Furthermore, the mRNA expression level of each gene was moderately, but significantly, inversely correlated with the promoter methylation level (P < 0.001; Fig. 1M,N), collectively suggesting that aberrant promoter hypermethylation may contribute to downregulation of ST6GALNAC3 and ZNF660 in PC. The gene discussed is ZNF660; the disease is pachyonychia congenita.