Summary In pregnancy, trophoblast invasion and uterine spiral artery remodeling are important for lowering maternal vascular resistance and increasing uteroplacental blood flow. Impaired spiral artery remodeling has long been implicated in preeclampsia, a major complication of pregnancy, but the underlying mechanisms remain unclear1, 2. Corin is a cardiac protease that activates atrial natriuretic peptide (ANP), a cardiac hormone important in regulating blood pressure3. Unexpectedly, corin expression was detected in the pregnant uterus4. Here we identify a novel function of corin and ANP in promoting trophoblast invasion and spiral artery remodeling. We show that pregnant corin- or ANP-deficient mice developed high blood pressure and proteinuria, characteristics of preeclampsia. In these mice, trophoblast invasion and uterine spiral artery remodeling were markedly impaired. Consistently, we find that ANP potently stimulated human trophoblasts in invading Matrigels. In patients with preeclampsia, uterine corin mRNA and protein levels were significantly lower than that in normal pregnancies. Moreover, we have identified corin gene mutations in preeclamptic patients, which decreased corin activity in processing pro-ANP. These results indicate that corin and ANP are essential for physiological changes at the maternal-fetal interface, suggesting that defects in corin and ANP function may contribute to preeclampsia.

Atrial natriuretic peptide (ANP) is a cardiac hormone essential for the regulation of blood pressure. In cardiac myocytes, ANP is synthesized as a precursor, pro-ANP, that is converted to biologically active ANP by an unknown membrane-associated protease. Recently, we cloned a transmembrane serine protease, corin, that is highly expressed in the heart. In this study, we examine effects of corin on pro-ANP processing. Our results show that recombinant human corin converts pro-ANP to ANP and that the cleavage in pro-ANP by corin is highly sequence specific. Our findings suggest that corin is the long-sought pro-ANP-converting enzyme and that the corin-mediated pro-ANP activation may play a role in regulating blood pressure.

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A novel cDNA has been identified from human heart that encodes an unusual mosaic serine protease, designated corin. Corin has a predicted structure of a type II transmembrane protein and contains two frizzled-like cysteine-rich motifs, seven low density lipoprotein receptor repeats, a macrophage scavenger receptor-like domain, and a trypsin-like protease domain in the extracellular region. Northern analysis showed that corin mRNA was highly expressed in the human heart. In mice, corin mRNA was detected by in situ hybridization in the cardiac myocytes of the embryonic heart as early as embryonic day (E) 9.5. By E11.5-13.5, corin mRNA was most abundant in the primary atrial septum and the trabecular ventricular compartment. Expression in the heart was maintained through the adult. In addition, mouse corin mRNA was also detected in the prehypertrophic chrondrocytes in developing bones. By fluorescent in situ hybridization analysis, the human corin gene was mapped to 4p12-13 where a congenital heart disease locus, total anomalous pulmonary venous return, had been previously localized. The unique domain structure and specific embryonic expression pattern suggest that corin may have a function in cell differentiation during development. The chromosomal localization of the human corin gene makes it an attractive candidate gene for total anomalous pulmonary venous return.