Aims Differentiated Vascular Smooth Muscle Cells (VSMCs) express a unique network of mRNA isoforms via smooth muscle specific alternative splicing (SM-AS) in functionally critical genes, including those comprising the contractile machinery. We previously described RNA Binding Protein Multiple Splicing (RBPMS) as a potent driver of differentiated SM-AS in the rat PAC1 VSMC cell line. What is unknown is how RBPMS affects VSMC phenotype and behaviour. Here, we aimed to dissect the role of RBPMS in SM-AS in human cells and determine the impact on VSMC phenotypic properties. Methods and Results We used human embryonic stem cell-derived VSMCs (hESC-VSMCs) as our platform. hESC-VSMCs are inherently immature and we found that they display only partially differentiated SM-AS patterns while RBPMS protein levels are low. We found that RBPMS overexpression induces SM-AS patterns in hESC-VSMCs akin to the contractile tissue VSMC splicing patterns. We present in silico and experimental findings that support RBPMS’ splicing activity as mediated through direct binding and via functional cooperativity with splicing factor RBFOX2 on a significant subset of targets. We also demonstrate that RBPMS can alter the motility and the proliferative properties of hESC-VSMCs to mimic a more differentiated state. Conclusions Overall, this study emphasizes a critical role for RBPMS in establishing the contractile phenotype splicing program of human VSMCs.

中文翻译：

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RBPMS促进人胚胎干细胞衍生的血管平滑肌细胞的收缩表型剪接


目的 分化的血管平滑肌细胞 (VSMC) 通过功能关键基因（包括构成收缩机制的基因）中的平滑肌特异性选择性剪接 (SM-AS) 表达独特的 mRNA 亚型网络。我们之前将 RNA 结合蛋白多重剪接 (RBPMS) 描述为大鼠 PAC1 VSMC 细胞系中分化 SM-AS 的有效驱动因素。目前尚不清楚 RBPMS 如何影响 VSMC 表型和行为。在这里，我们的目的是剖析 RBPMS 在人类细胞 SM-AS 中的作用，并确定对 VSMC 表型特性的影响。方法和结果我们使用人胚胎干细胞衍生的 VSMC（hESC-VSMC）作为我们的平台。 hESC-VSMC 本质上是不成熟的，我们发现它们仅表现出部分分化的 SM-AS 模式，而 RBPMS 蛋白水平较低。我们发现 RBPMS 过表达会在 hESC-VSMC 中诱导 SM-AS 模式，类似于收缩组织 VSMC 剪接模式。我们提出的计算机模拟和实验结果支持 RBPMS 的剪接活性是通过直接结合以及通过与剪接因子 RBFOX2 在重要靶标子集上的功能协同介导的。我们还证明 RBPMS 可以改变 hESC-VSMC 的运动性和增殖特性，以模拟更加分化的状态。结论 总的来说，本研究强调了 RBPMS 在建立人类 VSMC 收缩表型剪接程序中的关键作用。