Thoracic patterning by the Drosophila gap gene hunchback.
Thoracic patterning by the Drosophila gap gene hunchback.
复制标题
DOI：
10.1006/dbio.2001.0355
复制
发表时间：
2001-09
影响因子：
2.7
通讯作者：
X. Wu;V. Vasisht;D. Kosman;J. Reinitz;S. Small
中科院分区：
文献类型：
--
作者：
X. Wu;V. Vasisht;D. Kosman;J. Reinitz;S. Small
局部基因表达模式对于在所有多细胞动物中建立身体计划至关重要。在果蝇中，差距基因hunchback（hb）在胚胎的前部区域以动态模式表达。Hb蛋白首先被检测为一个浅的母体梯度，防止后间隙基因在前区域的表达。hb mRNA也在合子中表达，首先作为由Bicoid（Bcd）形态原控制的宽的前域，然后在parsegment 4（PS4）的位置处的条纹中表达。在这里，我们表明，PS4-血红蛋白条纹改变了前血红蛋白梯度的配置文件，通过产生一个本地化的蛋白质，持续到宽域后已经开始下降的峰值。该峰是形成中胸（T2）段所必需的。在分子水平上，PS4-Hb条纹是激活同源异型基因的同源异型足的关键，但不影响由母体和Bcd依赖性Hb的组合形成的Hb抑制活性的梯度。抑制梯度对于确定几个靶基因的位置至关重要，包括差距基因Kruppel（Kr）、knirps（kni）和giant（gt），以及同源异型基因Ultrabithorax（Ubx）。不同的Hb浓度足以抑制gt、kni和Ubx，但抑制Kr需要非常高水平的Hb或组合机制。这些结果表明hb转录的各个阶段在时间和空间上重叠，在早期胚胎发生中贡献了特定的模式功能。
Localized gene expression patterns are critical for establishing body plans in all multicellular animals. In Drosophila, the gap gene hunchback (hb) is expressed in a dynamic pattern in anterior regions of the embryo. Hb protein is first detected as a shallow maternal gradient that prevents expression of posterior gap genes in anterior regions. hb mRNA is also expressed zygotically, first as a broad anterior domain controlled by the Bicoid (Bcd) morphogen, and then in a stripe at the position of parasegment 4 (PS4). Here, we show that the PS4-hb stripe changes the profile of the anterior Hb gradient by generating a localized peak of protein that persists until after the broad domain has started to decline. This peak is required specifically for the formation of the mesothoracic (T2) segment. At the molecular level, the PS4-hb stripe is critical for activation of the homeotic gene Antennapedia, but does not affect a gradient of Hb repressive activity formed by the combination of maternal and Bcd-dependent Hb. The repressive gradient is critical for establishing the positions of several target genes, including the gap genes Kruppel (Kr), knirps (kni), and giant (gt), and the homeotic gene Ultrabithorax (Ubx). Different Hb concentrations are sufficient for repression of gt, kni, and Ubx, but a very high level of Hb, or a combinatorial mechanism, is required for repression of Kr. These results suggest that the individual phases of hb transcription, which overlap temporally and spatially, contribute specific patterning functions in early embryogenesis.