Original Article 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 im- portant function in the development of neurodegenerative diseases. The present study aimed to determine the ex- pression 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. Mi- croarray 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.