Biallelic variant in cyclin B3 is associated with failure of maternal meiosis II and recurrent digynic triploidy.

BACKGROUND: Triploidy is one of the most common chromosome abnormalities affecting human gestation and accounts for an important fraction of first-trimester miscarriages. Triploidy has been demonstrated in a few cases of recurrent pregnancy loss (RPL) but its molecular mechanisms are unknown. This study aims to identify the genetic cause of RPL associated with fetus triploidy. METHODS: We investigated genomic imprinting, genotyped sequence-tagged site (STS) markers and performed exome sequencing in a family including two sisters with RPL. Moreover, we evaluated oocyte maturation in vivo and in vitro and effect of the candidate protein variant in silico. RESULTS: While features of hydatidiform mole were excluded, the presence of triploidy of maternal origin was demonstrated in the fetuses. Oocyte maturation was deficient and all the maternally inherited pericentromeric STS alleles were homozygous in the fetuses. A deleterious missense variant (p.V1251D) of the cyclin B3 gene (CCNB3) affecting a residue conserved in placental mammals and located in a region that can interact with the cyclin-dependent kinase 1 or cyclin-dependent kinase 2 cosegregated in homozygosity with RPL. CONCLUSION: Here, we report a family in which a damaging variant in cyclin B3 is associated with the failure of oocyte meiosis II and recurrent fetus triploidy, implicating a rationale for CCNB3 testing in RPL.

Thrombophilic genes alterations as risk factor for recurrent pregnancy loss.

OBJECTIVE: The important polymorphisms leading to inherited thrombophilia are Factor V Leiden (FVL), Prothrombin G20210A and MTHFR C677T and A1298C. The frequencies also the correlation among these polymorphisms and RPL have been reported controversially in various populations. Our clinic is one of the referral centers in reproductive biomedicine in which patients in all over Iran refer to; thus the results of this study could be considered clinically beneficial. Besides, in the present study, not only the frequency of specific but also multiple thrombophilic gene alterations were compared in Iranian women with RPL and a control group. METHODS: The patients group comprised 330 women with three or more consecutive RPLs. The control population included 350 women with at least one child and no history of pregnancy loss. FVL, Prothrombin G20210A and MTHFR C677T polymorphisms were analyzed by Strip assay kit. MTHFR A1298C was genotyped by PCR-RFLP. RESULTS: The frequencies of FVL, Prothrombin G20210A, MTHFR C677T and MTHFR A1298C mutations in patients were 8.48, 4.24, 45.45 and 59.39%, and in controls were 2.86, 2.86, 34.28 and 6%, respectively. CONCLUSIONS: The present data showed that FVL, MTHFR polymorphisms also combined with thrombophilic gene mutations have a strong association with RPL.