The present invention discloses an agent for treating a polyglutamine aggregation-caused disease or suppressing its onset, which comprises, as an active ingredient, (1) (i) HGF protein, (ii) a partial peptide of HGF protein that is substantially equivalent in activity to HGF protein, or a salt of either of them, or (2) DNA containing (i) DNA encoding HGF protein, (ii) DNA encoding a partial peptide of HGF protein that is substantially equivalent in activity to HGF protein or (iii) DNA which encodes a protein or a peptide that is substantially equivalent in activity to HGF protein and hybridizes with DNA comprising a complementary base sequence of either of the above-mentioned DNAs under a stringent condition.
