SLC6A15 and major depressive disorder: For example, rare CNVs were found in SOX1, a transcriptional activator thought to play a role in neuronal development [59]; and near GM2A, which is highly expressed in the brain and can harbor mutations which result in a variant of Tay-Sachs disease [67]; and SLC6A15, an amino acid transporter expressed highly in the brain and associated with major depressive disorder [68].