@article{LeopoldZeilbeckWeberetal.2017,
  author    = {Leopold, Stephanie A. and Zeilbeck, Ludwig F. and Weber, Gregor and Seitz, Roswitha and B{\"o}sl, Michael R. and J{\"a}gle, Herbert and Fuchshofer, Rudolf and Tamm, Ernst R. and Ohlmann, Andreas},
  title     = {Norrin protects optic nerve axons from degeneration in a mouse model of glaucoma},
  series = {Scientific Reports},
  volume    = {7},
  journal   = {Scientific Reports},
  doi       = {10.1038/s41598-017-14423-8},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-173494},
  year      = {2017},
  abstract  = {Norrin is a secreted signaling molecule activating the Wnt/β-catenin pathway. Since Norrin protects retinal neurons from experimental acute injury, we were interested to learn if Norrin attenuates chronic damage of retinal ganglion cells (RGC) and their axons in a mouse model of glaucoma. Transgenic mice overexpressing Norrin in the retina (Pax6-Norrin) were generated and crossed with DBA/2J mice with hereditary glaucoma and optic nerve axonal degeneration. One-year old DBA/2J/Pax6-Norrin animals had significantly more surviving optic nerve axons than their DBA/2J littermates. The protective effect correlated with an increase in insulin-like growth factor (IGF)-1 mRNA and an enhanced Akt phosphorylation in DBA/2J/Pax6-Norrin mice. Both mouse strains developed an increase in intraocular pressure during the second half of the first year and marked degenerative changes in chamber angle, ciliary body and iris structure. The degenerations were slightly attenuated in the chamber angle of DBA/2J/Pax6-Norrin mice, which showed a β-catenin increase in the trabecular meshwork. We conclude that high levels of Norrin and the subsequent constitutive activation of Wnt/β-catenin signaling in RGC protect from glaucomatous axonal damage via IGF-1 causing increased activity of PI3K-Akt signaling. Our results identify components of a protective signaling network preventing degeneration of optic nerve axons in glaucoma.},
  language  = {en}
}
@article{MeirKannapinDiefenbacheretal.2021,
  author    = {Meir, Michael and Kannapin, Felix and Diefenbacher, Markus and Ghoreishi, Yalda and Kollmann, Catherine and Flemming, Sven and Germer, Christoph-Thomas and Waschke, Jens and Leven, Patrick and Schneider, Reiner and Wehner, Sven and Burkard, Natalie and Schlegel, Nicolas},
  title     = {Intestinal epithelial barrier maturation by enteric glial cells is GDNF-dependent},
  series = {International Journal of Molecular Sciences},
  volume    = {22},
  journal   = {International Journal of Molecular Sciences},
  number    = {4},
  issn      = {1422-0067},
  doi       = {10.3390/ijms22041887},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-258913},
  year      = {2021},
  abstract  = {Enteric glial cells (EGCs) of the enteric nervous system are critically involved in the maintenance of intestinal epithelial barrier function (IEB). The underlying mechanisms remain undefined. Glial cell line-derived neurotrophic factor (GDNF) contributes to IEB maturation and may therefore be the predominant mediator of this process by EGCs. Using GFAP\(^{cre}\) x Ai14\(^{floxed}\) mice to isolate EGCs by Fluorescence-activated cell sorting (FACS), we confirmed that they synthesize GDNF in vivo as well as in primary cultures demonstrating that EGCs are a rich source of GDNF in vivo and in vitro. Co-culture of EGCs with Caco2 cells resulted in IEB maturation which was abrogated when GDNF was either depleted from EGC supernatants, or knocked down in EGCs or when the GDNF receptor RET was blocked. Further, TNFα-induced loss of IEB function in Caco2 cells and in organoids was attenuated by EGC supernatants or by recombinant GDNF. These barrier-protective effects were blunted when using supernatants from GDNF-deficient EGCs or by RET receptor blockade. Together, our data show that EGCs produce GDNF to maintain IEB function in vitro through the RET receptor.},
  language  = {en}
}