The dpp/BMP family of TGFβ-related factors controls numerous events in pattern formation and morphogenesis. How these polypeptide signals are received and transduced by target cells is largely unknown. We combine molecular and genetic approaches to establish that the Drosophila saxophone (sax) gene encodes a dpp receptor. We compare the structural properties and expression patterns of sax with a second dpp receptor encoded by the thick veins (tkv) gene. While the sax gene is expressed ubiquitously, tkv is expressed in a highly localized and dynamic pattern during development. Some, but not all, of the tkv expression pattern parallels that of dpp. Ubiquitous expression of a tkv transgene rescues both tkv and sax loss-of-function mutations. Thus, there is at least partial functional overlap of the sax and tkv receptors in vivo. We consider these observations in terms of possible ligand-receptor interactions during Drosophila development.
Bibliographical noteFunding Information:
The first three authors have contributed equally to this work and should be considered co-first authors. We thank M. Hoffmann for wmmunica-tions prior to publication. We wish to thank T. Schilpbach. D. Gubb, S. Russo, S. Parks, C. Rushlow, and S. Roth for materials provided, useful discussions, or both. This work was supported by grants from the National Institutes of Health to J. M. and to Memorial Sloan-Kettering Cancer Center. J. L. W. and L. A. are Medical Research Council of Canada postdoctoral fellows. J. M. is a Howard Hughes Medical Institute Investigator. This work was also supported by an NIH grant to W. M. G. and to M. B. 0. V. T. was a National Research Service Award (NRSA) genetics trainee and S. N. is a NRSA poskloc-toral fellow. G. M. is a postdoctoral fellow of the United States-Spain Fulbright Program. Additionally, we thank J. Wozney for BMP-2.