Figure 2. F2rl1 is expressed by a small subset of sensory neurons.

DRG neurons (A–E) and hind paw skin (F) from F2rl1^floxPirt^+/+ and F2rl1^floxPirt^Cre mice were dissected and prepared for RNAscope in situ hybridization. White arrows indicate cells positive for F2rl1 mRNA. (A) Representative original magnification ×20 images of Calca (green), P2rx3 (red), and F2rl1 (white) mRNA signal in the DRG of F2rl1^floxPirt^+/+ and F2rl1^floxPirt^Cre mice. These images show that the F2rl1^floxPirt^Cre mice do not express F2rl1 mRNA in sensory neurons while the F2rl1^floxPirt^+/+ mice do. Scale bar: 50 μm. (B) Original magnification ×40 overlay image showing RNAscope signal at the cellular level. Scale bar: 10 μm. (C) Percentage of Calca⁺ and P2rx3⁺ neurons that coexpress F2rl1. Around 2% of Calca⁺ neurons express F2rl1 mRNA while around 6% of P2rx3⁺ neurons express F2rl1 mRNA. (D) Histogram illustrating the diameter of neurons expressing F2rl1. F2rl1⁺ neurons are small- to medium-diameter neurons (16–46 μm). (E) Pie chart illustration of the percentage of F2rl1⁺ cells that colocalize with Calca⁺ and P2rx3⁺ neurons. About 3%–4% of DRG neurons are F2rl1⁺, of which almost all are P2rx3⁺ neurons. (F) Representative hind paw skin images of F2rl1 (white) and DAPI (blue) signal from a F2rl1^floxPirt^+/+ mouse and a F2rl1^floxPirt^Cre mouse. The last image shows hind paw skin from a F2rl1^floxPirt^+/+ mouse stained with a negative probe control (bacterial dapB). These images show the specificity of conditional knockout of F2rl1 expression is restricted to only sensory neurons and not skin cells. Scale bar: 20 μm.