RAB13 is a member of the small GTPase superfamily which are nontransforming monomeric GTP-binding proteins that hold 4 extremely conserved regions that take part in GTP binding and hydrolysis. In addition, RAB proteins have a vital role in the endocytic pathways. The GTPase Rab13 regulates the assembly of functional epithelial tight junctions (TJs) and is expressed in every phase of preimplantation development.