Abstract
Purpose :
During postnatal development, the transcription factor NFIA is expressed in post-mitotic cells of the mouse retina. At P5, it is detected in a subset of cells, including AII amacrine cells, coalescing in the future amacrine cell layer, while by P10, it is also detected in the population of Müller glia and a subset of bipolar cells within the inner nuclear layer (Keeley & Reese, 2018, JCN, 526, p467). These observations suggest that NFIA may be critical for the specification and/or differentiation of particular types of cells in the mouse retina. This study sought to determine the role of NFIA on the final composition of retinal cells by ablating the gene from the eye during early development.
Methods :
Floxed Nfia mice were crossed with Rx-cre mice to conditionally remove Nfia from retinal progenitor cells (CKO mice). Retinas harvested from postnatal and adult mice were labeled via immunofluorescence to reveal different neuronal populations. Cell counts were performed in wholemount retinas to estimate the total cell number for each population.
Results :
CKO mice showed a conspicuous reduction in NFIA immunoreactivity in the mature retina, with entire quadrants completely lacking the transcription factor; NFIA-positive cells that remained was attributed to mosaicism in the expression of Cre during development. When compared to control retinas, CKO retinas exhibited no difference in the number of cone photoreceptors (ARR3+), horizontal cells (PROX1+), ganglion cells (BRN3B+), rod bipolar cells (PKC+), cone bipolar cells (CSEN+ and PKARIIβ+), amacrine cells (ChAT+, TH+, and VGluT3+), and Müller glia (GS+). The number of PROX1+ AII amacrine cells, however, was reduced by 78% in the CKO retina. In addition, there was a substantial reduction of GLYT1+ cell bodies immediately adjacent to the inner plexiform layer (IPL), as well as reduced CX36 staining in S5 of the IPL. The reduction in PROX1+/GLYT1+ cells was readily apparent in postnatal retinas of the CKO mouse, as early as P5.
Conclusions :
Removal of Nfia from retinal progenitor cells yielded a relatively selective effect upon the cellular composition of the retina: only the population of AII amacrine cells was appreciably altered. The reduction in PROX1 (a transcription factor), GLYT1 (a glycine transporter), and CX36 (a gap junction protein) immunoreactivity observed in the CKO retina suggests that NFIA is essential for establishing a functional population of AII amacrine cells.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.