Quantitative analysis of TRP channel genes in mouse organs.

The transient receptor potential (TRP) channel superfamily is a set of channel genes that mediate numerous physiological functions such as sensing irritants or detecting temperature changes. Despite their functions, expressional information on TRP channels in various organs is largely elusive. Therefore, we conducted a systematic quantitative comparison of each mRNA expression level of 22 mouse TRP channels in various organs. As a result, we found that average levels of TRP channel transcripts were very low reaching ∼3% of the GAPDH transcript level. Among 22 TRP channels, TRPC1 and TRPM7 were most abundant in the majority of organs. In contrast, TRPV3, TRPV5, TRPV6, TRPC7, TRPM1, and TRPM5 elicited very low message profiles throughout the major organs. Consistent with their functions as molecular sensors for irritants and temperature changes, TRPV1, TRPM8 and TRPA1 showed exclusive expression in sensory ganglia. TRPC3 and TRPM3 were abundant in the sensory ganglia and brain. High levels of transcripts of TRPV2, TRPC6, TRPM4, and TRPM6 were observed in the lung. In addition, channel transcript levels were very low except TRPM7 in the liver. In summary, the expression profile of TRP channels in major tissues provides insight to their physiological functions and therefore application to new drug development.