The rat, mouse and human genes encoding the receptor for parathyroid hormone and parathyroid hormone-related peptide are highly homologous.

The organization of the PTH/PTHrP receptor gene is highly homologous in three mammalian species, rat, human and mouse. This gene extends over 22 kb and contains at least 15 exons and 14 introns. The most 5' exon we have identified (exon U) is followed by an approximately 1kb intron. The second exon (exon S) encodes the initiator methionine and the putative signal peptide and is followed by the largest intron of this gene (about 11 kb). The amino-terminal extracellular region is encoded by 4 exons (E1, E2, E3 and G); exon G contains all 4 potential glycosylation sites. Membrane-spanning domains 1-4 and portions of their connecting intracellular and extracellular loops are encoded by 4 exons (M1, M2, M3 and M4). The second extracellular loop and portions of 4th and 5th membrane-spanning domains are encoded by one exon, EL2. The 5th membrane-spanning domain and portion of the 3rd intracellular loop are encoded by one exon, M5. The 6th membrane-spanning domain, the 3rd extracellular loop and the proximal part of the 7th membrane-spanning domain are encoded by one single exon (M6/7); the remaining sequence of the 7th membrane-spanning domain is encoded by a short exon, M7. The carboxy-terminal tail of the receptor and the 3' untranslated region are encoded by one single exon, exon T. The 3' untranslated region does not contain the classical polyadenylation signal, AATAAA. Expression in COS-7 cells of a minigene constructed of a 5' rat cDNA fragment (1.3 Kb) ligated in-frame to a 3' genomic fragment at the NsiI site, which is located in exon M6/7 resulted in a transcript that was translated into a functional receptor; it bound PTH and showed PTH-stimulated accumulation of intracellular cAMP. Therefore, the PTH/PTHrP receptor gene contains alternative 3' sequences that allow cleavage and polyadenylation of its transcript.