The targeting vector is designed to fuse a pH-sensitive super ecliptic pHluorin (SEP) variant of green fluorescent protein (GFP) sequence to the extracellular N-terminus by insertion into exon 1. A loxP-flanked neomycin resistance (neo) cassette was inserted downstream of exon 1. Cre-mediated recombination removed the loxP-flanked neo cassette. (J:321813)