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Fig. S2
In the adult retina, Glast-CreERT2 expression and activity is specific to MG cells. In the absence of tamoxifen, Glast promoter-driven CreERT2 protein is unable to translocate to the nucleus to mediate recombination between loxP sites (white cell in A). Upon intraperitoneal tamoxifen administration, CreERT2 is now able to translocate to the nucleus leading to recombination between loxP sites. Shown here (red cell in A) is an example of recombination of a loxP-flanked STOP cassette within ROSA26R-tdTomato Cre reporter mouse. Glast- CreERT2+/tg; R26R-tdTomato+/tg mice show Cre-mediated recombination specifically in tdTomato+ MGs spanning the retina and this identity was confirmed by overlapping SOX9 immunofluorescence in the nuclei of tdTomato+ MGs within the INL (B). Glast-CreERT2+/tg specificity was further validated by crossing to the ROSA26R-nTnG+/tg Cre reporter (Prigge et al., 2013; Schmidt, 2013). Nuclear GFP (indicative of Cre-mediated recombination) was observed specifically in the INL and co-localized to SOX9+ MGs (C, see magnified insets). We never observed GFP expression adjacent to the GCL among the retinal astrocyte population. N = 3 per sample. ONL = outer nuclear layer, INL = inner nuclear layer, GCL = ganglion cell layer.