Project description:Human cancer is often caused by dysfunctional developmental pathways, but such mechanisms do not always present clear opportunities for therapeutic intervention. This is exemplified by the Hippo tumor suppressor pathway, which is comprised of a kinase module that restrains the function of YAP/TAZ transcriptional coactivators; a pathway that becomes dysregulated in a wide array of human cancers. Hence, YAP/TAZ hyperactivation is a tumorigenic mechanism and a validated therapeutic target in oncology. In this study, we used a paralog co-targeting genetic screening strategy to identify the kinases MARK2/3 as co-dependencies of YAP/TAZ in diverse cancer contexts. We use biochemical and epistasis experiments to show that MARK2/3 phosphorylate and inhibit the activity of Hippo pathway components NF2, MST1/2, and MAP4Ks, which leads to indirect upstream control of LATS1/2 activity. In addition, MARK2/3 directly phosphorylate YAP/TAZ to shield these coactivators from LATS1/2-mediated inhibition. The net consequence of this multi-level regulation is that YAP/TAZ-dependent human cancers have an absolute requirement for MARK2/3 catalytic activity to sustain tumor cell proliferation and viability. To simulate therapeutic targeting of MARK2/3 in vivo, we adapted the EPIYA-repeat region of the CagA protein from H. pylori as a catalytic inhibitor of MARK2/3, which we show exerts potent anti-tumor activity via on-target mechanisms. Together, these findings reveal MARK2/3 as an obligate catalytic requirement for YAP/TAZ function in human cancer; kinase targets that may allow for novel pharmacology that restores Hippo-mediated tumor suppression.
Project description:Human cancer is often caused by dysfunctional developmental pathways, but such mechanisms do not always present clear opportunities for therapeutic intervention. This is exemplified by the Hippo tumor suppressor pathway, which is comprised of a kinase module that restrains the function of YAP/TAZ transcriptional coactivators; a pathway that becomes dysregulated in a wide array of human cancers. Hence, YAP/TAZ hyperactivation is a tumorigenic mechanism and a validated therapeutic target in oncology. In this study, we used a paralog co-targeting genetic screening strategy to identify the kinases MARK2/3 as co-dependencies of YAP/TAZ in diverse cancer contexts. We use biochemical and epistasis experiments to show that MARK2/3 phosphorylate and inhibit the activity of Hippo pathway components NF2, MST1/2, and MAP4Ks, which leads to indirect upstream control of LATS1/2 activity. In addition, MARK2/3 directly phosphorylate YAP/TAZ to shield these coactivators from LATS1/2-mediated inhibition. The net consequence of this multi-level regulation is that YAP/TAZ-dependent human cancers have an absolute requirement for MARK2/3 catalytic activity to sustain tumor cell proliferation and viability. To simulate therapeutic targeting of MARK2/3 in vivo, we adapted the EPIYA-repeat region of the CagA protein from H. pylori as a catalytic inhibitor of MARK2/3, which we show exerts potent anti-tumor activity via on-target mechanisms. Together, these findings reveal MARK2/3 as an obligate catalytic requirement for YAP/TAZ function in human cancer; kinase targets that may allow for novel pharmacology that restores Hippo-mediated tumor suppression.
Project description:YAP1 gene fusions have been observed in a subset of paediatric ependymomas. Here we show that, ectopic expression of active nuclear YAP1 (nlsYAP5SA) in ventricular zone neural progenitor cells using conditionally-induced NEX/NeuroD6-Cre is sufficient to drive brain tumour formation in mice. Neuronal differentiation is inhibited in the hippocampus. Deletion of YAP1’s negative regulators LATS1 and LATS2 kinases in NEX-Cre lineage in double conditional knockout mice also generates similar tumours, which are rescued by deletion of YAP1 and its paralog TAZ. YAP1/TAZ-induced mouse tumours display molecular and ultrastructural characteristics of human ependymoma. RNA sequencing and quantitative proteomics of mouse tumours demonstrate similarities to YAP1-fusion induced supratentorial ependymoma. Finally, we find that transcriptional cofactor HOPX is upregulated in mouse models and in human YAP1-fusion induced ependymoma, supporting their similarity. Our results show that uncontrolled YAP1/TAZ activity in neuronal precursor cells leads to ependymoma-like tumours in mice.
Project description:The optic vesicle comprises a pool of bi-potential progenitor cells from which the retinal pigment epithelium (RPE) and neural retina fates segregate during ocular morphogenesis. Several transcription factors and signaling pathways have been shown to be important for RPE maintenance and differentiation, but an understanding of the initial fate specification and determination of this ocular cell type is lacking. We show that Yap/Taz-Tead activity is necessary and sufficient for optic vesicle progenitors to adopt RPE identity in zebrafish. A Teadresponsive transgene is expressed within the domain of the optic cup from which RPE arises, and Yap immunoreactivity localizes to the nuclei of prospective RPE cells. yap (yap1) mutants lack a subset of RPE cells and/or exhibit coloboma. Loss of RPE in yap mutants is exacerbated in combination with taz (wwtr1) mutant alleles such that, when Yap and Taz are both absent, optic vesicle progenitor cells completely lose their ability to form RPE. The mechanism of Yap dependent RPE cell type determination is reliant on both nuclear localization of Yap and interaction with a Tead co-factor. In contrast to loss of Yap and Taz, overexpression of either protein within optic vesicle progenitors leads to ectopic pigmentation in a dosagedependent manner. Overall, this study identifies Yap and Taz as key early regulators of RPE genesis and provides a mechanistic framework for understanding the congenital ocular defects of Sveinsson’s chorioretinal atrophy and congenital retinal coloboma. 60 pooled eyes from 36 hpf wild type or vsx2:Gal4/dsRed:14xUAS:YapS87A embryos were pooled for one sample. Three wild type and three vsx2:Gal4/dsRed:14xUAS:YapS87A pools were analyzed for RNA.
Project description:The Hippo pathway plays a crucial in organ size control during development and tissue homeostasis in adult life. To examine a role for Hippo signaling in the intestinal epithelium, we analyzed gene expression patterns in the mouse intestinal epithelilum transfected with siRNAs or expression plasmids for shRNAs targeting the Hippo pathway effectors, YAP and TAZ. We performed two independent series of experiments (siGFP (n=3) vs siYAP/siTAZ (n=3), and shLacZ (n=1) vs shYAP/shTAZ (n=1)). Control siRNA (siGFP), YAP/TAZ siRNAs, or expression plasmids for control shRNA (shLacZ) or YAP/TAZ shRNAs were introduced into the mouse intestinal epithelium by the newly-developed in vivo transfection method. Four days after transfection, intestinal epithelial cells were isolated from the tissues and total RNA was extracted.