Cell-cell fusion or syncytialization is fundamental to the reproduction, development, and homeostasis of multicellular organisms. In addition to various cell type–specific fusogenic proteins, cell surface externalization of phosphatidylserine (PS), a universal eat-me signal in apoptotic cells, has been observed in different cell fusion events. Nevertheless, the molecular underpinnings of PS externalization and cellular mechanisms of PS-facilitated cell-cell fusion are unclear. Here, we report that TMEM16F, a Ca2+-activated phospholipid scramblase (CaPLSase), plays an essential role in placental trophoblast fusion by translocating PS to cell surface independent of apoptosis. The placentas from the TMEM16F knockout mice exhibit deficiency in trophoblast syncytialization and placental development, which lead to perinatal lethality. We thus identified a new biological function of TMEM16F CaPLSase in trophoblast fusion and placental development. Our findings provide insight into understanding cell-cell fusion mechanism of other cell types and on mitigating pregnancy complications such as miscarriage, intrauterine growth restriction, and preeclampsia.

AbstractCell-cell fusion or syncytialization is fundamental to the reproduction, development and homeostasis of multicellular organisms. In addition to various cell-type specific fusogenic proteins, cell surface externalization of phosphatidylserine (PS), a universal eat-me signal in apoptotic cells, has been observed in different cell-fusion events. Nevertheless, molecular underpinnings of PS externalization and cellular mechanisms of PS-facilitated cell-cell fusion are unclear. Here we report that TMEM16F, a Ca2+-activated phospholipid scramblase (CaPLSase), plays an indispensable role in placental trophoblast fusion by translocating PS to the cell surface independent of apoptosis. Consistent with its essential role in trophoblast fusion, the placentas from TMEM16F-deficient mice exhibit deficiency in syncytialization, placental developmental defects and perinatal lethality. Our findings thus identify a cell-cell fusion mechanism by which TMEM16F CaPLSase-dependent externalization of PS serves as a critical cell fusion signal to facilitate trophoblast syncytialization and placental development.

Angiogenesis is a regulated process involving the proliferation, migration, and remodeling of different cell types particularly mature endothelial and their progenitor cells, nominated as endothelial progenitor cells (EPCs). Tie2/Tek is a tyrosine kinase receptor expressed by endothelial cells that induces signal transduction pathways involved in endothelial biology. To address the potential importance of the various tyrosine residues of Tie2 in EPC development, we generated a series of Tie2 tyrosine mutated (Y1106F, Y1100F, and Y1111F) EPCs and then assess the biological features of these cells. Clonogenic, tubulogenic, proliferative, migratory, and functional properties of these cells were analyzed. Next, GFP-positive EPCs containing Tie2 tyrosine mutations were systemically transplanted into sublethaly irradiated mice to analyze the potency of these cells for marrow reconstitution. We found that mutation in the Tie2 tyrosine 1106 residue directed EPCs toward a mature endothelial phenotype, which was associated with augmented tubulogenic and migratory properties, and increased phosphorylation of the active site (tyrosine 992) as well as increased vascular perfusion in the in vivo Matrigel plug assay. Moreover, transplantation of 1106 Tie2 mutant EPCs failed to reconstitute the bone marrow after myeloablation, whereas transplantation of EPCs with the 1100 or 1111 Tie2 tyrosine mutation resulted in bone marrow engraftment, leading to improved survival of recipient mice. Our findings demonstrate that the tyrosine 1106 residue in Tie2 plays a key role to maintain the stemness features of EPCs. K E Y W O R D Sbone marrow reconstitution, endothelial progenitor cell, Tie2, tyrosine phosphorylation

Key points“Dyspnoea” during exercise is a common complaint in seemingly otherwise healthy athletes, which may be associated with fatigue and underperformance.Because dyspnoea is an general term and may be caused by numerous factors, ranging from poor aerobic fitness to serious, potentially fatal respiratory and nonrespiratory pathologies, it is important for clinicians to obtain an appropriate case history and ask relevant exercise-specific questions to fully characterise the nature of the complaint so that a targeted diagnostic plan can be developed.Exercise-induced bronchoconstriction and exercise-induced laryngeal obstruction are two common causes of dyspnoea in athletes, and both are regularly misdiagnosed and mismanaged due to poor adherence to available practice parameters.Aside from airway dysfunction, iron deficiency and anaemia, infectious disease, and musculoskeletal conditions are common problems in athletes which ultimately may lead to complaints of dyspnoea.Educational aimsTo inform readers of the common causes of dyspnoea encountered in athletes.To highlight that airway diseases, such as asthma and exercise-induced bronchoconstriction, are commonly misdiagnosed and mismanaged.To introduce readers to common nonairway causes of dyspnoea in athletes, including clinical features and general principles of diagnosis, and management.To emphasise the importance of a detailed case history and proper adherence to established protocols in evaluating and managing the dyspnoeic athlete.To provide readers with a general framework of appropriate questions that are useful for developing a targeted diagnostic plan for evaluating dyspnoeic athletes.Dyspnoea during exercise is a common chief complaint in athletes and active individuals. It is not uncommon for dyspnoeic athletes to be diagnosed with asthma, “exercise-induced asthma” or exercise-induced bronchoconstriction based on their symptoms, but this strategy regularly leads to misdiagnosis and improper patient management. Dyspnoea during exercise can ultimately be caused by numerous respiratory and nonrespiratory conditions, ranging from nonpathological to potentially fatal in severity. As, such it is important for healthcare providers to be familiar with the many factors that can cause dyspnoea during exercise in seemingly otherwise-healthy individuals and have a general understanding of the clinical approach to this patient population. This article reviews common conditions that ultimately cause athletes to report dyspnoea and associated symptoms, and provides insight for developing an efficient diagnostic plan.

We reported that maternal PFBS, an emerging pollutant, exposure is positively associated with preeclampsia which can result from aberrant trophoblasts invasion and subsequent placental ischemia. In this study, we investigated the effects of PFBS on trophoblasts proliferation/invasion and signaling pathways. We exposed a human trophoblast line, HTR8/SVneo, to PFBS. Cell viability, proliferation, and cell cycle were evaluated by the MTS assay, Ki-67 staining, and flow cytometry, respectively. We assessed cell migration and invasion with live-cell imaging-based migration assay and matrigel invasion assay, respectively. Signaling pathways were examined by Western blot, RNA-seq, and qPCR. PFBS exposure interrupted cell proliferation and invasion in a dose-dependent manner. PFBS (100 μM) did not cause cell death but instead significant cell proliferation without cell cycle disruption. PFBS (10 and 100 μM) decreased cell migration and invasion, while PFBS (0.1 μM) significantly increased cell invasion but not migration. Further, RNA-seq analysis identified dysregulated HIF-1α target genes that are relevant to cell proliferation/invasion and preeclampsia, while Western Blot data showed the activation of HIF-1α, but not Notch, ERK1/2, (PI3K)AKT, and P38 pathways. PBFS exposure altered trophoblast cell proliferation/invasion which might be mediated by preeclampsia-related genes, suggesting a possible association between prenatal PFBS exposure and adverse placentation. K E Y W O R D S invasion, PFBS, placenta cytotrophoblast, preeclampsia, proliferation | 14183 MARINELLO Et AL. 1 | INTRODUCTION Poly-and per-fluoroalkyl substances (PFAS) have attracted widespread attention in recent years due to their bioaccumulation, toxicity, and ubiquitous nature. 1 PFAS are a group of compounds characterized by a hydrophobic poly-fluorinated alkyl chain and a polar hydrophilic terminal functional group. PFAS are used in a variety of industrial and consumer products such as surfactants for soil/stain resistance, textiles, paper and metals, firefighting foam, and pesticides. 2,3 Humans are exposed to PFAS through contaminated drinking water, food, outdoor air, indoor dust, and soil. 4 One of the most widely known PFAS is perfluorooctane sulfonic acid (PFOS), which has an eight-carbon backbone with a sulfonate. Due to strong carbon-fluorine bonds (C8), PFOS is extremely stable and persistent in the environment (USEPA, Document# 822R14002) and is not readily eliminated from humans due to its half-life of 5.4 years. 5-16 Data from human and animal studies demonstrate numerous health and ecological risks resulting from PFOS exposure including increased risk of thyroid disease, blood cholesterol levels, and preeclampsia and decreased body's response to vaccine, fertility in women, and birth weight, liver, and immune system damage. 17-29 Thus, beginning in 2002, most manufacturing of PFOS in the United States was discontinued voluntarily by 3M and DuPont in favor of shorter chain PFAS (C4 or C6, Toni Krasnic, the U. S. Environmental Protection A...