The DCC protein is a type I transmembrane glycoprotein that belongs to the immunoglobulin (Ig) superfamily. The extracellular domain is composed of four Ig like domains and six fibronectin type III repeats. Native DCC is found in three isoforms. Two forms, a long and a short isoform, are produced from the same gene but have different initiation sites. The third isoform, produced by alternative splicing, is expressed only in embryonic tissue. Mouse DCC extracellular domain shares 97% and 99% homology with human and rat DCC extracellular domains, respectively. In adults, DCC is highly expressed in the brain but is also expressed at very low levels in multiple normal tissues. In the embyro, high levels of expression are detected in the brain and neural tube.