Huntington's disease (HD) is a genetic neurodegenerative disease caused by 
abnormal CAG expansion. MicroRNAs (miRNAs) are short RNA molecules regulating 
gene expression, and are implicated in a variety of diseases including HD. 
However, the profiles and regulation of miRNAs in HD are not fully understood. 
Here, we analyzed the miRNA expression and miRNA regulators in two transgenic 
models of HD, YAC128 and R6/2 mice, and in a 3-nitropropionic acid (3NP)-induced 
striatal degeneration rat model. After characterizing the phenotypes by 
behavioral tests and histological analyses, we profiled striatal miRNAs using a 
miRNA microarray and we measured the key molecules involved in miRNA biogenesis 
and function. YAC128 mice showed upregulation-dominant miRNA expressions at 5 
months and downregulation-dominant expressions at 12 months. Concomitantly, the 
expressions of Drosha-DGCR8, Exportin-5, and Dcp1 were increased at 5months, and 
the expression of Dicer was decreased at 12 months. In 10-week-old R6/2 mice, 
downregulation was dominant in the miRNA expressions and the level of Drosha 
decreased concomitantly. Nine miRNAs (miR-22, miR-29c, miR-128, miR-132, 
miR-138, miR-218, miR-222, miR-344, and miR-674*) were commonly down-regulated 
in both the 12-month-old YAC128 and 10-week-old R6/2 mice. Meanwhile, 3NP rats 
showed dynamic changes in the miRNA profiles during disease development and a 
few miRNAs with altered expression. Our results show that transgenic HD mice 
have abnormal miRNA biogenesis. This information should aid in future studies on 
therapeutic application of miRNAs in HD.