Actin remodeling is frequently regulated by antagonistic activities driving protrusion and contraction downstream of Rac and Rho small GTPases, respectively. WAVE regulatory complex (WRC), which primarily operates downstream of Rac, plays pivotal roles in neuronal morphogenesis. Recently, two independent studies described de novo mutations in the CYFIP2 subunit of WRC, which caused intellectual disability (ID) in humans. Although mutations had been proposed to effect WRC activation, no experimental evidence for this was provided. Here, we made use of CRISPR/Cas9-engineered B16-F1 cell lines that were reconstituted with ID-causing CYFIP variants in different experimental contexts. Almost all CYFIP2-derived mutations (7 out of 8) promoted WRC activation, but to variable extent and with at least two independent mechanisms. The majority of mutations occurs in a conserved WAVE-binding region, required for WRC transinhibition. One mutation is positioned closely adjacent to the Rac-binding A site and appears to ease Rac-mediated WRC activation. As opposed to these gain-of-function mutations, a truncating mutant represented a loss-of-function variant and failed to interact with WRC components. Collectively, our data show that explored CYFIP2 mutations frequently, but not always, coincide with WRC activation and suggest that normal brain development requires a delicate and precisely tuned balance of neuronal WRC activity.

中文翻译：

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CYFIP2中导致神经发育障碍突变的分子解剖。

肌动蛋白重塑经常受拮抗作用调节，这些拮抗作用分别驱动Rac和Rho小GTP酶下游的突出和收缩。主要在Rac下游运行的WAVE调节复合物（WRC）在神经元形态发生中起关键作用。最近，两项独立的研究描述了WRC的CYFIP2亚基中的从头突变，该突变导致人类的智力障碍（ID）。尽管提出了影响WRC激活的突变，但没有提供实验证据。在这里，我们利用了由CRISPR / Cas9设计的B16-F1细胞系，这些细胞系在不同的实验环境中都与引起ID的CYFIP变异体一起重建。几乎所有CYFIP2衍生的突变（8个中的7个）都促进WRC激活，但程度不同且具有至少两个独立的机制。大多数突变发生在WRC转抑制所需的保守WAVE结合区域中。一个突变紧邻Rac结合的A位点，似乎可以缓解Rac介导的WRC激活。与这些功能获得的突变相反，截短的突变体代表功能丧失的变体，并且无法与WRC组件相互作用。总的来说，我们的数据表明，探索CYFIP2突变的频率很高，但并非总是如此，这与WRC激活同时发生，并且表明正常的大脑发育需要神经元WRC活动的微妙和精确调整的平衡。截短的突变体代表功能丧失的变异体，无法与WRC组件相互作用。总的来说，我们的数据表明，探索CYFIP2突变的频率很高，但并非总是如此，这与WRC激活同时发生，并且表明正常的大脑发育需要神经元WRC活动的微妙和精确调整的平衡。截短的突变体代表功能丧失的变异体，无法与WRC组件相互作用。总的来说，我们的数据表明，探索CYFIP2突变的频率很高，但并非总是如此，这与WRC激活同时发生，并且表明正常的大脑发育需要神经元WRC活动的微妙和精确调整的平衡。