Previously, it was reported that loss of JNK1 or MKK4 caused motor phenotypes: Jnk1−/− mice showed impairment of fine motor coordination and balance accompanied by abnormal dendritic architecture in the motor cortex47; MKK4flox/floxNestin-Cre caused ataxia and awkward gait at P15-P16 due to misalignment of Purkinje cells in the cerebellum24. Here, MAP2K4 is linked to cerebellar ataxia.