Role of MicroRNA Genes miR-1000 and miR-375 in Forming Olfactory Conditional Memory in Drosophila melanogaster

Background: Learning and memory are basic aspects of neurogenetics as most of the neurological disorders start with dementia or memory loss. Several genes associated with memory formation have been discovered. MicroRNA genes, miR-1000 and miR-375, were reported to be associated with neural integration and glucose homeostasis in some insects and vertebrates. However, the neuronal function of these genes is yet to be established in D. melanogaster. Objective: The possible role of miR-1000 and miR-375 in learning and memory formation in this fly has been explored in the present study. Methods: Both types of appetitive and aversive olfactory conditional learning were tested in the miR- 1000 and miR-375 knockout (KO) strains and compared with the wild one. Five days old third instar larvae were trained by allowing them to be associated with an odor with reward (fructose) or punishment (salt). Then, the larvae were tested to calculate their preferences to the odor they were trained with. Learning Index (LI) values and larval locomotion speed were calculated for all strains. Results: Knockout strain of miR-1000 showed significant deficiency in both appetitive and aversive memory formation whereas miR-375 KO strain showed a significantly lower response only in appetitive one. Conclusion: The results of the present study indicate an important role of miR-1000 and miR-375 genes in forming short-term memory in D. melanogaster.