Cilia biogenesis is a complex, multistep process involving the coordination of multiple cellular trafficking pathways. Despite the importance of ciliogenesis in mediating the cellular response to cues from the microenvironment, we have only a limited understanding of the regulation of cilium assembly. We previously identified Tau tubulin kinase 2 (TTBK2) as a key regulator of ciliogenesis. Here, using CRISPR kinome and biotin identification screening, we identify the CK2 catalytic subunit CSNK2A1 as an important modulator of TTBK2 function in cilia trafficking. Superresolution microscopy reveals that CSNK2A1 is a centrosomal protein concentrated at the mother centriole and associated with the distal appendages. Csnk2a1 mutant cilia are longer than those of control cells, showing instability at the tip associated with ciliary actin cytoskeleton changes. These cilia also abnormally accumulate key cilia assembly and SHH-related proteins. De novo mutations of Csnk2a1 were recently linked to the human genetic disorder Okur-Chung neurodevelopmental syndrome (OCNDS). Consistent with the role of CSNK2A1 in cilium stability, we find that expression of OCNDS-associated Csnk2a1 variants in wild-type cells causes ciliary structural defects. Our findings provide insights into mechanisms involved in ciliary length regulation, trafficking, and stability that in turn shed light on the significance of cilia instability in human disease.

纤毛生物发生是一个复杂的多步骤过程，涉及多个细胞运输途径的协调。尽管纤毛发生在调节细胞对微环境线索的反应中很重要，但我们对纤毛组装的调节了解有限。我们之前将 Tau 微管蛋白激酶 2 (TTBK2) 鉴定为纤毛发生的关键调节因子。在这里，使用 CRISPR 激酶组和生物素鉴定筛选，我们将 CK2 催化亚基 CSNK2A1 鉴定为纤毛运输中 TTBK2 功能的重要调节剂。超分辨率显微镜显示 CSNK2A1 是一种集中在母中心粒并与远端附属物相关的中心体蛋白。CSNK2A1突变体纤毛比对照细胞长，显示出与纤毛肌动蛋白细胞骨架变化相关的尖端不稳定。这些纤毛还异常积累关键纤毛组装和 SHH 相关蛋白。Csnk2a1的从头突变最近与人类遗传病 Okur-Chung 神经发育综合征 (OCNDS) 有关。与 CSNK2A1 在纤毛稳定性中的作用一致，我们发现 OCNDS 相关Csnk2a1变体在野生型细胞中的表达会导致纤毛结构缺陷。我们的研究结果提供了对参与纤毛长度调节、运输和稳定性的机制的见解，这些机制反过来揭示了纤毛不稳定在人类疾病中的重要性。