Figure 7. Genetic fate mapping of the Vsx2-5.3-PRE-Cre transgene using tdTomato conditional reporter mice.

Vsx2-5.3-PRE-Cre mice were crossed with mice containing the Gt(ROSA)26Sor^{tm9(CAG-tdTomato)Hze} transgene. Offspring in which Cre-mediated recombination events were present continually express tdTomato in those cells. (A–C) The vast majority of tdTomato-expressing cells in Vsx2-5.3-PRE-Cre/CAG:cond-tdTomato mice were located in the outer portion of the inner nuclear layer. The morphology of these cells was consistent with that of a bipolar fate, including terminal lamination in the inner plexiform layer (bracketed region). Immunolabeling for Cre revealed tdTomato-expressing cells in which Cre expression does not persist in the adult (open arrowheads). A second population of tdTomato expressing cells is also evident in the outer nuclear layer, and bear morphological resemblance to photoreceptors (arrows).