Project description:Fetal bone development occurs by endochondral conversion of avascular cartilage to vascularized bone at the growth plate. This requires coordinated mobilization of osteoblast precursors with blood vessels. In adult bone, vessel-adjacent osteoblast precursors are maintained by mechanical stimuli; however, the mechanisms by which these cells mobilize and respond to mechanical cues during embryonic development are unknown. Here, we unify osteoblast precursor co-mobilization and mechanotransduction in a single signaling pathway, via the mechanosensitive transcriptional regulators YAP and TAZ. We show that YAP and TAZ spatially couple osteoblast precursor mobilization to angiogenesis, regulate vascular loop morphogenesis to control growth plate remodeling, and mediate mechanoregulation of load-induced osteogenesis in embryonic bone. Mechanistically, YAP and TAZ uniquely regulate a subset of osteoblast-lineage cells, identified by single-cell RNA sequencing as vessel-associated osteoblast precursors. Among these cells, YAP and TAZ regulate expression of the angiogenic chemokine, Cxcl12. Functionally, in 3D human cell co-culture, CXCL12 treatment rescued angiogenesis impaired by stromal cell YAP/TAZ depletion. Together, these data establish new functions of the vessel-associated osteoblast precursors in endochondral bone development.
Project description:Neural crest cells (NCCs) are multipotent stem cells with a remarkable ability to differentiate into multiple cell lineages, including osteoblasts and chondrocytes. NCCs contribute to the majority of craniofacial skeleton, yet the molecular mechanisms regulating NCCs diversification into osteoblasts or chondrocytes remain poorly understood. We found that Yap and Taz function redundantly as key determinants of the osteogenesis versus chondrogenesis fate decision and differentiation in NCCs in vitro, ex vivo and in vivo, and Yap/Taz-deficiency in NCCs resulted in a switch from osteogenesis to chondrogenesis. Comprehensive analysis of unbiased datasets including CUT&RUN-seq and RNA-seq indicated that Yap/Taz directly regulate key genes that govern osteogenesis and chondrogenesis. During NCC-derived osteogenesis, Yap/Taz promote expression of osteogenic genes such as Runx2 and Sp7 but repress expression of chondrogenic genes such as Sox9 and Col2a1. Further, we found Yap/Taz directly interact with β-catenin in NCCs to coordinately promote osteoblast differentiation and repress chondrogenesis. Together our data indicate that Yap/Taz promote osteogenesis in NCCs by preventing chondrogenesis, partly through interactions with the Wnt-β-catenin pathway.
Project description:The factors regulating cellular identity are critical for understanding the transition from health to disease and responses to therapies. Cell identity is generally assigned based on static phenotypes, like “omics” profiles. However, how such static features translate into dynamic responses to perturbations that determine cellular function is often unclear. We found that autophagy perturbation in different cell types can have opposite responses in growth-promoting oncogenic YAP/TAZ transcriptional signalling. These apparently contradictory responses can be resolved by a feedback loop where autophagy negatively regulates the levels of α-catenins LC3-interacting proteins, which inhibit YAP/TAZ, which, in turn, positively regulate autophagy. High basal levels of α-catenins enable autophagy induction to positively regulate YAP/TAZ, while low α-catenins cause YAP/TAZ activation upon autophagy inhibition. These data reveal how feedback loops enable post-transcriptional determination of cell identity and how levels of a single intermediary protein can dictate the direction of response to external or internal perturbations.
Project description:Angiogenesis, the process by which endothelial cells (ECs) form new blood vessels from existing ones, is intimately linked to the tissue's metabolic milieu and often occurs at nutrient-deficient sites. However, ECs rely on sufficient metabolic resources to support growth and proliferation. How endothelial nutrient acquisition and usage are regulated is unknown. Here we show that these processes are dictated by YAP/TAZ-TEAD – a transcriptional module whose function is highly responsive to changes in the tissue environment. ECs lacking YAP/TAZ or their transcriptional partners, TEAD1, 2, and 4 fail to divide, resulting in stunted vascular growth in mice. Conversely, activation of TAZ, the more abundant paralogue in ECs, boosts proliferation, leading to vascular hyperplasia. We find that YAP/TAZ promote angiogenesis by fueling nutrient mTORC1 signaling. By orchestrating the transcription of a repertoire of cell-surface transporters, YAP/TAZ-TEAD stimulate the import of amino acids and other essential nutrients, thereby enabling mTORC1 pathway activation. Dissociating mTORC1 from these nutrient inputs – elicited by the loss of Rag GTPases – inhibits mTORC1 activity and prevents YAP/TAZ-dependent vascular growth. These findings define a pivotal role for YAP/TAZ-TEAD in steering endothelial mTORC1 and illustrate the essentiality of coordinated nutrient fluxes in the vasculature.
Project description:VEGF is a major driver of blood vessel formation. However, the signal transduction pathways culminating into the biological consequences of VEGF signaling are partially understood. Here we show that the Hippo pathway effectors YAP and TAZ, work as a regulatory hub in mediating VEGF-VEGFR2 signaling during angiogenesis. We demonstrate that YAP/TAZ are essential for vascular development as endothelium specific deletion of YAP/TAZ leads to impaired vascularization and embryonic lethality. Mechanistically, we show that VEGF activates YAP/TAZ via its effects on actin cytoskeleton remodeling, and that activated YAP/TAZ induce a transcriptional program that results in the expression of a set of genes to further control cytoskeleton dynamics, and thus ensure a proper angiogenic response. YAP/TAZ deletion also results in VEGFR2 trafficking defects from the Golgi to the plasma membrane. Together, our study establishes YAP/TAZ as a central regulatory hub that mediates VEGF signaling, and hence, regulates angiogenesis.
Project description:VEGF is a major driver of blood vessel formation. However, the signal transduction pathways culminating into the biological consequences of VEGF signaling are partially understood. Here we show that the Hippo pathway effectors YAP and TAZ, work as a regulatory hub in mediating VEGF-VEGFR2 signaling during angiogenesis. We demonstrate that YAP/TAZ are essential for vascular development as endothelium specific deletion of YAP/TAZ leads to impaired vascularization and embryonic lethality. Mechanistically, we show that VEGF activates YAP/TAZ via its effects on actin cytoskeleton remodeling, and that activated YAP/TAZ induce a transcriptional program that results in the expression of a set of genes to further control cytoskeleton dynamics, and thus ensure a proper angiogenic response. YAP/TAZ deletion also results in VEGFR2 trafficking defects from the Golgi to the plasma membrane. Together, our study establishes YAP/TAZ as a central regulatory hub that mediates VEGF signaling, and hence, regulates angiogenesis.
Project description:Activation of endothelial YAP/TAZ signaling is crucial for physiological and pathological angiogenesis. The mechanisms of endothelial YAP/TAZ regulation are, however, incompletely understood. Here we report that the protocadherin FAT1 acts as a critical upstream regulator of endothelial YAP/TAZ which limits the activity of these transcriptional cofactors during developmental and tumor angiogenesis by promoting their degradation. We show that loss of endothelial FAT1 results in increased endothelial cell proliferation in vitro and in various angiogenesis models in vivo. This effect is due to perturbed YAP/TAZ protein degradation, leading to increased YAP/TAZ protein levels and expression of canonical YAP/TAZ target genes. We identified the E3 ubiquitin ligase Mind Bomb-2 (MIB2) as a novel FAT1-interacting protein mediating FAT1-induced YAP/TAZ ubiquitination and degradation. Loss of MIB2 expression in endothelial cells in vitro and in vivo recapitulated the effects of FAT1 depletion and caused decreased YAP/TAZ degradation and increased YAP/TAZ signaling. Our data identify a pivotal mechanism of YAP/TAZ regulation involving FAT1 and its associated E3 ligase MIB2, which is essential for YAP/TAZ-dependent angiogenesis.
Samples for proteomics were obtained from HUVECs transduced with the FAT1 intracellular part fused with the extracellular part and transmembrane domain of the IL-2 receptor and carrying a Flag tag on the C terminus (see above) for 36 h followed by lysis in IP buffer. Lysates were incubated with magnetic anti-FLAG beads (M8823, Sigma/Aldrich) overnight at 4Deg. Affinity purified samples were subjected to in-gel (4-12% NuPAGE Bis-Tris gels, ThermoFisher Scientific) digestion as described (DOI: 10.1038/nprot.2006.468). In brief, gel lanes were cut into nine blocks/fractions and finely diced. Embedded proteins were reduced (10 mM dithiothreitol) and alkylated (55 mM iodoacetamide), followed by overnight digestion using trypsin (Serva). Peptides were extracted by increasing concentrations of acetonitrile and lyophilized. Final desalting, concentration and storage utilized "stop and go extraction" (STAGE) tips (DOI: 10.1021/ac026117i). Eluted peptides where subjected to electrospray ionization (ESI)-mediated liquid chromatography/tandem mass spectrometry (LC/MS2) using in house-packed column emitters (15 cm length, 70 um ID, 1.9 um ReprsoSil-Pur 120 C18-AQ, Dr. Maisch) and a buffer system comprising solvent A (0.1% formic acid) and solvent B (80% acetonitrile, 0.1% formic acid). Instrumentation details and parameters were extracted and summarized using MARMoSET (DOI: 10.1074/mcp.TIR119.001505) and are repository deposited. Peptide/spectrum matching and label free quantitation were performed using the MaxQuant suite of algorithms (DOIs: 10.1038/nbt.1511, 10.1021/pr101065j, 10.1074/mcp.M113.031591) against the human UniProt database (canonical & isoforms; downloaded on 2019/01/23). Parameters are included here. Downstream statistical analysis used the limma-based (DOI: 10.1093/nar/gkv007) in-house package autonomics (https://doi.org/doi:10.18129/B9.bioc.autonomics).
Project description:The goal of this study was to identify YAP/TAZ direct transcriptional targets and transcriptional partners, through ChIP-sequencing and gene expression profiling. ChIP-seq analysis of YAP, TAZ, TEAD4 and JUN in MDA-MB-231 cells. Two independent replicates were analysed for each TF, as well as for negative controls.
Project description:Abstract Hippo pathway downstream effectors Yap and Taz play key roles in cell proliferation and regeneration, regulating gene expression especially via interaction with Tead transcription factors. To investigate their role in skeletal muscle stem cells, we analysed Taz in vivo and ex vivo in comparison to Yap. Taz was expressed in activated satellite cells. siRNA knockdown or constitutive expression of wildtype or constitutively active TAZ mutants showed that TAZ promoted proliferation, a function that was shared with YAP. However, at later stages of myogenesis, TAZ also enhanced myogenic differentiation of myoblasts, whereas YAP inhibits such differentiation. Functionally, while muscle growth was mildly affected in Taz (gene symbol Wwtr1-/-) knockout mice, there were no overt effect on regeneration. However, conditional knockout of Yap in satellite cells of Pax7Cre-ERT2/+ : Yapflox/flox : Rosa26Lacz mice produced a marked regeneration deficit. To identify potential mechanisms, microarray analysis showed many common Taz/Yap targets, but Taz also regulates some genes independently of Yap, including myogenic genes such as Pax7, Myf5 and Myod1. Proteomic analysis of Yap/Taz revealed many common binding partners, but Taz also interacts with proteins distinct from Yap, that are mainly involved in myogenesis and aspects of cytoskeleton organization. Neither TAZ nor YAP bind members of the Wnt destruction complex but both extensively changed expression of Wnt and Wnt-cross talking genes with known roles in myogenesis. Finally, TAZ operates through Tead4 to enhance myogenic differentiation. In summary, Taz and Yap have overlapping functions in promoting myoblast proliferation but Taz then switches to promote myogenic differentiation.
Project description:Adverse cardiac remodeling after myocardial infarction (MI) causes structural and functional changes in the heart leading to heart failure. The initial pro-inflammatory response followed by an anti-inflammatory or reparative response post-MI is essential for minimizing the myocardial damage, healing, and scar formation. Bone marrow-derived macrophages (BMDMs) are recruited to the injured myocardium and essential for cardiac repair as they can adopt both pro-inflammatory (M1) or anti-inflammatory/reparative (M2) phenotypes to modulate inflammatory and reparative response, respectively. YAP and TAZ are the key mediators of the Hippo signaling pathway and essential for cardiac regeneration and repair. However, their role in macrophage polarization and post-MI inflammation, remodeling, and healing are not well established. Here, we demonstrate that expression of YAP and TAZ is increased in macrophages undergoing M1 or M2 polarization. Genetic deletion of YAP/TAZ leads to impaired M1 polarization and enhanced M2 polarization. Consistently, YAP activation/overexpression enhanced M1 and impaired M2 polarization. We show that YAP/TAZ promote M1 polarization by increasing IL6 expression, and impede M2 polarization by decreasing Arg1 expression through interaction with the HDAC3-NCoR1 repressor complex. These changes in macrophages polarization due to YAP/TAZ deletion results in reduced fibrosis, and hypertrophy and increased angiogenesis, leading to improved cardiac function after MI. Also, YAP activation augmented MI-induced cardiac fibrosis and remodeling. In summary, we identify YAP/TAZ as important regulators of macrophage-mediated pro- and anti-inflammatory responses post-MI.