The targeting construct is designed to insert an adenosine to thymidine point mutation, resulting in a tyrosine to phenylalanine substitution at position 876 (Y876F). A loxP-flanked neomycin (neo) resistance cassette, in opposite orientation to the gene, is placed upstream of the mutated exon. Germ line, cre mediated recombination removed the neo cassette. (J:285753)