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Microsatellite DNA Genotyping and Flow Cytometry Ploidy Analyses of Formalin-fixed Paraffin-embedded Hydatidiform Molar Tissues

Hydatidiform mole (HM) is an abnormal human pregnancy characterized by excessive trophoblastic proliferation and abnormal embryonic development. There are ...

McGill University

Miscarriages affect 15% of clinically recognized pregnancies. Recurrent miscarriage (RM) is defined by the occurrence of at least two consecutive pregnancy losses and affects 1%-5% of couples trying to conceive. In an attempt to categorize patients with RM and identify the mechanisms leading to their miscarriages, we first used flow cytometry to assess the ploidy of 93 products of conception (POCs) from 53 patients with RM (≥3 miscarriages). We identified a single patient with four triploid POCs. We then used fluorescent in situ hybridization to confirm the triploidies and fluorescent microsatellite genotyping with distal and pericentromeric markers to determine their parental origin and the mechanisms leading to their formation. We found that all four triploidies were digynic and due to a failure in meiosis II (MII), suggesting a genetic predisposition. Upon further investigation into the family, we found a remarkable history of ovarian cysts and dysfunctions on the maternal side. Notably, one maternal cousin had a mature ovarian teratoma that we analyzed and found an identical mechanism at its origin, a failure in MII. The identification of two patients in the same family with two different manifestations-digynic triploid conceptions and mature ovarian teratomas, both resulting from the failure of MII-suggests an inherited genetic susceptibility toward an error in MII segregating in the family that may manifest in the form of a triploid digynic miscarriage or a mature ovarian teratoma. Our findings may facilitate the future identification of causative mutations for MII defects.

Recurrent triploid digynic conceptions and mature ovarian teratomas: Are they different manifestations of the same genetic defect?

Hydatidiform mole is an aberrant human pregnancy characterized by early embryonic arrest and excessive trophoblastic proliferation. Recurrent hydatidiform moles are defined by the occurrence of at least two hydatidiform moles in the same patient. Fifty to eighty percent of patients with recurrent hydatidiform moles have biallelic pathogenic variants in NLRP7 or KHDC3L. However, in the remaining patients, the genotypic types of the moles are unknown. We characterized 80 new hydatidiform mole tissues, 57 of which were from patients with no mutations in the known genes, and we reviewed the genotypes of a total of 123 molar tissues. We also reviewed mutation analysis in 113 patients with recurrent hydatidiform moles. While all hydatidiform moles from patients with biallelic NLRP7 or KHDC3L mutations are diploid biparental, we demonstrate that those from patients without mutations are highly heterogeneous and only a small minority of them are diploid biparental (8%). The other mechanisms that were found to recur in patients without mutations are diploid androgenetic monospermic (24%) and triploid dispermic (32%); the remaining hydatidiform moles were misdiagnosed as moles due to errors in the analyses and/or their unusual mechanisms. We compared three parameters of genetic susceptibility in patients with and without mutations and show that patients without mutations are mostly from non-familial cases, have fewer reproductive losses, and more live births. Our data demonstrate that patients with recurrent hydatidiform moles and no mutations in the known genes are, in general, different from those with mutations; they have a milder genetic susceptibility and/or a multifactorial etiology underlying their recurrent hydatidiform moles. Categorizing these patients according to the genotypic types of their recurrent hydatidiform moles may facilitate the identification of novel genes for this entity.

Article	Year
Recurrent triploid digynic conceptions and mature ovarian teratomas: Are they different manifestations of the same genetic defect? Genes, chromosomes & cancer\| PubMed ID: 28730668	2017
The genetics of recurrent hydatidiform moles: new insights and lessons from a comprehensive analysis of 113 patients. Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc\| PubMed ID: 29463882	2018

Yassemine Khawajkie

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