title: Coordinate post-transcriptional repression of Dpp-dependent transcription factors attenuates signal range during development.
abstract: Precise control of the range of signalling molecule action is crucial for correct cell fate patterning during development. For example, Drosophila ovarian germline stem cells (GSCs) are maintained by exquisitely short-range BMP signalling from the niche. In the absence of BMP signalling, one GSC daughter differentiates into a cystoblast (CB) and this fate is stabilised by Brain tumour (Brat) and Pumilio (Pum)-mediated post-transcriptional repression of mRNAs, including that encoding the Dpp transducer, Mad. However, the identity of other repressed mRNAs and the mechanism of post-transcriptional repression are currently unknown. Here, we identify the Medea and schnurri mRNAs, which encode transcriptional regulators required for activation and/or repression of Dpp target genes, as additional Pum-Brat targets, suggesting that tripartite repression of the transducers is deployed to desensitise the CB to Dpp. In addition, we show that repression by Pum-Brat requires recruitment of the CCR4 and Pop2 deadenylases, with knockdown of deadenylases in vivo giving rise to ectopic GSCs. Consistent with this, Pum-Brat repression leads to poly(A) tail shortening and mRNA degradation in tissue culture cells, and we detect a reduced number of Mad and shn transcripts in the CB relative to the GSC based on single molecule mRNA quantitation. Finally, we show generality of the mechanism by demonstrating that Brat also attenuates pMad and Dpp signalling range in the early embryo. Together our data serve as a platform for understanding how post-transcriptional repression restricts interpretation of BMPs and other cell signals in order to allow robust cell fate patterning during development.
authors: Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
authors: Fay G
authors: FG
authors: Newton
authors: Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
authors: Robin E
authors: RE
authors: Harris
authors: Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK.
authors: Catherine
authors: C
authors: Sutcliffe
authors: Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, UK hilary.ashe@manchester.ac.uk.
authors: Hilary L
authors: HL
authors: Ashe
mesh_terms: D053687:Adult Stem Cells / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004330:Drosophila / Q000254:growth & development*; D029721:Drosophila Proteins / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D017403:In Situ Hybridization; D010053:Ovary / Q000166:cytology*; D051901:Smad4 Protein / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C112506:MAD protein, Drosophila; C112504:Med protein, Drosophila; D051901:Smad4 Protein; D014157:Transcription Factors; C094066:shn protein, Drosophila
keywords: BMP; Brat; Differentiation; Mad; Medea; Post-transcriptional repression; Pum; Schnurri