Characterization of canonical Wnt signalling changes after induced disruption of Müller cell in murine retina

Müller cells are the primary glia in the retina, playing a critical role in retinal homeostasis and retinal pathology. This study evaluated the canonical Wnt signalling pathway and its downstream effects on retinal degeneration in a transgenic mouse model of inducible Müller cell disruption. Increased expression of the LacZ reporter gene in the retina suggested Wnt signalling had been activated after induced Müller cell disruption. Activation was validated by observing nuclear translocation of β-Catenin. The mRNA expression of 80 Wnt related genes were assessed using real-time PCR. The Wnt signalling inhibitors Dkk1, Dkk3 and sFRP3 were significantly downregulated. Furthermore, the ubiquitin-mediated β-Catenin proteolysis genes β-TrCP and SHFM3, were also significantly downregulated. The downstream target genes of the Wnt signalling, including Fra1, CyclinD2 and C-Myc were upregulated. The changes of these genes at the protein level were validated by Western blot. Their distributions in the retina were evaluated by immunofluorescent staining. Our findings indicate that Müller cells are involved in retinal Wnt signalling. Activation of Wnt signalling and its downstream target genes may play important roles in photoreceptor degeneration and neovascularization occurring in the retina after induced disruption of Müller cells.