Advances in the studies of the expansion of (CAG)n·(CTG)n trinucleotide repeats and mechanisms underlying its related diseases

The dynamic expansion of (CAG)n·(CTG)n trinucleotide repeat in certain human genes is tightly associated with the occurrences of neuromuscular degenerative diseases, including multiple types of Spinal-cerebellar Ataxias. The repeating numbers of the relating (CAG)n·(CTG)n trinucleotide repeats in normal individuals are lower than a threshold level, while such repeating numbers of the repeats are beyond the threshold in the affiliated genes in patients, leading to the penetrations of different disease symptoms that mainly involve the neuro-and muscular systems. This review summarizes the disease condition and the pathological characteristics of the (CAG)n·(CTG)n repeat expansion-associated human diseases in China while discussing the possible molecular mechanisms underlying the (CAG)n·(CTG)n repeat expansion in vivo.