BRCA1 regulates HMGA2 levels in the Swan71 trophoblast cell line

Regulatory roles of non-coding RNAs and m6A modification in trophoblast functions and the occurrence of its related adverse pregnancy outcomes

Adverse pregnancy outcomes, such as preeclampsia, gestational diabetes mellitus, fetal growth restriction, and recurrent miscarriage, occur frequently in pregnant women and might further induce morbidity and mortality for both mother and fetus. Increasing studies have shown that dysfunctions of human trophoblast are related to these adverse pregnancy outcomes. Recent studies also showed that environmental toxicants could induce trophoblast dysfunctions. Moreover, non-coding RNAs (ncRNAs) have been reported to play important regulatory roles in various cellular processes. However, the roles of ncRNAs in the regulation of trophoblast dysfunctions and the occurrence of adverse pregnancy outcomes still need to be further investigated, especially with exposure to environmental toxicants. In this review, we analyzed the regulatory mechanisms of ncRNAs and m6A methylation modification in the dysfunctions of trophoblast cells and the occurrence of adverse pregnancy outcomes and also summarized the harmful effects of environmental toxicants. In addition to DNA replication, mRNA transcription, and protein translation, ncRNAs and m6A modification might be considered as the fourth and fifth elements that regulate the genetic central dogma, respectively. Environmental toxicants might also affect these processes. In this review, we expect to provide a deeper scientific understanding of the occurrence of adverse pregnancy outcomes and to discover potential biomarkers for the diagnosis and treatment of these outcomes.

The Role of LIN28-let-7-ARID3B Pathway in Placental Development

Placental disorders are a major cause of pregnancy loss in humans, and 40–60% of embryos are lost between fertilization and birth. Successful embryo implantation and placental development requires rapid proliferation, invasion, and migration of trophoblast cells. In recent years, microRNAs (miRNAs) have emerged as key regulators of molecular pathways involved in trophoblast function. A miRNA binds its target mRNA in the 3ʹ-untranslated region (3ʹ-UTR), causing its degradation or translational repression. Lethal-7 (let-7) miRNAs induce cell differentiation and reduce cell proliferation by targeting proliferation-associated genes. The oncoprotein LIN28 represses the biogenesis of mature let-7 miRNAs. Proliferating cells have high LIN28 and low let-7 miRNAs, whereas differentiating cells have low LIN28 and high let-7 miRNAs. In placenta, low LIN28 and high let-7 miRNAs can lead to reduced proliferation of trophoblast cells, resulting in abnormal placental development. In trophoblast cells, let-7 miRNAs reduce the expression of proliferation factors either directly by binding their mRNA in 3ʹ-UTR or indirectly by targeting the AT-rich interaction domain (ARID)3B complex, a transcription-activating complex comprised of ARID3A, ARID3B, and histone demethylase 4C (KDM4C). In this review, we discuss regulation of trophoblast function by miRNAs, focusing on the role of LIN28-let-7-ARID3B pathway in placental development.

Maternal Obesity Alters Placental Cell Cycle Regulators in the First Trimester of Human Pregnancy: New Insights for BRCA1

In the first trimester of pregnancy, placental development involves a wide range of cellular processes. These include trophoblast proliferation, fusion, and differentiation, which are dependent on tight cell cycle control. The intrauterine environment affects placental development, which also includes the trophoblast cell cycle. In this work, we focus on maternal obesity to assess whether an altered intrauterine milieu modulates expression and protein levels of placental cell cycle regulators in early human pregnancy. For this purpose, we use first trimester placental tissue from lean and obese women (gestational week 5+0-11+6, n = 58). Using a PCR panel, a cell cycle protein array, and STRING database analysis, we identify a network of cell cycle regulators increased by maternal obesity in which breast cancer 1 (BRCA1) is a central player. Immunostaining localizes BRCA1 predominantly to the villous and the extravillous cytotrophoblast. Obesity-driven BRCA1 upregulation is not able to be explained by DNA methylation (EPIC array) or by short-term treatment of chorionic villous explants at 2.5% oxygen with tumor necrosis factor α (TNF-α) (50 mg/mL), leptin (100 mg/mL), interleukin 6 (IL-6) (100 mg/mL), or high glucose (25 nM). Oxygen tension rises during the first trimester, but this change in vitro has no effect on BRCA1 (2.5% and 6.5% O2). We conclude that maternal obesity affects placental cell cycle regulation and speculate this may alter placental development.