Ecdysone receptor expression in the CNS correlates with stage-specific responses to ecdysteroids during Drosophila and Manduca development.
Ecdysone receptor expression in the CNS correlates with stage-specific responses to ecdysteroids during Drosophila and Manduca development.
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发表时间：
1994
期刊：
影响因子：
4.6
通讯作者：
J. Truman;W. S. Talbot;S. Fahrbach;D. Hogness
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文献类型：
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作者：
J. Truman;W. S. Talbot;S. Fahrbach;D. Hogness
在昆虫中，外皮类固醇的作用是将中枢神经系统从幼虫转变为成虫。这种反应的一个关键基因是蜕皮激素受体（EcR），它在果蝇中被证明可以编码3种蛋白质同种异构体。其中两种异构体，EcR-A和EcR-B1，在中枢神经系统中显著表达，我们已经使用异构体特异性抗体来检查它们在胚胎后生命中的波动。在变态开始时，EcR的表达是非常多样化的，但特定的EcR表达模式与不同的类固醇反应模式相关。大多数幼虫神经元在变态开始时显示出高水平的EcR-B1，这是它们对蜕皮类固醇反应失去幼虫特征的时候。早些时候，在幼虫蜕皮期间，相同的细胞没有可检测到的受体，并且对循环蜕皮类固醇没有反应；后来，在蛹-成虫转化过程中，它们转换到EcR-A表达，并以成熟为成虫形式作出反应。在后期，一部分幼虫神经元超表达EcR-A，这些细胞在成体出现后注定会死亡。成像神经元干细胞在其主要增殖期的最后幼虫期表现出显著的EcR-B1表达。相比之下，大多数想象神经元在变态开始时仅表达EcR-A。蘑菇体的想象神经元在变态开始时表达B1亚型在想象神经元中是不寻常的，但在这个时候它们也表现出退行性变化，因为它们失去了幼虫轴突。当细胞间相互作用对于在中枢神经系统的这一区域内建立连接很重要时，视叶的想象神经元显示出EcR-B1的延迟表达。总的来说，细胞中两种受体同种异构体的出现与不同类型的类固醇反应相关：当细胞经历成熟反应时，EcR-A占主导地位，而在增殖活性或退行性反应时，EcR-B1占主导地位。变态开始时EcR表达的异质性可能反映了神经元的不同起源和需求，尽管它们都暴露在一个共同的激素信号下。
In insects, the ecdysteroids act to transform the CNS from its larval to its adult form. A key gene in this response is the ecdysone receptor (EcR), which has been shown in Drosophila to code for 3 protein isoforms. Two of these isoforms, EcR-A and EcR-B1, are prominently expressed in the CNS and we have used isoform-specific antibodies to examine their fluctuations through postembryonic life. EcR expression at the onset of metamorphosis is extremely diverse but specific patterns of EcR expression correlate with distinct patterns of steroid response. Most larval neurons show high levels of EcR-B1 at the start of metamorphosis, a time when they lose larval features in response to ecdysteroids. Earlier, during the larval molts, the same cells have no detectable receptors and show no response to circulating ecdysteroids; later, during the pupal-adult transformation, they switch to EcR-A expression and respond by maturing to their adult form. During the latter period, a subset of the larval neurons hyperexpress EcR-A and these cells are fated to die after the emergence of the adult. The stem cells for the imaginal neurons show prominent EcR-B1 expression during the last larval stage correlated with their main proliferative period. Most imaginal neurons, by contrast, express only EcR-A when they subsequently initiate maturation at the start of metamorphosis. The imaginal neurons of the mushroom bodies are unusual amongst imaginal neurons in expressing the B1 isoform at the start of metamorphosis but they also show regressive changes at this time as they lose their larval axons. Imaginal neurons of the optic lobe show a delayed expression of EcR-B1 through the period when cell-cell interactions are important for establishing connections within this region of the CNS. Overall, the appearance of the two receptor isoforms in cells correlates with different types of steroid responses: EcR-A predominates when cells are undergoing maturational responses whereas EcR-B1 predominates during proliferative activity or regressive responses. The heterogeneity of EcR expression at the start of metamorphosis presumably reflects the diverse origins and requirements of the neurons that nevertheless are all exposed to a common hormonal signal.