Vector contains exon 4 through the 3' end of intron 6 then PGK-driven NEO in orientation reverse to the gene followed by the 3' end of exon 7 through the end of exon 8. Correct targeting replaces the intron 6/exon 7 splice site and a portion of exon 7 with the neo casette. Northern and Western blot analysis confirmed the absence of transcription and translation.