Heberlein U, Hariharan I K, Rubin G M
Howard Hughes Medical Institute, University of California, Berkeley 94720.
Dev Biol. 1993 Nov;160(1):51-63. doi: 10.1006/dbio.1993.1285.
The photoreceptor cells R8, R2, and R5 are the first cells to initiate neuronal differentiation in the Drosophila eye imaginal disc. We have shown previously that these three cells require Star gene function for proper ommatidial assembly. Due to the embryonic lethality associated with mutations in Star, we have analyzed the consequence of loss of Star function in mosaic eye imaginal discs. Presumptive R8, R2, and R5 cells that lack Star function fail to differentiate neuronally and die a few hours later. Enhancer trap insertions reveal that Star expression in the eye disc is restricted to the developing R8, R2, and R5 cells. Taken together, these data suggest that Star is required for the reception of a signal and/or the execution of a developmental program that leads to the neuronal differentiation of R8, R2, and R5. Star is also required for the formation of wing veins and is expressed in developing veins, suggesting that at least partially overlapping pathways may operate during photoreceptor cell differentiation and wing vein formation. The role of Star in cell-cell signaling is supported by the observation of genetic interactions between Star and mutations that reduce signaling through both sevenless and the Drosophila EGF-receptor homologue, including Ras1 and Son of sevenless.
感光细胞R8、R2和R5是果蝇眼成虫盘（imaginal disc）中最早启动神经元分化的细胞。我们之前已经表明，这三种细胞需要星状基因（Star gene）的功能来进行正常的小眼（ommatidium）组装。由于与星状基因突变相关的胚胎致死性，我们分析了星状基因功能缺失在嵌合眼成虫盘中的后果。缺乏星状基因功能的推定R8、R2和R5细胞无法进行神经元分化，并在数小时后死亡。增强子陷阱插入显示，眼盘中星状基因的表达仅限于发育中的R8、R2和R5细胞。综合这些数据表明，星状基因对于接收信号和/或执行导致R8、R2和R5神经元分化的发育程序是必需的。星状基因对于翅脉的形成也是必需的，并且在发育中的翅脉中表达，这表明在感光细胞分化和翅脉形成过程中可能存在至少部分重叠的信号通路。星状基因与降低通过七无（sevenless）和果蝇表皮生长因子受体同源物（包括Ras1和七无之子）的信号传导的突变之间存在遗传相互作用，这一观察结果支持了星状基因在细胞间信号传导中的作用。
