Developmental Biology, Tokyo University of Agriculture and Technology, 3-5-8, Fuchu-shi, Tokyo 183-8509, Japan.
Dev Biol. 2013 Feb 1;374(1):127-41. doi: 10.1016/j.ydbio.2012.11.002. Epub 2012 Nov 10.
The adult optic lobe of Drosophila develops from the primordium during metamorphosis from mid-3rd larval stage to adult. Many cells die during development of the optic lobe with a peak of the number of dying cells at 24 h after puparium formation (h APF). Dying cells were observed in spatio-temporal specific clusters. Here, we analyzed the function of a component of the insect steroid hormone receptor, EcR, in this cell death. We examined expression patterns of two EcR isoforms, EcR-A and EcR-B1, in the optic lobe. Expression of each isoform altered during development in isoform-specific manner. EcR-B1 was not expressed in optic lobe neurons from 0 to 6h APF, but was expressed between 9 and 48 h APF and then disappeared by 60 h APF. In each cortex, its expression was stronger in older glia-ensheathed neurons than in younger ones. EcR-B1 was also expressed in some types of glia. EcR-A was expressed in optic lobe neurons and many types of glia from 0 to 60 h APF in a different pattern from EcR-B1. Then, we genetically analyzed EcR function in the optic lobe cell death. At 0 h APF, the optic lobe cell death was independent of any EcR isoforms. In contrast, EcR-B1 was required for most optic lobe cell death after 24 h APF. It was suggested that cell death cell-autonomously required EcR-B1 expressed after puparium formation. βFTZ-F1 was also involved in cell death in many dying-cell clusters, but not in some of them at 24 h APF. Altogether, the optic lobe cell death occurred in ecdysone-independent manner at prepupal stage and ecdysone-dependent manner after 24 h APF. The acquisition of ecdysone-dependence was not directly correlated with the initiation or increase of EcR-B1 expression.
果蝇成虫复眼的发育始于 3 龄幼虫中期到成虫变态期间的原基。在复眼发育过程中，许多细胞死亡，在蛹形成后 24 小时（hAPF）达到细胞死亡的高峰期。死亡细胞以时空特异性簇的形式出现。在这里，我们分析了昆虫类固醇激素受体成分 EcR 在这种细胞死亡中的功能。我们检查了两种 EcR 同工型，EcR-A 和 EcR-B1，在视神经叶中的表达模式。每种同工型的表达在发育过程中以同工型特异性的方式改变。EcR-B1 在 0 到 6hAPF 期间不在视神经叶神经元中表达，但在 9 到 48hAPF 之间表达，然后在 60hAPF 时消失。在每个皮质中，其表达在较老的神经胶质鞘细胞中的表达强于较年轻的神经胶质鞘细胞。EcR-B1 也在一些类型的神经胶质细胞中表达。EcR-A 在 0 到 60hAPF 期间以与 EcR-B1 不同的模式在视神经叶神经元和许多类型的神经胶质细胞中表达。然后，我们从遗传上分析了 EcR 在视神经叶细胞死亡中的功能。在 0hAPF 时，视神经叶细胞死亡与任何 EcR 同工型无关。相反，EcR-B1 在 24hAPF 后大多数视神经叶细胞死亡中是必需的。这表明细胞死亡在细胞自主中需要在蛹形成后表达的 EcR-B1。βFTZ-F1 也参与了许多死亡细胞簇中的细胞死亡，但在 24hAPF 时的一些细胞簇中没有参与。总的来说，在 prepupal 阶段，视神经叶细胞死亡以蜕皮激素独立的方式发生，在 24hAPF 后以蜕皮激素依赖的方式发生。获得蜕皮激素依赖性与 EcR-B1 表达的开始或增加没有直接关系。
