PVALB and major depressive disorder: However, the direct relationship between DNA methylation and gene expression of PVALB is unknown, although the findings described above in schizophrenia and its animal model show both increased methylation and reduced expression of PVALB. In contrast, previous studies in postmortem brain in MDD have demonstrated no changes of PVALB gene expression or neuronal immunoreactivity in most brain regions studied 27-29,33, other than the anterior cingulate 30.