PLEK2 and nicotine dependence: As shown in Figure 7, GSEA analyses revealed that RPL3L, PLEK2, PYCRL, CD99P1, LOC100133130, MELK, LINC01101, and DLG3-AS1 were mainly involved in glycosaminoglycan biosynthesis – heparan sulfate/heparin, histidine metabolism, nicotine addiction, diabetes, protein export, taste transduction, fatty acid degradation, propanoate metabolism, endocrine, and other factor–regulated calcium reabsorption, GABAergic synapse, steroid biosynthesis, synaptic vesicle cycle, carbohydrate digestion and absorption, proteasome, and asthma (Figure 7).