A loxP site flanked lacZ and neomycin resistance gene cassette was inserted downstream of the Shh enhancer in intron 5 of the Lmbr1 gene and the 3' end of the region including all but the first ETS binding site was deleted via homologous recombination. The one remaining ETS1/GABPA binding site was mutated to prevent binding of ETS1/GABPA . (J:208849)