Abstract
Purpose :
In the damaged adult zebrafish retina, Müller glia re-enter the cell cycle to produce neuronal progenitor cells that ultimately differentiate into neuronal cell types that were lost and those unaffected by the damage stimulus. The generation of all neuronal cell types suggests that developmental fate determinants also act in neuronal progenitor cells during regeneration. Therefore, we assessed whether factors governing cell fate choices during development are expressed during retinal regeneration.
Methods :
Light-damaged retinal sections from albino; Tg[atoh7:GFP] or albino; Tg[vsx1:GFP] zebrafish were immunolabeled for GFP, PCNA (Proliferating Cellular Nuclear Antigen) or HuC/D (amacrine/ganglion cells). Tg[atoh7:GFP] fish were injected with EdU 1 hour prior to eye collection. RNA was isolated from dorsal retinas of light-damaged adult albino zebrafish (0, 36, 48, 60, 72, 84 and 96 hours of light, hLT) or those that subsequently recovered under normal light/dark cycles (2, 5 or 7 days). Quantitative real-time polymerase chain reaction (qRT-PCR) was performed using the DDCt method with primers to 18 S, atoh7, alcama, dlx2a, ptf1a, barhl2a, vsx1, prdm1a and nrl.
Results :
In light-damaged retinas, the ganglion cell commitment marker, atoh7:GFP was expressed in a large number of proliferating cells at 72 hLT, but only 10 and 14% of atoh7:GFP-positive cells incorporated EdU in the INL and ONL, respectively, suggesting that some of these cells had exited the cell cycle. Additionally, a few atoh7:GFP-positive cells co-labeled with HuC/D, a postmitotic marker of ganglion/amacrine cells. At 72 and 96 hLT, a small number of proliferating cells also expressed the bipolar cell commitment marker, vsx1:GFP. Quantitative RT-PCR revealed that the cone photoreceptor commitment factor, prdm1a, transiently increased prior to the upregulation of the amacrine specification marker, ptf1a, and atoh7, which displayed a similar onset. prdm1 transcript levels peaked after atoh7 reached its maximal expression. Expression of nrl first decreased during photoreceptor death, but subsequently rose during the recovery phase. We also began investigating the expression of both Atoh7 and Ptf1a downstream targets.
Conclusions :
A subset of transcription factors driving retinal neuron specification in development are also expressed in the adult regenerating zebrafish retina.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.