Tepaß Ulrich, Knust Elisabeth
Institut für Entwicklungsphysiologie, Universität zu Köln, Gyrhofstraße 17, D-5000, Köln 41, Federal Republic of Germany.
Rouxs Arch Dev Biol. 1990 Apr;199(4):189-206. doi: 10.1007/BF01682078.
The genecrumbs (crb) ofDrosophila melanogaster provides an essential function for the embryonic development of ectodermally derived epithelia. Complete loss of function alleles of thecrb gene are recessive embryonic lethals and lead to a disorganization of the primordia of these epithelia, followed by cell death in some tissues. Incrb mutant embryos, different organs are affected to a different extent. Some tissues die almost completely (as the epidermis, the atrium and the pharynx) while others partially survive and conserve their basic epithelial structure (as the tracheal system, the oesophagus, the proventriculus, the salivary glands, the hindgut and the Malpighian tubules). Degeneration is first visible at stage 11 and continues successively throughout development. There is evidence that the loss of epithelial cell polarity may be the cause for the degeneration of these tissues, suggesting that thecrb gene product is involved in stabilizing the apico-basal polarity of epithelial cells. As previously shown, thecrb protein is specifically expressed on the apical side of embryonic epithelia in a reticular pattern outlining the borders of the cells. Here we demonstrate that thecrb protein shows the same subcellular localization in epithelial cells of imaginal discs and in follicle cells, indicating a similar function ofcrb during the development of embryonic, imaginal and follicle epithelia. Clonal analysis experiments indicate that the genecrb is not cell-autonomous in its expression, suggesting that the gene product may act as a diffusible factor and may serve as a signal in a cell-cell communication process. This signal is thought to be required for the formation and/or maintenance of the cell and tissue structure of the respective epithelia.
黑腹果蝇的基因crumbs（crb）对外胚层来源上皮的胚胎发育具有重要作用。crb基因功能完全丧失的等位基因是隐性胚胎致死基因，会导致这些上皮原基的紊乱，随后一些组织发生细胞死亡。在crb突变胚胎中，不同器官受到的影响程度不同。一些组织几乎完全死亡（如表皮、心房和咽部），而其他组织部分存活并保留其基本上皮结构（如气管系统、食道、前胃、唾液腺、后肠和马氏管）。退化首先在第11阶段可见，并在整个发育过程中持续相继发生。有证据表明上皮细胞极性的丧失可能是这些组织退化的原因，这表明crb基因产物参与稳定上皮细胞的顶-基极性。如先前所示，crb蛋白在胚胎上皮的顶端以勾勒细胞边界的网状模式特异性表达。在这里，我们证明crb蛋白在成虫盘的上皮细胞和卵泡细胞中显示相同的亚细胞定位，表明crb在胚胎、成虫和卵泡上皮发育过程中具有相似的功能。克隆分析实验表明，crb基因在表达上不是细胞自主的，这表明该基因产物可能作为一种可扩散因子，并可能在细胞间通讯过程中作为一种信号。该信号被认为是相应上皮细胞和组织结构形成和/或维持所必需的。
