Tansey T, Mikus M D, Dumoulin M, Storti R V
EMBO J. 1987 May;6(5):1375-85. doi: 10.1002/j.1460-2075.1987.tb02378.x.
In the Drosophila flightless mutant Ifm(3)3, a transposable element inserted into the alternatively spliced fourth exon of the tropomyosin I (TmI) gene prevents proper expression of Ifm-TmI, the tropomyosin isoform found in indirect flight muscle. We have rescued the flightless phenotype of Ifm(3)3 flies using P-element-mediated transformation with a segment of the Drosophila genome containing the wild-type TmI gene plus 2.5 kb of 5' flanking and 2 kb of 3' flanking DNA. The inserted TmI gene is expressed with the proper developmental and tissue specificity, although its level of expression varies among the five transformed lines examined. These conclusions are based on analyses of flight, myofibrillar morphology, and TmI RNA and protein levels. A minimum of two copies of the inserted TmI gene per cell is necessary to restore flight to most of the flies in each line. We also show that the Ifm-TmI isoform is expressed in the leg muscle of wild-type flies and is decreased in Ifm(3)3 leg muscle. Homozygous Ifm(3)3 mutants do not jump. The ability to jump can be restored with a single copy of the wild-type TmI gene per cell.
在果蝇飞行缺陷突变体Ifm(3)3中，一个转座元件插入到原肌球蛋白I（TmI）基因可变剪接的第四外显子中，阻止了间接飞行肌中发现的原肌球蛋白异构体Ifm-TmI的正常表达。我们使用P因子介导的转化方法，用一段包含野生型TmI基因以及2.5 kb的5'侧翼和2 kb的3'侧翼DNA的果蝇基因组片段，挽救了Ifm(3)3果蝇的飞行缺陷表型。尽管在所检测的5个转化系中，插入的TmI基因的表达水平有所不同，但它以适当的发育和组织特异性表达。这些结论基于对飞行、肌原纤维形态以及TmI RNA和蛋白质水平的分析。每个细胞中至少有两个插入的TmI基因拷贝，才能使每个系中的大多数果蝇恢复飞行能力。我们还表明，Ifm-TmI异构体在野生型果蝇的腿部肌肉中表达，而在Ifm(3)3腿部肌肉中表达减少。纯合的Ifm(3)3突变体不会跳跃。每个细胞中有一个野生型TmI基因拷贝就能恢复跳跃能力。
