Genome-wide association studies (GWAS) have successfully identified genetic loci associated with major depressive disorder (MDD), yet the complex gene networks underpinning this polygenic risk remain Show more
Genome-wide association studies (GWAS) have successfully identified genetic loci associated with major depressive disorder (MDD), yet the complex gene networks underpinning this polygenic risk remain largely uncharacterised. Here, we elucidate the neurobiological mechanisms of MDD by analyzing co-expression networks of 94 risk genes in the human prefrontal cortex. By linking these networks to individual symptoms, we identify the FADS1 (fatty acid desaturase 1) network as a central integrator across symptom clusters. We find that the FADS1 network functions primarily in astrocytes to regulate fatty acid metabolism and influence oligodendrocyte-related cell states. Furthermore, we identify FGF2 as a synaptic effector of this pathway and highlight PPARα (peroxisome proliferator-activated receptor alpha) as a putative therapeutic target. These results establish astrocyte fatty acid metabolism as a critical mechanistic contributor to MDD and a promising avenue for treatment. Show less