A new triple fluorescence reporter system for discrimination of Apobec1 and Apobec3 C-to-U RNA editing activities and editing-dependent protein expression

The human body is composed of many different cell types which communicate with each other. In particular, the brain consists of billions of neurons and non-neuronal cells which are interconnected and require tight and precise regulation of cellular processes. RNA editing is a cellular process that diversifies gene function by enzymatic deamination of cytidine or adenine. This can result in changes of protein structure and function. Altered RNA editing is becoming increasingly associated with all kind of disease, but most approaches use advanced sequencing technologies to analyze bulk material. However, it is also becoming progressively evident that changes in RNA editing have to be analyzed and considered in a cell type specific way. We present here a triple fluorescence reporter system that discriminates between Apobec1- and Apobec3-dependent C-to-U RNA editing at the single cell level. In particular, the Apobec3 reporter enables C-to-U RNA editing inducible protein expression through generation of a RNA splice donor site. We used the new system here to analyze Apobec1- and Apobec3-dependent RNA editing in primary neuron culture. The results reveal a large heterogeneity of C-to-U RNA editing in neurons and glia cells, and they show that GABAergic neurons are not able to perform Apobec1-dependent RNA editing, but Apobec3-dependent editing. Altogether, the new system can be the foundation of therapeutic application systems that counteract changes in Apobec3-dependent RNA editing in disease while simultaneously monitoring Apobec1-dependent RNA editing at the single cell level.