Experiments in cultured cells with Ran-binding protein M (RanBPM) suggest that it links cell surface receptors and cell adhesion proteins. In this study, we undertake a genetic study of RanBPM function in the germline stem cell (GSC) niche of Drosophila melanogaster ovaries. We find that two RanBPM isoforms are produced from alternatively spliced transcripts, the longer of which is specifically enriched in the GSC niche, a cluster of somatic cells that physically anchors GSCs and expresses signals that maintain GSC fate. Loss of the long isoform from the niche causes defects in niche organization and cell size and increases the number of GSCs attached to the niche. In genetic mosaics for a null RanBPM allele, we find a strong bias for GSC attachment to mutant cap cells and observe abnormal accumulation of the adherens junction component Armadillo (β-catenin) and the membrane skeletal protein Hu-li tai shao in mutant terminal filament cells. These results implicate RanBPM in the regulation of niche capacity and adhesion.
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机译：在带有Ran结合蛋白M（RanBPM）的培养细胞中进行的实验表明，它可以连接细胞表面受体和细胞粘附蛋白。在这项研究中，我们对果蝇卵巢种系干细胞（GSC）生态位中的RanBPM功能进行了遗传研究。我们发现，从交替剪接的转录本中产生了两种RanBPM异构体，其中更长的一种在GSC生态位中得到了专门的丰富，GSC生态位是一组物理锚定GSC并表达维持GSC命运信号的体细胞。生态位失去了长的同工型，导致生态位组织和细胞大小的缺陷，并增加了附着在生态位上的GSC的数量。在无效RanBPM等位基因的遗传镶嵌中，我们发现GSC附着在突变帽细胞上存在强烈偏见，并观察到突变末端细丝中粘附的连接成分Armadillo（β-catenin）和膜骨架蛋白Hu-li tai shao的异常积累细胞。这些结果暗示RanBPM在小生境能力和附着力的调节。
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