BMP1-Related Metalloproteinases Promote the Development of Ventral Mesoderm in Early Xenopus Embryos

AbstractBone morphogenetic protein 1 (BMP1) is a metalloproteinase closely related toDrosophilaTolloid (Tld). Tld regulates dorsoventral patterning in earlyDrosophilaembryos by enhancing the activity of Dpp, a member of the TGF-β family most closely related to BMP2 and BMP4. InXenopusBMP4 appears to play an essential role in dorsoventral patterning, promoting the development of ventral fates during gastrula stages. To determine if BMP1 has a role in regulating the activity of BMP4, we have isolated cDNAs forXenopusBMP1 and a novel closely related gene that we have calledxolloid(xld). Whereasxbmp1is uniformly expressed at all stages tested, the initial uniform expression ofxldbecomes localized to two posterior ectodermal patches flanking the neural plate and later to the inner ectoderm of the developing tailbud.xldis also expressed in dorsal regions of the brain during tailbud stages and is especially abundant in the ventricular layer of the dorsal hindbrain caudal to the otic vesicle. Overexpression of either gene inhibits the development of dorsoanterior structures in whole embryos and ventralizes activin-induced dorsal mesoderm in animal caps. Since ventralization of activin-induced animal caps can be blocked by coinjecting a dominant-inhibitory receptor for BMP2 and BMP4, we suggest a role for BMP1 and Xld in regulating the ventralizing activity of these molecules