Genetic variation in human NPY expression affects stress response and emotion

Understanding inter- individual differences in stress response requires the explanation of genetic influences at multiple phenotypic levels, including complex behaviours and the metabolic responses of brain regions to emotional stimuli. Neuropeptide Y ( NPY) is anxiolytic(1,2) and its release is induced by stress(3). NPY is abundantly expressed in regions of the limbic system that are implicated in arousal and in the assignment of emotional valences to stimuli and memories(4-6). Here we show that haplotype- driven NPY expression predicts brain responses to emotional and stress challenges and also inversely correlates with trait anxiety. NPY haplotypes predicted levels of NPY messenger RNA in postmortem brain and lymphoblasts, and levels of plasma NPY. Lower haplotype- driven NPY expression predicted higher emotion- induced activation of the amygdala, as well as diminished resiliency as assessed by pain/ stress- induced activations of endogenous opioid neurotransmission in various brain regions. A single nucleotide polymorphism ( SNP rs16147) located in the promoter region alters NPY expression in vitro and seems to account for more than half of the variation in expression in vivo. These convergent findings are consistent with the function of NPY as an anxiolytic peptide and help to explain inter- individual variation in resiliency to stress, a risk factor for many diseases.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62768/1/nature06858.pd

Amygdala function and 5-HTT gene variants in adolescent anxiety and major depressive disorder

BACKGROUND: Associations between a functional polymorphism in the serotonin transporter gene and amygdala activation have been found in healthy, depressed, and anxious adults. This study explored these gene–brain associations in adolescents by examining predictive effects of serotonin transporter gene variants (S and L(G) allele carriers vs. L(A) allele homozygotes) and their interaction with diagnosis (healthy vs. patients) on amygdala responses to emotional faces. METHODS: Functional magnetic resonance data were collected from 33 healthy adolescents (mean age: 13.71, 55% female) and 31 medication-free adolescents with current anxiety or depressive disorders (or both; mean age: 13.58, 56% female) while viewing fearful, angry, happy, and neutral facial expressions under varying attention states. RESULTS: A significant three-way genotype-by-diagnosis-by-face-emotion interaction characterized right amygdala activity while subjects monitored internal fear levels. This interaction was decomposed to map differential gene–brain associations in healthy and affected adolescents. First, consistent with healthy adult data, healthy adolescents with at least one copy of the S or L(G) allele showed stronger amygdala responses to fearful faces than healthy adolescents without these alleles. Second, patients with two copies of the L(A) allele exhibited greater amygdala responses to fearful faces relative to patients with S or L(G) alleles. Third, although weaker, genotype differences on amygdala responses in patients extended to happy faces. All effects were restricted to the fear-monitoring attention state. CONCLUSIONS: S/L(G) alleles in healthy adolescents, as in healthy adults, predict enhanced amygdala activation to fearful faces. Contrary findings of increased activation in patients with L(A)L(A) relative to the S or L(G) alleles require further exploration

Zhou et al. reply

Replying to: C. H. Cotton, J. Flint & T. G. Campbell Nature 458, 10.1038/nature07927 (2009)The inability of Cotton et al. to detect an effect of a functional haplotype (and locus) of neuropeptide Y (NPY), a stress regulatory neuropeptide, on neuroticism is interesting. Although it is important to measure effects of functional loci on complex behaviours, the strength of our study, and primary basis of its conclusions, was the larger and convergent effects of NPY on intermediate phenotypes, including regional brain responses to emotional stimuli and pain, and brain NPY messenger RNA and plasma NPY levels. Eysenck Neuroticism is a trait that we did not directly investigate. We reported modest association of NPY with two Harm Avoidance subscales from the Tridimensional Personality Questionnaire. Association of NPY with the complex trait of anxiety, especially when measured differently, is not the first place we would look to validate our results