Inverse regulation of target genes at the brink of the BMP morphogen activity gradient
BMP-dependent patterning in the Drosophila melanogaster wing imaginal disc serves as a paradigm to understand how morphogens specify cell fates. Profile of the transcriptional response to the graded signal of BMP, relies upon two counter active gradients of pMad and Brinker (Brk). This patterning model is inadequate to explain the expression of target genes, like vestigial and spalt, in lateral regions of the wing disc where BMP signal decline and Brk levels peak. Here we show that in contrast
... w that in contrast to the reciprocal repressor gradient mechanism, where Brk represses BMP targets in medial regions, in lateral regions target expression is downregulated by BMP signaling and activated by Brk. Brk induces lateral expression indirectly apparently through repression of a negative regulator. Our findings provide a model explaining how the expression of an established BMP target is differentially and inversely regulated along the anterior-posterior axis of the wing disc. Journal of Cell Science Accepted manuscript Bangi, E. and Wharton, K. (2006). Dpp and Gbb exhibit different effective ranges in the establishment of the BMP activity gradient critical for Drosophila wing patterning. Dev Biol 295, 178-93.