Three distinct roles for notch in Drosophila R7 photoreceptor specification.
Three distinct roles for notch in Drosophila R7 photoreceptor specification.
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DOI：
10.1371/journal.pbio.1001132
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发表时间：
2011-08
期刊：
影响因子：
9.8
通讯作者：
Struhl G
中科院分区：
文献类型：
--
作者：
Tomlinson A;Mavromatakis YE;Struhl G
During specification of the R7 photoreceptor in the <I>Drosophila</I> eye, activation of Notch signaling leads to multiple responses within the cell, including antagonistic ones. Receptor tyrosine kinases (RTKs) and Notch (N) proteins are different types of transmembrane receptors that transduce extracellular signals and control cell fate. Here we examine cell fate specification in the Drosophila retina and ask how N acts together with the RTKs Sevenless (Sev) and the EGF receptor (DER) to specify the R7 photoreceptor. The retina is composed of many hundred ommatidia, each of which grows by recruiting surrounding, undifferentiated cells and directing them to particular fates. The R7 photoreceptor derives from a cohort of three cells that are incorporated together following specification of the R2-R5 and R8 photoreceptors. Two cells of the cohort are specified as the R1/6 photoreceptor type by DER activation. These cells then activate N in the third cell (the R7 precursor). By manipulation of N and RTK signaling in diverse combinations we establish three roles for N in specifying the R7 fate. The first role is to impose a block to photoreceptor differentiation; a block that DER activation cannot overcome. The second role, paradoxically, is to negate the first; Notch activation up-regulates Sev expression, enabling the presumptive R7 cell to receive an RTK signal from R8 that can override the block. The third role is to specify the cell as an R7 rather than an R1/6 once RTK signaling has specified the cells as a photoreceptor. We speculate why N acts both to block and to facilitate photoreceptor differentiation, and provide a model for how N and RTK signaling act combinatorially to specify the R1/6 and R7 photoreceptors as well as the surrounding non-neuronal cone cells. Cells are often directed to their developmental fates by the signals they receive from other cells. The Drosophila eye has become a classic paradigm for studying such signaling, and in this system direct neighbor-to-neighbor signaling plays a large role. The R7 photoreceptor is directed to its fate by signals derived from two different neighboring cell types. One sends a signal that activates tyrosine kinase signaling in the R7 precursor, whereas the other activates the Notch signaling pathway. Here we examine Notch signaling and find that it induces three responses in the R7 precursor. We show that one role acts to inhibit the specification of the cell as a photoreceptor, while another role opposes this function, and acts to direct the cell to the photoreceptor fate. The third role specifies the cell as the specialized R7 photoreceptor rather than as the generic photoreceptor type. These results demonstrate that activation of a single signaling pathway can result in multiple cellular responses, even antagonistic ones.
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影响因子：
64.5
作者：
Li, SH;Li, Y;Lai, ZC
通讯作者：
Lai, ZC
DOI：
10.1073/pnas.86.16.6245
发表时间：
1989-08-01
影响因子：
11.1
作者：
BOWTELL, DDL;KIMMEL, BE;RUBIN, GM
通讯作者：
RUBIN, GM
影响因子：
64.5
作者：
BASLER, K;CHRISTEN, B;HAFEN, E
通讯作者：
HAFEN, E
影响因子：
64.5
作者：
Freeman, M
通讯作者：
Freeman, M
影响因子：
10.5
作者：
BAILEY, AM;POSAKONY, JW
通讯作者：
POSAKONY, JW