Genome editing system for repeat expansion mutation

The present specification pertains to an artificial manipulation or modification in an expression regulatory gene of an over-amplified repeat sequence. More specifically, the present specification pertains to an expression regulatory system of an over-amplified repeat sequence, comprising an artificially manipulated gene to decrease the expression of an over-amplified repeat sequence. The artificially manipulated gene includes at least one selected from the group consisting of a SPT4 gene, a SPT5 gene, a SUPT4H gene, and a SUPT5H gene. The artificially manipulated gene includes an artificial mutation in the genomic sequence of the gene. The artificially manipulated gene includes a gene which is functionally damaged or has an expression level reduced.