The transgene contains a tagged 27 kb of the mouse gene encompassing three exons, two introns, and 13 kb of the 5' and 8 kb of 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. During embryonic development the transgene is expressed in the arcuate nucleus of the hypothalamus and the developing diencephalon, spinal cord, and nucleus of the tractus solitarius. (J:49226)