Ent9_Apoa4, which highly expressed Clca4a (enterocyte apical membrane protein45) and Ada (an IBD candidate biomarker46) and was enriched in pathways associated with microbial infection and endocytosis, was identified as a cluster of mature enterocytes involved in mucosal immunity (Fig. 3c–f). The gene discussed is APOA4; the disease is inflammatory bowel disease.