The transgene contains a tagged 10.2 kb of the mouse gene encompassing three exons, two introns, and 2 kb of the 5' and 3' flanking sequences. The modification involves the insertion of a random 34 bp sequence in the coding sequence of exon 3, allowing for distinguishing transgene transcripts from endogenous transcripts. Six lines were generated, which all show expression in the pituitary, but lines 35 and 36 exhibit ectopic expression in the hippocampal dentate gyrus.