The genomic sequence for the coding part of exon 1 plus exons 2-5 (coding for amino-acids 2-208) was replaced with a lacZ reporter gene cassette and a loxP site flanked neomycin resistance gene cassette. The neo cassette was removed through subsequent Cre-mediated recombination, leaving a combined reporter null allele. Northern blot and RT-PCR analysis confirmed the absence of endogenous transcripts from this allele.