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Session 2, Abstract 10

UNDERSTANDING THE ROLE OF MICRORNAS IN BMP-7-INDUCED DENDRITIC GROWTH IN PNS PRIMARY RAT SYMPATHETIC NEURONS

Kristina Pravoverov*1, Slesha Thapa1 and Pamela Lein2 (Vidya Chandrasekaran1 ), 1Department of Biology, Saint Mary’s College of California, Moraga, CA 94575, 2Department of Molecular Biosciences, University of California at Davis, Davis, CA 95616

Dendritic growth is a hallmark of synaptic plasticity. Therefore, it is important to elucidate the regulators of dendritic growth. Previous studies have shown that the family of proteins called bone morphogenetic proteins (BMPs) promote dendritic growth in central and peripheral neurons by mediating transcriptional gene expression. In non-neuronal cells, BMPs modulate gene expression post-transcriptionally by regulating the processing of microRNAs (miRNAs). Therefore, the goal of this study was to determine whether post-transcriptional gene regulation by miRNAs occurs in BMP-induced dendritic growth. To determine whether miRNA expression was altered during the initiation of BMP-7-induced dendritic growth, cultured rat embryonic sympathetic neurons were grown in the absence or presence of BMP-7 (50 ng/mL) for 6 and 24 hours. Total RNA isolated from these cultures was subjected to microarray analysis, followed by quantitative PCR of 5 miRNAs that showed significant changes: miR-21-5p, miR-23b-3p, miR-26a-5p, miR-335, and miR-664-1-5p. Furthermore, functional significance of each of these miRNAs was examined by transfecting embryonic sympathetic neurons with mimics or inhibitors, in the presence or absence of BMP-7 (50 ng/mL) for 5 days. Dendritic growth was them analyzed by immunocytochemistry. Our data showed that miR-21-5p, miR-23b-3p, and miR-26a-5p were upregulated, while miR-335 and miR-664-1-5p were downregulated in BMP-7-induced dendritic growth. The data also indicates that of the 5 miRNA, miR-23b-3p may be an inhibitor and miR-664-1-5p may be an activator of dendritic growth, which suggests that miRNA- mediated post-transcriptional gene regulation is important for BMP-7-induced dendritic growth in sympathetic neurons.