Non‐Invasive Visualization of Cells Expressing Unmodified Target mRNA Using a Programmable RNA ‐Mediated BiFC Platform

ABSTRACT Real‐time visualization of specific mRNA expression in living cells is essential for understanding diverse biological processes; however, many existing approaches require modifications to target genes. In this study, we developed a programmable RNA‐mediated bimolecular fluorescence complementation (RmBiFC) system by fusing split Venus fluorescent protein fragments with the Pumilio homology domain as a modular RNA‐binding domain. Using murine leukemia virus mRNA as a model target, we systematically optimized the orientation of the probes and demonstrated robust detection of cells expressing target mRNA. This system enables live‐cell imaging of target mRNA‐expressing cells without modifying the target gene. This provides a valuable means of tracking cells expressing wild‐type genes, which is challenging to achieve using conventional reporter‐based approaches. The RmBiFC system represents a versatile and non‐invasive platform with broad potential for identifying specific cell populations based on their transcriptomic profiles at the cellular level.