For example, CDKN1A, IL1B, and TP53 are associated with gastritis; MPP1, MPP3, MPP9, PLAT, and SERPINE1 are associated with gastric ulcer; ADRA2A, SLC6A2, and SLC6A4 are associated with gastrointestinal disease. The gene discussed is ADRA2A; the disease is gastritis.