The targeting vector was designed (by site-directed mutagenesis) to insert the arginine to histidine amino acid substitution at position 76 (R76H) (human 79) into exon 1 and place a loxP-flanked neomycin cassette into intron 3. R79H is associated with Alexander disease in humans. Cre-mediated recombination removed the floxed neo cassette. Quantitative real-time PCR showed that Gfap expression is elevated. (J:114689)