Heparin-binding EGF-like growth factor: characterization of rat and mouse cDNA clones, protein domain conservation across species, and transcript expression in tissues.
Clones were obtained that encode the rat and mouse forms of heparin-binding EGF-like growth factor (HB-EGF), a potent mitogen for smooth muscle cells, fibroblasts and keratinocytes that is proposed to be derived from a transmembrane precursor. Within the HB-EGF precursor sequences predicted from these cDNAs, the region corresponding to the secreted ("mature") factor was found to represent one of the least well conserved areas when compared to human or monkey HB-EGF (73-76% sequence identity). Regions of high sequence conservation included the proposed juxtamembrane and transmembrane domains, as well as a proposed heparin-binding region within the "mature" factor. Northern blotting experiments using the HB-EGF clones as probes revealed HB-EGF transcript expression in multiple tissues, particularly lung, skeletal muscle, brain, and heart.