Department of Molecular and Cellular Physiology, Shinshu University School of Medicine, Matsumoto 390-8621, Japan.
College of Life Science and Oceanography, Shenzhen University, Shenzhen 518071, China.
Cells. 2023 Apr 18;12(8):1177. doi: 10.3390/cells12081177.
Microcephaly with pontine and cerebellar hypoplasia (MICPCH) syndrome is a neurodevelopmental disorder caused by the deficiency of the X-chromosomal gene CASK. However, the molecular mechanisms by which CASK deficiency causes cerebellar hypoplasia in this syndrome remain elusive. In this study, we used CASK knockout (KO) mice as models for MICPCH syndrome and investigated the effect of CASK mutants. Female CASK heterozygote KO mice replicate the progressive cerebellar hypoplasia observed in MICPCH syndrome. CASK KO cultured cerebellar granule (CG) cells show progressive cell death that can be rescued by co-infection with lentivirus expressing wild-type CASK. Rescue experiments with CASK deletion mutants identify that the CaMK, PDZ, and SH3, but not L27 and guanylate kinase domains of CASK are required for the survival of CG cells. We identify missense mutations in the CaMK domain of CASK derived from human patients that fail to rescue the cell death of cultured CASK KO CG cells. Machine learning-based structural analysis using AlphaFold 2.2 predicts that these mutations disrupt the structure of the binding interface with Liprin-α2. These results suggest that the interaction with Liprin-α2 via the CaMK domain of CASK may be involved in the pathophysiology of cerebellar hypoplasia in MICPCH syndrome.
小头伴桥脑小脑发育不良（MICPCH）综合征是一种神经发育障碍，由 X 染色体基因 CASK 缺乏引起。然而，CASK 缺乏导致该综合征小脑发育不良的分子机制仍不清楚。在这项研究中，我们使用 CASK 敲除（KO）小鼠作为 MICPCH 综合征的模型，研究了 CASK 突变体的影响。雌性 CASK 杂合子 KO 小鼠复制了在 MICPCH 综合征中观察到的进行性小脑发育不良。CASK KO 培养的小脑颗粒（CG）细胞显示进行性细胞死亡，可通过共感染表达野生型 CASK 的慢病毒来挽救。用 CASK 缺失突变体进行的挽救实验表明，CASK 的 CaMK、PDZ 和 SH3 结构域，但不是 L27 和鸟苷酸激酶结构域，对于 CG 细胞的存活是必需的。我们从人类患者中鉴定出 CASK 的 CaMK 结构域中的错义突变，这些突变不能挽救培养的 CASK KO CG 细胞的细胞死亡。使用 AlphaFold 2.2 进行的基于机器学习的结构分析预测，这些突变会破坏与 Liprin-α2 的结合界面的结构。这些结果表明，通过 CASK 的 CaMK 结构域与 Liprin-α2 的相互作用可能参与了 MICPCH 综合征中小脑发育不良的病理生理学。
