RUNX1 and major depressive disorder: However, the current results with RUNX1 in the male subgroup of UKB could further support the important role of the CLDN5 gene in stress-associated depression and BBB integrity, as this transcription factor repressing claudin-5 expression could be influenced by various inflammatory cytokines [45], suggesting that a biological pathway-level approach would be advisable during the investigation of the role of CLDN5 in stress-associated depression.