Abstract
Purpose :
In mammals, loss of the retinal neurons is irreversible due to the limited proliferative and regenerative ability of the retina. In contrast, teleost fish MG autonomously re-enter cell cycle and regenerate functional retinal neurons following injury. In zebrafish, dynamic regulation of Notch signaling is required for MG proliferation and neurogenesis, underlying successful retinal regeneration. The previous study in our lab showed that simultaneous P27kip1 knockdown and Cyclin D1 overexpression can efficiently drive mouse MG to re-enter cell cycle without retinal injury. However, Notch signaling remains highly active in the postmitotic MG, and no mature rod photoreceptors were regenerated. In this study, we tested the hypothesis that inhibition of Notch signaling could promote neuronal differentiation of the postmitotic MG in adult mice.
Methods :
Rbpj, the key mediator of Notch signaling pathway, was selectively deleted in MG in GlastCreERT2;Rbpjflox/flox;tdTomato mice. Rbpj knockout was induced at various postnatal days to examine the effect of Notch signaling suppression on late retinal progenitor cells (RPCs) or MG. Moreover, cell cycle re-activation was induced by AAV-mediated P27kip1 knockdown and Cyclin D1 overexpression in the Rbpj depleted MG, and EdU was injected to label and track proliferating MG. The identities of the MG daughter cells were assessed by immunohistochemistry (IHC) and RNAscope of MG and neuronal markers.
Results :
We found that Rbpj deletion in the late RPCs in postnatal mouse retinas leads to overproduction of retinal neurons at the expense of MG, while Rbpj deletion has limited influence on the cell fate of mature MG. Furthermore, we showed that, in combination with MG cell cycle re-activation, loss of Rbpj further promoted the neuronal differentiation of a subset of the postmitotic MG.
Conclusions :
In summary, we found that Rbpj knockout alone does not lead to the cell fate conversion of mature MG, but Rbpj knockout in combination with cell cycle re-activation promoted the neuronal cell fate of MG daughter cells.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.