The sequence of exon 16 was humanized and the Swedish mutations (KM670/671NL) were introduced, the Arctic (E22G) and Beyreuther/Iberian mutations (I716F) were inserted into exon 17 and a floxed neo cassette was inserted in intron 16 via homologous recombination. Cre mediated recombination removed the neo cassette. (J:212758)