Chromosome 15q13.3 microduplications are associated with treatment refractory major depressive disorder

Major depressive disorder (MDD) affects approximately 15 million Americans. Approximately 2 million of these are classified as being refractory to treatment (TR-MDD). Because of the lack of available therapies for TR-MDD, and the high risk of suicide, there is interest in identifying new treatment modalities and diagnostic methods. Understanding of the impact of genomic copy number variation in the etiology of a variety of neuropsychiatric phenotypes is increasing. Low copy repeat elements at 15q13.3 facilitate non-allelic homologous recombination, resulting in recurrent copy number variants (CNVs). Numerous reports have described association between microdeletions in this region and a variety of neuropsychiatric phenotypes, with CHRNA7 implicated as a candidate gene. However, the pathogenicity of 15q13.3 duplications is less clear. As part of an ongoing study, in which we have identified a number of metabolomic anomalies in spinal fluid from TR-MDD patients, we also evaluated genomic copy number variation in patients (n = 125) and controls (n = 26) via array-based copy number genomic hybridization (CGH); the case frequency was compared with frequencies reported in a prior study as well as a larger population-sized cohort. We identified five TR-MDD patients with microduplications involving CHRNA7. CHRNA7 duplications are the most common CNVs identified by clinical CGH in this cohort. Therefore, this study provides insight into the potential involvement of CHRNA7 duplications in the etiology of TR-MDD and informs those involved with care of affected individuals.