The present invention is intended to elucidate the cause of severe cardiomyopathy in subline (T) not manifesting the macroscopic cardiac hypertrophy, which has been separated from a hamster (B) with hypertrophic cardiomyopathy and clarify the pathogenic cause of dilated cardiomyopathy, thereby establishing a method of detecting and identifying dilated cardiomyopathy and a method of preventing and treating the same. The present invention relates to a desmin gene having a point mutation at the site corresponding to the 571-position of the base sequence in the cDNA translation region of Syrian hamster; a polypeptide thereof; and an oligonucleotide consisting of 5 to 250 bases including the point mutation site or an oligonucleotide having a sequence complementary thereto. Moreover, the present invention relates to a method of detecting and identifying the point mutation at the site corresponding to the 571-position of the base sequence in the cDNA translation region of Syrian hamster to judge whether or not it is a gene causative of hereditary cardiomyopathy.