Developmental Biology

Converging Signals

Science's STKE  09 Jul 2002:
Vol. 2002, Issue 140, pp. tw246-TW246
DOI: 10.1126/stke.2002.140.tw246

Takesu et al. studied the development of the trachea in Drosophila in order to understand how multiple signaling pathways may converge to control branching morphogenesis. A subset of tracheal cells express the transforming growth factor-β protein Decapentaplegic (Dpp). The expression of a Dpp enhancer-driven reporter was decreased in Drosophila with mutations in genes of the Wg (also known as Wnt) signaling pathway (arm and zw3) and the Dpp signaling pathway (Med), and in the gene for the Drosophila homolog of the transcriptional coactivator family p300/adenosine 3',5'-monophosphate (cAMP) response element binding protein (CBP), Nejire (nej). The fact that each of the Wg mutations inhibited Dpp enhancer-driven expression suggested the involvement of an unconventional Wg pathway. Furthermore, in Wg pathway mutants, the initiation of Dpp enhancer-driven expression in these tracheal precursor cells was inhibited, suggesting that Wg signaling is important for initiation of the Dpp expression, as well as maintenance of the Dpp expression in these cells. Finally, a genetic interaction between Dpp signaling and Wg signaling was observed, with flies heterozygous for Med and with mutations in Wg signaling showing a suppression of Dpp enhancer-driven expression below that seen with either mutants independently. The authors propose that transcription factors activated by Dpp signaling and unconventional Wg signaling, along with the p300 coactivator, form a multiprotein complex to regulate expression from this Dpp enhancer.

N. T. Takesu, A. N. Johnson, O. H. Sultani, S. J. Newfeld, Combinatorial signaling by an unconventional Wg pathway and the Dpp pathway requires Nejire (CBP-p300) to regulate dpp expression in posterior tracheal branches. Dev. Biol. 247, 225-236 (2002). [Online Journal]