p11 co-localizes with 5-HT4R in brain regions that play an important role in major depressive disorder like cingulate cortex, hippocampus, amygdala and striatum as seen by in situ hybridization and immunohistochemistry using the transgenic bac-GFP mice where GFP is expressed under the 5-HT4R promoter. Here, HTR4 is linked to major depressive disorder.