RNA-binding proteins with intrinsically disordered regions (IDRs) such as Rbm14 can phase separate in vitro. To what extent the phase separation contributes to their physiological functions is however unclear. Here we show that zebrafish Rbm14 regulates embryonic dorsoventral patterning through phase separation. Zebrafish rbm14 morphants displayed dorsalized phenotypes associated with attenuated BMP signaling. Consistently, depletion of mammalian Rbm14 downregulated BMP regulators and effectors Nanog, Smad4/5, and Id1/2, whereas overexpression of the BMP-related proteins in the morphants significantly restored the developmental defects. Importantly, the IDR of zebrafish Rbm14 demixed into liquid droplets in vitro despite poor sequence conservation with its mammalian counterpart. While its phase separation mutants or IDR failed to rescue the morphants, its chimeric proteins containing an IDR from divergent phase separation proteins were effective. Rbm14 complexed with proteins involved in RNA metabolism and phase separated into cellular ribonucleoprotein compartments. Consistently, RNA deep sequencing analysis on the morphant embryos revealed increased alternative splicing events as well as large-scale transcriptomic downregulations. Our results suggest that Rbm14 functions in ribonucleoprotein compartments through phase separation to modulate multiple aspects of RNA metabolism. Furthermore, IDRs conserve in phase separation ability but not primary sequence and can be functionally interchangeable.

具有内在无序区域（IDR）的RNA结合蛋白（如Rbm14）可以在体外进行相分离。然而，相分离在多大程度上有助于其生理功能尚不清楚。在这里，我们显示斑马鱼Rbm14通过相分离调节胚胎背腹模式。斑马鱼rbm14morph变体显示了与减弱的BMP信号传导相关的背性表型。一致地，哺乳动物Rbm14的耗竭下调了BMP调节剂和效应物Nanog，Smad4 / 5和Id1 / 2，而在吗啡酮中BMP相关蛋白的过表达则显着恢复了发育缺陷。重要的是，尽管与哺乳动物对应的序列保守性较差，但斑马鱼Rbm14的IDR在体外却分散成液滴。虽然其相分离突变体或IDR无法挽救该吗啡，但其包含来自不同相分离蛋白的IDR的嵌合蛋白却是有效的。Rbm14与参与RNA代谢的蛋白质复合并相分离成细胞核糖核蛋白区室。始终如一 对吗啡胚的RNA深度测序分析表明，增加的剪接事件以及大规模的转录组下调。我们的结果表明，Rbm14通过相分离在核糖核蛋白区室中起作用，以调节RNA代谢的多个方面。此外，IDR保留相分离能力，但不保留一级序列，并且可以在功能上互换。