Collagen XIIIa1 is a trimeric type 2 transmembrane molecule that localizes to intercellular adherens junctions and cell-matrix focal adhesions. It is extensively spliced and can be shed from the plasma membrane or Golgi membranes. Collagen XIIIa1 mediates cellular adhesion with Fibronectin, Heparin, Integrin alpha 1, Nidogen-2, and Perlecan. It is found in most soft connective tissues including skin, lung, and the vascular system, often in association with Collagen type I. Defective Collagen type III is a cause of Ehlers-Danlos syndrome types III and IV as well as arterial aneurisms.