Imaging neuronal subsets in transgenic mice expressing multiple spectral variants of GFP

We generated transgenic mice in which red, green, yellow, or cyan fluoresce nt proteins (together termed XFPs) were selectively expressed in neurons. A ll four XFPs labeled neurons in their entirety, including axons, nerve term inals, dendrites, and dendritic spines. Remarkably, each of 25 independentl y generated transgenic lines expressed XFP in a unique pattern, even though all incorporated identical regulatory elements (from the thy1 gene). For e xample, all retinal ganglion cells or many cortical neurons were XFP positi ve in some lines, whereas only a few ganglion cells or only layer 5 cortica l pyramids were labeled in others. In some lines, intense labeling of small neuronal subsets provided a Golgi-like vital stain. In double transgenic m ice expressing two different XFPs, it was possible to differentially label 3 neuronal subsets in a single animal.