A targeting vector was designed to replace a 600 kb fragment from intron 4 up to the 5' end of exon 6 (which contains the sequence encoding the Zinc-binding motif in the putative active site of the endogenous protein) with a neomycin resistance cassette. RT-PCR verified absence of mRNA in splenocytes and no protein is detected in hepatocytes by immunoblot. (J:122479)