Structure and expression of the bovine oxytocin receptor gene

The gene for the bovine oxytocin receptor has been sequenced using a combination of clones derived from a bovine endometrial cDNA library from estrus and a bovine genomic DNA library, with confirmation of structure using reverse transcription PCR programmed by term myometrial RNA. The receptor belongs to the seven transmembrane domain family and predicts a protein of 391 amino acids. A comparison of the genomic sequence with the cDNA structure, as well as reverse transcription polymerase chain reaction (RT-PCR) analysis, shows there are two introns, one in the 5'noncoding region that appears to be differentially spliced in the bovine uterus and a conserved intron within the open reading frame between the regions encoding the transmembrane domains VI and VII. Northern blot analysis indicated three major transcripts in myometrium and endometrium in vivo at approximately 6.5 kb, 3.5 kb, and 2.0 kb. In situ hybridization analysis of uterine tissue at term showed highest mRNA concentrations in the endometrial epithelium, particularly in the deep glands, a pattern confirmed also at the immunohistochemical level by monoclonal antibodies raised against a human amino-terminal peptide. Further confirmation of the identity of the receptor was obtained by transient transfection of a reconstituted receptor construct into COS-7 cells. The expressed receptor was shown to have identical pharmacological properties in respect to various oxytocin analogs to the natural bovine endometrial receptor.