A fluorescent protein C-terminal fusion knock-in is functional with TRPA1 but not TRPC5

Transgenic mice with fluorescent protein (FP) reporters take full advantage of new in vivo imaging technologies. Therefore, we generated a TRPC5- and a TRPA1-reporter mouse based on FP C-terminal fusion, providing us with better alternatives for studying the physiology, interaction and coeffectors of these two TRP channels at the cellular and tissue level.

We generated transgenic constructs of the murine TRPC5- and TRPA1-gene with a 3*GGGGS linker and C-terminal fusion to mCherry and mTagBFP, respectively. We microinjected zygotes to generate reporter mice. Reporter mice were examined for visible fluorescence in trigeminal ganglia with two-photon microscopy, immunohistochemistry and calcium imaging.

Both TRPC5-mCherry and TRPA1-mTagBFP knock-in mouse models were successful at the DNA and RNA level. However, at the protein level, TRPC5 resulted in no mCherry fluorescence. In contrast, sensory neurons derived from the TRPA1-reporter mice exhibited visible mTag-BFP fluorescence, although TRPA1 had apparently lost its ion channel function.

Creating transgenic mice with a TRP channel tagged at the C-terminus with a FP requires detailed investigation of the structural and functional consequences in a given cellular context and fine-tuning the design of specific constructs for a given TRP channel subtype. Different degrees of functional impairment of TRPA1 and TRPC5 constructs suggest a specific importance of the distal C-terminus for the regulation of these two channels in trigeminal neurons.