The neurogenic genes egghead and brainiac define a novel signaling pathway essential for epithelial morphogenesis during Drosophila oogenesis.
The neurogenic genes egghead and brainiac define a novel signaling pathway essential for epithelial morphogenesis during Drosophila oogenesis.
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发表时间：
1996-12
期刊：
影响因子：
4.6
通讯作者：
S. Goode;M. Melnick;T. Chou;N. Perrimon
中科院分区：
文献类型：
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作者：
S. Goode;M. Melnick;T. Chou;N. Perrimon
Notch（N）和其他神经源性基因参与了两个基本过程，细胞命运的侧向特化和上皮发育。先前的研究已经表明，神经原性基因brainiac（brn）是上皮发育所特别需要的（Goode，S.，摩根，M.，Liang，Y-P.和Mahowald，A. P.（1996年）。Dev. 178，35-50）。在这份报告中，我们表明egghead（egh），一个与brn表型相同的基因，编码一种新的，推定的分泌或跨膜蛋白。我们描述了在卵泡上皮细胞从出生到卵子发生后期向卵母细胞迁移的形态发生中，egh和brn生殖细胞功能的作用。通过比较胚系egh和brn在卵子发生过程中对N的作用，我们获得了Notch参与卵泡上皮细胞维持的直接证据，以及brn和egh在卵子发生过程中上皮发育的特异性。所有三个基因观察到的最显著的表型是顶部-基底极性的丧失和卵母细胞周围多层滤泡上皮细胞的积累。这种腺瘤样表型的时空发生与卵子发生第4阶段卵母细胞中egh转录本的差异积累有关。与N相反，我们发现brn和egh是必不可少的组织，但不规范，柄和极细胞。brn，egh和N的表达模式和功能要求使我们提出这些基因通过调节生殖细胞-卵泡细胞粘附来介导卵泡形态发生。这一提议提供了以下解释：（1）egh和brn参与N-介导的上皮发育，但不参与侧向特化;（2）为什么brn和egh胚胎神经原性表型不如N表型严重;（3）egh和brn如何影响egfr介导的过程。卵母细胞中egh的差异表达与维持卵母细胞周围滤泡上皮对brn，egh和N的差异需求之间的相关性表明，Egghead是差异卵母细胞-滤泡细胞粘附系统的关键组成部分。
Notch (N) and other neurogenic genes have been implicated in two fundamental processes, lateral specification of cell fates, and epithelial development. Previous studies have suggested that the neurogenic gene brainiac (brn) is specifically required for epithelial development (Goode, S., Morgan, M., Liang, Y-P. and Mahowald, A. P. (1996). Dev. Biol. 178, 35-50). In this report we show that egghead (egh), a gene with phenotypes identical to brn, encodes for a novel, putative secreted or transmembrane protein. We describe the role of egh and brn germline function in the morphogenesis of the follicular epithelium from the time it is born through the time that it migrates towards the oocyte late in oogenesis. By comparing the function of germline egh and brn to N during oogenesis, we have obtained direct evidence for the involvement of Notch in maintenance of the follicle cell epithelium, and the specificity of brn and egh in epithelial development during oogenesis. The most striking phenotype observed for all three genes is a loss of apical-basal polarity and accumulation of follicular epithelial cells in multiple layers around the oocyte. The spatiotemporal onset of this adenoma-like phenotype correlates with the differential accumulation of egh transcripts in the oocyte at stage 4 of oogenesis. In contrast to N, we find that brn and egh are essential for the organization, but not specification, of stalk and polar cells. The expression patterns and functional requirements of brn, egh, and N lead us to propose that these genes mediate follicular morphogenesis by regulating germline-follicle cell adhesion. This proposal offers explanations for (1) the involvement of egh and brn in N-mediated epithelial development, but not lateral specification, (2) why brn and egh embryonic neurogenic phenotypes are not as severe as N phenotypes, and (3) how egh and brn influence Egfr-mediated processes. The correlation between the differential expression of egh in the oocyte and the differential requirement for brn, egh, and N in maintaining the follicular epithelium around the oocyte, suggests that Egghead is a critical component of a differential oocyte-follicle cell adhesive system.