Exons 7 to 12 as well as part of exon 13 were replaced with a floxed neomycin resistance gene. In the process, exon 1 of Ovca2 which is located between exons 12 and 13 was also deleted. Targeting took place in PC3 ES cells homozygous for Tg(Prm-cre)70Og, which expresses Cre recombinase under control of the male-germline specific protamine promoter. Cre mediated excision subsequently removed the neomycin cassette upon transmission from male chimeric mice. RT-PCR indicated that no full length transcripts were produced but transcripts were produced from exons 1-6.