Catechol-O-methyltransferase (COMT) is an ubiquitously expressed enzyme that maintains basic biologic functions by inactivating catechol substrates. In humans, polymorphic variance at the COMT locus has been associated with modulation of pain sensitivity (Andersen & Skorpen, 2009) and risk for developing psychiatric disorders (Harrison & Tunbridge, 2008). A functional haplotype associated with increased pain sensitivity was shown to result in decreased COMT activity by altering mRNA secondary structure-dependent protein translation (Nackley et al., 2006). However, the exact mechanisms whereby COMT modulates pain sensitivity and behavior remain unclear and can be further studied in animal models. We have pursued a genome-wide approach to examining gene expression in multiple brain regions in inbred strains of mice and have discovered that Comt1 is differentially expressed. This expression difference was validated with qPCR. A B2-B4 Short Interspersed Element (SINE) was inserted in the 3'UTR of Comt1 in 14 strains that also shared a common haplotype. Experiments using mammalian expression vectors of full-length cDNA clones with and without the SINE element demonstrate that strains with the SINE haplotype (+SINE) have greater Comt1 enzymatic activity. +SINE mice also exhibit behavioral differences in anxiety assays and decreased pain sensitivity. These results suggest that a haplotype, defined by a 3'UTR B2-B4 SINE element, regulates Comt1 expression and mouse behavior.

Comt, Comt1