NEXN and nicotine dependence: The results of GSEA enrichment analysis indicated that in AAA, upregulation of NEXN was associated with activation of pathways such as Proteasome, Protein export, Ribosome, Ubiquinone and other terpenoid-quinone biosynthesis, and Valine, leucine, and isoleucine degradation, while downregulation of NEXN was associated with activation of pathways such as African trypanosomiasis, Linoleic acid metabolism, Maturity onset diabetes of the young, Nicotine addiction, and Taste transduction (Fig. 5C).