Gene-level expression data for controls and alcoholics were assigned separately into organized clusters sharing highly similar expression patters (i.e. modules) using a signed weighted gene coexpression network analysis (WGCNA) 32. The modular organization of coexpression systems is suggested as an important underlying aspect of cellular function and in the pathogenesis of disease 33, 34. Coexpression analysis was applied separately for controls and alcoholics to contrast network structure between disease cohorts, and designate those PFC modules most related to excessive alcohol consumption within dependent individuals. Depicting expression data in the form of modules condenses a large number of expression characteristics into manageable units in order to clarify and prioritize systems within the human brain 35-37, as well as define representative expression profiles that can be associated with specific traits. Our analysis identified 32 and 38 gene expression modules for controls and alcoholics. RNA-Seq defined modules were significantly conserved in relation to previous network-based studies from human cortex (Table S1), forming distinctive functional categories that demonstrate consistency of networks with previous human brain studies. Alcoholic modules were further over-represented for a similar
