A loxP site was inserted between exons 7 and 8 and a loxP and frt-flanked neomycin selection cassette was inserted between exons 13 and 14. After FLP and Cre-mediated recombination, a deletion of exons 8-13 was created, with a single loxP and a single frt site remaining at the deletion site. This deletion removes K homology (KH) motifs 2, 3 and the amino terminal half of KH4, yielding an allele that is incapable of expressing a protein that binds properly with single-strand nucleic acids. Immunoblot analysis confirmed the absence of protein expression in primary MEFs derived from E13.5 homozygous mutant embryos. (J:229985)