An association of GRIK3 Ser310Ala functional polymorphism with personality traits

Personality traits are under genetic control, and have been associated with genes implicated in dopaminergic, serotoninergic and noradrenergic neurotransmission systems, often with conflicting results. There have been few studies assessing the involvement of the glutamatergic pathway instead upon personality traits. In the gene family of glutamate receptors, there is a T/G polymorphism at codon 928 in the ionotropic glutamate receptor kainite 3 gene (GRIK3) that causes a serine to alanine change at position 310 in the extracellular N terminus of the protein. This polymorphism has been recently associated with susceptibility to some major psychoses such as major depression (MD). In order to test whether the functional Ser310Ala polymorphism is involved in the development of specific personality traits, and thus to MD, we conducted the first association study on 195 selected healthy Italian individuals. The personality traits were measured by the self-rating Temperament and Character Inventory (TCI) scale. The results indicated that the Ala allele in homozygosity is associated with higher scores in harm avoidance and respective subscales: anticipatory worry HA1 and shyness HA3, as well as lower scores in exploratory excitability NS1, responsibility SD1, resourcefulness SD3, helpfulness C3 and compassion C4 subscales, in addition to lower self-directedness and cooperativeness scores. This pattern of TCI scores is akin to that observed in depressed patients. Because of the small size of the sample, this work represents a pilot study, and reports the first pieces of evidence for a specific involvement of the GRIK3 gene in these traits, suggesting a role of the glutamatergic system in the genetic background of human personality traits.