Two cDNAs of RXR were isolated, for the first time, from the ivory shell, Babylonia japonica, and the transcriptional activities were tested in vitro to compare with other gastropod (Thais clavigera and Nucella lapillus) RXR isoforms. The transcriptional activities of all of these RXR isoforms were significantly induced by mammalian RXR agonist, 9-cis retinoic acid (9cRA). The transcriptional activity of T. clavigera RXR-1 was also examined by using 9cRA and 16 organotin compounds, and significant ligand-dependent transactivations were observed by 9cRA and 5 organotins (tributyltin (TBT), tetrabutyltin (TeBT), tripropyltin (TPrT), tricyclohexyltin (TcHT) and triphenyltin (TPhT)). These 5 organotins also induced significant transcriptional activities in N. lapillus and B. japonica RXR isoforms. These 4 organotins, except for TeBT, have been reported to promote the development of imposex after a month of a single injection each, using female T. clavigera. To investigate the function of gastropod RXR isoforms, the effects of mammalian specific pan-agonist, PA024, and pan-antagonist, HX531, were examined, and significant induction of transcriptional activity by PA024 was demonstrated in these gastropod RXR isoforms. The additions of HX531 significantly suppressed the transcriptional activities of these gastropod RXR isoforms by 9cRA and 5 organotins. Using the mammalian two retinoic acid response elements, the transcriptional activities by 2 agonists, 9cRA and PA024, were different among the RXR isoforms of each gastropod species. With retinoid X response element (RXRE), transcriptional activities of TcRXR-1, BjRXR-1, and NlRXRa were significantly higher than those of TcRXR-2, BjRXR-2, and NlRXRb. Transcriptional activities of TcRXR-2, BjRXR-2, and NlRXRb, however, were significantly higher than those of TcRXR-1, BjRXR-1, and NlRXRa with thyroid hormone response element, TREpal. Thus, induction of imposex in prosobranch gastropods is strongly suggested to be triggered by 9cRA and certain organotins, such as TBT and TPhT through the activation of RXRs. These gastropod RXRs might control the different gene transcription by forming homo- or heterodimer complex with their own isoforms. These findings will contribute to our understanding of the fundamentals of the endocrine system in molluscs, particularly on RXR signaling pathway.

RXR的两种cDNA中分离得到，首次从象牙壳，东风粳稻和转录活性进行了测试在体外与其他腹（以比较蚵岩螺和狗峨螺）RXR同种型。哺乳动物RXR激动剂9-顺式视黄酸（9cRA）显着诱导了所有这些RXR亚型的转录活性。克氏锥虫的转录活性还通过使用9cRA和16种有机锡化合物检查了RXR-1，并且通过9cRA和5种有机锡（三丁基锡（TBT），四丁基锡（TeBT），三丙基锡（TPrT），三环己基锡（TcHT）和三苯锡（ TPhT））。这5种有机素还可以在天牛N.lapillus和粳稻B.japonica RXR同工型中诱导显着的转录活性。据报道，这四种有机锡（除TeBT外）均使用雌性克氏梭菌在单次注射一个月后可促进脓疱症的发展。。为了研究腹足动物RXR同工型的功能，研究了哺乳动物特异性泛激动剂PA024和泛拮抗剂HX531的作用，并证明了PA024在这些腹足类RXR同工型中显着诱导了转录活性。HX531的添加显着抑制了9cRA和5种有机锡对这些腹足类RXR亚型的转录活性。使用哺乳动物的两个视黄酸响应元件，每个腹足动物物种的RXR亚型之间，两种激动剂9cRA和PA024的转录活性是不同的。使用类维生素X反应元件（RXRE），TcRXR-1，BjRXR-1和NlRXRa的转录活性显着高于TcRXR-2，BjRXR-2和NlRXRb的转录活性。但是，TcRXR-2，BjRXR-2和NlRXRb的转录活动 显着高于具有甲状腺激素反应元件TREpal的TcRXR-1，BjRXR-1和NlRXRa。因此，强烈建议由9cRA和某些有机锡（如TBT和TPhT）通过激活RXR来触发前分支腹足动物中的侵染。这些腹足类动物的RXR可能通过与它们自己的同工型形成同型或异型二聚体复合物来控制不同的基因转录。这些发现将有助于我们理解软体动物内分泌系统的基本原理，尤其是在RXR信号通路上。这些腹足类动物的RXR可能通过与它们自己的同工型形成同型或异型二聚体复合物来控制不同的基因转录。这些发现将有助于我们理解软体动物内分泌系统的基本原理，尤其是在RXR信号通路上。这些腹足类动物的RXR可能通过与它们自己的同工型形成同型或异型二聚体复合物来控制不同的基因转录。这些发现将有助于我们理解软体动物内分泌系统的基本原理，尤其是在RXR信号通路上。