The targeting construct was designed to insert an FRT-flanked neomycin (neo) resistance cassette downstream of exon 4 of the gene. A GAC to AAC mutation (G358A) was introduced in exon 4, converting an aspartic acid to an asparagine (D120N) similar to a mutation found in humans with Lennox-Gastaut Syndrome (LGS). Flp-mediated recombination removed the FRT-flanked neo cassette. (J:292112)