PROBLEM TO BE SOLVED: To provide a therapeutic composition which is effective to a central nervous system myelinogenesis failure caused by the hyperergasia of PLP1 protein.SOLUTION: The therapeutic composition for a central nervous system myelinogenesis failure caused by the hyperergasia of PLP1 protein contains active type Cdk5. Further, the therapeutic composition for a central nervous system myelinogenesis failure caused by the hyperergasia of PLP1 protein contains Cdk5 activated protein. As the Cdk5 activated protein, e.g., is p35.