miRNA-9 expression is upregulated in the spinal cord of G93A-SOD1 transgenic mice.

The pathogenesis of amyotrophic lateral sclerosis (ALS) remains unclear. Accumulating evidence indicates that various miRNAs expressed in a spatially and temporally controlled manner in the nervous system have an important function in the development of neurodegenerative diseases. The present study aimed to determine the expression and cellular distribution of miRNA-9 in the spinal cord of G93A-SOD1 mutant mice at different time points (post-natal 95, 108 and 122 d). miRNA expression was evaluated by microarray analysis; differentially expressed miRNAs were validated by RT-qPCR. The cellular distribution of miRNA-9 was analyzed by in-situ hybridization. Microarray results indicated for the first time that various miRNAs were differentially expressed between the G93A-SOD1 mutant mice and the littermate control mice. miRNA-9 expression was upregulated at 95, 108, and 122 d as validated by microarray analysis, RT-qPCR, and ISH. ISH results also showed that the miRNA-9-positive cells mainly expressed in the cytoplasm were located in the dorsal horn and the ventral horn of the spinal cord. The majority of miRNA-9-positive cells were located in the ventral horn of the gray matter, the locus of neurodegeneration. These results indicated that the differential expression of miRNA-9 may have an important function in the pathogenesis of G93A-SOD1 transgenic mice.