Earl James B, Britt Steven G
Department of Cell and Developmental Biology, University of Colorado at Denver and Health Sciences Center, School of Medicine, RC1 South, Aurora, 80045, USA.
Gene Expr Patterns. 2006 Oct;6(7):687-94. doi: 10.1016/j.modgep.2006.01.003. Epub 2006 Feb 21.
The R7 and R8 photoreceptor cells of the Drosophila retina are thought to mediate color discrimination and polarized light detection. This is based on the patterned expression of different visual pigments, rhodopsins, in different photoreceptor cells. In this report, we examined the developmental timing of retinal patterning. There is genetic evidence that over the majority of the eye, patterned expression of opsin genes is regulated by a signal from one subtype of R7 cells to adjacent R8 cells. We examined the onset of expression of the rhodopsin genes to determine the latest time point by which photoreceptor subtype commitment must have occurred. We found that the onset of rhodopsin expression in all photoreceptors of the compound eye occurs during a narrow window from 79% to 84% of pupal development (approximately 8 h), pupal stages P12-P14. Rhodopsin 1 has the earliest onset, followed by Rhodopsins 3, 4, and 5 at approximately the same time, and finally Rhodopsin 6. This sequence mimics the model for how R7 and R8 photoreceptor cells are specified, and defines the timing of photoreceptor cell fate decisions with respect to other events in eye development.
果蝇视网膜的R7和R8光感受器细胞被认为介导颜色辨别和偏振光检测。这是基于不同视觉色素（视紫红质）在不同光感受器细胞中的模式化表达。在本报告中，我们研究了视网膜模式形成的发育时间。有遗传学证据表明，在眼睛的大部分区域，视蛋白基因的模式化表达受来自一种R7细胞亚型向相邻R8细胞发出的信号调控。我们研究了视紫红质基因表达的起始时间，以确定光感受器亚型确定必定发生的最晚时间点。我们发现，复眼中所有光感受器的视紫红质表达起始于蛹发育的79%至84%这一狭窄时间段内（约8小时），即蛹期P12 - P14。视紫红质1的起始时间最早，随后视紫红质3、4和5大约同时出现，最后是视紫红质6。这个顺序模拟了R7和R8光感受器细胞如何被确定的模型，并确定了光感受器细胞命运决定相对于眼睛发育中其他事件的时间。
