FIGURE 3. XFP expression in Brainbow transgenic mice.

a, b, Thy1-Brainbow-1.0 and Thy1-Brainbow-1.1 transgenic mice were crossed with CreERT2-expressing animals. Tamoxifen injection led to mosaic XFP expression throughout the brain. a, Brainstem, line H; b, hippocampal mossy fibre axons and their terminals (see insets), line M. c, In Thy1-Brainbow-2.0 mice, transient recombination with the CreERT2/tamoxifen system triggers expression of M-CFP (peripheral motor axons, line N). d, In Thy1-Brainbow-2.1 mice, CreERT2-mediated recombination leads to expression of multiple XFPs. Left: oculomotor nerve, line R. Right: hippocampus (dentate gyrus), line Q (labelled neurons and astrocytes). e, Sagittal brain sections of Thy1-Brainbow-1.0 mice line H crossed with the retina-specific Chx10-Cre driver. Recombination is almost completely restricted to retinal ganglion cells, as shown by label of their axons arborizing in the superior colliculus. The boxed area in the left panel is shown at greater magnification in the right panel. Scale bars: a–c, 10 m; d, 20 m; e (left), 250 m; e (right), 50 m.