Abstract: Polynucleotides comprising the following base sequences: (a) a base sequence encoding a fusion protein of a nuclease-deficient CRISPR effector protein and a transcriptional repressor, and (b) a base sequence encoding a guide RNA targeting a continuous region of 18 to 24 nucleotides in length in a region set forth in SEQ ID NO: 127, SEQ ID NO: 46, SEQ ID NO: 128, SEQ ID NO: 129, SEQ ID NO: 130, SEQ ID NO: 131, SEQ ID NO: 132, SEQ ID NO: 88, SEQ ID NO: 91, SEQ ID NO: 133, SEQ ID NO: 137, SEQ ID NO: 117, or SEQ ID NO: 119 in an expression regulatory region of a human DMPK gene, are expected to be useful for treating muscular dystrophy.