Development of the cerebellum requires precise regulation of granule neuron progenitor (GNP) proliferation. Although it is known that primary cilia are necessary to support GNP proliferation, the exact molecular mechanism governing primary cilia dynamics within GNPs remains elusive. Here, we establish the pivotal roles for the centrosomal kinase TTBK2 (Tau tubulin kinase-2) and the E3 ubiquitin ligase HUWE1 in GNP proliferation. We show that TTBK2 is highly expressed in proliferating GNPs under Sonic Hedgehog (SHH) signaling, coinciding with active GNP proliferation and the presence of primary cilia. TTBK2 stabilizes primary cilia by inhibiting their disassembly, thereby promoting GNP proliferation in response to SHH. Mechanistically, we identify HUWE1 as a novel centrosomal E3 ligase that facilitates primary cilia disassembly by targeting TTBK2 degradation. Disassembly of primary cilia serves as a trigger for GNP differentiation, allowing their migration from the external granule layer (EGL) of the cerebellum to the internal granule layer (IGL) for subsequent maturation. Moreover, we have established a link between TTBK2 and SHH-type medulloblastoma (SHH-MB), a tumor characterized by uncontrolled GNP proliferation. TTBK2 depletion inhibits SHH-MB proliferation, indicating that TTBK2 may be a potential therapeutic target for this cancer type. In summary, our findings reveal the mechanism governing cerebellar development and highlight a potential anti-cancer strategy for SHH-MB.

小脑的发育需要精确调节颗粒神经元祖细胞 （GNP） 增殖。尽管已知初级纤毛是支持 GNP 增殖所必需的，但控制 GNP 内初级纤毛动力学的确切分子机制仍然难以捉摸。在这里，我们确定了中心体激酶 TTBK2 （Tau 微管蛋白激酶-2） 和 E3 泛素连接酶 HUWE1 在 GNP 增殖中的关键作用。我们表明，TTBK2 在 Sonic Hedgehog （SHH） 信号传导下的增殖 GNP 中高度表达，与活跃的 GNP 增殖和初级纤毛的存在相吻合。TTBK2 通过抑制初级纤毛的分解来稳定初级纤毛，从而促进 GNP 增殖以响应 SHH。从机制上讲，我们将 HUWE1 鉴定为一种新型中心体 E3 连接酶，它通过靶向 TTBK2 降解来促进初级纤毛分解。初级纤毛的分解是 GNP 分化的触发因素，允许它们从小脑的外部颗粒层 （EGL） 迁移到内部颗粒层 （IGL） 以进行后续成熟。此外，我们已经确定了 TTBK2 与 SHH 型髓母细胞瘤 （SHH-MB） 之间的联系，SHH 型髓母细胞瘤 （SHH-MB） 是一种以 GNP 增殖不受控制为特征的肿瘤。TTBK2 耗竭抑制 SHH-MB 增殖，表明 TTBK2 可能是该癌症类型的潜在治疗靶点。总之，我们的研究结果揭示了控制小脑发育的机制，并强调了 SHH-MB 的潜在抗癌策略。