Project description:Nuclear Envelope Membrane Protein 1 (NEMP1) is crucial for metazoan fertility; loss of Nemp1 causes primordial oocyte death, residing in the mechanically challenging ovarian cortex. Here, we show that softening the ovary rescues oocyte loss and restores fertility in NEMP1 knockout mice. In cell culture, NEMP1 depletion on stiff substrates leads to death, while cells remain viable on soft substrates. We further show that NEMP1 regulates YAP nuclear translocation, essential for mechanotransduction. Mechanistically, Nemp1-depleted cells on stiff substrates or subjected to stretching exhibit reduced nuclear YAP localization, and expressing nuclear YAP5SA restores cell viability. Loss of NEMP1 disrupts actin organization, inhibiting YAP nuclear translocation. Inducing actin polymerization rescues nuclear YAP, indicating an F-actin-dependent mechanism for NEMP1-mediated mechanotransduction. NEMP1 forms a novel complex with NESPRIN2's KASH domain, strengthening the actin cytoskeleton to withstand mechanical forces, independently of SUN proteins. Thus, NEMP1-Nesprin complex, named hereafter ALT-LINC, creates a mechanosensitive pathway parallel to the LINC complex and is crucial for YAP mechanotransduction, enabling cellular response to mechanical stress in vitro and in vivo.
Project description:Hippo effectors YAP/TAZ act as on-off mechanosensing switches by sensing modifications in extracellular matrix (ECM) composition and mechanics. The regulation of their activity has been described so far through a hierarchical model in which elements of Hippo pathway are under the control of Focal Adhesions (FAs). Here we unveiled the molecular mechanism by which cell spreading and RhoA GTPase control FA formation through YAP to stabilize the anchorage of actin cytoskeleton to cell membrane. This mechanism required YAP co-transcriptional function and involved the activation of genes encoding for integrins and FA docking proteins. Tuning YAP transcriptional activity led to the modification of cell mechanics, force development, adhesion strength, determined cell shaping, migration and differentiation. These results provide new insights into the mechanism of YAP mechanosensing activity and qualify Hippo effector as the key determinant of cell mechanics in response to ECM cues.
Project description:Increased extracellular matrix (ECM) stiffness has been implicated in esophageal adenocarcinoma (EAC) progression, metastasis, and resistance to therapy. However, the underlying pro-tumorigenic pathways are yet to be defined. Additional work is needed to develop physiologically relevant in vitro 3D culture models that better recapitulate the human tumor microenvironment and can be used to dissect the contributions of matrix stiffness to EAC pathogenesis. Here, we describe a modular, tumor ECM-mimetic hydrogel platform with tunable mechanical properties, defined presentation of cell-adhesive ligands, and protease-dependent degradation that supports robust in vitro growth and expansion of patient-derived EAC 3D organoids (EAC PDOs). Hydrogel mechanical properties control EAC PDO formation, growth, proliferation, and activation of tumor-associated pathways that elicit stem-like properties in the cancer cells, as highlighted through in vitro and in vivo environments. We also demonstrate that the engineered hydrogel serves as a platform to identify potential therapeutic targets to disrupt the contribution of pro-tumorigenic matrix mechanics in EAC. Together, these studies show that an engineered PDO culture platform can be used to elucidate underlying matrix-mediated mechanisms of EAC, and inform the development of therapeutics that target ECM stiffness in EAC.
Project description:It is now obvious that the majority of cellular transcripts do not code for proteins, and a significant subset of them are long noncoding RNAs (lncRNAs). Many lncRNAs show aberrant expression in cancer, and some of them have been linked to cellular transformation. However, the underlying mechanisms remain poorly understood. Here we characterize the function of the p53-regulated human lncRNA LINC-PINT in cancer. We found that LINC-PINT acts as tumor suppressor lncRNA. Its expression is downregulated in multiple types of cancer and correlates with good prognosis in lung adenocarcinoma. LINC-PINT inhibits the migration capacity and invasive phenotype of cancer cells in vitro and in vivo, and it does so by repressing a proinvasion gene signature in a PRC2-dependent manner. By applying cross-species conservation analysis combined with functional experimental validations we found that the function of LINC-PINT is highly dependent on a short sequence conserved across mammals, sequence that mediates the interaction with PRC2. We propose that LINC-PINT may function as a molecular exchanger that provides PRC2 to active gene promoters for their silencing, mechanisms that could be shared by other PRC2-interacting lncRNAs.
Project description:YAP transcriptional regulator controls cell mechanics by activating genes involved in cell-matrix interaction following extracellular matrix (ECM) remodelling and stiffening. YAP is needed for cardiogenesis in mouse but is repressed in adult cardiomyocytes. The protein is reactivated following ischemic insults, although the timing and mechanisms underlying YAP depletion during heart development and the reason for its reactivation are unclear. Here, we combine pluripotent stem cell (PSC) cardiac differentiation, mouse embryo development and human heart tissue analysis to demonstrate that the fine-tuning of cell mechanics, as controlled by YAP multiphasic activation through TEAD transcription, is crucial for mesoderm commitment and cardiac progenitor specification. Finally, by adopting induced PSC models of dilated cardiomyopathy, we prove that YAP-TEAD reactivation in diseased cardiomyocytes empowers calcium handling apparatus and increases cell contractility. Given YAP prompt activation following myocardial infarction, we unveil a novel role for mechanosensing in connecting ECM remodelling to cardiomyocyte function in pathological heart.
Project description:YAP transcriptional regulator controls cell mechanics by activating genes involved in cell-matrix interaction following extracellular matrix (ECM) remodelling and stiffening. YAP is needed for cardiogenesis in mouse but is repressed in adult cardiomyocytes. The protein is reactivated following ischemic insults, although the timing and mechanisms underlying YAP depletion during heart development and the reason for its reactivation are unclear. Here, we combine pluripotent stem cell (PSC) cardiac differentiation, mouse embryo development and human heart tissue analysis to demonstrate that the fine-tuning of cell mechanics, as controlled by YAP multiphasic activation through TEAD transcription, is crucial for mesoderm commitment and cardiac progenitor specification. Finally, by adopting induced PSC models of dilated cardiomyopathy, we prove that YAP-TEAD reactivation in diseased cardiomyocytes empowers calcium handling apparatus and increases cell contractility. Given YAP prompt activation following myocardial infarction, we unveil a novel role for mechanosensing in connecting ECM remodelling to cardiomyocyte function in pathological heart.
Project description:Microgravity is known to affect the organization of the cytoskeleton, cell and nuclear morphology and to elicit differential expression of genes associated with the cytoskeleton, focal adhesions and the extracellular matrix. Although the nucleus is mechanically connected to the cytoskeleton through the LInker of Nucleoskeleton and Cytoskeleton (LINC) complex, the role of this group of proteins in these responses to microgravity has yet to be defined. Therefore, we used simulated microgravity achieved by growing cells on a 3d clinostat to investigate whether the LINC complex acts to mediate responses to the microgravity environment. We show that nuclear shape and differential gene expression are both responsive to simulated microgravity in a LINC-dependent manner and that this response changes with the duration of exposure to simulated microgravity. These LINC-dependent genes likely represent elements normally regulated by the mechanical forces imposed by gravity on Earth.