CLONING AND EXPRESSION OF THE NEUROMEDIN-B RECEPTOR AND THE 3RD SUBTYPE OF BOMBESIN RECEPTOR GENES IN THE MOUSE

We cloned the genes for the mouse homologue of the neuromedin B recept or (NMB-R) and the bombesin receptor subtype 3 (BRS-3). Both receptor genes consist of three exons with well-conserved intron-exon borders. Although the NMB-R gene spans more than 10 kb, the BRS-3 gene spans on ly about 4 kb. Comparison of the mouse and human receptor sequences in dicates 90% (NMB-R) and 85% (BRS-3) sequence homology at the amino-aci d level. In the adult mouse, the NMB-R mRNA is expressed in the brain, testis, esophagus, intestine and uterus, whereas the BRS-3 mRNA is ex pressed predominantly in the brain. In the brain, the NMB-R gene expre ssion is prominent in the thalamic and olfactory regions, and the BRS- 3 gene is expressed particularly in the hypothalamic region. In mouse testis, the NMB-R gene expression is prominent, and the expression of BRS-3 mRNA is barely detected. In contrast, BRS-3 has been shown to be expressed in rat testis and guinea-pig uterus, therefore it is possib le that a different subtype of the bombesin receptor mediates the same response in different species. Together with the mouse GRP-R gene clo ned previously, cloning of the mouse NMB-R and BRS-3 genes permits com parison of function and structure of the three bombesin receptor subty pes in the mouse. (C) 1997 Elsevier Science B.V.