Mice with Mutations in Trpm1, a Gene within the locus of 15q13.3 Microdeletion Syndrome, Display Pronounced Hyperactivity and Decreased Anxiety-Like Behavior.

Abstract

15q13.3 microdeletion syndrome is a genetic disorder caused by a deletion of a region containing seven genes on chromosome 15, MTMR10, FAN1, TRPM1, MIR211, KLF13, OTUD7A, and CHRNA7, and characterized by a wide spectrum of psychiatric disorders. The contribution of each gene in this syndrome has been studied using mutant mouse models, but the phenotypes of these mice do not account for human phenotypes and the results are still controversial. The behavior of Trpm1−/− mice with relation to 15q13.3 microdeletion syndrome has not been investigated due to the visual impairment in these mice, which may confound the results of behavior tests that involve vision. We have now applied a comprehensive behavioral test battery to examine the relationship of TRPM1 and 15q13.3 microdeletion syndrome by using Trpm1 null mutant mice. Our data indicate abnormal behavior of Trpm1−/− mice which may explain some phenotypes of 15q13.3 microdeletion syndrome, including reduction of anxiety behavior, abnormality of social interaction, attenuation in fear memory, and hyperactivity, which is the most prominent phenotype of Trpm1 mutant mice. While the ON visual transduction pathway is impared in Trpm1−/− mice, we did not detect compensatory high sensitivities for other sensory modalities. Although Trpm1−/− mice share the same pathway for visual impairment with mGluR6−/− mice, hyperlocomotion activity has not been reported in mGluR6−/− mice. These data suggest that the phenotype of Trpm1−/− mice extends beyond that expected from visual impairment alone. This is the first evidence to associate TRPM1 with impairment of cognitive function similar to that found in the phenotypes of 15q13.3 microdeletion syndrome.