Decapentaplegic (dpp), a TGFβ-related ligand, plays a key role in Drosophila development. Although dpp receptors have been isolated, the downstream components of the signaling pathway remain to be identified. We have cloned the schnurri(shnn) gene and show that it encodes a putative zinc finger transcription factor homologous to the human major histocompatibility complex-binding proteins 1 and 2. Mutations in shn affect multiple events that require dpp signaling as well as the transcription of dpp-responsive genes. Genetic interactions and the strikingly similar phenotypes of mutations in shn and the dpp receptors encoded by thick veins and punt suggest that shn plays a downstream role in dpp signaling.
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tion to study shn. We gratefully acknowledge B. Chase for providing us with a restriction map of his genomic walk in the region and M. Frasch for innumerable discussions and helpful advice. We thank W. M. Gelbart and V. Twombly for sharing information prior to publication. A. L. would like to thank the Wasserman lab for help in isolating shn 4~ and M. Honeggar for technical support. A. Andres generously lent us a Northern blot. We thank N. Arnheim, L Bell, K. Moses, and J. Tower for comments on the manuscript. This work was supported bythe March of Dimes Birth Defects Foundation and National Institutes of Health grant GM48659 to R. W.; National Institutes of Health grants GM 47462 and GM 00599 to M. B. O.; and grants from the March of Dimes Birth Defects Foundation and the American Cancer Society toA. L.