Talk abstracts

Talk on Friday 04:15-04:30pm submitted by Sarah Deffit

A-to-I editing within the C. elegans nervous system

Sarah N. Deffit (Medical Sciences Program, Indiana University, Bloomington, IN 47405), Pranathi Vadlamani (Medical Sciences Program, Indiana University, Bloomington, IN 47405), Brian A. Lee, Emily C. Wheeler, Gene W. Yeo (Bioinformatics and Systems Biology Program, University of California, San Diego, La Jolla, CA 92093), Heather A. Hundley (Medical Sciences Program, Indiana University, Bloomington, IN 47405)

The conversion of adenosine (A) to inosine (I) by ADAR enzymes is one of the most prevalent forms of RNA editing, occurring in all metazoa. Inosine is a biological mimic of guanosine, and thus, A-to-I editing alters coding potential, splicing patterns and small RNA mediated gene silencing. In mammals, A-to-I editing is most abundant in the central nervous system, where a number of ion channels and receptors are edited in coding regions, thus changing amino acid sequence and protein function. These edits are important for proper neuronal function as aberrant editing of ion channels and receptors occur in a number of neuropathological diseases, including brain tumors, ALS and Alzheimers disease. Loss of ADARs in model organisms also affects neuronal function, however the substrates that are responsible for these phenotypes are unknown. To attempt to identify these substrates, we performed the first unbiased assessment of editing in the C. elegans nervous system. FACS was used to purify neural cells from which the neural transcriptome was isolated and the neural editome identified. Consistent with previous editing site identification in whole worms, most neural editing events were found in noncoding regions such as 5’ and 3’ UTRs; however, a few coding editing events were identified. Furthermore, we identified editing dependent and independent effects on gene expression. Editing of clec-41, a gene involved in the immune response and chemotaxis, altered its expression level, with neural cells deficient in editing having 75% reduced expression of clec-41. Interestingly, this was specific for neural cells as whole worm lysates deficient in editing express similar levels of clec-41 as their wildtype counterparts. Loss of ADARs is associated with reduced chemotaxis in C. elegans and our studies identified several edited targets that regulate this biological function including clec-41. Future studies assessing the role of editing in regulating these proteins may shed light onto the mechanisms resulting in chemotaxis defects in worms deficient in editing. In this study we developed a novel methodology for cell/tissue-type specific identification of editing targets, opening the door for future studies assessing tissue-specific factors that regulate A-to-I RNA editing.

Keywords: A-to-I RNA editing, ADAR, Neuron