Wnt/β‐catenin‐signaling and the formation of Müller glia‐derived progenitors in the chick retina

ABSTRACT
Müller glia can be stimulated to de‐differentiate, proliferate, and form Müller glia‐derived progenitor cells (MGPCs) that are capable of producing retinal neurons. The signaling pathways that influence the de‐differentiation of mature Müller glia and proliferation of MGPCs may include the Wnt‐pathway. The purpose of this study was to investigate how Wnt‐signaling influences the formation of MGPCs in the chick retina in vivo. In NMDA‐damaged retinas where MGPCs are known to form, we find dynamic changes in retinal levels of potential readouts of Wnt‐signaling, including dkk1, dkk3, axin2, c‐myc, tcf‐1, and cd44. We find accumulations of nuclear β‐catenin in MGPCs that peaks at 3 days and rapidly declines by 5 days after NMDA‐treatment. Inhibition of Wnt‐signaling with XAV939 in damaged retinas suppressed the formation of MGPCs, increased expression of ascl1a and decreased hes5, but had no effect upon the differentiation of progeny produced by MGPCs. Activation of Wnt‐signaling, with GSK3β‐inhibitors, in the absence of retinal damage, failed to stimulate the formation of MGPCs, whereas activation of Wnt‐signaling in damaged retinas stimulated the formation of MGPCs. In the absence of retinal damage, FGF2/MAPK‐signaling stimulated the formation of MGPCs by activating a signaling network that includes Wnt/β‐catenin. In FGF2‐treated retinas, inhibition of Wnt‐signaling reduced numbers of proliferating MGPCs, whereas activation ...

Source: Journal of Neurobiology - December 30, 2015 Category: Neurology Authors: Donika Gallina, Isabella Palazzo, Lillia Steffenson, Levi Todd, Andy J. Fischer Tags: Research Article Source Type: research