In biopsies taken from patients with diarrhea-predominant irritable bowel syndrome, there were increased levels of micro-RNA 29A and B and reduced levels of claudin-1 (CLDN1) and nuclear factor-kB-repressing factor (NKRF), which was replicated in a knockout animal model that documented the fact that increased micro-RNA 29A and B decreased the levels of CLDN1 and NKRF mRNA [25]. The gene discussed is CLDN1; the disease is irritable bowel syndrome.