiple proteins, including KHDC3L, NLRP5, TLE6, OOEP, NLRP2, and PADI6. The NLRP5 (also known as MATER) has been extensively studied. In humans, inactivating variants in specific NLRP genes in the mother are associated with distinct phenotypes in the offspring, such as biparental hydatidiform moles (BiHMs) and preterm birth. Maternal-effect recessive mutations in KHDC3L and NLRP5 (and NLRP7) are associated with reduced reproductive outcomes, BiHM, and broad multilocus imprinting perturbations. The precise mechanisms of NLRPs are unknown, but research strongly indicates their pivotal roles in the establishment of genomic imprints and post-zygotic methylation maintenance, among other processes. Challenges for the future include translations of findings from the mouse model into human contexts and implementation in therapies and clinical fertility management.

NLRP7 plays a functional role in regulating BMP4 signaling during differentiation of patient-derived trophoblasts

Complete hydatidiform mole (HM) is a gestational trophoblastic disease resulting in hyperproliferation of trophoblast cells and absence of embryo development. Mutations in the maternal-effect gene NLRP7 are the major cause of familial recurrent complete HM. Here, we established an in vitro model of HM using patient-specific induced pluripotent stem cells (iPSCs) derived trophoblasts harboring NLRP7 mutations. Using whole transcriptome profiling during trophoblast differentiation, we showed that impaired NLRP7 expression results in precocious downregulation of pluripotency factors, activation of trophoblast lineage markers, and promotes maturation of differentiated extraembryonic cell types such as syncytiotrophoblasts. Interestingly, we found that these phenotypes are dependent on BMP4 signaling and BMP pathway inhibition corrected the excessive trophoblast differentiation of patient-derived iPSCs. Our human iPSC model of a genetic placental disease recapitulates aspects of trophoblast biology, highlights the broad utility of iPSC-derived trophoblasts for modeling human placental diseases and identifies NLRP7 as an essential modulator of key developmental cell fate regulators.

NLRP7 is expressed in the ovine ovary and associated with in vitro pre-implantation embryo development

NLRP (NACHT, LRR and PYD domain-containing proteins) family plays pivotal roles in mammalian reproduction. Mutation of NLRP7 is often associated with human recurrent hydatidiform moles. Few studies regarding the functions of NLRP7 have been performed in other mammalian species rather than humans. In the current study, for the first time, the function of NLRP7 has been explored in ovine ovary. NLRP7 protein was mainly located in ovarian follicles and in in vitro pre-implantation embryos. To identify its origin, 763 bp partial CDS of NLRP7 deriving from sheep cumulus oocyte complexes (COCs) was cloned, it showed a great homology with Homo sapiens. The high levels of mRNA and protein of NLRP7 were steadily expressed in oocytes, parthenogenetic embryos or IVF embryos. NLRP7 knockdown by the combination of siRNA and shRNA jeopardized both the parthenogenetic and IVF embryo development. These results strongly suggest that NLRP7 plays an important role in ovine reproduction. The potential mechanisms of NLRP7 will be fully investigated in the future.

Genetic diagnosis of subfertility: the impact of meiosis and maternal effects

During reproductive age, approximately one in seven couples are confronted with fertility problems. While the aetiology is diverse, including infections, metabolic diseases, hormonal imbalances and iatrogenic effects, it is becoming increasingly clear that genetic factors have a significant contribution. Due to the complex nature of infertility that often hints at a multifactorial cause, the search for potentially causal gene mutations in idiopathic infertile couples has remained difficult. Idiopathic infertility patients with a suspicion of an underlying genetic cause can be expected to have mutations in genes that do not readily affect general health but are only essential in certain processes connected to fertility. In this review, we specifically focus on genes involved in meiosis and maternal-effect processes, which are of critical importance for reproduction and initial embryonic development. We give an overview of genes that have already been linked to infertility in human, as well as good candidates which have been described in other organisms. Finally, we propose a phenotypic range in which we expect an optimal diagnostic yield of a meiotic/maternal-effect gene panel.

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.

Novel mutations in genes encoding subcortical maternal complex proteins may cause human embryonic developmental arrest

Successful human reproduction initiates from normal gamete formation, fertilization and early embryonic development. Abnormalities in any of these steps will lead to infertility. Many infertile patients undergo several failures of IVF and intracytoplasmic sperm injection (ICSI) cycles, and embryonic developmental arrest is a common phenotype in cases of recurrent failure of IVF/ICSI attempts. However, the genetic basis for this phenotype is poorly understood. The subcortical maternal complex (SCMC) genes play important roles during embryonic development, and using whole-exome sequencing novel biallelic mutations in the SCMC genes TLE6, PADI6 and KHDC3L were identified in four patients with embryonic developmental arrest. A mutation in TLE6 was found in a patient with cleaved embryos that arrested on day 3 and failed to form blastocysts. Two patients with embryos that arrested at the cleavage stage had mutations in PADI6, and a mutation in KHDC3L was found in a patient with embryos arrested at the morula stage. No mutations were identified in these genes in an additional 80 patients. These findings provide further evidence for the important roles of TLE6, PADI6 and KHDC3L in embryonic development. This work lays the foundation for the genetic diagnosis of patients with recurrent IVF/ICSI failure.

Identification of mutations in HEXA and HEXB in Sandhoff and Tay-Sachs diseases: a new large deletion caused by Alu elements in HEXA

G_M2 gangliosides are a group of lysosomal lipid storage disorders that are due to mutations in HEXA, HEXB and GM2A. In our study, 10 patients with these diseases were enrolled, and Sanger sequencing was performed for the HEXA and HEXB genes. The results revealed one known splice site mutation (c.346+1G>A, IVS2+1G>A) and three novel mutations (a large deletion involving exons 6–10; one nucleotide deletion, c.622delG [p.D208Ifsx15]; and a missense mutation, c.919G>A [p.E307K]) in HEXA. In HEXB, one known mutation (c.1597C>T [p.R533C]) and one variant of uncertain significance (c.619A>G [p.I207V]) were identified. Five patients had c.1597C>T in HEXB, indicating a common mutation in south Iran. In this study, a unique large deletion in HEXA was identified as a homozygous state. To predict the cause of the large deletion in HEXA, RepeatMasker was used to investigate the Alu elements. In addition, to identify the breakpoint of this deletion, PCR was performed around these elements. Using Repeat masker, different Alu elements were identified across HEXA, mainly in intron 5 and intron 10 adjacent to the deleted exons. PCR around the Alu elements and Sanger sequencing revealed the start point of a large deletion in AluSz6 in the intron 6 and the end of its breakpoint 73 nucleotides downstream of AluJo in intron 10. Our study showed that HEXA is an Alu-rich gene that predisposes individuals to disease-associated large deletions due to these elements.

A novel large fragment deletion in PLS3 causes rare X-linked early-onset osteoporosis and response to zoledronic acid

We identified a novel large fragment deletion from intron 9 to 3'UTR in PLS3 (E10-E16del) in one Chinese boy with X-linked early-onset osteoporosis and vertebral fractures, which expanded the pathogenic spectrum of X-linked early-onset osteoporosis. Treatment with zoledronic acid was beneficial for increasing BMD and reshaping the vertebral bodies of this patient.

INTRODUCTION

X-linked early-onset osteoporosis is a rare disease, which is characterized by low bone mineral density (BMD), vertebral compression fractures (VCFs), and/or long bone fractures. We aimed to detect the phenotype and the underlying pathogenic mutation of X-linked early-onset osteoporosis in a boy from a nonconsanguineous Chinese family.

METHODS

We investigated the pathogenic mutation of the patient with X-linked early-onset osteoporosis by targeted next-generation sequencing and confirmed it by Sanger sequencing. We also observed the effects of zoledronic acid on fracture frequency and BMD of the patient.

RESULTS

Low BMD and multiple VCFs were the main phenotypes of X-linked early-onset osteoporosis. We identified a total of 12,229 bp deletion in PLS3, involving intron 9 to the 3'UTR (E10-E16 del). This large fragment deletion might be mediated by Alu repeats and microhomology of 26 bp at each breakpoint junction. Zoledronic acid treatment could significantly increase the Z-score of BMD and reshape the compressed vertebral bodies.

CONCLUSION

We identified a large fragment deletion mutation in PLS3 for the first time and elucidated the possible mechanism of the deletion, which led to X-linked early-onset osteoporosis and multiple vertebral fractures. Our findings would enrich the etiology spectrum of this rare disease.