title: Role of substratum stiffness in modulating genes associated with extracellular matrix and mechanotransducers YAP and TAZ.
abstract: OBJECTIVE
  Primary open-angle glaucoma is characterized by increased resistance to aqueous humor outflow and a stiffer human trabecular meshwork (HTM). Two Yorkie homologues, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif, encoded by WWTR1 (TAZ), are mechanotransducers of the extracellular-microenvironment and coactivators of transcription. Here, we explore how substratum stiffness modulates the YAP/TAZ pathway and extracellular matrix genes in HTM cells and how this may be play a role in the onset and progression of glaucoma.
  
  
  METHODS
  HTM cells from normal donors were cultured on hydrogels mimicking the stiffness of normal (5 kPa) and glaucomatous (75 kPa) HTM. Changes in expression of YAP/TAZ related genes and steroid responsiveness were determined. Additionally, transglutaminase-2 expression was determined after YAP silencing.
  
  
  RESULTS
  YAP and TAZ are both expressed in human trabecular meshwork cells. In vitro, YAP and TAZ were inversely regulated by substratum stiffness. YAP and 14-3-3σ were downregulated to different extents on stiffer substrates; TAZ, tissue transglutaminase (TGM2), and soluble frizzled-related protein-1 (sFRP-1) were significantly upregulated. CTGF expression appeared to be altered differentially by both YAP and TAZ. Myocilin and angiopoietin-like 7 expression in response to dexamethasone was more pronounced on stiffer substrates. We demonstrated a direct effect by YAP on TGM2 when YAP was silenced by small interfering RNA.
  
  
  CONCLUSIONS
  The expression of YAP/TAZ and ECM-related-genes is impacted on physiologically relevant substrates. YAP was upregulated in cells on softer substrates. Stiffer substrates resulted in upregulation of canonical Wnt modulators, TAZ and sFRP-1, and thus may influence the progression of glaucoma. These results demonstrate the importance of YAP/TAZ in the HTM and suggest their role in glaucoma.
authors.affiliation: Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California-Davis, Davis, CA 95616, USA.
authors.forename: Vijay Krishna
authors.initials: VK
authors.lastname: Raghunathan
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Morgan
authors.forename: Britta
authors.initials: B
authors.lastname: Dreier
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Reilly
authors.forename: Sara M
authors.initials: SM
authors.lastname: Thomasy
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Wood
authors.forename: Irene
authors.initials: I
authors.lastname: Ly
authors.forename: Binh C
authors.initials: BC
authors.lastname: Tuyen
authors.forename: Marissa
authors.initials: M
authors.lastname: Hughbanks
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Murphy
authors.forename: Paul
authors.initials: P
authors.lastname: Russell
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D001082:Aqueous Humor / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D005902:Glaucoma, Open-Angle / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D006023:Glycoproteins; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000235:genetics*; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D012313:RNA / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014129:Trabecular Meshwork / Q000378:metabolism; D015534:Trans-Activators; D014157:Transcription Factors; D000091364:Transcriptional Coactivator with PDZ-Binding Motif Proteins; D000091102:YAP-Signaling Proteins; D000099274:Frizzled-Related Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012313:RNA; D015534:Trans-Activators; D014157:Transcription Factors; D000091364:Transcriptional Coactivator with PDZ-Binding Motif Proteins; D000091102:YAP-Signaling Proteins; D000099274:Frizzled-Related Proteins; C551991:WWTR1 protein, human; C088374:YAP1 protein, human