Insertion of an IRES-tau-lacZ-loxP-tk-neo-loxP expression cassette placed the inserted sequences under control of the endogenous regulatory sequences. Transient expression of Cre recombinase in C57BL/6 blastocysts excised the thymidine kinase and neomycin sequences. This allele expresses a bicistronic mRNA encoding the receptor and a bovine tau-beta-galactosidase fusion protein. (J:36595, J:99181)