An En1 cDNA and an 825 base-pair piece of the E. Coli lacZ were inserted in the EcoRV site of the pWEXP2 plasmnid. This plasmid contains a Wnt1 genomic fragment which has been modified in such a way that the Wnt1 translation initiation codon has been replaced with a polylinker containing NruI, EcoRV, SacII, and BstBI restriction sites. (J:16386, J:35491)