EXPRESSION OF SQ10 (A PREPRORELAXIN-LIKE GENE) IN THE PREGNANT RABBITPLACENTA AND UTERUS

A Northern blot containing poly(A)(+) RNA isolated from pregnant rabbi t placenta, uterus, ovary, mammary gland, psoas muscle, and intestine was hybridized with an oligonucleotide probe to porcine preprorelaxin. Only the placenta and uterus exhibited high levels of a l-kb mRNA tha t hybridized to the probe. Porcine preprorelaxin primers were used to generate and amplify cDNAs from placental and uterine poly(A)(+) RNA. Southern blot analysis of the placental and uterine cDNAs each reveale d a single PCR product that hybridized with the porcine relaxin probe. The sequence of the cDNAs exhibited 100% identity with SQ10, a prepro relaxin-like gene identified in rabbit tracheobronchial epithelial cel ls. Identical results were obtained with primers specific for SQ10. SQ 10 is expressed in tracheobronchial epithelial cells during abnormal c onditions, such as mechanical or toxic injury. The protein is believed to have a role in tracheal epithelial cell differentiation and transf ormation that occurs under the above conditions. This work shows, for the first time, the presence of high levels of message for SQ10 in nor mal reproductive tissues. The expression of SQ10 in the uterus and pla centa may suggest an important role in cell differentiation and transf ormation that occurs in these tissues during pregnancy.