A potential ethnic difference in the association between 5-HTTLPR polymorphisms and the brain default mode network

The serotonin-transporter-linked polymorphic region (5-HTTLPR) is associated with mood disorders. This association is thought to be due to amygdala hyperresponsiveness to negative emotional stimuli as a result of reduced frontal cortical control. In Caucasians, the short form is associated with this effect, but in Han Chinese we recently found that the long form is involved. Serotonin receptors have rich expression in default mode network (DMN) regions and the recent studies have found an association between the short form of the 5-HTTLPR and DMN functional connectivity (FC) in Caucasians. The present study has investigated whether there may also be an ethnic difference in this influence of 5-HTTLPR on the DMN. We recruited 233 young Han Chinese subjects and calculated the resting-state default-network FC. Our study found that the L carriers had decreased FC in the bilateral medial prefrontal cortex, right parahippocampal gyrus, left middle temporal gyrus, and increased FC in left precuneus (Pcu) compared to SS. The PCC-Pcu FC in L carriers was significantly negatively correlated with the depression scores. Our findings, therefore, suggest that there is also a difference between Caucasian and Han Chinese subjects in the association between the different forms of the 5-HTTLPR and DMN functional connectivity.