Personality Traits and the R668Q Polymorphism Located in the MMP-9 Gene

Matrix metalloproteinases (MMPs) are enzymes involved in degradation of proteins in the extracellular matrix and have been shown to contribute to neuroinflammation by several mechanisms such as blood-brain barrier breakdown. Among the MMPs, MMP-9 (gelatinase B) has been suggested to be of relevance also for synaptic and behavioural plasticity. In order to explore the role of MMP-9 for mental functions a polymorphism in MMP-9 was analysed with respect to personality traits. The two studied populations consisted of women and men, respectively, both recruited from the population registry and assessed by means of the Karolinska Scales of Personality. The non-synonymous single nucleotide polymorphism (R668Q, rs17577) studied is located in the coding region of MMP-9 and is believed to affect the activity of the enzyme. The present study found that an amino acid change from arginine (R) to glutamine (Q) was associated with higher scores of the personality trait inhibition of aggression in the female population whilst this substitution was associated with higher scores of verbal aggression and irritability in men. These findings give support for an influence of MMP-9 on mental functions.