Expression of SQ10 (a preprorelaxin-like gene) in the pregnant rabbit placenta and uterus

A Northern blot containing poly(A)+ RNA isolated from pregnant rabbit 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 1-kb mRNA that 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 revealed a single PCR product that hybridized with the porcine relaxin probe. The sequence of the cDNAs exhibited 100% identity with SQ10, a preprorelaxin-like gene identified in rabbit tracheobronchial epithelial cells. Identical results were obtained with primers specific for SQ10. SQ10 is expressed in tracheobronchial epithelial cells during abnormal conditions, such as mechanical or toxic injury. The protein is believed to have a role in tracheal epithelial cell differentiation and transformation that occurs under the above conditions. This work shows, for the first time, the presence of high levels of message for SQ10 in normal reproductive tissues. The expression of SQ10 in the uterus and placenta may suggest an important role in cell differentiation and transformation that occurs in these tissues during pregnancy.