A bacterial artificial chromosome (BAC) was modified by inserting a humanized Renilla GFP (hrGFP, Stratagene) sequence into the translational start site of the mouse neuropeptide Y (Npy) gene. Correctly transformed and targeted bacteria were used to isolate the ~200 kb transgenic construct (called "NPY-GFP"). This NPY-GFP transgene was used for pronuclear injection into fertilized one-cell stage FVB embryos. Founder line 1 showing germline transmission was established. Brain tissues show GFP fluorescence when exposed to UV light.