Szüts D, Bienz M
MRC Laboratory of Molecular Biology, Hills Road, CB2 2QH, Cambridge, UK.
Mech Dev. 2000 Nov;98(1-2):71-6. doi: 10.1016/s0925-4773(00)00455-x.
The endoderm of Drosophila is patterned during embryogenesis by an inductive cascade emanating from the adhering mesoderm. An immediate-early endodermal target gene of this induction is Dfos whose expression is upregulated in the middle midgut by Dpp signalling. Previous evidence based on a dominant-negative Dfos construct indicated that Dfos may cooperate with Dpp signalling to induce the HOX gene labial, the ultimate target gene of the inductive cascade. Here, we examine kayak mutants that lack Dfos to establish that Dfos is indeed required for labial induction. We provide evidence that Dfos acts through a CRE-like sequence, previously identified to be a target for signalling by Dpp and by the Epidermal growth factor receptor (Egfr) in the embryonic midgut. We show that Dfos expression is stimulated by Egfr signalling. Finally, we find that Dfos function is required for its own upregulation. Thus, endoderm induction is based on at least four tiers of positive autoregulatory feedback loops.
果蝇的内胚层在胚胎发育过程中通过源自附着中胚层的诱导级联形成模式。这种诱导的一个早期内胚层靶基因是Dfos，其表达通过Dpp信号在中肠中部上调。先前基于显性负性Dfos构建体的证据表明，Dfos可能与Dpp信号协同作用以诱导HOX基因唇，这是诱导级联的最终靶基因。在这里，我们研究缺乏Dfos的kayak突变体，以确定Dfos确实是诱导唇所必需的。我们提供的证据表明，Dfos通过一个类似CRE的序列起作用，该序列先前被确定为胚胎中肠中Dpp和表皮生长因子受体（Egfr）信号传导的靶标。我们表明，Egfr信号刺激Dfos表达。最后，我们发现Dfos功能是其自身上调所必需的。因此，内胚层诱导至少基于四层正自调节反馈环。
