Project description:PURPOSE. During retinal degeneration, Müller glia cells respond to photoreceptor loss by undergoing reactive gliosis, with both detrimental and beneficial effects. Increasing our knowledge of the complex molecular response of Müller cells to retinal degeneration is thus essential for the development of new therapeutic strategies. The purpose of this work was to identify new factors involved in Müller cell response to photoreceptor cell death. METHODS. Whole transcriptome sequencing was performed from wild-type and degenerating rd10 mouse retinas at P30. The changes in mRNA abundance for several deregulated genes were assessed by RT-qPCR. Protein expression level and retinal cellular localization were determined by western-blot and immunohistochemistry, respectively. RESULTS. Pathway-level analysis from whole transcriptomic data revealed the Hippo/YAP pathway as one of the main signaling pathways altered in response to photoreceptor degeneration in rd10 retinas. We found that downstream effectors of this pathway, YAP and TEAD1, are specifically expressed in Müller cells and that their expression, at both the mRNA and protein levels, is increased in rd10 reactive Müller glia after the onset of photoreceptor degeneration. The expression of Ctgf and Cyr61, two target genes of the transcriptional YAP/TEAD complex, is also upregulated following photoreceptor loss. CONCLUSIONS. This work reveals for the first time that YAP and TEAD1, key downstream effectors of the Hippo pathway, are specifically expressed in Müller cells. We also uncovered a deregulation of the expression and activity of Hippo/YAP pathway components in reactive Müller cells under pathological conditions.
Project description:In mammals, retinal damage is followed by Müller glia cell activation and proliferation. While retinal gliosis persists in adult mammals after an insult or disease, some vertebrates, including zebrafish, have the capacity to regenerate. We believe we are the first group to show that gliosis is a fibrotic-like process in mammals’ eyes caused by differential activation of canonical and non-canonical TGFβ signaling pathways.
Project description:Contrasting with fish or amphibian, retinal regeneration from Müller glial cells is largely limited in mammals. In our quest towards the identification of molecular cues that may boost their stemness potential, we investigated the involvement of the Hippo pathway effector YAP, which we previously found to be upregulated in Müller cells following retinal injury. We report that conditional Yap deletion in Müller cells prevents the upregulation of cell cycle genes that normally accompanies reactive gliosis upon photoreceptor cell death. This occurs as a consequence of defective EGFR signaling. Consistent with a function of YAP in triggering Müller glia cell cycle re-entry, we further show that in Xenopus, a species endowed with efficient regenerative capacity, YAP is required for their injury-dependent proliferative response. Finally, and noteworthy, we reveal that YAP overactivation in mouse Müller cells is sufficient to induce their reprogramming into highly proliferative cells. Overall, we unravel a pivotal role for YAP in tuning Müller cell response to injury and highlight a novel YAP-EGFR axis by which Müller cells exit their quiescence state, a critical step towards regeneration.
Project description:Retinal damage triggers reactive gliosis in Müller glia across vertebrate species, but only in regenerative animals, such as teleost fish, do Müller glia initiate repair; proliferating and undergoing neurogenesis to replace lost cells. We found that Plagl1, a maternally imprinted gene, is dynamically regulated in reactive Müller glia post-insult, with transcript levels transiently increasing before stably declining. To study Plagl1 retinal function, we examined Plagl1+/-pat null mutants postnatally, revealing defects in retinal architecture, visual signal processing and a reactive gliotic phenotype. Plagl1+/-pat Müller glia proliferate ectopically and give rise to inner retinal neurons and photoreceptors. Transcriptomic and ATAC-seq profiles revealed similarities between Plagl1+/-pat retinas and neurodegenerative and injury models, including an upregulation of pro-gliogenic and pro-proliferative pathways, such as Notch, not observed in wild-type retinas Plagl1 is thus an essential component of the transcriptional regulatory networks that retain mammalian Müller glia in quiescence.
Project description:Retinal damage triggers reactive gliosis in Müller glia across vertebrate species, but only in regenerative animals, such as teleost fish, do Müller glia initiate repair; proliferating and undergoing neurogenesis to replace lost cells. We found that Plagl1, a maternally imprinted gene, is dynamically regulated in reactive Müller glia post-insult, with transcript levels transiently increasing before stably declining. To study Plagl1 retinal function, we examined Plagl1+/-pat null mutants postnatally, revealing defects in retinal architecture, visual signal processing and a reactive gliotic phenotype. Plagl1+/-pat Müller glia proliferate ectopically and give rise to inner retinal neurons and photoreceptors. Transcriptomic and ATAC-seq profiles revealed similarities between Plagl1+/-pat retinas and neurodegenerative and injury models, including an upregulation of pro-gliogenic and pro-proliferative pathways, such as Notch, not observed in wild-type retinas Plagl1 is thus an essential component of the transcriptional regulatory networks that retain mammalian Müller glia in quiescence.
Project description:Glaucoma is a multifactorial neurodegenerative disease characterized by the progressive and irreversible degeneration of the optic nerve and retinal ganglion cells. Despite medical advances aiming at slowing degeneration down, around 40% of treated glaucomatous patients will undergo vision loss. It is thus of utmost importance to have a better understanding of the disease and to investigate more deeply its early causes. The transcriptional coactivator YAP, an important regulator of eye homeostasis, has recently drawn attention in the glaucoma research field. Here we show that Yap conditional knockout mice (Yap cKO), in which the deletion of Yap is induced in both Müller glia (i.e. the only retinal YAP-expressing cells) and the non-pigmented epithelial cells of the ciliary body, exhibit a breakdown of the aqueous-blood barrier, accompanied by a progressive collapse of the ciliary body. A similar phenotype is observed in human samples that we obtained from patients presenting with uveitis. In addition, aged Yap cKO mice harbor glaucoma-like features, including deregulation of key homeostatic Müller-derived proteins, retinal vascular defects, optic nerve degeneration and retinal ganglion cell death. Finally, transcriptomic analysis of Yap cKO retinas pointed to early-deregulated genes involved in extracellular matrix organization potentially underlying the onset and/or progression of the observed phenotype. Together, our findings reveal the essential role of YAP in preserving the integrity of the ciliary body and retinal ganglion cells, thereby preventing the onset of uveitic glaucoma-like features.
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: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:Regulation of organ size is important for development and tissue homeostasis. In Drosophila, Hippo signaling controls organ size by regulating the activity of a TEAD transcription factor, Scalloped, through modulation of its coactivator protein Yki. The role of mammalian Tead proteins in growth regulation, however, remains unknown. Here we examined the role of mouse Tead proteins in growth regulation. In NIH3T3 cells, cell density and Hippo signaling regulated the activity of Tead proteins by modulating nuclear localization of a Yki homologue, Yap, and the resulting change in Tead activity altered cell proliferation. Tead2-VP16 mimicked Yap overexpression, including increased cell proliferation, reduced cell death, promotion of EMT, lack of cell contact inhibition, and promotion of tumor formation. Growth promoting activities of various Yap mutants correlated with their Tead-coactivator activities. Tead2-VP16 and Yap regulated largely overlapping sets of genes. However, only a few of the Tead/Yapregulated genes in NIH3T3 cells were affected in Tead1-/-;Tead2-/- or Yap-/- embryos. Most of the previously identified Yap-regulated genes were not affected in NIH3T3 cells or mutant mice. In embryos, levels of nuclear Yap and Tead1 varied depending on cell types. Strong nuclear accumulation of Yap and Tead1 were seen in myocardium, correlating with requirements of Tead1 for proliferation. However, their distribution did not always correlate with proliferation. Taken together, mammalian Tead proteins regulate cell proliferation and contact inhibition as a transcriptional mediator of Hippo signaling, but the mechanisms by which Tead/Yap regulate cell proliferation differ depending on cell types, and Tead, Yap and Hippo signaling may play multiple roles in mouse embryos. We used microarrays to know the gene expression profiles regurated by Tead2-VP16, Tead2-EnR, Yap, and cell density in NIH3T3 cells. Keywords: Cell density, genetic modification Tead2-VP16-, Tead2-EnR-, Yap- and control vector-expressing cells were cultured at low or high density for RNA extraction and hybridization on Affymetrix microarrays.