Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.
Sara Endosomes and the Maintenance of Dpp Signaling Levels Across Mitosis
During development, cells acquire positional information byreading the concentration of morphogens. In the developing flywing, a gradient of the transforming growth factorß(TGF-ß)type morphogen decapentaplegic (Dpp)is transduced into a gradient of concentration of the phosphorylatedform of the R-Smad transcription factor Mad. The endosomal proteinSara (Smad anchor for receptor activation) recruits R-Smadsfor phosphorylation by the type I TGF-ß receptor.We found that Sara, Dpp, and its type I receptor Thickveinswere targeted to a subpopulation of apical endosomes in thedeveloping wing epithelial cells. During mitosis, the Sara endosomesand the receptors therein associated with the spindle machineryto segregate into the two daughter cells. Daughter cells therebyinherited equal amounts of signaling molecules and thus retainedthe Dpp signaling levels of the mother cell.
1 Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany. 2 Department of Biochemistry and Department of Molecular Biology, Geneva University, Sciences II, 30 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland.