STX3 and microvillus inclusion disease: In this regard, analysis of subcellular distribution of STX3 and MUNC18-2 in enterocytes of intestinal biopsies from patients withMYO5B orSTXBP2 mutations showed that MUNC18-2 and STX3 accumulated in intracellular puncta in the enterocytes of MVID patients as compared to apical localization in brush border plasma membrane in control enterocytes.