Thérèse-Marie Mignot

Combination of promoter hypomethylation and PDX1 overexpression leads to TBX15 decrease in vascular IUGR placentas.

Preeclampsia (PE) and vascular intra-uterine growth restriction (vIUGR) are two pathological obstetrical conditions originating from placental dysfunction. Recently, methylation changes at the placental level have been shown to be indicative of these diseases. The alteration of such epigenetic marks is therefore a novel pathway that might be critical for these pathologies. Here, we identified a region located in the distal promoter of the T-box-containing transcription factor TBX15 that is differentially methylated in pathological placentas. The level of methylation correlated significantly with the weight and stature of the newborn. The promoter was found to be hypomethylated in vIUGR coinciding with the down-regulation of its expression. PDX1, a transcription factor important for the regulation of insulin metabolism regulation was able to repress the TBX15 promoter in a methylation-dependent manner, which might, at least partially, explain the specific mRNA decrease of TBX15 observed in vIUGR placentas. Overall, the data presented herein suggest that TBX15 might be involved in the pathophysiology of placental diseases.

Non-random, individual-specific methylation profiles are present at the sixth CTCF binding site in the human H19/IGF2 imprinting control region

Expression of imprinted genes is classically associated with differential methylation of specific CpG-rich DNA regions (DMRs). The H19/IGF2 locus is considered a paradigm for epigenetic regulation. In mice, as in humans, the essential H19 DMR—target of the CTCF insulator—is located between the two genes. Here, we performed a pyrosequencing-based quantitative analysis of its CpG methylation in normal human tissues. The quantitative analysis of the methylation level in the H19 DMR revealed three unexpected discrete, individual-specific methylation states. This epigenetic polymorphism was confined to the sixth CTCF binding site while a unique median-methylated profile was found at the third CTCF binding site as well as in the H19 promoter. Monoallelic expression of H19 and IGF2 was maintained independently of the methylation status at the sixth CTCF binding site and the IGF2 DMR2 displayed a median-methylated profile in all individuals and tissues analyzed. Interestingly, the methylation profile was genetically transmitted. Transgenerational inheritance of the H19 methylation profile was compatible with a simple model involving one gene with three alleles. The existence of three individual-specific epigenotypes in the H19 DMR in a non-pathological situation means it is important to reconsider the diagnostic value and functional importance of the sixth CTCF binding site.

Endothelin-1 binding sites and immunoreactivity in the cultured human placental trophoblast: evidence for an autocrine and paracrine role for endothelin-1.

In human placenta, endothelin (ET) could derive from maternal, fetal, and/or endogenous sources. Therefore, localization of ET-1 was investigated by immunohistochemistry in human term placenta and in cultured trophoblasts. In sections of placenta, ET-1 immunoreactivity (ET-1 IR) was specifically detected in the endothelium of the vessels and in the syncytiotrophoblasts of the villi. ET-1 IR was also detected in the decidual cells and in the extravillous cytotrophoblasts of the basal plate. The extravillous cytotrophoblasts of the chorionic plate and of the placental septa also exhibited strong ET-1 IR. For trophoblast culture, cytotrophoblastic cells were obtained from placental villi by trypsin-DNAse dispersion, further purified on a Percoll gradient, and enriched by employing a monoclonal anti-HLA class I antibody. After different periods of culture of purified cytotrophoblastic cells (1-5 days), ET-1 IR was observed in 95% of cells: cytotrophoblastic cells, trophoblast aggregates, and syncytiotrophoblasts. The presence of ET-1,2 immunoreactivity (ET-1,2 IR) in the culture media was demonstrated by radioimmunoassay. A uniform daily production of the peptide was observed over at least 5 days (approximately 50 fmol/10(6) cells/24 h). Furthermore, trophoblastic cells that had been cultured for 5 days contained significant amounts of ET-1,2 IR (24 fmol/10(6) cells). These results suggest a trophoblastic origin for ET-1 and support the hypothesis of a paracrine and autocrine action of the peptide in the physiology of the trophoblast and placenta.