Commercially available primer sets from Qiagen (Redwood City, CA, USA) were utilized for the CDH22 (in a nearby CpG island ~300 base pairs away) and CCDC8 genes (same CpG island).
The top five CpG sites met a predefined FDR cutoff of <0.05 and were found in the following genes: cadherin-like 22 (CDH22), family with sequence similarity 19 (chemokine- (C-C motif-) like), member A2 (FAM19A2), cadherin-like 22 (CDH5), casein kinase 1 (CSNK1E), and Delta/notch-like EGF repeat (DNER).
For validation, methylation was analyzed by site-specific pyrosequencing at three sites: (1) the top differentially methylated CpG site in the overall discovery sample (CDH22) and (2) the top differentially methylated CpG islands for males (CCDC8) and (3) females (MAP3K13).
The top site, located in the cadherin-like 22 (CDH22) gene, had increased methylation in subjects with metabolic syndrome (i.e., hypermethylation).
Classical cadherins can be further subdivided into the type I classical cadherins consisting of CDH1 (E-cad), CDH2 (N-cad), CDH3 (P-cad), CDH4 (R-cad), and CDH15 (M-cad); the type II classical cadherins include CDH5 (VE-cad), CDH6 (K-cad), CDH7, CDH8, CDH9 (T1-cad), CDH10 (T2-cad), CDH11 (OB-cad), CDH12 (N-cad-2), CDH18, CDH19, CDH20, CDH22
, and CDH24.
All CDH genes (n = 27) screened in this study include CDH1 (E-cadherin), CDH2 (N-cadherin), CDH3 (P-cadherin), CDH4 (R-cadherin), CDH5 (VE-cadherin), CDH6 (K-cadherin), CDH7 (cadherin 7), CDH8 (cadherin 8), CDH9 (T1-cadherin), CDH10 (T2-cadherin), CDH11 (OB-cadherin), CDH12 (N-cadherin 2), CDH13 (H-cadherin), CDH15 (M-cadherin), CDH16 (KSP-cadherin), CDH17 (LI-cadherin), CDH18 (cadherin 18), CDH20 (cadherin 20), PCDHGA12 (CDH21), CDH22
CDH23 CDH24 DCHS1 (CDH19, or CDH25), CDH26 DCHS2 (CDH27), CDHR3 (CDH28), and CDHR4 (CDH29).
In 2017, CDH22
mRNA was identified as a hypoxic eIF4E2 target that encodes cadherin-22, a cell-cell adhesion molecule providing cancer cells with collective migratory and invasive properties specifically in hypoxia .