Through EWAS analyses adjusted for sex, age, flow-cytometry based blood cell composition, and twin relatedness structure in the data we identified depression symptomatology score to be associated with blood DNA methylation levels in promoter regions of neuropsin (KLK8, p-value = 4.7 × 10<sup>-7</sup>) and DAZ associated protein 2 (DAZAP2, p-value = 3.13 × 10<sup>-8</sup>) genes.
Neuropsin cleaves mature NRG1 (bound to extracellular glycosaminoglycans) in response to long-term potentiation or depression, liberating a soluble ligand that activates its receptor, ErbB4.
The main aim of this paper is to compare expression of the human neuropsin gene on the mRNA level in a group of patients diagnosed with depression and in a group of healthy subjects who have never been treated psychiatrically.