Cyan fluorescent protein (CFP) expressing cells in the retina of Thy1-CFP transgenic mice before and after optic nerve injury

We investigated the specificity of cyan fluorescent protein (CFP) expression in retinal ganglion cells (RGCs) of the transgenic Thy1-CFP (B6.Cg-Tg(Thy1-CFP)23Jrs/J) mouse line, and the characteristics of these cells after optic nerve injury. RGCs of adult Thy1-CFP mice were retrogradely labeled with fluorochrome (2% fluorogold [FG]) from the superior colliculi (SC). Animals were sacrificed 7 days after RGC labeling. Retinas were fixed and whole-mounted. CFP and FG-positive cells were visualized and imaged separately. Cells positive for CFP, FG, or co-labeled were counted. In another group of animals, the left optic nerves were transected 7 days after FG labeling. They were sacrificed 7 or 21 days after transection. The retinas were whole-mounted and the characteristics of CFP-expressing cells examined. CFP-expressing cells were distributed evenly throughout the retinas of Thy1-CFP mice. The average densities of CFP and FG-positive cells in the retina were 2778 +/- 216 and 3230 +/- 157 cells/mm(2), respectively. 93.2 +/- 1.6% of CFP-expressing cells were also labeled with FG. However, only 79.9 +/- 2.5% of FG-labeled RGCs expressed CFP. The number of CFP-expressing cells decreased dramatically after transection. Cells with spindle shape, immunohistochemically identified as microglia, were seen in the retina with CFP expression at both 7 and 21 days after optic nerve transection. In retinas of Thy1-CFP mice, CFP is expressed by the large majority of RGCs, but not exclusively by RGCs. CFP is internalized by phagocytosing cells after injury to RGCs. (C) 2009 Elsevier Ireland Ltd. All rights reserved.