Profound alterations of the chromatin architecture at chromosome 11p15.5 in cells from Beckwith-Wiedemann and Silver-Russell syndromes patients

Beckwith-Wiedemann syndrome (BWS) and Silver-Russell syndrome (SRS) are imprinting-related disorders associated with genetic/epigenetic alterations of the 11p15.5 region, which harbours two clusters of imprinted genes (IGs). 11p15.5 IGs are regulated by the methylation status of imprinting control regions ICR1 and ICR2. 3D chromatin structure is thought to play a pivotal role in gene expression control; however, chromatin architecture models are still poorly defined in most cases, particularly for IGs. Our study aimed at elucidating 11p15.5 3D structure, via 3C and 3D FISH analyses of cell lines derived from healthy, BWS or SRS children. We found that, in healthy cells, IGF2/H19 and CDKN1C/KCNQ1OT1 domains fold in complex chromatin conformations, that facilitate the control of IGs mediated by distant enhancers. In patient-derived cell lines, we observed a profound impairment of such a chromatin architecture. Specifically, we identified a cross-talk between IGF2/H19 and CDKN1C/KCNQ1OT1 domains, consisting in in cis, monoallelic interactions, that are present in healthy cells but lost in patient cell lines: an inter-domain association that sees ICR2 move close to IGF2 on one allele, and to H19 on the other. Moreover, an intra-domain association within the CDKN1C/KCNQ1OT1 locus seems to be crucial for maintaining the 3D organization of the region.

4q-D4Z4 chromatin architecture regulates the transcription of muscle atrophic genes in facioscapulohumeral muscular dystrophy

Despite increasing insights in genome structure organization, the role of DNA repetitive elements, accounting for more than two thirds of the human genome, remains elusive. Facioscapulohumeral muscular dystrophy (FSHD) is associated with deletion of D4Z4 repeat array below 11 units at 4q35.2. It is known that the deletion alters chromatin structure in cis, leading to gene up-regulation. Here we show a genome-wide role of 4q-D4Z4 array in modulating gene expression via 3D nuclear contacts. We have developed an integrated strategy of 4q-D4Z4–specific 4C-seq and chromatin segmentation analyses, showing that 4q-D4Z4 3D interactome and chromatin states of interacting genes are impaired in FSHD1 condition; in particular, genes that have lost the 4q-D4Z4 interaction and with a more active chromatin state are enriched for muscle atrophy transcriptional signature. Expression level of these genes is restored by the interaction with an ectopic 4q-D4Z4 array, suggesting that the repeat directly modulates the transcription of contacted targets. Of note, the up-regulation of atrophic genes is a common feature of several FSHD1 and FSHD2 patients, indicating that we have identified a core set of deregulated genes involved in FSHD pathophysiology.

Priming of Human Resting NK Cells by Autologous M1 Macrophages via the Engagement of IL-1β, IFN-β, and IL-15 Pathways

The cross talk between NK cells and macrophages is emerging as a major line of defense against microbial infections and tumors. This study reveals a complex network of soluble mediators and cell-to-cell interactions allowing human classically activated (M1) macrophages, but not resting (M0) or alternatively activated (M2) macrophages, to prime resting autologous NK cells. In this article, we show that M1 increase NK cell cytotoxicity by IL-23 and IFN-β-dependent upregulation of NKG2D, IL-1β-dependent upregulation of NKp44, and trans-presentation of IL-15. Moreover, both IFN-β-dependent cis-presentation of IL-15 on NK cells and engagement of the 2B4-CD48 pathway are used by M1 to trigger NK cell production of IFN-γ. The disclosure of these synergic cellular mechanisms regulating the M1-NK cell cross talk provides novel insights to better understand the role of innate immune responses in the physiopathology of tumor biology and microbial infections.

Systemic increase in human maternal circulating CD14+CD16- MCP-1+ monocytes as a marker of labor

OBJECTIVES

To study the influence of pregnancy and labor on the proportion and level of activation of monocyte subpopulations in human pregnancy.

STUDY DESIGN

Peripheral blood samples were obtained from healthy nonpregnant women (n = 6); women in the third-trimester of healthy pregnancies (n = 18) and women with preterm premature rupture of membranes (n = 46), just before delivery for the last 2 groups. Monocyte subpopulations were characterized by flow cytometry using CD14, CD16, and activation level using macrophage chemoattractant protein-1 (MCP-1) and CCR2 antibodies.

RESULTS

The relative proportion of each monocyte subset in nonpregnant women was similar to that in women with healthy or complicated pregnancies. However, pregnancy was associated with a significant decrease in MCP-1 expressing monocytes (79.5% ± 19.8% vs 9.3% ± 6.8% and 11.9% ± 8.3% for nonpregnant, healthy pregnancy, and preterm premature rupture of membranes (respectively, P < .05). Spontaneous labor was associated with a return to nonpregnant values for the proportion of MCP-1 expressing monocytes in both normal (74.4% ± 16.9) and preterm premature rupture of membranes pregnancy (68.4% ± 35.6), irrespective of the mode of delivery (vaginal or cesarean section). This was not observed in women who delivered without spontaneous labor onset. CCR-2 (MCP-1 receptor) expression was not modified in monocytes at the time of labor, but was significantly increased in granulocytes (3646 ± 1080 vs 7338 ± 2718 for nonlaboring and laboring preterm premature rupture of membranes, respectively, P < .05) CONCLUSION: In light of previous reports of a role for MCP-1 in labor, our results suggest the downregulation of activation levels of monocytes, via MCP-1 expression might be involved in maternofetal immune tolerance. Monocyte reactivation might be associated with labor.

Peroxisome proliferator-activated receptor δ (PPARδ) activation protects H9c2 cardiomyoblasts from oxidative stress-induced apoptosis

OBJECTIVE

Activation of peroxisome proliferator-activated receptor alpha (PPARalpha) and PPARgamma plays beneficial roles in cardiovascular disorders such as atherosclerosis and heart reperfusion. Although PPARalpha and gamma have been documented to reduce oxidative stress in the vasculature and the heart, the role of PPARdelta remains poorly studied.

METHODS AND RESULTS

We focused on PPARdelta function in the regulation of oxidative stress-induced apoptosis in the rat cardiomyoblast cell line H9c2. Using semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), we showed that PPARdelta is the predominantly expressed isotype whereas PPARalpha was weakly detected. By performing cell viability assays, we also showed that the selective PPARdelta agonist GW501516 protected cells from H(2)O(2)-induced cell death. The protective effect of GW501516 was due to an inhibition of H(2)O(2)-triggered apoptosis as shown by annexin-V labeling, DNA fragmentation analysis, and caspase-3 activity measurement. We demonstrated by transient transfection of a dominant negative mutant of PPARdelta that the protection induced by GW501516 was totally dependent on PPARdelta. Semi-quantitative RT-PCR and Western blotting analysis demonstrated that GW501516 treatment upregulated catalase. Moreover, forced overexpression of catalase inhibited H(2)O(2)-triggered apoptosis, as evidenced by annexin-V labeling.

CONCLUSION

Taken together, our results account for an important role of PPARdelta in inhibiting the onset of oxidative stress-induced apoptosis in H9c2 cells. PPARdelta appears to be a new therapeutic target for the regulation of heart reperfusion-associated oxidative stress and stimulation of enzymatic antioxidative defences.

Antiapoptotic effect of calcitonin gene-related peptide on oxidative stress-induced injury in H9c2 cardiomyocytes via the RAMP1/CRLR complex

Calcitonin gene-related peptide (CGRP) plays an important role in the mediation of protective effects observed in situations such as ischemic preconditioning in rat hearts. In this study, we investigated in H9c2 rat cardiomyoblasts if the protective effect of CGRP could be linked to an inhibitory effect on the apoptotic pathway. We also determined the specificity of observed effects by treatment with adrenomedullin (ADM) in stress conditions generated by 100 microM hydrogen peroxide. Using MTT assays, we demonstrate that a pretreatment with CGRP decreases by half the loss of cell viability induced by H(2)O(2). CGRP inhibits phosphatidylserine externalization, caspase 3 activation and DNA fragmentation due to oxidative stress. Using RT-PCR, we observed an increase in Bcl-2 mRNA expression induced by CGRP treatment. Dot blotting experiments showed that, in stress conditions, Bcl-2 protein level decreases while Bax is increased. CGRP administration prior to stress prevents these effects. The three-receptor activity modifying protein (RAMP) isotypes were detected by RT-PCR in H9c2 cells and in left ventricle rat tissue, RAMP1 and RAMP3 being the most abundant in both cases. RAMP1 expression was upregulated by CGRP while RAMP3 mRNA level was decreased. Cell viability assessed by MTT indicates that, contrary to CGRP, pretreatment of stressed cells with ADM, a RAMP2 agonist, fails to protect them while treatment with CGRP(8-37) (a RAMP1 and 2 inhibitor) abolished CGRP protective effect. Taken together, these data suggest that CGRP has antiapoptotic properties through the RAMP1/CRLR complex. CGRP could be used to prevent apoptosis in an ischemia-reperfusion context.