Figure 5.

Visualization of corneal axons in Ret:cre^ER adult mice. B–I, Maximal intensity z-projection confocal stacks from adult whole-mount corneas. A, Description of the mouse lines Rosa^Tom and Tau^GFP (see Fig. 2). In Ret:cre^ER knockin mice, the coding sequence of cre^ERT2 was inserted in the first exon of the Ret gene by homologous recombination. B, In the absence of tamoxifen, no GFP signal is detected in the cornea of Ret:cre^ER;Tau^GFPmice. C–E, The number of GFP⁺ axons increases with the dose of tamoxifen injected (0.25 mg-1 mg). Corneas were collected 14 d (D14) or 60 d (D60) after injection. F, Immunostaining for anti-βIII-tubulin shows that GFP is only expressed in a fraction of βIII-Tub⁺ corneal axons. G–I, Corneas from Ret:cre^ER;Rosa^Tom mice injected with increasing doses of tamoxifen injected (0.25–3 mg). At the lowest dose (G), many Tomato⁺ corneal cells are seen and mask Tomato⁺ axons. H, I, At higher doses, highly fluorescent cells are seen in the limbal region, and more Tomato⁺ axons are observed.