SPARC: Development of a TRPA1 reporter mouse model

Abstract

TRPA1 is a non‐selective cation channel activated by electrophiles including environmental irritants, and pungent stimuli. It is expressed in a subset of nociceptive sensory neurons and thus plays a key role in defensive reflexes. The contribution of TRPA1 to certain physiological effects is complicated by its expression in non neuronal cell types such as fibroblasts and epithelial cells, so it is not clear to what extent TRPA1 effects are restricted to sensory afferents. We have created a mouse model that co‐expresses the red fluorescent protein tdTomato in TRPA1 expressing cells. A TRPA1‐Flp knock‐in strain was generated by incorporating a 2A‐FlpO after the last endogenous TRPA1 exon. The TRPA1‐Flp was crossed with a tdTomato reporter strain carrying a frt‐flanked STOP codon (RC::FLTG) to produce cells that produce tdTomato in TRPA1 expressing cells. From these animals, we collected sensory vagal and thoracic dorsal root ganglia to visualize tdTomato‐expressing cells in combination with immunohistochemistry. We also collected brain, brainstem, spinal cord and esophagus to visualize tdTomato‐expression to map their central and peripheral projections. tdTomato positive cells were observed primarily in the nodose ganglion and the majority of these coincided with TRPV1 expression. There was also a population of tdTomato expressing cells in the dorsal root ganglia. We confirmed, using calcium imaging, that these tdTomato positive cells are activated by the TRPA1 agonist AITC. We saw strong tdTomato expression in the nucleus of solitary tract (NTS) and in the lamina II region of the dorsal horn of the spinal cord but no expression was evident in the brain. Finally, we were able to observe tdTomato expression in peripheral fibers extending into different regions of the esophagus. In summary, we have created a transgenic knock‐in FlpO mouse model which selectively labels vagal sensory neurons with AITC‐sensitivity. This strain can be used to identify peripheral and central terminals of TRPA1 expressing nerves.Support or Funding InformationThis study is funded by National Institutes of Health Common Fund SPARC OT2 (2016–2019): “Functional mapping of peripheral and central circuits for airway protection and breathing”