Identification of significantly different modules between permanent and deciduous teeth by network and pathway analyses.

The differences in genetic backgrounds between deciduous and permanent teeth might contribute to the differences in developmental processes, histological characteristics, and tooth life cycles. Here, we attempted to identify significantly different modules between permanent and deciduous teeth via network and pathway analyses. We identified 291 differentially expressed genes (DEGs) between permanent and deciduous teeth using significance analysis of microarray methods. Co-expression networks of DEGs were constructed by weighted gene co-expression network analysis (WGCNA). Three pathways with a significant number of DEGs and P value <0.01 were identified. Integrated co-expression network and pathway (pathway and adjacent gene) analyses were used to extract three pathway-related modules: the calcium signaling pathway-related, ECM-receptor interaction pathway-related, and neuroactive ligand-receptor interaction pathway-related modules. We also attempted to analyze the topological centralities (degree, closeness, stress, and betweenness) of co-expression networks and modules. Four genes (TMEM229A, PPAPDC1A, LEPREL1, and GAD1) and three pathway-related modules that were significantly different in the deciduous and permanent teeth showed similar properties and good centralities. The relative expression levels of key genes were validated, and the differential expression of TMEM229A, LEPREL1, and GAD1 was confirmed by reverse transcription-polymerase chain reaction (P < 0.05). In conclusion, the results of this study may provide a greater understanding of the molecular pathogenesis and potential biomarkers of the progression from deciduous to permanent teeth.