EcR isoforms in Drosophila:: testing tissue-specific requirements by targeted blockade and rescue
EcR isoforms in Drosophila:: testing tissue-specific requirements by targeted blockade and rescue
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DOI：
10.1242/dev.00205
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发表时间：
2003-01-01
期刊：
影响因子：
4.6
通讯作者：
Cherbas, P
中科院分区：
文献类型：
--
作者：
Cherbas, L;Hu, X;Cherbas, P
果蝇的三种EcR亚型仅在它们的N端不同；因此，它们共享保守的配体结合域转录激活功能（AF2），而仅在非保守的A/B区域有所不同，该区域包含第二种亚型特异性激活功能（AF1）。我们开发了一种显性阴性突变体EcR (EcR- dn)，通过GAL4/UAS系统在果蝇中表达，并利用它在8个组织或组织群中阻断蜕激素信号传导。局部EcR-DN阻止靶细胞中蜕皮激素依赖性的发育，并且通常-由于蜕皮检查点-阻止全局发育。在相同的靶组织中同时表达单个野生型EcR异构体可以抑制EcR- dn表型，并将拯救异构体识别为足以支持目标发育的异构体。每个异构体，甚至是缺少任何AF1的n端截断的EcR，都支持脂肪体、眼盘、唾液腺、分泌eh的神经分泌细胞和dpp表达域的发育，这意味着AF1在这些组织中是必不可少的。相比之下，只有EcR-A能够支持翅瓣边缘的发育，只有EcR-B2能够支持幼虫表皮和发育中的卵室边缘细胞的发育。根据我们的研究结果，对EcR同种异构体滴度广泛的时空变化的最简单解释似乎是站不住脚的。
The three Drosophila EcR isoforms differ only at their N termini; thus, they share the conserved ligand-binding domain transcriptional activation function (AF2) and only differ in the unconserved A/B region, which contains a second, isoform-specific, activation function (AF1). We have developed a dominant-negative mutant EcR (EcR-DN), expressed it in flies with the GAL4/UAS system, and used it to block ecdysone signaling in eight tissues or groups of tissues. Localized EcR-DN arrests ecdysone-dependent development in the target cells and often - because of a molting checkpoint - arrests development globally. Simultaneously expressing individual wild-type EcR isoforms in the same target tissues suppresses the EcR-DN phenotype and identifies the rescuing isoform as sufficient to support the development of the target. Every isoform, and even an N-terminal truncated EcR that lacks any AF1, supports development in the fat body, eye discs, salivary glands, EH-secreting neurosecretory cells and in the dpp expression domain, implying that AF1 is dispensable in these tissues. By contrast, only EcR-A is able to support development in the margins of the wing discs, and only EcR-B2 can do so in the larval epidermis and the border cells of the developing egg chamber. In light of our results, the simplest explanations for the widespread spatial and temporal variations in EcR isoform titers appear untenable.