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Amanda Leung, Edward Levine; Cell-intrinsic regulation of the onset of retinal neurogenesis by Vsx2. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1774. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The process of retinal development depends on the proper timing of developmental transitions. In the Vsx2-null retina (orJ allele), the initiation of neurogenesis is delayed through an unknown mechanism. The objectives of this research are 1) to understand how Vsx2 regulates the timing of neurogenesis and 2) whether retinal progenitor cells (RPCs) undergo a transition at the onset of neurogenesis, and how they are maintained once neurogenesis begins.
We are testing the hypothesis that Pax6 activity facilitates the neurogenic delay observed in Vsx2-null RPCs by crossing in the semi-dominant Pax6sey allele. The mutants were assayed with several cell markers to assess the timing of neurogenesis initiation.We are also testing the hypothesis that RPCs transition from a Notch-independent state prior to neurogenesis to a Notch-dependent state once neurogenesis begins. We pharmacologically inhibited the Notch pathway with DAPT in retinal explant cultures and assayed for the presence of neurogenic markers in both Vsx2-null and wild-type retinas between E10.5-E14.5.
The Vsx2, Pax6 double-mutant retina did not display a wild type neurogenic time course at the time points assayed: E11.5, E12.5, or E13.5.RPCs in both control and Vsx2-null retinas did not undergo premature neurogenesis after DAPT treatment prior to the onset of neurogenesis, but did exhibit enhanced neurogenesis once neurogenesis began.
Reduced Pax6 activity was not sufficient to rescue neurogenic timing in the absence of Vsx2. This could be because Pax6 is not a factor in the neurogenic timing mechanism or because of insufficient reduction in Pax6 expression or activity and follow up studies on Pax6 gene expression and protein activity are underway. Our experiments with DAPT suggest that wild type and Vsx2-null RPCs transition from a Notch-independent to a Notch-dependent state for their maintenance as part of the transition into neurogenesis. These observations indicate that this state change is maintained in Vsx2-null RPCs and that further analysis of how neurogenic timing is controlled in mice with altered Vsx2 function could provide information on how to regulate neurogenic behavior in retinal reprogramming or regeneration.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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