Hoshizaki D K
Department of Biochemistry, University of Illinois at Chicago 60612.
Dev Biol. 1994 May;163(1):133-40. doi: 10.1006/dbio.1994.1129.
The Drosophila gap gene Krüppel (Kr) codes for a Zn2+ finger transcription factor important in embryo patterning, segment identity, and specification of various cell types. Based on Northern blot analysis, Kr function has been thought to be restricted to embryogenesis. I report here that Kr is also expressed during larval development, primarily in the fat body. Using both a P-element enhancer-trap line and a portion of the Kr promoter fused to lacZ, I find the activation of Kr in the fat body does not begin until the early-third-instar stage. Earlier in larval development, Kr is detected in the nerve cells associated with the gut. Kr's role as a transcription factor during early embryogenesis is well established. After gastrulation Kr protein is detected in a variety of cell types and is probably involved in cell specification. Kr is not detected in fat cells during embryogenesis nor during the first- and second-instar stages. The delayed expression of Kr in the fat cells occurs at a time in which the larva is undergoing a reprogramming in preparation for metamorphosis. It is possible that Kr serves as a transcriptional regulator in the fat body in this last larval instar. During this last larval stage, several fat-body-specific genes are transcriptionally activated in response to increasing levels of ecdysone. The possible role of Kr in the expression of these ecdysone-regulated genes is discussed.
果蝇缺口基因Krüppel（Kr）编码一种锌指转录因子，它在胚胎模式形成、体节特征以及各种细胞类型的特化过程中发挥着重要作用。基于Northern印迹分析，人们一直认为Kr的功能仅限于胚胎发生阶段。我在此报告，Kr在幼虫发育过程中也有表达，主要在脂肪体中。通过使用P因子增强子捕获系以及将Kr启动子的一部分与lacZ融合，我发现脂肪体中Kr的激活直到三龄早期才开始。在幼虫发育的早期阶段，在与肠道相关的神经细胞中可检测到Kr。Kr在早期胚胎发生过程中作为转录因子的作用已得到充分证实。原肠胚形成后，在多种细胞类型中可检测到Kr蛋白，它可能参与细胞特化过程。在胚胎发生期间以及一龄和二龄阶段，脂肪细胞中均未检测到Kr。Kr在脂肪细胞中的延迟表达发生在幼虫为变态发育进行重新编程的时期。在最后一龄幼虫阶段，Kr有可能作为脂肪体中的转录调节因子发挥作用。在这最后一龄幼虫阶段，随着蜕皮激素水平的升高，几个脂肪体特异性基因被转录激活。本文讨论了Kr在这些蜕皮激素调节基因表达中的可能作用。
