XB-ART-18040Development July 1, 1996; 122 (7): 2099-108.
Mothers against dpp encodes a conserved cytoplasmic protein required in DPP/TGF-beta responsive cells.
The proteins necessary for signal transduction in cells responding to ligands of the TGF-beta family are largely unknown. We have previously identified Mad (Mothers against dpp), a gene that interacts with the TGF-beta family member encoded by decapentaplegic (dpp) in Drosophila. Assay of Mad''s role in the DPP-dependent events of embryonic midgut development demonstrates that Mad is required for any response of the visceral mesoderm or endoderm to DPP signals from the visceral mesoderm. Replacement of the normal DPP promoter with a heterologous (hsp70) promoter fails to restore DPP-dependent responses in Mad mutant midguts. Experiments utilizing Mad transgenes regulated by tissue-specific promoters show that MAD is required specifically in cells responding to DPP. Immunohistochemical studies localize MAD to the cytoplasm in all tissues examined. Experiments in Xenopus embryos demonstrate that Drosophila MAD can function in the signaling pathway of BMP-4, a vertebrate homolog of dpp. Based on these results, we propose that Mad is a highly conserved and essential element of the DPP signal transduction pathway.
PubMed ID: 8681791
Article link: Development
Genes referenced: actl6a bmp4 dspp hsp70 hspa1l ncam1 tbx2 tgfb1
Article Images: [+] show captions
|Fig. 7. Drosophila MAD induces ventral mesoderm in Xenopus. (A) Assay of MAD function in Xenopus animal caps. 1-cell embryos were injected at the animal pole. At the blastula stage, animal caps were explanted and cultured until sibling embryos developed to stage 35 (tadpole). (B) Autoradiograph of an assay from embryos injected with RNA encoding Drosophila MAD (2 ng). After injection, animal caps were dissected, cultured and total RNA harvested. The RNA was analyzed by RT-PCR for the presence of actin, globin, NCAM and EF-1a transcripts. The lane marked E contains total RNA harvested from whole embryos as a positive control. The lane marked -RT, is identical to the E lane except that reverse transcriptase (RT) was not included as a negative control. The lane marked C corresponds to animal caps treated identicaly to other samples except no RNA was injected. EF-1a is a ubiquitously expressed transcript (Krieg et al., 1989) and demonstrates that roughly equal amounts of RNA are included in each reaction. (C) Embryos were injected with mRNA that encodes MAD (100 pg), BMP-4 (250 pg), MAD (100 pg) + BMP-4 (250 pg), Receptors: BMP-4 type I receptor (10 pg) + activin type II receptor (10 pg), or MAD (100 pg) + Receptors (10 pg each). After injection embryos were treated as for B.|