Chromatin three-dimensional interactions mediate genetic effects on gene expression.

Studying the genetic basis of gene expression and chromatin organization is key to characterizing the effect of genetic variability on the function and structure of the human genome. Here we unravel how genetic variation perturbs gene regulation using a dataset combining activity of regulatory elements, gene expression, and genetic variants across 317 individuals and two cell types. We show that variability in regulatory activity is structured at the intra- and interchromosomal levels within 12,583 cis-regulatory domains and 30 trans-regulatory hubs that highly reflect the local (that is, topologically associating domains) and global (that is, open and closed chromatin compartments) nuclear chromatin organization. These structures delimit cell type-specific regulatory networks that control gene expression and coexpression and mediate the genetic effects of cis- and trans-acting regulatory variants on genes.

Overexpression of GRP78 in complete hydatidiform moles.

OBJECTIVE: Hydatidiform moles, subdivided into partial moles (PM) and complete moles (CM), are abnormal pregnancies with a disturbed invasive behavior. We had previously shown that MMP-2 and p53 proteins are overexpressed in CM versus PM, and that in primary cytotrophoblasts p53 protein is stabilized by complexing to the 78kDa glucose-regulated protein (GRP78) which is involved in cytotrophoblasts invasion process. The present study aims to compare the transcript expression profile of p53, MMP-2 and GRP78 in hydatidiform moles. METHODS: A retrospective study was performed by RT-qPCR and immunostaining on paraffin-embedded tissues of 19 PM, 16 CM and 16 control (CTRL) samples of gestational age 8-12 weeks. RESULTS: Expression of MMP-2 transcript was significantly overexpressed in CM compared to CTRL samples (p=0.031). In contrast, expression of p53 transcript was similar among the samples. This suggests a regulation of p53 in CM at the protein level. GRP78 cDNA was significantly overexpressed in CM compared to CTRL (p=0.021) and to PM (p=0.011). At the protein level, immunostaining of GRP78 was on average stronger in CM than PM samples. CONCLUSIONS: Collectively, present data suggest that in CM, p53 is normally expressed at the mRNA level but probably complexes at the protein level with the overexpressed GRP78, leading to accumulation of p53 protein. Moreover, since GRP78 and MMP-2 are increased in CM and known to play key roles in invasion, our results suggest that GRP78 and MMP-2 should be investigated as prognostic markers of hydatidiform moles.

Comparative analysis of secreted proteins from normal and preeclamptic trophoblastic cells using proteomic approaches.

Preeclampsia (PE) is a pathology of pregnancy which represents the main cause of maternal and perinatal morbidity and mortality. Defective placentation is the first event of this pathology. The purpose of this study was to identify the proteins secreted by cytotrophoblastic cells (CTB) using proteomic approach that are associated with PE. Comparison of secreted proteins by mass spectrometry allowed us to identify 21 proteins which were significantly differentially secreted by control and PE CTB. One protein has been detected exclusively in supernatant of control CTB and was identified as factor XIII chain A. To determine if this observation is due to a difference of protein secretion or gene expression, its mRNA was quantified in all CTB. We found that it was significantly decreased in PE CTB compared to control. Collectively, these data suggest that decrease of factor XIII chain A might be associated with development of PE.

Reversibility of electrophysiological changes induced by chronic high-altitude hypoxia in adult rat heart.

Recent studies indicate that regression of left ventricular hypertrophy normalizes membrane ionic current abnormalities. This work was designed to determine whether regression of right ventricular hypertrophy induced by permanent high-altitude exposure (4,500 m, 20 days) in adult rats also normalizes changes of ventricular myocyte electrophysiology. According to the current data, prolonged action potential, decreased transient outward current density, and increased inward sodium/calcium exchange current density normalized 20 days after the end of altitude exposure, whereas right ventricular hypertrophy evidenced by both the right ventricular weight-to-heart weight ratio and the right ventricular free wall thickness measurement normalized 40 days after the end of altitude exposure. This morphological normalization occurred at both the level of muscular tissue, as shown by the decrease toward control values of some myocyte parameters (perimeter, capacitance, and width), and the level of the interstitial collagenous connective tissue. In the chronic high-altitude hypoxia model, the regression of right ventricular hypertrophy would not be a prerequisite for normalization of ventricular electrophysiological abnormalities.

Voltage-gated sodium channel (SkM1) content in dystrophin-deficient muscle.

The membrane cytoskeleton is increasingly considered as both an anchor and a functional modulator for ion channels. The cytoskeletal disruptions that occur in the absence of dystrophin led us to investigate the voltage-gated sodium channel (SkM1) content in the extensor digitorum longus (EDL) muscle of the dystrophin-deficient mdx mouse. Levels of SkM1 mRNA were determined by semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR). A C-terminal portion of the mouse-specific SkM1 alpha-subunit cDNA (mScn4a) was identified first. SkM1 mRNA levels were as abundant in mdx as in normal muscle, thus suggesting that the transcriptional rate of SkM1 remains unchanged in mdx muscle. However, SkMI density in the extrajunctional sarcolemma was shown to be significantly reduced in mdx muscle, using confocal immunofluorescence image analysis. This decrease was found to be associated with a reduction in the number of SkM1-rich fast-twitch IIb fibres in mdx muscle. In addition, lowered SkM1 sarcolemmal labelling was found in all mdx fibres regardless of their metabolic type. These results suggest the existence of a perturbation of SkM1 anchorage to the plasma membrane. Such an alteration is likely to be related to the 50% decrease in mdx muscle of the dystrophin-associated syntrophins, which are presumed to be involved in SkM1 anchorage. However, the moderate reduction in SkM1 density (-12.7%) observed in mdx muscle argues in favour of a non-exclusive role of syntrophins in SkM1 anchorage and suggests that other membrane-associated proteins are probably also involved.