WNK2 and chronic obstructive pulmonary disease: In particular, the co-methylation in “gene modules” involved in cell growth and development, such as Wnt, phosphatidylinositol 3-kinase (Pi3K)/serine/threonine kinase (AKT), mitogen-activated protein kinase (MAPK), and serine/threonine-protein kinase (Hippo), in fetal lung tissues exposed to maternal smoking matched with the same co-methylation perturbations found in adult COPD [15].