Association of the neurotrophic tyrosine kinase receptor 3 (NTRK3) gene and childhood-onset mood disorders.

Genome scans have revealed significant evidence for linkage of depression to chromosome 15q25.3-q26.2. The gene for neurotrophic tyrosine kinase receptor 3 (NTRK3), the receptor for neurotrophin-3 (trkC) and a key gene in neurotrophin signaling, is located within this region and, given evidence for synaptic plasticity as a mechanism in mood disorders, was considered a prime candidate. The authors investigated NTRK3 as a susceptibility gene for childhood-onset mood disorders. The study sample consisted of 603 families with 723 affected children and adolescents diagnosed with a mood disorder with onset of the first episode by age 15. The authors genotyped 18 polymorphic markers across the NTRK3 gene in this sample and tested for association. Results identified significant evidence for association for five of the markers using the transmission disequilibrium test. Four of the five markers were located in a region of strong linkage disequilibrium and were highly correlated. Haplotype results provided significant evidence for association to haplotypes composed of markers located in two haplotype blocks. The results for NTRK3 as well as the authors' previous finding for association to brain-derived neurotrophic factor in this sample support synaptic plasticity as a mechanism contributing to mood disorders that begin during childhood and adolescence and specifically implicate the NTRK3 gene as a contributing factor in the 15q-linked region.