In recent years, genetic studies of bronchial epithelial cells have discovered several genes, such as protocadherin 1 (PCDH1) (44), periostin (POSTN), serpin family B member 2 (SERPINB2), and chloride channel accessory 1 (CLCA1) (45), associated with asthma phenotypes. The gene discussed is POSTN; the disease is asthma.