Exon 7 was replaced with an exon 7 carrying an arginine to cysteine amino acid substitution at position 451 (R451C). A neo cassette used as a selectable marker was removed via flip-mediated recombination leaving a floxed exon 7 carrying the mutation. The R451C substitution in the extracellular esterase-homology domain that results in increased endoplasmic reticulum retention in humans with autism spectrum disorder. PCR was used to confirm the insertion. Western blot analysis reveal a decrease in protein expression to 10% of wild-type levels. Authors state that this mutation is likely to cause a gain-of-function mutation. (J:125344)