Our studies identified mutations in MYO5B, STX3, and STXBP2 to be causative for MVID (Müller et al., 2008; Ruemmele et al., 2010; Wiegerinck et al., 2014; Vogel et al., 2017b); they revealed that a molecular transport machinery involving myosin Vb (myo5b), the small Rab-GTPases Rab11a and Rab8a, the t-SNARE syntaxin3 (stx3), and the v-SNAREs slp4a and vamp7 is essential for apical cargo delivery (Vogel et al., 2015b; Vogel et al., 2017b). This evidence concerns the gene STX3 and microvillus inclusion disease.