Abstract

Oxytocin (OT) is a hypophyseal nonapeptide which exerts a wide spectrum of central and peripheral effects. One of its well-known functions is its involvement in uterine contractions during labor. These functions are mediated by specific oxytocin receptors (OTRs). In order to study the molecular mechanisms underlying the OT/OTR system. I have isolated and characterized 2 identical recombinant phage n-DASH II genomic clones containing the mouse OTR gene using sequence information available from the human and rat OTR genes. Restriction enzyme mapping of the phage showed that the OTR gene spans >20 kbp. A 6.0 kbp Sst I fragment was subcloned and sequenced. Comparison of this sequence to that of the published rat OTR gene sequence confirmed that the fragment was indeed the mouse OTR. The predicted amino acid sequence is 94% and 97% identical to the human and rat OTR sequences, respectively. The transcription start site was mapped by 5 ' rapid amplification of cDNA ends (RACE). The major start site was mapped at 307 by upstream of the ATG codon. The mouse OTR lacks an apparent TATA or CCAAT box as is the case for the rat and human OTR genes. The mouse OTR gene contains three exons and two introns. The first intron lies within the 5 ' -UT region and is 97 bp long. The second intron interrupts the region encoding the sixth and seventh transmembrane domains and is at least 12 kbp long. The OTR gene is highly expressed at parturition and gives rise to at least two transcripts of 5.0 and 3.6 kbp, respectively.