The R8-photoreceptor equivalence group in Drosophila:: fate choice precedes regulated Delta transcription and is independent of Notch gene dose
The R8-photoreceptor equivalence group in Drosophila:: fate choice precedes regulated Delta transcription and is independent of Notch gene dose
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DOI：
10.1016/s0925-4773(98)00054-9
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发表时间：
1998-06-01
影响因子：
2.6
通讯作者：
Yu, SY
中科院分区：
文献类型：
--
作者：
Baker, NE;Yu, SY
有研究表明，Notch信号对细胞命运的横向指定依赖于Notch (N)和Delta （Dl）转录的反馈，以在蛋白质水平上建立受体及其配体的互反分布。在果蝇神经发生中，预测的互反蛋白分布尚未观察到。无论是横向规范模型还是N和/或Dl蛋白分布的描述都必须是不完整的。我们重新检查了发育中的眼睛中的Rs光感受器规格，以解决本例侧向规格的问题。在整个细胞和细胞表面评估N和Dl蛋白水平，这些蛋白主要存在于细胞间细胞连接处。在野生型中，蛋白质水平与Notch信号不一致。然而，在突变基因型中，DI转录和蛋白水平确实与N信号的改变有关。我们的研究结果表明，这种差异与体内横向规范的速度有关。N信号抑制ato表达所需的时间最多为90分钟，但突变基因型中Dl蛋白分布的变化更为缓慢。N的表达很少受N信号的调控，但由N-tsl等位基因编码的蛋白质在细胞表面的外观对温度敏感。Dl蛋白模式的某些方面似乎是由于内吞作用。我们得出结论，氮信号对DI转录的反馈确实发生，但太慢，无法解释R8规范的模式。在半限制性温度下，对Notch复制或N-tsl等位基因的小叶镶嵌研究发现，开始时N活性较低的细胞不一定倾向于被选择为R8分化。我们的数据表明，其他信号可能负责N. R8细胞命运分配的模式，并讨论了与其他神经发生区域的潜在相关性。(C) 1998爱思唯尔科学爱尔兰有限公司版权所有。
It has been suggested that lateral specification of cell fate by Notch signaling depends on feedback on Notch (N) and Delta (Dl) transcription to establish reciprocal distributions of the receptor and its ligand at the protein level. In Drosophila neurogenesis the predicted reciprocal protein distributions have not been observed. Either this model of lateral specification or the description of N and/or Dl protein distributions must be incomplete. We have reexamined Rs photoreceptor specification in the developing eye to resolve this question for this example of lateral specification. N and Dl protein levels were assessed in the cell as a whole and at the cell surface, where these proteins were mostly found at the intercellular cell junctions. Protein levels did not correspond to Notch signaling in wild type. However, DI transcription and protein levels did correlate with altered N signaling in mutant genotypes. Our findings suggest the difference relates to the speed of lateral specification in vivo. The time required for N signaling to inhibit ato expression was at most 90 min, but changes in the Dl protein distribution in mutant genotypes arose more slowly. N expression was little regulated by N signaling, but protein encoded by the N-tsl allele was temperature-sensitive for appearance at the cell surface. Some aspects of the pattern of Dl protein appeared to be due to endocytosis. We conclude that feedback of N signaling on DI transcription does occur but is too slow to account for the pattern of R8 specification. Studies of ommatidia mosaic for a Notch duplication, or for the N-tsl allele at semi-restrictive temperatures, found that cells beginning with less N activity were not necessarily predisposed to be selected for R8 differentiation. Our data argue that other signals may be responsible for the pattern of R8 cell fate allocation by N. Potential relevance to other neurogenic regions is discussed. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.