JNK Inhibitor Suppresses CASK Deficiency-Induced Cerebellar Granular Cell Death in MICPCH Syndrome Model Mice

Microcephaly with pontine and cerebellar hypoplasia (MICPCH) syndrome is a severe neurodevelopmental disorder caused by a deficiency in the X-linked gene calcium/calmodulin-dependent serine protein kinase (CASK). A better understanding of the role of CASK in the pathophysiology of neurodevelopmental disorders may provide insights into novel therapeutic and diagnostic strategies for MICPCH syndrome and other neurodegenerative diseases. To investigate this, we generated CASK knockout (KO) cerebellar granule (CG) cell culture from CASK floxed (CASKflox/flox) mice by infecting lentiviruses expressing iCre. We performed RNA-sequencing (RNA-seq) on these cells and found that CASK-KO CG cells underwent apoptosis by activating intracellular Jun N-terminal kinase (JNK) signaling and upregulating reactive oxygen species (ROS) -related gene expression. We also performed mouse gait analysis and limb clasping behavior experiments on trans-heterozygous CASK-KO and Hprt-eGFP (CASK+/-HprteGFP/+) mice. The CASK+/-HprteGFP/+ mice exhibited cerebellar ataxic phenotypes as judged by the scores of these experiments compared to the CASK wild-type control (CASK+/-HprteGFP/+) mice. Interestingly, the administration of the JNK inhibitor, JNK-IN-8, in CASK-KO CG cell cultures increased CG cell survival by reducing ROS generation. Moreover, injection of JNK-IN-8 into the cerebellum of CASK+/-HprteGFP/+ mice suppressed CG cell death and alleviated cerebellar ataxic phenotypes in vivo. In conclusion, JNK-IN-8 suppresses the cell death and activation of ROS pathway in CASK-KO CG cells in both in vitro and in vivo models, suggesting its potential as a therapeutic strategy for cerebellar neurodegeneration in MICPCH syndrome.