Nat. Methods, published online 25 December 2011, doi:10.1038/nmeth.1827

Credit: JAMES JEPSON

Adenosine deaminase that acts on RNA (ADAR) regulates neuronal functions by catalyzing the conversion of adenosine to inosine in target codons of double-stranded RNAs. Now, Jepson et al. develop a method to monitor Drosophila ADAR (dADAR) activity in vivo at the level of single neurons. The authors generated a GFP reporter (GFPedit), which consists of the GFP coding sequence fused to a previously identified ADAR target sequence. They detected GFP fluorescence—and therefore dADAR activity—in distinct regions of the mushroom body and the antennal lobes of the Drosophila nervous system, depending on developmental stage. Next, the authors identified the regions in which dADAR activity was physiologically repressed by taking advantage of an autoediting mechanism by which dADAR inhibits its own activity. They introduced mutations at the endogenous dADAR locus to express a noneditable and constitutively active variant and compared the regions of activity in these flies to those in the wild type. They detected an increase of GFPedit fluorescence only in specific cell types of the mushroom bodies of adult flies, indicating a well-defined spatial regulation of dADAR activity. Using the same reporter system, the authors observed variations in dADAR activity between individuals of the same population, potentially accounting for differences in behavior. This approach may be used to follow alterations in RNA editing in vivo and relate them to neuronal functions and neurological diseases.