Integrated Single‐Cell RNA‐seq and ATAC‐seq Reveals Heterogeneous Differentiation of CD4+ Naive T Cell Subsets is Associated with Response to Antidepressant Treatment in Major Depressive Disorder

Abstract The mechanism involved in major depressive disorder (MDD) is well‐studied but the mechanistic origin of the heterogeneous antidepressant effect remains largely unknown. Single‐cell RNA‐sequencing (scRNA‐seq) and assay for transposase‐accessible chromatin using sequencing (ATAC‐seq) on peripheral blood mononuclear cells from 8 healthy individuals and 8 MDD patients before or after 12 weeks of antidepressant treatment is performed. scRNA‐seq analysis reveals a lower proportion of naive T cells, particularly CD4 + naive T cells, in MDD patients compared to controls, and in nonresponders versus responders at the baseline. Flow cytometry data analysis of an independent cohort of 35 patients and 40 healthy individuals confirms the findings. Enrichment analysis of differentially expressed genes indicated obvious immune activation in responders. A specific activated CD4 + naive T population in responders characterized by enhanced mitogen‐activated protein kinases (MAPK) pathway is identified. E‐twenty six (ETS) is proposed as an upstream regulator of the MAPK pathway and heterogeneous differentiation in activated CD4 + naive T population is associated with the response to antidepressant treatment in MDD patients. A distinct immune feature manifested by CD4 + naive T cells during antidepressant treatment in MDD is identified. Collectively, this proposes the molecular mechanism that underlies the heterogeneous antidepressant outcomes for MDD.