Peri F, Bökel C, Roth S
Max-Planck-Institut für Entwicklungsbiologie, Spemannstr. 35/II, 72076, Tübingen, Germany.
Mech Dev. 1999 Mar;81(1-2):75-88. doi: 10.1016/s0925-4773(98)00228-7.
During Drosophila melanogaster oogenesis Gurken, a TGF-alpha like protein localized close to the oocyte nucleus, activates the MAPK cascade via the Drosophila EGF receptor (DER). Activation of this pathway induces different cell fates in the overlying follicular epithelium, specifying the two dorsolaterally positioned respiratory appendages and the dorsalmost cells separating them. Signal-associated internalization of Gurken protein into follicle cells demonstrates that the Gurken signal is spatially restricted and of constant intensity during mid-oogenesis. At the same time MAPK activation evolves in a spatially and temporally dynamic way and resolves into a complex pattern that presages the position of the appendages. Therefore, different dorsal follicle cell fates are not determined by a Gurken morphogen gradient. Instead they are specified by secondary signal amplification and refinement processes that integrate the Gurken signal with positive and negative feedback mechanisms generated by target genes of the DER pathway.
在黑腹果蝇卵子发生过程中， Gurken是一种定位在卵母细胞核附近的类转化生长因子α蛋白，它通过果蝇表皮生长因子受体（DER）激活丝裂原活化蛋白激酶（MAPK）级联反应。该信号通路的激活在上皮滤泡中诱导不同的细胞命运，决定了两个背外侧位置的呼吸附属器以及分隔它们的最背侧细胞。Gurken蛋白与信号相关的内化进入滤泡细胞表明，在卵子发生中期，Gurken信号在空间上受到限制且强度恒定。与此同时，MAPK激活以时空动态方式演变，并形成一种复杂模式，预示着附属器的位置。因此，不同的背侧滤泡细胞命运不是由Gurken形态发生素梯度决定的。相反，它们是由次级信号放大和细化过程决定的，这些过程将Gurken信号与DER信号通路靶基因产生的正反馈和负反馈机制整合在一起。
