The construct targeted to the locus contains a floxed neomycin resistance/STOP cassette, the human EIF1AX promoter, a Caldocellum saccharolyticum gene that encodes a beta-glucosidase (bglA) and a polyadenylation sequence. Cre-mediated recombination is required to achieve expression of the reporter except in the small intestine where background activity is detected. (J:196052)