Klingler M, Gergen J P
Department of Biochemistry and Cell Biology, State University of New York at Stony Brook 11794.
Mech Dev. 1993 Sep;43(1):3-19. doi: 10.1016/0925-4773(93)90019-t.
The runt gene plays an important role in the genetic hierarchy that generates the segmented body pattern during the early stages of Drosophila embryogenesis. We studied mRNA expression in mutant embryos in order to investigate the regulation of runt transcription during these stages. We used sensitive whole-mount in situ hybridization procedures to identify the earliest, and therefore most likely direct regulatory effects. There are several distinct phases of runt expression in the early embryo. We find that each phase depends on a different set of regulators. The first phase of expression is a broad-field of mRNA accumulation in the central regions of syncytial blastoderm stage embryos. This pattern is due to terminal repression by the anterior and terminal maternal systems. The effect of the terminal system, even at this early stage, is mediated by two zygotic gap genes, tailless and huckebein. A 7 stripe pattern of runt mRNA accumulation emerges during the process of cellularization. The initial formation of this pattern depends on position-specific repression by zygotic gap genes. Examination of the early RNA patterns of the pair-rule genes even-skipped, hairy, and fushi tarazu indicate that they are also regulated in a similar manner. Three pair-rule genes, hairy, even-skipped, and runt itself, also affect runt's 7 stripe pattern. The effects of runt are stripe specific; the effects of hairy are more uniform; and the patterns obtained in even-skipped mutant embryos show a combination of both stripe specific and uniform regulatory effects. A third distinct phase of expression occurs at the onset of gastrulation when runt becomes expressed in 14 stripes. fushi tarazu plays a negative regulatory role in generating this pattern, whereas the pair-rule genes paired and odd-paired are required for activating or maintaining runt expression during these stages.
矮胖基因在果蝇胚胎发生早期形成分节身体模式的遗传层次结构中起重要作用。我们研究了突变胚胎中的mRNA表达，以探讨这些阶段中矮胖基因转录的调控。我们使用灵敏的全胚胎原位杂交技术来确定最早的，因此很可能是直接的调控效应。早期胚胎中矮胖基因的表达有几个不同阶段。我们发现每个阶段都依赖于不同的调控因子组合。表达的第一阶段是合胞体胚盘阶段胚胎中央区域广泛的mRNA积累区域。这种模式是由前部和末端母体系统的末端抑制导致的。即使在这个早期阶段，末端系统的作用也是由两个合子间隙基因无尾和驼背介导的。在细胞化过程中出现了矮胖基因mRNA积累的7条纹模式。这种模式的最初形成依赖于合子间隙基因的位置特异性抑制。对配对规则基因偶数缺失、毛状和腹节基因早期RNA模式的研究表明，它们也以类似的方式受到调控。三个配对规则基因，毛状、偶数缺失和矮胖基因本身，也会影响矮胖基因的7条纹模式。矮胖基因的影响是条纹特异性的；毛状基因的影响更均匀；在偶数缺失突变胚胎中获得的模式显示出条纹特异性和均匀调控效应的组合。第三个不同的表达阶段发生在原肠胚形成开始时，此时矮胖基因在14条纹中表达。腹节基因在形成这种模式中起负调控作用，而配对规则基因配对和奇配对在这些阶段激活或维持矮胖基因表达是必需的。
