Abstract
Purpose :
The majority of retinal degenerative diseases (RDDs) are associated with the irreversible loss of the cone photoreceptors, which eventually leads to blindness. Unfortunately, there is a lack of a good animal model that emulates the human condition. We hypothesize that the cone-dominant, 13-lined ground squirrel (13-LGS) can be developed as a complementary animal model over the traditional species (mice and rats).
Methods :
13-LGS eyes collected between embryonic day (E18) to 3 years of age were paraformaldehyde-fixed, OCT-embedded, and characterized by Toluidine blue staining and immunohistochemistry. A panel of antibodies recognizing the proteins localized on different retinal cell types, such as retinal pigment epithelium (RPE), photoreceptor cells, cells of the inner nuclear layer, ganglion cells, plexiform layers, and the retinal progenitor cells (RPCs) were used to comprehensively assess the retinal development in 13-LGS.
Results :
Chx10, Pax6, PH3, Sox2, and Lhx2 labeling show the multipotent RPCs at all embryonic stages. MITF-expressing RPE is present at the earliest time point tested, E18. Expression of Brn3, Islet1 and HuC/D at E19.5 revealed the transition of a subset of RPCs towards the generation of the first neural retinal cell type: ganglion cells. Otx2 expression is observed in RPE cells at E18 and is subsequently seen in the developing photoreceptor at E24 which continues to persist in postnatal photoreceptors and bipolars. RXRy and Rcvrn positive staining confirm for photoreceptor differentiation at E25.5. Color-sensitive cone subtypes, which are positive for opsin proteins along with peanut agglutinin (PNA) appear only at postnatal stages. Plexiform layers stained by VGlut1, are present in postnatal and adult retinae. Other retinal cell types, such as muller glia and bipolars, marked by CRALBP and CABP5 respectively, are seen starting at postnatal retinae. Toluidine blue-stained images provided further insight into post-natal differentiation and retinal layer formation.
Conclusions :
Our data demonstrate the developmental timeline of retinal cell type generation and maturation with a clear preponderance of cones, as expected in an adult mosaic of 13-LGS with ca. 85% cones. Furthermore, these findings will serve as a foundation for developing novel whole animal models and stem cell-based models of RDDs using this non-traditional rodent species.
This is a 2020 ARVO Annual Meeting abstract.