MEK kinase 1 regulates c-Jun phosphorylation in the control ofcorneal morphogenesis

[摘要] Purpose: To study the in vivo role of MEK kinase 1 (MEKK1) incorneal development.Methods: Wild type and Mekk1ΔKD/ΔKD mice eyetissues were examined by staining with hematoxylin and eosin formorphogenesis and Masson's trichrome for extracellular matrix (ECM)deposition. The cells expressing ECM gene transcripts of Collagen I,Keratocan, and Lumican in corneal stroma were identified by insitu hybridization and the level of Collagen I mRNA in thedeveloping cornea was quantified by real-time RT-PCR.Immunohistochemistry staining was employed to study the expression andN-terminal phosphorylation of c-Jun and the expression of epitheliumdifferentiation markers and intercellular structural proteins of thecorneal epithelium.Results: Mekk1ΔKD/ΔKD mice exhibited the "eyeopen at birth" phenotype (EOB), and developed eye defects and severepathology secondary to impaired eyelid formation. The corneal stroma ofMekk1ΔKD/ΔKD fetuses, although exhibiting normalmorphology, thickness, and keratocyte proliferation, showed reducedextracellular matrix (ECM) accumulation, corresponding to a decrease intranscription of Lumican, Keratocan, and Collagen I.Immunohistochemistry studies demonstrated that MEKK1 ablation caused aremarkable reduction in the expression of occludin and zonula occludenprotein-1 (ZO-1), components of tight junction, but had no effect on theexpression of E-cadherin and β-catenin for adherens junctions,desmoplakin and desmoglein for desmosomes and cytokeratins 12 and 14 forcornea-type epithelial differentiation in the developing cornea. c-Junwas abundantly expressed in the developing corneal epithelium and itsphosphorylation was considerably reduced in Mekk1ΔKD/ΔKD fetuses.Conclusions: In addition to its role in eyelid morphogenesis, MEKK1is crucial for corneal development such that its ablation caused areduction of ECM deposition in corneal stroma and disturbance of tightjunctions in corneal epithelium. c-Jun phosphorylation in cornealepithelium is a downstream event of the MEKK1 pathway, likelycontributing to corneal development and function. Altogether, MEKK1plays a major role in ocular surface morphogenesis and its ablationleads to damage and various eye manifestations at postnatal stages.

[学科分类] 生物化学/生物物理